Preface

Since the Swedish National Council for Nuclear Waste (KASAM) was established in 1985, KASAM has regularly published reports of its independent review of the state-ofthe-art in the nuclear waste area. According to the terms of reference for KASAM, decided by the Government in 1992 (Dir. 1992:72), such a review must be submitted once every three years.

KASAM herewith submits its report, Nuclear Waste. Stateof-the-art Report 2004, to the Government.

The report is the eighth in this series. The first four reports have been published in 1986 (ISBN 91-38-09767-2), in 1987 (ISBN 91-38-009938-1), in 1989 (ISBN 91-38-12264-2) and in 1992 (ISBN 91-38-12749-0). The following three reports were published in the Swedish official government report (SOU) series (SOU 1995:50, SOU 1998:68 and SOU 2001:35). English translations of the 1998 and 2001 reports were also published in the SOU-series.

None of KASAM’s state-of-the-art reports can provide an entirely comprehensive view of the state-of-the-art in the nuclear waste area. This is not KASAM’s aim. Instead, each report deals with current issues in the debate at the time of publication and for which there may be a need to present an accurate and accessible overview. The choice of subject areas covered is also, to some extent, affected by the competence profiles of KASAM’s members. A detailed description of the structure of this state-of-the-art report is provided in an introduction.

Precface SOU 2004:67

A long-term, sustainable solution to issues concerning the disposal of spent nuclear fuel and other long-lived radioactive waste as well as the decommissioning of nuclear power plants requires co-operation between three main actors: the reactor licensees, the Government and the population of one or more municipalities where a repository or an encapsulation plant will be built. KASAM hopes that this state-of-the-art report will be studied also outside the Government offices and experts in the field, thereby facilitating the necessary dialogue between the nuclear industry, the government authorities, the municipalities, the general public and the organisations concerned.

Stockholm, June 2004

Kristina Glimelius Chairperson, KASAM

Preface

KASAM has the following members (June 2004)

Members Kristina Glimelius (Chairperson), Professor, Swedish

University of Agricultural Sciences, Uppsala, Genetics and Plant Breeding

Rolf Sandström (Vice Chairperson), Professor, Royal

Institute of Technology, Stockholm, Materials Technology

Lena Andersson-Skog, Professor, Umeå University,

Economic History

Carl Reinhold Bråkenhielm, Professor, Uppsala University,

Theology

Willis Forsling, Professor, Luleå Technical University,

Inorganic Chemistry

Tuija Hilding-Rydevik, Associate Professor, Nordregio,

Stockholm, Environment and Planning Processes

Gert Knutsson, Professor Emeritus, Royal Institute of

Technology, Stockholm, Hydrogeology

Inga-Britt Lindblad, Associate Professor, Umeå University,

Media and Communication Science

Sören Mattsson, Professor, Lund University, Malmö,

Radiation Physics

Marie Nisser, Professor Emeritus, Royal Institute of

Technology, Stockholm, Industrial Heritage Research

Jimmy Stigh, Professor, Göteborg University, Geology

Experts to KASAM Hannu Hänninen, Professor, Helsinki University of

Technology, Finland, Engineering materials

Olof Söderberg, PhD Sören Norrby, MSc

Secretary to KASAM Mats Lindman, MSc

Precface SOU 2004:67

All of KASAM’s members, apart from Inga-Britt Lindblad who was appointed after the report had been finalised, contributed to the drafting of this state-of-the-art report. The following were responsible for drafting the different chapters:

Chapter 1: Sören Norrby, KASAM Chapter 2: Olof Söderberg, Tuija Hilding-Rydevik and Mats Lindman, KASAM Chapter 3: Herbert Henkel and Bo Olofsson, Department of Land and Water Resources Engineering, Royal Institute of Technology (Stockholm) as well as Gert Knutsson and Jimmy Stigh, KASAM Chapter 4: Bo Olofsson, Department of Land and Water Resources Engineering, Royal Institute of Technology (Stockholm) as well as Gert Knutsson, KASAM Chapter 5: Douglas Baxter, Analytica AB, Luleå and Willis Forsling, KASAM Chapter 6: Hannu Hänninen, KASAM Chapter 7: Sören Mattsson, KASAM Chapter 8: Henri Condé, Uppsala University, Tor Leif Andersson, Tellus Energi AB, Nyköping, as well as Rolf Sandström and Sören Norrby, KASAM Chapter 9: Mikael Stenmark, Uppsala University and Carl Reinhold Bråkenhielm, KASAM

Contents

Introduction .................................................................. 17

Section I The Nuclear Waste Issue in Sweden and Abroad

1 Nuclear Waste Management in Some Countries ......... 25

1.1 Introduction ........................................................................25

1.2 Canada .................................................................................28 1.2.1 Nuclear Power Programme .....................................28 1.2.2 Relevant Institutions ...............................................28 1.2.3 Nuclear Waste Management ...................................29

1.3 Finland .................................................................................31 1.3.1 Nuclear Power Programme .....................................31 1.3.2 Relevant Institutions ...............................................32 1.3.3 Management of Nuclear Waste ...............................33

1.4 France ..................................................................................35 1.4.1 Nuclear Power Programme .....................................35 1.4.2 Relevant Institutions ...............................................36 1.4.3 Nuclear Waste Management ...................................37

1.5 Germany ..............................................................................40 1.5.1 Nuclear Power Programme .....................................40

Contents SOU 2004:67

1.5.2 Relevant Institutions ...............................................41 1.5.3 Nuclear Waste Management ...................................42

1.6 Japan ....................................................................................44 1.6.1 Nuclear Power Programme .....................................44 1.6.2 Relevant Institutions ...............................................44 1.6.3 Nuclear Waste Management ...................................45

1.7 Russia ...................................................................................48 1.7.1 Nuclear Power Programme .....................................48 1.7.2 Relevant Institutions ...............................................48 1.7.3 Nuclear Waste Management ...................................49

1.8 Switzerland ..........................................................................53 1.8.1 Nuclear Power Programme .....................................53 1.8.2 Relevant Institutions ...............................................53 1.8.3 Nuclear Waste Management ...................................54

1.9 United Kingdom .................................................................59 1.9.1 Nuclear Power Programme .....................................59 1.9.2 Relevant Institutions ...............................................60 1.9.3 Management of Nuclear Waste ...............................61

1.10 USA ....................................................................................64 1.10.1 Nuclear Power Programme .....................................64 1.10.2 Relevant Institutions ...............................................64 1.10.3 Nuclear Waste Management ...................................64

1.11 International Organisations ...............................................69 1.11.1 Nuclear Energy Agency, NEA ...............................69 1.11.2 International Atomic Energy Agency, IAEA ........................................................................ 72 1.11.3 The European Commission ....................................74

1.12 Conclusion ..........................................................................76

Contents

2 The Municipalities – One of the Main Actors in the Nuclear Waste Issue ...................................... 83

2.1 Introduction ........................................................................83

2.2 The Nuclear Waste Issue – a Joint Concern for Industry, the State and the Municipalities ..................84

2.3 Where Are We in the Siting Process? ................................85 2.4 Expectations and Anxieties in the Municipalities Concerned ..................................................88 2.4.1 Important Issues for the Municipal Leaders ......................................................................89 2.4.2 View of the Allocation of Responsibilities among the Municipality and Other Actors ............93 2.4.3 Nuclear Waste Issues and Areas of Municipal Responsibility .........................................95

2.5 Sequence of Events 2002

Municipality ........................................................................96

2.5.1 Facts about the Municipality ..................................96 2.5.2 Council Decision to Allow SKB to Conduct Site Investigations in Forsmark ..............98 2.5.3 The Municipality’s Organisation for Following the Site Investigation Work ..................99 2.5.4 Examples of Issues relating to the Site Investigation that Have Been Dealt with by the Municipal Organisation of Östhammar ........101

2.6 Sequence of Events 2002-2004 in Oskarshamn Municipality ......................................................................103 2.6.1 Facts about the Municipality ................................103 2.6.2 Council Decision to Allow SKB to Start Site Investigations on Simpevarp ..........................105 2.6.3 The Municipality’s Organisation for Following the Site Investigation Work ................105

Contents SOU 2004:67

2.6.4 Examples of Site Investigation-related Issues that Have Been Discussed in the Framework of the Municipal Organisation in Oskarshamn ....................................................... 111

2.7 Sequence of Events, 2002-2004 in Hultsfred Municipality .......................................................................113 2.7.1 Facts about the Municipality .................................113 2.7.2 The Municipality and the Final Disposal Issue ........................................................................ 114

2.8 Consultation under the Environmental Code ................116 2.8.1 Requirements on Consultation .............................116 2.8.2 Consultation in Uppsala County .........................119 2.8.3 Consultation in Kalmar County ...........................123

2.9 KASAM’s Comments .......................................................130 2.9.1 Östhammar and Oskarshamn – Different but Similar? ............................................130 2.9.2 Site Selection in Certain Possible Scenarios .........134 2.9.3 Availability of the Necessary Competence at the Regulatory Authorities ...............................136 2.9.4 Competition between the Municipalities? ...........137 2.9.5 Consultation under the Environmental Code ....................................................................... 138 2.9.6 Conclusions ............................................................139

Section II Handling the Risks of Nuclear Waste. An Overview of Methods, Problems and Possibilities

3 Some Geological, Geodynamic and Geophysical Investigation Methods Used for the Siting of a Repository in Hard Rock ........................................149

3.1 Introduction ......................................................................149

Contents

3.2 Geological Methods ..........................................................153 3.2.1 Structural and Rock Mechanical Studies ..............153 3.2.2 Drilling Methods, Borehole Measurements and Drillcore Analysis ...........................................159 3.2.3 Rock Mechanics Testing and Rock Materials Testing ....................................................................159 3.2.4 Dating and Evolution Studies ...............................161

3.3 Geodynamic Methods ......................................................163 3.3.1 Measurement of the Change in Gravity ...............164 3.3.2 Geodetic Networks ...............................................165 3.3.3 Seismic Networks ..................................................169

3.4 Geophysical Methods .......................................................170 3.4.1 Problems and Objectives ......................................170 3.4.2 Processing and Presentation of Geophysical Data ........................................................................171 3.4.3 Measurements of the Physical Properties of Rock and Soil Materials ....................................173 3.4.4 Strategies in Site Selection .....................................176 3.4.5 Geophysical Measurement Systems .....................178 3.4.6 Limitations Due to Terrain and Artificial Objects ...................................................................182 3.4.7 Airborne Geophysics .............................................183 3.4.8 Ground Geophysics ...............................................185 3.4.9 Borehole Geophysics .............................................197 3.4.10 Databases at SGU and the Swedish Maritime Administration .......................................................200

3.5 Conclusions .......................................................................201

3.6 Appendix: Geodynamic Processes ...................................204 3.6.1 Topography ............................................................208 3.6.2 Land Uplift .............................................................211 3.6.3 Earthquakes ............................................................212 3.6.4 Fault Movements ...................................................216

Contents SOU 2004:67

4 Some Hydrogeological Methods for Determining Groundwater Recharge and Groundwater Flow .........225

4.1 Introduction ......................................................................225

4.2 Hydrometeorological and Hydrological Data ................225

4.3 Measurement of Surface and Groundwater Levels .........229

4.4 Groundwater Recharge – Measurement Methods and Calculations ................................................................235

4.5 Tracer Methods and Isotope Techniques ........................249

4.6 Conclusions and Recommendations ................................263

5 Analysis and Fractionation of Isotopes ....................273

5.1 Introduction ......................................................................273

5.2 The elements, isotopes and mass numbers ......................275 5.2.1 What is fractionation? ...........................................276 5.2.2 Radioactive isotopes ..............................................277 5.2.3 The isotopic composition of the elements ...........278 5.2.4 The properties of isotopes .....................................279 5.2.5 Fissionable isotopes ...............................................280

5.3 Analytical methods and their limitations ........................281 5.3.1 Mass spectrometry .................................................281 5.3.2 Infrared spectroscopy ............................................286

5.4 Applications of isotope ratio measurements ...................287 5.4.1 Dating of groundwater ..........................................288 5.4.2 Tracing radioactive sources ...................................290

5.5 Processes leading to isotopic fractionation .....................295

5.6 Conclusions .......................................................................304

Contents

6 Copper Canisters – Fabrication, Sealing, Durability ............................................................. 309

6.1 Introduction ......................................................................309

6.2 Fabrication .........................................................................314 6.2.1 Copper Shell ...........................................................314 6.2.2 Cast Iron Insert .....................................................315 6.2.3 Lid Welding ............................................................316 6.2.4 Residual Stresses ....................................................318 6.2.5 Non-Destructive Testing (NDT) ........................318 6.2.6 Encapsulation Plant ...............................................319

6.3 Durability ..........................................................................320 6.3.1 Corrosion Properties .............................................320 6.3.2 Creep Properties ....................................................321

6.4 Summary ............................................................................322

7 An Attempt at a Comparable Classification of Radioactive Waste and Hazardous Chemical Waste ................................................................. 327

7.1 Introduction ......................................................................327

7.2 Proposal for a Comparable Classification of Radioactive and Chemical Waste .....................................329

7.3 Designations for Risks to Individuals .............................330

7.4 Proposed Risk Index for Waste Classification (NCRP) .............................................................................332

7.5 A Risk-based Waste Classification System .....................333

7.6 Risk Estimates and Risk Comparisons ............................335

7.7 Calculation of Risk Figures ..............................................339

Contents SOU 2004:67

7.8 Examples of Comparative Limits for Radiation, Asbestos and Nickel .........................................................340

7.9 Consequences of the Proposed Classification System................................................................................ 341

Section III The Nuclear Waste Issue and the Future

8 Partitioning and Transmutation – An Alternative to Final Disposal. An Issue in Focus .......................347

8.1 Introduction ......................................................................347

8.2 Basic Principles of P&T ....................................................349 8.2.1 The Fuel in the Reactor Core ...............................350 8.2.2 The Basic Principle of P&T ...................................354 8.2.3 Thermal or Fast Neutrons .....................................355 8.2.4 Partitioning ............................................................356 8.2.5 Technical Alternatives ...........................................358

8.3 State-of-the-Art ................................................................367

8.4 Ongoing and Planned Research .......................................371 8.4.1 European Research ................................................371 8.4.2 Research in the USA ..............................................380 8.4.3 Research in Japan ...................................................384 8.4.4 Research in South Korea .......................................385 8.4.5 International Atomic Energy Agency (IAEA).... 386 8.4.6 OECD Nuclear Energy Agency (OECD/NEA) ......................................................387 8.4.7 Swedish Participation in International Research ..................................................................387

8.5 Scenarios ............................................................................394 8.5.1 Components in the P&T System ..........................394 8.5.2 Three Scenarios ......................................................395

Contents

8.5.3 Costs .......................................................................399 8.5.4 Discussion of the Scenarios ..................................401

8.6 Concluding Remarks ........................................................405

9 Nuclear Waste, Ethics and Responsibility for Future Generations ............................................... 413

9.1 Introduction ......................................................................413

9.2 Ethics and Morality ...........................................................416

9.3 What Is Environmental Ethics? .......................................419

9.4 Nuclear Power and Environmental Ethics ......................421 9.4.1 The Principle of Minimal Risk ..............................421 9.4.2 Intragenerational Justice and/or Intergenerational Justice .......................................423 9.4.3 Ethics of Sustainable Development – Four Principles of Justice ......................................427

9.5 The Nuclear Waste Issue as an Existential Dilemma ............................................................................ 434 9.5.1 The Concept of “Diminishing Moral Responsibility” .......................................................434 9.5.2 Three Time Periods – Three Principles of Justice .................................................................439 9.5.3 The Concept of the “Rolling Present” .................441 9.5.4 Applications ...........................................................445

9.6 Conclusions .......................................................................455

Concluding Remarks ..................................................... 461

Introduction

Nuclear Power and Energy Policy

Several examples of technical projects that have been the subject of debate and discussion, not only among politicians but also among the general public, can be found during the Post-war period. The building of the Öresund Bridge, linking Sweden and Denmark, was preceded by an extensive environmental debate. The construction of railways, cell phone masts, windpower farms and genetic engineering have all been questioned by the public and by politicians. However, none of these discussions are of quite the same magnitude as the debate that nuclear power and nuclear waste has generated, starting in the early 1970’s, in Sweden and abroad.

The referendum on nuclear power, which was conducted in March 1980, resulted in a majority of the Swedish parliament setting a deadline for the complete phase-out of nuclear power in 2010.

The reactor accident in Chernobyl, former Soviet Union in 1986 brought the risks associated with nuclear power into focus. In spite of this, the Swedish phase-out decision was modified as early as by 1991 – partly in order to achieve the objective of not allowing an increase of carbon dioxide emissions from fossil fuels beyond the 1988 level. In the energy policy guidelines that the parliament decided on in 1997 and 2002, a specific year was no longer given for the phase-out of nuclear power.

One reactor at Barsebäck nuclear power plant was closed down in 1999. Since autumn 2002, negotiations have been

Introduction SOU 2004:67

underway between the Government and the electricity producers with the aim of preparing an agreement to create favourable conditions for the commercially viable continued operation and successive phase-out of nuclear power.

Conflicts between different perceptions of nuclear power and nuclear waste decreased in the 1990’s and, today, there are other important environmental issues that have also come to the fore. In spite of this, the disposal of spent nuclear waste entails an important decision, at national level, on a technically and morally complex large-scale project.

Nuclear waste is the focus of this report as are the scientific conditions, consultations and decision-making processes that exist in order to find a safe disposal solution for the 200 to 300 tonnes of high-level, long-lived waste which are generated every year from the operation of Swedish nuclear power plants. Altogether, about 4,000 tonnes of such waste are in storage at the Central Interim Storage Facility for Spent Nuclear Fuel (CLAB) in Simpevarp, Oskarshamn municipality.

Nuclear Waste – a State-of-the-art Report

Most Swedes would probably recognize the claim that the nuclear waste issue is not exclusively a technical and economic issue. The nuclear waste issue has other concerns besides bedrock types, groundwater flow, mechanical strength and welding methods. Nuclear energy and nuclear waste issues also relate to moral and ethical values and priorities: Who is responsible for the safe disposal of high-level waste? Should we wait for new and improved technology to become available in the future? If not, which municipality and landowner should give up a site for the repository? What does our responsibility towards future generations require us to do?

1

The negotiations were interrupted in autumn 2004 without a result. The second reactor

at Barsebäck nuclear power plant was closed down in May 2005.

SOU 2004:67 Introduction

At the stage that we have reached on the nuclear waste issue today, we need broad and deep knowledge of the ways in which the selection of different technical solutions will affect society in the future. To choose between different alternatives and to prioritise always means that we must balance ethical, economic, technical, environmental, health-related and social conditions against each other. This is never easy, especially since knowledge of and values relating to these issues are not static. However, KASAM hopes that this overview can provide a good basis for reporting facts and presenting perspectives as well as for encouraging the public and decision-makers to ask relevant questions.

The report investigates some of the issues that are important for the continued consulting and decision-making process prior to the construction of a repository for spent nuclear fuel and other long-lived, radioactive waste. In this report, the nuclear waste issue is presented from a broad, scientific perspective, where findings from research in the humanities, social sciences as well as technology and science are presented in an accessible manner.

Nuclear Waste. State-of-the-Art Report 2004 contains nine independent chapters. These chapters have been grouped into three sections and each section deals with specific themes.

Section I The Nuclear Waste Issue in Sweden and Abroad deals with how the nuclear waste issue has so far been handled and organised. This section starts with an international overview, Nuclear Waste Management in Some Countries. This overview provides an indication of how, in each country, solutions are sought that are considered suitable in the country in question. The overview also clearly shows that the responsibility for nuclear waste, to a large extent, covers both private and public actors, even if this is to a varying degree. An in-depth presentation of the Swedish process is provided in the chapter – The Municipalities – One of the Main Actors in the Nuclear Waste Issue. Given the international overview, this chapter shows that

Introduction SOU 2004:67

the Swedish consultation process is based on strong and conscious efforts to achieve local participation and mutual understanding.

Section II Handling the Risks of Nuclear Waste. An Overview of Methods, Problems and Possibilities gives an overview of knowledge to calculate and handle different risks as well as of methods to obtain data for assessments relating to the storage of nuclear waste from a scientific perspective. This section starts off with two presentations of geoscientific methods used to calculate bedrock stability and permeability: Some Geological, Geodynamic and Geophysical Investigation Methods Used for the Siting of a Repository in Hard Rock and Some Hydrogeological Methods for Determining Groundwater Recharge and Groundwater Flow. In the next chapter, Analysis and Fractionation of Isotopes, the possibility is discussed of taking into account the properties of different isotopes in order to determine transport rates of different radioactive substances from a repository for spent nuclear fuel or other radioactive waste so as to obtain a basis for risk assessments and a safety assessment. The next chapter, Copper Canisters – Fabrication, Sealing, Durability, provides an overview of the methods used for the manufacturing and control of copper canisters which are one of the engineered barriers surrounding the waste in connection with geological disposal in accordance with the KBS-3 method. The final chapter, An Attempt at a Comparable Classification of Radioactive Waste and Hazardous Chemical Waste, discusses the possibility of comparing the risks of radioactive waste with the risks of hazardous chemical waste.

Section III The Nuclear Waste Issue and the Future is the final section. The question of the long-term responsibility that we have for the various choices that we make regarding the handling of nuclear waste is problematised. The first chapter, Partitioning and Transmutation – An Alternative to Final Disposal. An Issue in Focus, examines the question of partitioning and transmutation

SOU 2004:67 Introduction

from a scenario perspective and investigates the extent to which this method is realistic. The final chapter, Nuclear Waste, Ethics and Responsibility for Future Generations, focuses on the question of our responsibility for future generations with respect to the choices that we make regarding the nuclear waste issue. The significance of various ethical approaches for the decisions that we make – not only with respect to this issue – is discussed more in depth. In this way, we, the members of KASAM, hope to facilitate a public discussion which is necessary as a basis for decisions that will have to be made in the next few years.

Section I The Nuclear Waste Issue in Sweden and Abroad

1. Nuclear Waste Management in Some Countries

1.1. Introduction

This chapter provides an overview of nuclear waste management in some countries. The overview is a shortened and updated version of the corresponding account presented in the previous Nuclear Waste State-of-the-Art Report (2001). Although the focus is on high-level waste and spent nuclear fuel (see Table 1), certain information on low-level waste (LLW) and short-lived intermediate-level waste (ILW) has also been included since a number of questions concerning repository siting etc. in many respects concern all types of radioactive waste. In addition, an overview of current activities concerning waste management within some of the major international organisations (IAEA, OECD/NEA, EU) is presented.

This account deals with countries with very different nuclear policies and many different waste management programmes. A number of European countries as well as Canada, Japan and the USA are presented here. Some of the countries (for example, Finland, France and Japan) have a growing nuclear power programme while most other countries have a more static or diminishing programme, as is the case in Sweden.

A brief evaluation shows that Finland, Sweden and the USA have come the furthest with respect to realising the final disposal of spent nuclear fuel, both with respect to method selection and the site selection process. France has a highly advanced and extensive research and development programme (R&D programme) for methods for the treatment, storage and disposal

Nuclear Waste Management in Some Countries SOU 2004:67

of radioactive waste which will be reported in 2006. Germany, Japan, Canada and Great Britain all have advanced research programmes although much remains to be done before concrete solutions can be presented.

SOU 2004:67 Nuclear Waste Management in Some Countries

Table 1.1. Quantities of high-level waste (HLW) and spent nuclear fuel for disposal

Country Number of

nuclear reactors

* **

Planned Operational time (years)

Spent nuclear fuel (t HM if no other information given)

HLW (according to specification below)

Remarks

Sweden

11 1 Varying

ca 9 000 0 Calculated total amount for the Swedish programme

Canada 14 8 Varying 3,6 millions of assemblies (CANDU) 76 000 assemblies (other)

0 Calculated amount until year 2035

Finland 4 40

2 600 to 4 000

0 Calculated total amount for the Finnish programme

France

59 11

15 000 3 500 m

3

Calculated total amount from existing reactors and other nuclear facilities

Germany

19 18 Varying

9 000 22 000 m

3

Calculated total amount for the German programme. The amount includes encapsulation material

Japan

51 1

0

ca 40 000 canisters

Corresponding to accumulated amount until year 2020 (1 canister = ca 1,35 t HM)

Russia 30 30

  • n.i. n.i.

Switzerland 5 40 or more ca 1 800 ca 1 000 m

3

Calculated amount for the operation time for the reactors

Great Brittain 35 10 30 to 46 ca 1 890 m

3

Calculated until year 2013

USA

103 15 Up to 40 83 500 (from commercial reactors), 21 000 (from other reactors)

640 t HM (commercial) 5 000 waste packages à 4 to 5 canisters (military)

Calculated amount from existing reactors. 105 000 t HM is expected from these including prolonged time for operation

* Reactors in operation ** Shut-down reactors n.i. = no information t HM = ton Heavy Metal, in this compilation equal to tons of uranium CANDU = Canada Deuterium Uranium (reactor)

Nuclear Waste Management in Some Countries SOU 2004:67

In many other countries, radioactive waste research is underway. Questions concerning the long-term financing of nuclear waste disposal and reactor decommissioning are also increasingly attracting international interest.

The contents of this chapter are largely based on National Profiles, which are a set of information sheets prepared by Phil Richardsson, EnvirosQuantiSci (UK) for a number of countries in the world and which are regularly updated. Additional information has been obtained from the OECD/NEA, IAEA and EU.

The information provided in Table 1.1 is taken from IAEA-TECHDOC-1323 Institutional Framework for Long-term Management of High Level Waste and/or Spent Nuclear Fuel (December 2002).

1.2. Canada

1.2.1. Nuclear Power Programme

In early 2004, there were 22 licensed nuclear power reactors in Canada. Of these, 14 are currently in operation. One is located in Quebec, one in New Brunswick and the rest are in Ontario. The reactors are owned and operated by the federal energy utilities, Hydro Quebec, New Brunswick Power and Ontario Power Generation Inc. (OPG). The other eight reactors have been shut down.

1.2.2. Relevant Institutions

Nuclear power in Canada is regulated by the Canadian Nuclear Safety Commission (CNSC). The CNSC is a federal authority which licenses sites for radioactive waste storage and disposal and promulgates guidelines for disposal. Atomic Energy of Canada Ltd (AECL) is a government-owned company charged

SOU 2004:67 Nuclear Waste Management in Some Countries

with the task of developing and promoting the use of nuclear power and of selling reactors abroad.

The immediate responsibility for the management of nuclear waste in Canada rests with the waste producers. New legislation for the final management of spent nuclear fuel entered into force in 2002. Under the Nuclear Fuel Waste Act (NFWA), the Nuclear Waste Management Organisation (NWMO) was formed. The NWMO is owned by the nuclear industry and will act independently of AECL and the federal government.

1.2.3. Nuclear Waste Management

LLW and Short-lived ILW

In Canada, a distinction is made between current arisings and historic waste. Historic waste originates from past uranium milling activities. Options studies for a disposal site for current LLW are being performed by OPG and operation is planned to begin by 2015.

In order to identify an acceptable disposal site for historic waste, the Co-operative Siting Process was established in 1986. A Task Force undertook extensive public consultation and invited interested communities to volunteer for site selection. Two municipalities were finally identified in 1994, although one withdrew shortly after. Following a positive referendum vote in 1995, the remaining municipality signed an Agreement in Principle to allow work to continue, but this lapsed by the end of 1996 when the federal government refused to accept the terms of the Agreement. However, there are now two possible sites which were announced early in 2004 (Port Hope Area Initiative 2004).

Nuclear Waste Management in Some Countries SOU 2004:67

Spent Nuclear Fuel and/or HLW

Canada does not intend to reprocess any of its spent nuclear fuel although a certain quantity of high-level waste will be generated from the reprocessing of fuel from research projects. Over the past 25 years, commercial spent nuclear fuel has been stored at nuclear power plants.

In the mid-1990’s, AECL presented a concept for the disposal of spent nuclear fuel. The concept entails placing spent nuclear fuel at a depth of 500 to 1,000 metres in the crystalline bedrock of the Canadian Shield. The repository was originally planned to be in service by 2025 and to take some 40 years to fill, before being sealed and abandoned. However, no siting-related work was permitted before concept approval. The disposal concept was reviewed in a series of public hearings before a federally nominated panel of experts in 1996 to 1997. In March 1998, the panel recommended that although the technical aspects of the concept appeared to be satisfactory, there was insufficient public acceptance to allow siting to begin.

Among its recommendations, the panel stated that the government needed to take measures to achieve a broad public support. Furthermore, in the view of the panel, AECL should not be responsible for the management of the spent nuclear fuel. Instead, a new federal unit should be set up for this task. The unit should be solely financed by the waste producers and the board of directors should include representatives from all key stakeholders. Furthermore, a strong and active advisory council should be formed, with representatives from all interested parties. Finally, the panel concluded that the search for a specific repository site should not proceed until the measures recommended above had been implemented and a broader public acceptance of the proposed management concept had been achieved.

The Ministry of Natural Resources (NRCan) issued its response statement to the panel’s report in December 1998. Whilst agreeing to the establishment of a semi-independent

SOU 2004:67 Nuclear Waste Management in Some Countries

agency (namely, an agency formally attached to a government department but with great freedom to act autonomously on most matters) to carry out future work on waste management and disposal, NRCan rejected the suggestion that siting work for a repository should be postponed. It also gave overall responsibility for establishing the new agency to the waste producers and owners, who will have total control over the makeup of the board of directors.

After a period of uncertainty, the Canadian parliament made a decision in 2002 which was based on the previous inquiry proposals. Under the Nuclear Fuel Waste Act (NFWA), the Nuclear Waste Management Organisation (NWMO) was formed. The NWMO is owned by the nuclear industry and it is to act independently from the AECL and the federal government. The legislation places responsibility with the NWMO to conduct a study within three years and to present a plan for the disposal of spent nuclear fuel to the federal government in 2005. An advisory group has been established to support the NWMO in its work. The results of the NWMO’s most recent work have been reported (NWMO 2003). A special waste financing system has been set up.

1.3. Finland

1.3.1. Nuclear Power Programme

There are two commercial nuclear power plant sites in Finland, each currently with two reactors, one at Loviisa near to Helsinki, operated by the largely state-owned Fortum (former IVO), with two Russian-built VVER 440’s and one at Olkiluoto, about 100 kilometres north of Åbo. The plant is operated by TVO, which is partly owned by the Finnish industry and the power companies, and has two Swedish-designed boiling water reactors. An application for a “decision in principle” was made to the government concerning a fifth reactor, to be built at one of the

Nuclear Waste Management in Some Countries SOU 2004:67

two nuclear power plant sites. The application was approved by the Finnish government and by the Finnish parliament in 2002. It is planned to construct the reactor at Olkiluoto by a European consortium under French management.

1.3.2. Relevant Institutions

The two energy utilities are responsible for the safe management of waste and for the necessary research and development as well as for covering the costs of the whole operation. The objectives and schedules of waste management are set out in a government policy from 1983, with the regulatory basis set out in the 1988 Nuclear Energy Act and Ordinance. The Ministry of Trade and Industry (HIM) supervises waste management activities and the R&D work. It also finances research in order to maintain independent expertise. The Finnish Centre for Radiation and Nuclear Safety (STUK) is responsible for the regulation and supervision of the safety of nuclear facilities and review and assessment of waste management plans and activities. Facilities must be licensed by the government. Every year, the HIM decides the fees that the utilities must pay into the governmentcontrolled Nuclear Waste Fund, designed to cover the future costs of waste management.

In the past, the two utilities applied different spent nuclear fuel management strategies. Fuel from Loviisa was shipped back to Russia for storage and reprocessing, whereas at Olkiluoto, the fuel was stored on site in a water pool storage facility. After the collapse of the Soviet Union, the procedure for the fuel from Loviisa changed so that this fuel is now also stored on site in the same way as Olkiluoto. According to an amendment of the Nuclear Energy Act in 1994, no spent nuclear fuel may be exported after 1996. IVO and TVO have formed a joint company, Posiva, which is responsible for all spent nuclear fuel disposal work.

SOU 2004:67 Nuclear Waste Management in Some Countries

1.3.3. Management of Nuclear Waste

Waste classification in Finland distinguishes between low and intermediate level waste and spent nuclear fuel which is not to be reprocessed.

LLW and Short-lived ILW

Both nuclear utilities have developed rock cavern repositories adjacent to their existing reactor sites, using vertical silos and/or horizontal caverns. These facilities were taken into operation in 1992 and 1998, respectively.

Spent Nuclear Fuel and Long-lived ILW

Following a decision in principle by the Government in 1983, which was formally ratified in 1988 in the Nuclear Energy Act and Ordinance, HIM decided in 1991 that deep disposal would be the chosen method for spent nuclear fuel.

A list of 85 possible repository sites was prepared between 1983 and 1985. After more detailed investigations, three sites were chosen: Olkiluoto (near the nuclear power plant) in Euraåminne municipality, Romuvaara in Kuho municipality and Kivetty in Äänenkoski municipality. According to the proposal in the “TILA-99 Safety Assessment”, which was published in 1999, Posiva recommended a repository in accordance with a disposal concept similar to the KBS-3 concept in Sweden. The repository is to be located at a depth of 400 to 700 metres. The exact depth is to be determined by the conditions at the chosen site.

Posiva proposed that the ultimate design of the repository at the chosen site should not be decided until the start of construction. This would make it possible to take the actual geological conditions into consideration in the design and

Nuclear Waste Management in Some Countries SOU 2004:67

construction work. The cost of the disposal of spent nuclear fuel is estimated at about EUR 850 million (about SEK 7,500 million).

In addition to these sites, Posiva also undertook detailed investigations near the nuclear power plant at Loviisa, on the island of Hästholmen.

In January 1998, Posiva submitted an Environmental Impact Assessment Programme to HIM. The programme was also circulated to Swedish, Estonian and Russian authorities, in accordance with the requirements of the Espoo Convention.

Following a series of public hearings in spring 1998, HIM presented its review of the programme to Posiva in June 1998. HIM required additional work to be carried out to estimate the radiological risk of a “zero alternative” (whereby the proposed facility is not built). Furthermore, HIM required that retrievability should be investigated as well as a number of alternative disposal methods. Posiva published the final Environmental Impact Assessment in May 1999 and then applied to the Government for a decision in principle concerning siting in Olkiluoto.

An international panel was appointed by STUK to review the safety assessment in Posiva’s application for a decision in principle. The panel submitted its report in 1999 and, in accordance with this, STUK was recommended to conduct an additional number of review projects after the Government had made its decision in principle. The recommendation included regular reviews (every 3 to 4 years) of Posiva’s research and development programme and the results achieved (as is also conducted in Sweden). The recommendation also included a review of Posiva’s preliminary safety assessments as well as the application of important parts of the recommendations from independent reviews in order to increase the general public’s confidence in the activity.

In January 2000, STUK issued its own report based on the panel’s review and this supported Posiva’s request to continue with its plans for Olkiluoto. Under the law, permission must be

SOU 2004:67 Nuclear Waste Management in Some Countries

obtained from the municipality for a proponent to construct a repository for spent nuclear fuel. Therefore, a referendum was held in the municipal council in the Euraåminne municipality in January 2000. The outcome was 20 votes for and 7 against a facility there.

All of the review material as well as the Ministry’s summary became available to the public in spring 2000.

A decision in principle regarding a repository was made by the Government in December 2000 and the parliament made its decision in spring 2001.

In June 2002, Posiva announced its opinion to construct a tunnel for the first stage of the repository (ONKALO), which includes investigations and development work. The intention is for the investigation phase to continue until 2010 and to then construct the repository part. Deposition of the spent fuel is expected to start in 2020. In 2003, Posiva submitted an application for permission to start the construction of the facility.

In December 2003, Posiva presented a research programme for the disposal of spent nuclear fuel and nuclear waste in Finland. Such a programme will be presented once every three years in the future.

1.4. France

1.4.1. Nuclear Power Programme

At the end of 2003, there were 59 PWR reactors in France and one reprocessing facility in operation on the northern coast of Cap de la Hague. Nuclear power accounts for about 70 % of the electricity generation in France.

Nuclear Waste Management in Some Countries SOU 2004:67

1.4.2. Relevant Institutions

Under legislation passed in 1975, a waste producer must arrange for the disposal of the waste, at its own cost, by a body approved by the public authorities. For this purpose, the Government set up a special organisation, the National Agency for Radioactive Waste Management (ANDRA) in 1979, within the Atomic Energy Commission (CEA). ANDRA is responsible for designing, constructing and operating long-term disposal facilities as well as undertaking all necessary studies to this end, and for promoting the application of technical specifications for waste treatment to be carried out by producers prior to storage.

ANDRA is financed by the waste producers, in particular Electricité de France (EdF), the CEA and fuel cycle companies, such as COGEMA which operates the reprocessing plant in la Hague. The activities of these companies are reviewed by the safety authorities which report to the Ministry of Industry and the Ministry of Health and a few other ministries. In 2001, the regulatory function was re-organised, so that safety and radiation protection merged under “Direction Générale de la Sûreté Nucléaire et de la Radioprotection – DGSNR”. Furthermore, certain support functions were re-organised by merging the institutions responsible for research and development within the areas of safety and radiation protection, through the formation of a new organisation, “Institut de Radioprotection et de Sûreté Nucléaire – IRSN”.

At present, ANDRA is not responsible for managing all of the radioactive waste, especially not the waste originating from reprocessing plants or material from defence-related work. However, in a report from 1999, a member of a parliamentary advisory group recommended that ANDRA should be given such responsibility as quickly as possible.

SOU 2004:67 Nuclear Waste Management in Some Countries

1.4.3. Nuclear Waste Management

In France, radioactive waste is classified into two categories – short-lived and long-lived – depending on the length of time that the waste poses a hazard. Long-lived waste is also classified as B waste (corresponds to long-lived ILW in other countries) or C waste (corresponds to HLW) and spent nuclear fuel. Most spent nuclear fuel is reprocessed.

LLW and Short-lived ILW (A Waste)

These waste categories are deposited in a near-surface facility in northeastern France.

Spent Nuclear Fuel and/or HLW (B and C Waste)

Originally, the intention was to reprocess all spent nuclear fuel. The low and intermediate-level waste (B waste), high-level vitrified waste and fission product waste (C waste) as well as spent nuclear fuel that is not reprocessed would be deposited in a deep repository after interim storage. However, in 1998, in an unpublished report to the Government, it was maintained that the future strategy had to take into account the fact that as much as one-third of the spent nuclear fuel generated in France would probably not be reprocessed as was previously anticipated. It was also suggested that France would immediately attempt to return to their countries of origin a part of the plutonium which was obtained in connection with the reprocessing of spent nuclear fuel from these countries.

Four areas with different geological conditions, such as clay, granite, slate and salt were selected for investigations and the development of a deep repository. However, all work was stopped at all four sites as a result of intensive public resistance. The Waste Act was supplemented in December 1991 and, under

Nuclear Waste Management in Some Countries SOU 2004:67

this Act, ANDRA became a public service company reporting to the Ministry of Environment and the Ministry of Industry and was organisationally separated from the CEA. This measure was implemented in order to signal the independence of the organisation and to achieve increased transparency and openness.

Act No. 91-1381 defined the following three main areas, within which ANDRA would conduct research:

  • Partitioning and transmutation
  • Waste packaging and the effects of long-term surface storage
  • Development of at least two underground laboratories in locations with different geologies.

A site should only be selected after local consultation with the participation of the general public. The law states that the identification of a site for an underground laboratory requires a public hearing and government approval. It should not be possible to propose a site for a repository until 15 years after the entry into force of the Act and, even in this case, public review and licensing is required. Furthermore, it is the responsibility of the ministries concerned to keep the parliament continuously informed of progress. It is ANDRA’s responsibility to present a final status report in 2005 and a proposal for the siting of a repository in 2006.

A site for a facility – Installation Centrale d’Entreposage (ICE) – for long-term interim storage of spent nuclear fuel has not yet been selected. The facility will probably be of the pooltype design, like the Swedish facility, CLAB.

To follow progress in research within these areas and to report to the parliament, the law stipulates that a CNE (National Evaluation Commission) should be set up. The CNE holds regular hearings on the main topics. ANDRA supplements these hearings with presentations upon request. Reports are submitted to the Government on an annual basis and they are evaluated by the Parliamentary Commission on the Assessment of Scientific

SOU 2004:67 Nuclear Waste Management in Some Countries

and Technological Choices (OPECST). The CNE is also responsible for the organisation and submission of the overall repository project report due in 2005.

CNE consists of 12 people, of which six are qualified experts appointed by the OPECST. At least two of these are from abroad (currently from Sweden and Spain). Two experts are appointed by the Government and four by the French Academy of Sciences.

Through the legislation passed in 1991, a new position was created – a “mediator” – in order to simplify site selection and the development of underground laboratories. The member of parliament, Christian Bataille, was appointed to the position in 1992. Bataille was given the mandate to use up to 60 million francs (about SEK 80 million) per year for support to municipalities which are positive to further investigations. Bataille’s task was to consult with selected politicians, with the public and with local environmental organisations. In December 1993, he presented a report, where four areas were identified for further studies, of which three had sedimentary bedrock and one had crystalline bedrock. In 1994, ANDRA announced that a number of sites had been identified as suitable. One of them was adjacent to two of the previously identified areas. Detailed site investigations were started this year and a total of 15 holes were drilled at a depth of up to 1,100 metres at three different sites.

Since the drilling was completed, meetings have been held with public hearings between February and May 1997. In December 1998, the Government gave ANDRA permission to build an underground laboratory in a clay formation under one of the selected sites, the site at Bure in northeastern France. At the same time, two other sites were eliminated for geological reasons, one with marl bedrock near to Marcoule in the department of Gard and one with granite bedrock in Vienne. According to a government decision in August 1999, permission was obtained for the construction and operation at Bure up to 2006. However, the Government also gave ANDRA the task of locating additional candidate sites with granite bedrock before

Nuclear Waste Management in Some Countries SOU 2004:67

2002. In spite of the fact that 20 such sites were investigated in Bretagne and the Massif Central, the project was terminated in June 2000, largely due to excessive resistance by the public at all sites. Excavation of the first shaft at Bure began in early September 2001. Due to an accident in 2002, work was delayed and was later resumed in April 2003. A number of geotechnical, hydrogeological and other boreholes have been drilled and instrumented so as to allow the impact on the rock of the shaft sinking process to be studied. A number of geophysical measurements are to be conducted as the work continues and these will be correlated with measurements conducted in 1999 on the ground surface. A number of investigation niches will be established on different levels as the shaft goes deeper. Some of these will be located in clay at possible repository depth.

1.5. Germany

1.5.1. Nuclear Power Programme

In November 2003, there were 18 nuclear reactors in operation in Germany. None of these were located in the former German Democratic Republic (DDR), after closure of the nuclear power plant in Rheinsburg in 1990 and of the four reactors that were in operation (and a fifth under construction) in Greifswald.

In a coalition agreement in October 1998, the Social Democrats (SPD) and the Green Party agreed on a phase-out of nuclear power in Germany. After lengthy negotiations, an agreement was signed in June 2000 (the June 2000 agreement) between the Government and the power utilities on nuclear policy. According to the agreement, all reactors are to be shut down at the end of their expected lifetimes. Each reactor will be allocated a maximum amount of electricity which can be generated, thus allowing capacity to be added to newer, more efficient reactors, thereby extending their operation and allowing

SOU 2004:67 Nuclear Waste Management in Some Countries

closure of the less efficient reactors. The amount of electric power agreed on roughly corresponds to an operating lifetime of 32 years. No new reprocessing contracts will be allowed and, after July 1

st

, 2005, all spent fuel will be subjected to direct

disposal. Only reprocessing contracts effective up to that time will be honoured. A new Atomic Energy Act was passed in 2002, based on the new policy.

1.5.2. Relevant Institutions

When the Federal Office for Radiation Protection (BfS) was established in 1989, it assumed responsibility for the safe disposal of all types of radioactive waste from the Federal Institute for Science and Technology (PTB). A special company, the German Company for the Construction and Operation of Waste Repositories (DBE) was set up as a “third party” (contractor) to carry out the tasks assigned to it by BfS.

According to the new Atomic Energy Act from 2002, the waste producer is responsible for the interim storage of spent nuclear fuel at each reactor site. Applications for permission to construct such facilities have been submitted. Twelve such facilities are expected to exist by 2005 for use as storage facilities for 40 years. In the case of some of the reactors, other solutions are being planned for the storage of spent nuclear fuel.

According to the new Atomic Energy Act, the federal governments are responsible for all licensing. Previously, the intention was for all spent nuclear fuel to be reprocessed. An amendment was added in 1994 which also allowed direct disposal of spent nuclear fuel. Some utilities have already cancelled reprocessing options after 2000.

Nuclear Waste Management in Some Countries SOU 2004:67

1.5.3. Nuclear Waste Management

Since the plan is to dispose of all of the waste, independent of category, in a deep repository, the waste is basically classified into two categories, namely heat-generating and non-heatgenerating. According to the agreement between the coalition parties in 1998, it is enough for a single geological repository to deposit all types of radioactive waste. This repository will be located in rock, of a type that has not yet been decided, and at a site that has not yet formally been identified. This will naturally substantially affect the execution of the development programme for a repository.

LLW and ILW (Non-Heat-Generating)

Until recently, non-heat-generating waste (with alpha emitter concentrations up to 4.0 x 10

8

Bq/m

3

) were disposed of in the

ERAM facility (Endlager für Radioaktive Abfälle Morsleben) at the Bartensleben salt mine. According an order issued in September 1998 by the Superior Administrative Court of the state of Saxony-Anhalt, BfS must immediately stop further radioactive waste disposal in the eastern emplacement field of the Morsleben repository. In November 2001, BfS announced that measures had to be implemented to close the repository in a safe manner.

A licence application for a new deep repository for non-heatgenerating low and intermediate-level waste (LLW/ILW) at the abandoned Schacht Konrad iron-ore mine near Salzgitter in Lower Saxony was submitted as long ago as 1982. After the longest Public Inquiry in German history – between September 1992 and March 1993 – the Lower Saxony government (headed at the time by the present Federal Chancellor) continued to refuse to grant a licence for the facility, against the wishes of the Federal Authorities. According to the June 2000 Agreement, the responsible authorities are to conclude the licensing procedure

SOU 2004:67 Nuclear Waste Management in Some Countries

for Schacht Konrad as legislated. BfS withdrew the application for the immediate enforcement of the licence in order to allow a court examination on the merits of the main proceedings. The Ministry of Environment in Lower Saxony granted permission to Schacht Konrad in May 2002. A number of legal processes are underway, initiated by repository opponents. According to the agreement of 2002, only a repository for all types of waste is to be built and this also means that the future for Schacht Konrad is uncertain.

Spent Nuclear Fuel and/or HLW (Heat-Generating)

Before the 1994 amendment of the Atomic Energy Act, the only alternative for spent nuclear fuel was reprocessing which took place in France or the UK. Plans to establish a reprocessing plant in Wackersdorf were abandoned in 1989 due to intense, sometimes violent, opposition.

Repatriation of existing vitrified HLW began in May 1996, following the licensing of the interim storage facility at Gorleben in Lower Saxony in early June 1995. According to the new Atomic Energy Act, the waste producer is responsible for building the interim storage facilities for spent nuclear fuel at the reactor sites. The licence applications are currently being evaluated.

Until recently, it was assumed that Germany would develop a deep repository for HLW (and possibly also for spent nuclear fuel) in a suitable salt formation. The salt dome in Gorleben was selected as the only candidate site. However, according to the June 2000 agreement, the entire disposal problem will be reevaluated. The deep disposal method is preferred, although more types of rock must be investigated before a decision on siting is made.

As it became clear that several potential repository sites with other types of bedrock had to be investigated, BMU formed a new committee, AKEND, in February 1999, with the task of

Nuclear Waste Management in Some Countries SOU 2004:67

developing a new procedure for site selection. A programme was presented in three phases in order to obtain a new siting procedure. In the first phase, proposals for the new procedure will be formulated. In the second phase, a political and legal basis for this procedure will be obtained and decided upon. The third phase will consist of implementation.

Phase 1 has concluded with AKEND, in 2002, submitting its report to the Government. Phase 2 is in progress, through discussions with different stakeholders. This discussion is expected to be completed in 2004. During Phase 3, a site selection process will be started. However, there are indications that difficulties have arisen: The waste producers want Gorleben to be included as an alternative while BMU would like to exclude it.

1.6. Japan

1.6.1. Nuclear Power Programme

Japan currently has 54 reactors in operation (2003), owned by Japan Atomic Energy Company and nine other independent electricity companies. However, several of these reactors have been closed down due to technical problems. The need for an additional 13 reactors by the year 2010 has been announced by the Japanese industry. The only breeder reactor in the country, the experimental reactor in Monju, is currently closed down due to an accident which occurred in December 1995 and which led to a loss of coolant (sodium).

1.6.2. Relevant Institutions

The Atomic Energy Commission (AEC) and the Nuclear Safety Commission (NSC) determine the basic guidelines for radioactive waste management. The AEC is responsible for the

SOU 2004:67 Nuclear Waste Management in Some Countries

planning and determination of basic policy, whilst the NSC is responsible for safety criteria and regulations.

The Ministry of Economy, Trade and Industry (METI) and the Ministry of Education, Culture, Sports, Science and Technology (MECCST) issues licences for waste management and disposal based on the Act for the Regulation of Nuclear Source Material, Nuclear Fuel Material and Reactors. A new Special Radioactive Waste Final Disposal Act to deal with HLW disposal, was passed (2000). The Act includes stipulations that a plan for disposal should be presented every fifth year, with a complete re-evaluation after ten years. Through the Act, a new implementation organisation was also set up for work on site selection, construction, operation etc. of a deep repository. This organisation is known as NUMO. With the Act, a financing system for nuclear waste was also established.

The Japan Nuclear Cycle Development Institution (JNC) is responsible for work on advanced reactor designs, fuel cycle technology and R&D associated with HLW disposal. This organisation replaced the larger Power Reactor and Nuclear Fuel Development Corporation (PNC) in 1998, which was restructured after a number of incidents at several of its sites.

1.6.3. Nuclear Waste Management

The current Japanese programme includes reprocessing of spent fuel and utilisation of the plutonium and enriched uranium, including the development of Mixed Oxide (MOX) fuel fabrication. Previously, spent fuel has been reprocessed abroad, although an experimental reprocessing facility was in operation at PNC’s Tokai site until March 1997, when there was an explosion and fire. The facility was restarted in November 2000.

A commercial-scale reprocessing facility has been under construction since 1993 at Rokkasho, in Aomori Prefecture, which is also the site of an operational LLW repository and a storage facility for returned HLW (from reprocessing abroad).

Nuclear Waste Management in Some Countries SOU 2004:67

Japan Nuclear Fuel Service Co. Ltd (JNFL) manages both of these facilities.

LLW and Short-lived ILW

These types of waste are disposed of in a near-surface facility at Rokkasho in the Aomori Prefecture. The facility began operations in December 1992. The repository was co-sited with the reprocessing plant mentioned above and this is expected to start operation in 2005.

Spent Fuel and/or HLW

In its 1994 long-term plan, the AEC stated “some time in 2030 or no later than by 2045” as the time when a waste disposal facility would be granted an operating licence and taken into operation. The 1994 long-term plan repeated a previously presented plan to create, in around 2000, a special organisation to implement the disposal programme. In agreement with this and the new Waste Act, the Japanese utilities applied, in October 2000, to the Government for permission to establish such an organisation. The Government immediately approved the proposal and the Nuclear Waste Management Organisation (NUMO) was formed in October 2000, with its headquarters in Tokyo.

It is expected that a number of siting alternatives for a repository will be investigated starting in 2001. A number of sites for preliminary site investigations will be selected in 2004 and a few sites will then – in around 2010 – be selected for detailed characterisations. It is expected that the ultimate site will be decided upon in around 2025.

In August 1989, it was decided that an underground rock laboratory would be constructed at the disused Kamaishi mine (iron/copper) in the Iwate Prefecture, in spite of the strong local

SOU 2004:67 Nuclear Waste Management in Some Countries

opposition which is delaying the start of the project. The work was completed in March 1998 when the contract with the municipality expired.

An experimental shaft, some 150 metres deep, in a sandstone formation containing uranium and covering crystalline bedrock has also been used since 1986 in the Tono area in the Gifu Prefecture in central Japan.

Permission to construct a new underground facility in Mizunami within the same area was granted in December 1995. Surface-based investigations started late in 1997 and it is planned that the investigations will continue for up to five years. This site will take over Kamaishi’s role as the most important site for research on crystalline bedrock and like the facility it has been characterised as a facility which is only used for research.

After many years of discussion between JNC, the Hokkaido Prefecture and Horonobe city, these three parties reached an agreement in November 2000 on an underground laboratory in Horonobe on condition that it would not be used for radioactive material. A detailed research programme is being prepared and investigation drilling will start shortly. The underground laboratory in Honorobe is intended to be a centre for research on sedimentary rock types, while Mizunami has a corresponding role with respect to granite.

In Japan, as in many other countries, there is public opposition to nuclear power and nuclear waste and attempts have been made to respond to this resistance by providing information and by conducting dialogue and opening up possibilities for public influence over the work of NUMO and other bodies.

Nuclear Waste Management in Some Countries SOU 2004:67

1.7. Russia

1.7.1. Nuclear Power Programme

In May 2003, there were 30 nuclear reactors in operation in Russia. 11 of these were of the RBMK type, 14 were VVER reactors, 4 were BWRs and one was a breeder reactor. Four reactors have been decommissioned. Furthermore, Russia has had 118 research reactors in operation, although many have now been shut down. Apart from the nuclear power plants, there are a number of facilities for uranium mining, fuel fabrication, reprocessing, isotope production etc. Furthermore, military activities are conducted, including plutonium production and nuclear reactor-powered ships for the Northern Fleet in the Kola Peninsula and the Pacific Fleet around Vladivostok. There is a commercial reprocessing plant at Chelyabinsk (now referred to as Ozersk). Another was under construction at Krasnoyarsk (now referred to as Zheleznogorsk), but work has now been terminated. There are also a number of reprocessing facilities for spent nuclear fuel from military activities.

1.7.2. Relevant Institutions

Previously, responsibility for radioactive waste was split between four different ministries, namely

  • The Ministry of Atomic Power (Minatom) had the responsibility for waste from civilian nuclear power and from the production of nuclear weapons. It was founded in 1992. There are approximately 150 companies associated with Minatom, including 15 “closed cities”, where a total of 13 plutonium-producing reactors have been operated. Some of these are still in operation. Rosenergoatom is responsible for Minatom for operation of all nuclear power plants and management of the associated waste.

SOU 2004:67 Nuclear Waste Management in Some Countries

  • The Ministry of Defence had the responsibility for waste from nuclear-powered naval ships.
  • The Ministry of Marine Transport was responsible for waste from nuclear-powered icebreakers.
  • The Ministry of Construction and Housing Policies which is managing the special “Radon” facility (for the treatment and disposal of low and intermediate-level waste) was responsible for the management of radioactive waste generated in industry, medicine, research etc.

Gosatomnadzor (GAN) is the authority that regulates activities in Russia. According to the Act on Nuclear Energy, from November 1995, this authority is responsible for the licensing and inspection of all nuclear power utilities, including military utilities. According to the Act, all companies that produce and handle active waste must apply for permission for a new operating licence. In the case of certain companies, these licences are not yet ready.

1.7.3. Nuclear Waste Management

LLW and Short-lived ILW

Proposals have been made to develop a repository for military LLW in an area in northern Russia, with permafrost, and a deep repository for industrial (non-power reactor) waste near to Moscow in salt or clay. GAN explained at a later stage that the idea of constructing a repository in permafrost is being abandoned. Russia is not currently looking for a site for the disposal of LLW and ILW waste from reactor operation. Such waste is currently being stored at the nuclear power plants.

Nuclear Waste Management in Some Countries SOU 2004:67

Spent Nuclear Fuel and/or HLW

From the start, Russia planned to only reprocess spent nuclear fuel from certain reactor types, namely VVER-440, VVER-1000, BN-350 and BN-600. No plans exist to reprocess RBMK fuel. VVER-440 fuel is being reprocessed in the RT-1 facility, operated by the Majak group Ozersk in southern Ural. It was taken into operation in 1948 and was used for military fuel but was modified in 1976 so that civil fuel could also be reprocessed. The construction of RT-2 facility in Zheleznogorsk for the reprocessing of VVER-1000 fuel was interrupted in 1989 and was completely stopped in 1998, for technical and financial reasons.

RBMK fuel is stored for three to five years in the reactor hall pools and then transferred to special interim storage pools at the nuclear power plants. Such interim facilities only exist at the stations in Leningrad, Kursk and in Smolensk.

Liquid waste, including HLW of different origins has been injected into deep boreholes in Ozersk, Zheleznogorsk, Dimitrovgrad and Seversk for many years.

The Institute of Geology, Ore Deposits, Petrography, Mineralogy and Geochemistry (IGEM) is responsible for developing a strategy for the treatment and disposal of spent nuclear fuel and HLW. Furthermore, the Khlopin Radium Institute in St. Petersburg has been given the task of developing a better system for waste treatment from the reprocessing in Zheleznogorsk (if RT-2 is put into operation).

Several different deep disposal concepts are currently being studied. Since the authorities do not consider that retrievability is desirable, both mining shafts and deep boreholes may be used for disposal.

Since, as before, the aim is to concentrate the activity and to site it geographically near the sites where waste is produced, interest has centred on the areas around the Zheleznogorsk and Ozersk facilities.

SOU 2004:67 Nuclear Waste Management in Some Countries

The Khlopin Radium Institute in St. Petersburg has investigated sites around Zheleznogorsk. Other institutes have studied basal and granite bedrock in the Baltic Shield. Of the eight sites which were originally considered suitable for further investigation, two candidate sites remained in 1996. One of these has been selected and will be further studied on condition that the activity can be financed. The work has been supported by the IAEA’s Expert Contact Group and funds have been made available from PNC in Japan, DOE in the USA and authorities in Finland.

The work at Ozersk has been financed by the former USSR Academy of Sciences. A site within the boundaries of the complex was selected and four holes were drilled to a depth of at least 900 metres. The aim is to build an underground laboratory to conduct experiments and in-situ characterisation. However, recent studies show that it can be difficult to site a repository there due to uncertainties concerning the tectonic conditions. The work in this project is being conducted as part of an EUsupported PHARE programme and contains technical contributions from several organisations in the west. So far, IGEM has identified three possible disposal zones at the same time that it was dubious to the suitability of the originally selected site.

The treatment and disposal of spent fuel and other waste from repository-related industry, especially the large quantities from reactor-powered submarines, have also become an urgent problem. Much of this waste – in the from of spent fuel and different types of liquids – is stored under unsatisfactory conditions, either at the bases of the Russian Northern Fleet on the Kola Peninsula around Murmansk and Arkangelsk or at the Pacific Ocean bases near to Vladivostok. At the Northern Fleet bases, it is expected that up to 48,000 fuel elements with spent nuclear fuel have been deposited in storage facilities that are leaking and in poor condition.

In February 1998, an IAEA working group, the Contact Expert Group, reported that the waste management in the

Nuclear Waste Management in Some Countries SOU 2004:67

Russian northwestern area was in such poor condition that the area had been prioritised for global co-operation projects.

Three alternatives have been examined: A new wet storage facility, a new dry storage facility or renovation of the existing wet storage facility. In the case of a dry storage facility, according to an agreement in February 1998, about USD 50 million would be placed at the disposal of Sweden, Norway, France and Russia. To this must be added EU support, which was confirmed in May 1998.

In July 1998, the USA stated that it was prepared to pay for the cost of the transport of spent nuclear fuel from Vladivostok to Ozersk since it was concerned about the inadequate safety at the existing facilities.

The Kola Mining Institute has conducted a number of studies concerning the development of underground repositories for the Northern Fleet HLW. A proposal was presented already in 1994, which included a four-year programme for a deep repository on the Kola peninsula. This would be of the conventional type and would be located in hard crystalline bedrock. An experimental facility would first be constructed although it seems as though only very limited work has been conducted so far.

In April 1999, it emerged that a US company, Nonproliferation Trust, Inc. (NPT) had been formed to develop an international interim storage facility for spent nuclear fuel at Zheleznnogorsk. This facility was intended to have a capacity of about 6,000 tonnes of uranium and a lifetime of at least 40 years. The earnings from this activity would be used to clean up Russian’s military defence facilities in order to secure the handling of up to 50 tonnes of plutonium which exist and to support the defence project that is under way. However, for this project to be realised, Russian legislation must be amended to allow the import of foreign waste.

In July 2001, President Putin signed an act that allows the import of foreign spent nuclear fuel to Russia. The fuel can be stored there until 2021, when reprocessing can start in the reprocessing facility that is under construction at Zhelez-

SOU 2004:67 Nuclear Waste Management in Some Countries

nogorsk. The imports must be approved by a special commission set up in 2002.

1.8. Switzerland

1.8.1. Nuclear Power Programme

There are currently five nuclear reactors in Switzerland, divided into four power stations. Furthermore, there are six research reactors. A moratorium means that no new reactors will be built for the time being. However, this situation may change if a revised Atomic Energy Act is passed.

1.8.2. Relevant Institutions

In Switzerland, nuclear power producers are responsible for the nuclear waste generated. In 1972, the power utilities and the Swiss state which is responsible for waste from medical, research and industrial activities formed NAGRA, which is responsible for radioactive waste disposal and related treatment. ZWILAG in Würenlingen is responsible for the central interim storage and the Co-operative for Nuclear Waste Management Wellenberg (GNW) runs the project which aims at building a repository for LLW and ILW in Wellenberg (see below). The utilities are themselves responsible for transport, reprocessing of spent nuclear fuel and for waste preparation and interim storage at the plants.

The federal government receives support from the Federal Interagency Working Group on Nuclear Waste Management (AGNEB), from the Federal Commission for Safety in Nuclear Installations (KSA) and by the Federal Commission on Nuclear Waste Management (KNE) which, in turn, is a sub-committee of the Federal Geology Commission (EGK).

Nuclear Waste Management in Some Countries SOU 2004:67

The responsible authority for radioactive waste in Switzerland in the Swiss Federeal Nuclear Safety Inspectorate (HSK), which reports to the Federal Energy Office (BEW). In turn, BEW is part of the Federal Department of the Environment, Transport, Energy and Communication (UVEK).

Due to the fact that public acceptance for the siting work is slow to obtain, the federal government has appointed several working groups over the past few years. The question of “indefinitely monitored retrievable storage” or “passively safe geological disposal” has been discussed. For this reason, the federal government discussed, in June 1999, the appointment of an expert group (EKRA) which would work with different disposal concepts for radioactive waste. This group has developed a concept based on monitored long-term retrieval storage.

EKRA came to the conclusion that geological disposal, which isolates the waste, is the only method that meets the requirements on long-term safety. However, the general public’s requirements that the waste must be accessible (retrievable) must also be taken into account. Therefore, EKRA suggests a stepwise process which includes a phase of monitoring and a higher degree of accessibility before the geological repository is closed. In addition to the large-scale repository, the concept also includes a pilot facility, where a small part of the waste is placed in a small but representative copy of the full-scale facility. The facility is designed allow the waste to be retrieved from the pilot facility if its performance does not meet expectations. Naturally, the idea of a monitored long-term geological repository must be adapted to the geology at the site and to the waste types that occur in a certain repository.

1.8.3. Nuclear Waste Management

Until the repository for different types of waste has been built, most of the waste will be stored in the ZWILAG facility in

SOU 2004:67 Nuclear Waste Management in Some Countries

Würenlingen in Canton Aargau in northern Switzerland. ZWILAG was taken into operation in April 2000.

LLW and Short-lived ILW

Due to the high population density in Switzerland, there are no plans to construct repositories near the surface for short-lived LLW or ILW. According to the plans, this type of waste will be disposed of in bedrock in a suitable rock formation at a depth of several hundred metres and with repository access possibilities via a horizontal tunnel. NAGRA found a suitable site in 1993, namely Wellenberg in Canton Nidwalden in central Switzerland. The municipality accepted the project in two different referendums in 1994 with 63 % and 70 % of the votes, respectively. In spite of this, a referendum in the Canton – concerning the mining concession required by law in the Canton – led to a vote of rejection.

Since this, the geological suitability of the site has once again been evaluated, which was also confirmed by the Federal Safety Inspectorate. GNW decided to limit its application in the first step, to include an extended period of monitoring and to apply a stepwise process for repository closure. Bearing in mind this, the federal government started a new discussion with the Cantonal government. The discussion led to an agreement in June 2000.

According to the agreement, an expert group from the Canton (KFW) was established to prepare and subsequently monitor the project. The KFW started its work in July 2000. After a series of negotiations with GNW, with NAGRA (which functions as a scientific and technological competence centre from GNW) and with the Nuclear Safety Inspectorate (HSK), the modifications that would be achieved in the project were agreed. These were described by GNW in a report that was submitted in November 2000. In December 2000, KFW stated that it expected that the report was satisfactory and the Cantonal

Nuclear Waste Management in Some Countries SOU 2004:67

government stated that it was willing to receive a new application from GNW for a mining licence, limited to the research tunnel.

However, in September 2002, a referendum in Canton showed that there was strong resistance, also to this project. The Government therefore explained that Wellenberg was no longer under consideration and that no new attempts to site a repository at Wellenberg would be made.

Spent Nuclear Fuel and/or HLW

For about one-third of the spent nuclear fuel, the utilities have a contract with reprocessing facilities in France and Great Britain. However, a new Atomic Energy Act does not allow any reprocessing to be conducted beyond the contracts that already exist. Vitrified HLW will be returned to Switzerland for interim storage in ZWILAG and ZWIBEZ (storage facility adjacent to the Beznaureaktorn). The first transport from France arrived in 2001. Spent nuclear fuel will also be put in interim storage at the two facilities just mentioned, pending disposal.

Swiss law requires that radioactive waste should be permanently disposed of in a geological repository. As a condition for the continued operation of existing nuclear power plants or the construction of new plants, a Government ruling of 1979 called for a project demonstrating the feasibility of the safe disposal of all waste generated in Switzerland to be submitted by 1985. This project, Project Gewähr, was submitted to the federal government by 1985.

In June 1988, the project was approved. The project was based on the use of a crystalline host rock, was approved by the Government. Although the safety case and the technical feasibility of repository construction were fully accepted by the safety authorities, the authorities did not consider that the existence of a sufficiently extensive body host rock with the required properties for making the safety case was adequately shown. Since Project Gewähr was based exclusively on

SOU 2004:67 Nuclear Waste Management in Some Countries

crystalline bedrock, the safety authorities requested that future work should also include other alternatives.

NAGRA follows a strategy with three phases. Phase 1 comprises regional studies based on a series of deep boreholes with accompanying geological general studies. Phase 2 comprises a detailed characterisation (from the ground surface) of small areas. Phase 3 includes underground investigations.

Crystalline Basement Alternative

The regional fieldwork (Phase 1) was completed in 1989 and the report was presented in 1994. The most important parts of the report include a summary of geological information and a performance assessment.

At the end of 1994, NAGRA applied for federal permits to conduct two site investigation programmes, one for opalinus clay in Zürcher Weinland and one for crystalline basement in Böttstein/Leuggern. The programme proposals were examined by the federal authorities and their experts.

An underground laboratory in crystalline basement – the Grimsel facility in central Switzerland – has been in operation since 983. When this laboratory was constructed, a horizontal tunnel system was constructed from an existing hydro power facility at the Grimsel pass. An extensive test programme including geology, rock mechanics etc. has been conducted since 1984 with wide international participation.

Opalinus Clay Alternative

The Opalinus Clay (OPA) had been considered as a potential host formation prior to Project Gewähr, in 1979. Desk studies carried out in 1986/87 had also evaluated six other potential sedimentary formations and the options were narrowed down to two final candidates, namely the OPA and the Lower Freshwater

Nuclear Waste Management in Some Countries SOU 2004:67

Molasse (USM). The latter can reach a thickness of up to 4 km and contains units of high clay content and low permeability. (Molasse is a sedimentation of soft rock types along a newly formed mountain chain).

Two areas were selected for studying OPA. These, like the crystalline basement areas are in the northern parts of Switzerland. As a part of the Phase 1 programme, a regional twodimensional seismic study, extending over 230 kilometres, was conducted from 1991 to 1992.

Based on these investigations, in 1994, a preliminary evaluation of the sedimentary alternatives was conducted in cooperation with the authorities. USM was given second priority and, since then, has been considered as a reserve option. The eastern OPA area was given first priority. After additional selections in the region, the area at Zürcher Weinland in the Zürch Canton was identified for further investigation.

These further investigations (Phase 2) comprised a threedimensional seismic study of an area of about 50 km

2

and a deep

borehole at Benken. In Zürcher Weinland, sedimentary rock types are almost horizontally contained and the opalinus clay is of an adequate thickness (100-200 metres) at a suitable depth (400-900 metres below the surface). Since these sediments were formed, the region has almost not been exposed to any tectonic movement at all and the original sedimentation are still undisturbed, which means that the site seems to be an ideal candidate site.

Another important information source with respect to the properties “in situ” at the opalinus clay and clay in general is the work conducted at the Mont-Terri rock laboratory in the Jura Canton within the framework of an international project under the management of Switzerland’s hydrological and geological surveys. This facility is located near to an investigation tunnel (for a motorway) which intersects the clay at a depth of about 300 metres.

SOU 2004:67 Nuclear Waste Management in Some Countries

The Next Milestone in the Swiss HLW Programme

The next milestone in the Swiss HLW programme will be the conclusion of a project called “Project Entsorgungsnachweis”. The aim of the project is to be able to demonstrate the feasibility of disposal of HLW in Switzerland. This means that it must be possible to show that there are sufficiently large rock volumes with suitable properties for constructing a repository, and that the requirements on safety and constructability can be met. Due to the good accessibility from the ground surface and the positive results so far obtained, this project will be conducted focusing exclusively on constructing a repository in the Opalinus Clay. However, this does not mean that crystalline basement has been excluded as an alternative for the ultimate construction of a repository for HLW.

The most important reports from Project Entsorgungsnachweis will, together with other relevant information, be submitted to the safety authorities for evaluation. A decision from the authorities regarding how to proceed is not expected until around 2006 at the earliest.

1.9. United Kingdom

1.9.1. Nuclear Power Programme

The UK currently operates 19 Magnox reactors, 14 advanced gas cooled reactors (AGRs) and one pressurised water reactor (PWR). British Energy Generation is responsible for the operation of the AGR and PWR reactors. British Energy Generation comprises the formerly state-owned companies, Nuclear Electric and Scottish Nuclear Corporation. These companies merged in January 1999. The Magnox reactors are still state owned and operated by Magnox Electric which, in turn, was taken over by British Nuclear Fuels Ltd (BNFL) in 1998. BNFL has announced that it intends to successively by

Nuclear Waste Management in Some Countries SOU 2004:67

2012, shut down the Magnox reactors. BNFL and British Energy have also started a study on the phase-out of the AGR reactors.

1.9.2. Relevant Institutions

The regulatory authority in the UK is the Nuclear Installations Inspectorate (NII), assisted by the Environment Agency (EA) and the Ministry of Agriculture, Fisheries and Food. Since July 1997, NII has also been responsible for regulating waste held on sites operated by the Ministry of Defence. In Scotland, the EA’s responsibility has been assumed by the Scottish Environmental Protection Agency (SEPA).

The Government is advised on waste management issues by the Radioactive Waste Management Advisory Committee (RWMAC), whose members are appointed by a minister. These come from the nuclear industry, academia, public bodies (health authorities etc.) and, more recently, a number of independent experts have been appointed. In 2003, a new Committee on Radioactive Waste Management (CoRWM) was appointed to advise the Government on issues relating to disposal of radioactive waste. It seems that both of these committees will exist in parallel but with different foci of activities.

A major commercial reprocessing facility run by BNFL exists at Sellafield. A smaller facility is located in Dounreay in northern Scotland (where the now shut down experimental breeder reactor was located). The operation of the Dounreay facility was managed by the United Kingdom Atomic Energy Authority (UKAEA), built to reprocess specialist fuels and highly enriched uranium from research reactors. The facility in Dounreay will successively be taken out of operation.

Currently, spent nuclear fuel from the AGR and Magnox reactors are placed in pools at the nuclear power plants to cool off. This will also apply to the fuel from the pressurized water reactor at Sizewell. The fuel will then be transported to Sellafield for a long period of interim storage and possible reprocessing.

SOU 2004:67 Nuclear Waste Management in Some Countries

Dry storage of Magnox fuel has only been conducted at one of the plants. Design problems led to the corrosion of the fuel canisters.

The Thermal Oxide Reprocessing Plant (THORP) in Sellafield was taken into operation in 1994 and its purpose is to reprocess about 7,000 tonnes of spent oxide fuel (from AGRs, PWRs, LWRs etc.) by the year 2005.

The Government has taken the initiative to clarify the responsibility for existing spent nuclear fuel and nuclear waste, “Managing the Nuclear Legacy”. A new authority, the Liabilities Management Authority, has been created. The authority will be responsible for waste from previous activities at BNFL, UKAEA etc. A new organisation, National Decommissioning Agency, will start to work in 2004 on issues concerning the nuclear power plant decommissioning.

1.9.3. Management of Nuclear Waste

LLW and ILW

The responsibility for short-lived LLW and HLW lies with the producer of the waste. The Nuclear Industry Radioactive Waste Management Executive (called UK Nirex), is responsible for the disposal of long-lived ILW (since 1982), future LLW and shortlived ILW. NIREX was formed in 1981 by all of the companies in the nuclear power industry and each of these is represented on the board. Nirex has never been responsible for HLW.

A commercial repository near to the ground surface for LLW and short-lived ILW has been operated by BNFL in Drigg, near Sellafield, since the 1960’s. Nirex originally proposed that, when this repository was full, disposal should be continued near to the ground surface for these types of waste at another site and that an abandoned anhydrite mine for a deep repository for longlived waste should be used as a repository for long-lived ILW.

Nuclear Waste Management in Some Countries SOU 2004:67

However, due to opposition from the local population, the mine project was abandoned in 1985.

When three other sites were proposed in 1986 for an LLW repository near to the ground surface, as a complement to the originally exclusive candidate, there was once again intense local opposition with extensive civil disobedience. These site proposals were abandoned in 1987, just prior to the general elections. It was then suggested that a disposal solutions should be found for all LLW and ILW. This proposal was then soon modified and the alternative deep proposal for long-lived ILW was taken up again, while LLW and short-lived ILW would be sent to Drigg.

After two years of nationwide mapping, two sites for further investigation were selected in 1991, both near the existing nuclear facilities at Sellafield and Dounreay. A list of a further ten sites were established but these have not been published.

The investigation work focussed on Sellafield in 1993 and over GPB 250 million was used for characterisation from the ground surface. In 1992, Nirex announced its attention to construct a Rock Characterisation Facility (RCF). This would allow a limited development and experimental activity to be conducted before a large-scale repository could be constructed. Nirex requested permission to start construction of the RCF in 1994. However, this request was rejected after a hearing in 1995. The inspector granting the licence announced that Nirex had not been able to convince him that their geological interpretation was correct. Furthermore, he considered that the design was poor and not well thought through. Nirex immediately stated that they would withdraw from Sellafield but retained the right to return in the future.

In November 1997, the UK House of Lords Select Committee on Science and Technology, HoL) announced that an extensive, independent hearing would be conducted concerning all issues relating to the handling of nuclear waste, including the future role of Nirex. The verbal hearing started in February 1998 and the final report was published in March 1999.

SOU 2004:67 Nuclear Waste Management in Some Countries

The report concentrated on the development of waste management in phases, especially for LLW and ILW and resulted in a proposal to at least develop a repository for long-lived ILW. The report also emphasised the need, within 15 to 25 years for a facility near the ground surface as a replacement for Drigg.

Spent Fuel and/or HLW

According to current plans, domestic HLW is to be stored at Sellafield for cooling for 50 to 100 years, after which time the Government is to make a decision concerning how it will be disposed of. In the past, the only certainty as regards disposal was that it would involve deep disposal, in a rock type yet to be determined, at a site yet to be determined.

Until 1981, investigation work was conducted with trial drilling and other research for a possible disposal. A certain investigation into crystalline basement and sedimentary rock occurred at the end of the 1970’s, including detailed studies close to Dounreay. This system was abandoned due to wide opposition on the part of the public and now only general research is conducted. Concepts concerning waste disposal at great depths were once again included in proposed legislation which was abandoned by the Government in 1995, although no special programme was presented. A timetable for the development work for the repository was presented to the Government in 1999 although no significant work has so far been conducted.

As was previously mentioned, a new committee was appointted, “Committee on Radioactive Waste Management”, CoRWM, in 2003. This committee is to provide advice to the Government on questions concerning the final disposal of radioactive waste and prepare a programme. The programme is to be presented in 2005.

Nuclear Waste Management in Some Countries SOU 2004:67

1.10. USA

1.10.1. Nuclear Power Programme

The USA currently has 104 nuclear power reactors in operation, located at over more than 80 sites. In 2001, the Department of Energy, DOE) invited the nuclear power facilities to show their interest in the construction of new nuclear power plants in the USA (which would be the first for more than 25 years). Several companies have evinced interest in this.

1.10.2. Relevant Institutions

In the USA, nuclear waste disposal is paid for by the nuclear power producers. However, the responsibility for implementing the disposal of spent nuclear fuel and HLW lies with the DOE, and more specifically, the Office of Civilian Nuclear Waste Management (OCRWM). According to contracts with the nuclear utilities as a result of the 1982 act on nuclear policy (Nuclear Waste Policy Act, NWPA), the OCRWM was to have managed and disposed of the nuclear utilities’ spent fuel for final disposal in January 1998.

The Nuclear Regulatory Commission (NRC) is the main regulatory authority for the disposal of HLW. With respect to transport of HLW, the NRC shares the responsibility with the Department of Transportation (DOT). The US Environmental Protection Agency (EPA) plays an important role in that it promulgates general regulations that set standards, also for the disposal of HLW.

1.10.3. Nuclear Waste Management

Since commercial reprocessing of spent nuclear fuel was stopped in 1977, HLW from non-military sources is only a fraction of the quantity of waste for which a management solution must be

SOU 2004:67 Nuclear Waste Management in Some Countries

found. More than 95 percentage by volume originates from military-related reprocessing under the DOE’s jurisdiction and is stored in tanks at different sites under DOE control pending vitrification. Two facilities were taken into operation in 1996, one of which is located in South Carolina and the other in New York State.

In the USA, waste which contains small quantities of plutonium and other long-lived radionuclides is called transuranic or TRU waste. The waste must contain more than 100 nanocurie per gram (corresponding to 3,700 Bq/g) of transuranic elements (namely, substances with atomic weights that are higher than those of uranium) with half-lives exceeding 20 years to be classified as TRU waste. All other waste, including spent nuclear fuel, is either LLW or HLW.

LLW

In the USA, the waste producers are responsible for the management of LLW and the federal states are responsible for waste disposal. Co-operation between individual states has been established in certain cases and in many states attempts have been made to find suitable sites for disposal facilities. The latest development is that a commercial facility (Envirocaire) for toxic waste in Utah recently received permission. This facility may only receive naturally occurring and class A LLW. An application for permission to also receive class B and class C waste has been preliminarily accepted but final permission has not yet been applied for by the company (2003).

TRU Waste

Since 1999, the DOE has been disposing of TRU waste from nuclear power production in the Waste Isolation Pilot Plant

Nuclear Waste Management in Some Countries SOU 2004:67

(WIPP) in New Mexico at a depth of about 650 metres in a salt formation.

Spent Nuclear Fuel and/or HLW

Spent nuclear fuel from civil nuclear reactors is currently stored at nuclear power plants. The available pool area is not adequate for the volumes that are likely to be generated in all existing and planned reactors in operation (estimated quantity, about 87,000 tonnes). If we assume that no repository is in operation, an additional 80,000 tonnes of storage capacity will be needed in 2030. At present, there are about 35,000 tonnes stored at the different nuclear power plants and the quantity is increasing by about 2,000 tonnes per year. In 2046 the quantity of spent nuclear fuel could be about 105,000 tonnes.

As indicated in Section 1.10.2, according to the 1982 Act on Nuclear Power Policy, the DOE would be able to receive spent nuclear fuel from 1998. In 1993, when the federal states and nuclear utilities realised that the goals that were written into their contracts with the DOE would not be realised in time, a series of legal processes started. The aim was to force the DOE to take responsibility to start receiving spent nuclear fuel for disposal in 1998 and to try to find ways of obtaining damages if the DOE did not take responsibility. After a number of legal processes, it emerged in 2000 that if the utilities and the DOE could not reach an agreement, the DOE would have to carry out legal processes in at least 20 different cases to establish the damages that would have to be paid. These damages can (according to calculations conducted in March 2003) amount to a total of several tens of billions of USD if a repository is never constructed.

During 1998, 1999 and the first part of 2000, an attempt was made to get the senate to introduce new legislation which would entail an amendment of the original nuclear waste policy situation (NWPA) from 1982. Several proposals have also been

SOU 2004:67 Nuclear Waste Management in Some Countries

put forward concerning constructing a central interim storage facility for spent nuclear fuel. The pressure on the utilities to construct their own interim storage facility at the nuclear power plants would therefore be reduced. The bill also proposed removing the upper boundary of 70,000 tonnes of capacity at the proposed repository.

A site selection process for the repository had previously been initiated where a large number of sites and geological media were included as possible candidates. However, through an amendment to the NWPA (1987), the instruction for the site selection procedure was eliminated. This meant that a number of sites had to be investigated, before a final candidate site could be appointed. The DOE could thereby select a site in Yucca Mountain, Nevada near to the DOE’s investigation site, as the only candidate.

Through the 1987 amendment (NWPAA) to the NWPA, the Office of the Waste Negotiator was also established with the task of locating a site that affected parties could voluntarily make available for the siting of Monitored Retrievable Storage Facility (MRS). In addition, the Nuclear Waste Technical Review Board, NWTRB) was established to evaluate the scientific and technical work that the DOE was conducting on the disposal of spent nuclear fuel and HLW, including transportation issues and the waste canister design.

The latest conceptual design for an underground repository in Yucca Mountain includes one primary area that is crossed by parallel emplacement drifts that will be used for final disposal. The repository will be constructed in a geological formation comprising lithophysal welded tuff, some 300 metres above the water table.

Through surface investigations, it has been possible to identify and characterise most of the properties of the ground structure. Extensive research is underway at the Exploratory Studies Facility (ESF) which is a spiral-shaped tunnel construction completed in 1997. The main project is the Drift-Scale Heater

Nuclear Waste Management in Some Countries SOU 2004:67

Test, in which rock temperatures of up to 200 ºC. The experiment is not expected to be completed before 2004.

Other work focuses on testing, analysis, models and designs that are needed as a basis for supporting the suitability of the site. The current timetable anticipates licensing in 2002-2005, construction in 2005-2008 and commissioning in 2010.

The actual design is somewhat different from the design that was presented as a basis for a preliminary evaluation in 1998 (Viability Assessment). At that time, a strategy was presented, based on an average temperature load, according to which the waste containers were located near to each other. The heat from the fuel would raise the temperature of the surrounding mounted to over 100 ºC. Water, which would otherwise corrode the containers and expose the waste in the short term, would boil away. The DOE is now planning to study a strategy, based on low temperature loads which is recommended by NWTRB. In this case, heat production is about 25 % of the amount envisaged in the previous concept (about 40 kW/hectare).

It is proposed that the repository should be kept open and available for 100 years from the time when the waste is deposited. Future generations would therefore make decisions concerning backfilling and closure. The repository is therefore referred to as a “monitored, geological repository”.

Through a decision in congress and by the president, in 2002, it was decided that Yucca Mountain would be accepted as a repository site. The DOE will now apply to the NRC for permission to construct the repository. The NRC’s approval is required before construction can start and for the subsequent operation of the repository. The NRC is preparing for an extensive review which will include a number of review groups.

SOU 2004:67 Nuclear Waste Management in Some Countries

1.11. International Organisations

1.11.1. Nuclear Energy Agency, NEA

At OECD/NEA, the Radioactive Waste Management Committee, (RWMC) is supervising the work within the nuclear waste area. The work is mainly divided into three areas, each of them supervised by a Working Party:

  • The Integration Group for the Safety Case (IGSC).
  • Forum on Stakeholder Confidence (FSC).
  • Working Party on Decommissioning and Dismantling

(WPDD).

In addition to these groups, there is also a Co-operative Programme on Decommissioning Projects (CPD) and a Regulators Forum.

The RWMC has initiated discussions on a common approach to issues such as retrievability, the benefit of underground laboratories, stepwise decision-making, etc. The RWMC has also organised international peer reviews which have reviewed various national programmes. On behalf of the Swedish Nuclear Power Inspectorate, such a group reviewed SKB’s SR-97 safety assessment in spring 2000.

The Integration Group for the Safety Case (IGSC) works in a discipline-oriented way on technical safety for repositories with questions such as, for instance, the development of performance assessment and how this can be used to communicate technical information and develop confidence between concerned stakeholders, how safety assessments may be used as a basis for decision-making, scenario development etc.

The purpose of the FSC is to formulate questions on the decision-making process and its structure, on the organisation and on trust as well as to develop principles for how different stakeholders can be involved.

The WPDD’s task is to work with policy issues on decommissioning and dismantling. Experience from the Co-

Nuclear Waste Management in Some Countries SOU 2004:67

operative Programme on Decommissioning Projects (CPD) and other projects is compiled and reported.

In CPD, more than 20 years of experience from decommissioning and dismantling of nuclear facilities has been collected. In total, around 40 projects are included. In addition to the exchange of experience and technical collaboration, the CPD also publishes reports on radiological data from the dismantling of reactors.

Based on information from consultants and experts in the member countries, the NEA has published a number of status reports on the state-of-art in deep geological disposal. The material is based on work in different countries over the past ten years.

“Progress towards the Geological Disposal of Radioactive Waste: Where Do We Stand?”, published in 1999 (ref. 2, also translated into Swedish in 2000, see list of references at the end of this chapter) formulates a number of claims on which the specialists in the area appear to agree. These include:

  • Deep geological disposal is the most appropriate means of long-term management of the various disposal options considered.
  • Significant progress has been made in relevant scientific understanding and in the technology required for geological disposal in the past ten years.
  • The technology for constructing and operating repositories is mature enough for deployment.
  • The time-scales envisioned in the past for the implementtation of geological disposal were too optimistic.
  • There is a high level of confidence among the scientific and technical community engaged in waste disposal that geological disposal is technically safe.
  • However, the broader public does not necessarily share the high level of confidence of the scientific and technical community.

SOU 2004:67 Nuclear Waste Management in Some Countries

  • There is a need for continued high-quality scientific and technical work.
  • There is a need for a consistent policy and strict regulatory licensing, with clear decision points which also allow for public dialogue.

The report points to a number of specific areas where it suggests that significant progress has been made over the past ten years in terms of the technical activities required to implement disposal. These are:

  • The development and construction of facilities for the treatment and interim storage of waste.
  • Experience from laboratory and field experiments, including studies of natural analogues.
  • Construction and operation of underground rock laboratories.
  • Experience in site characterisation.
  • Development of the design of engineered barriers.
  • Improved safety assessment methods.
  • Improved co-ordination between site characterisation, design and safety assessment.
  • Development of regulatory frameworks, including requirements, on safety and radiation protection reporting.

In a report from the Forum on Stakeholders Confidence (Strategic Directions of the RWMC Forum on Stakeholder Confidence, May 2002), the importance of the decision-making process and certain basic elements are emphasised:

  • A clear strategy for a long-term solution and support from the Government and policy-creating organisations, based on responsibility and needs.
  • A flexible decision-making process which incorporates influence from the public and the needs of those concerned.
  • Involvement from all of those concerned, including municipalities and authorities.

Nuclear Waste Management in Some Countries SOU 2004:67

  • A well-structured process for dialogue/interaction between industry, authorities, politicians and the general public.

1.11.2. International Atomic Energy Agency, IAEA

In 1995, the IAEA published “Principles of Radioactive Waste Management”. This is the IAEA’s main document in the Safety Standards Series. Since this time, the IAEA has put considerable effort into developing the principles presented in the document. A consensus statement has been prepared by the member states on safety issues in all important areas relating to the management of radioactive waste. This important document is also a basis – with respect to technical issues – for the Joint Convention on the Safety of Spent Fuel Management and on the Safety of Radioactive Waste Management), which was adopted at a diplomatic conference in 199 7.

1

The International Conference on the Safety of Radioactive Waste Management was held in Córdoba, Spain, in March 2000 within the framework of the IAEA’s safety programme for 2000. The main purpose of the conference was to facilitate an open dialogue between different interested parties – scientists and representatives from waste producers, for companies responsible for waste management, for units with regulatory functions and for the general public. Conclusions and recommendations from the conference were compiled in a document that was submitted to the IAEA’s Board of Governors General Conference in September 2000. The document contains a proposal for the development of a form of Roundtable on Stakeholder Consensus. The following text has been taken from the document.

The evolution, under the aegis of the IAEA, of a

“de facto”

international radiation and nuclear safety regime was noted. In the area of radioactive waste safety, this regime consists of the

“Joint

Convention on the Safety of Spent Fuel Management and on the Safety of Radioactive Waste Management” (which, it is hoped, will

1

Sweden ratified the Convention in 1999. The Convention entered into force in 2001.

SOU 2004:67 Nuclear Waste Management in Some Countries

enter into force soon), the body of international waste safety standards published by the IAEA and other international organisations, and the IAEA’s mechanisms for providing for the application of those standards.

Progress has been made in the development of technology and disposal alternatives for the radioactive waste, but further R&D work is still necessary. Regardless of which alternative a country finally chooses for high level and long lived waste, it will be necessary to continue the development and assessment of deep geological disposal. This type of alternative will most certainly be utilized in the future.

International co-operation is important for reaching a common understanding among technical experts and the general public and support for the national programs. The following tools are especially important in this aspect:

  • “Joint Convention”, an important legal instrument that presupposes engagement on a high level of the contracting parties concerning safe management of radioactive waste
  • International standards, already existing
  • International systems that will help to implement the standards

The first review conference for the “Joint Convention” has now taken place and some of the conclusions are summarized below:

  • The main purpose of the convention is to support the safe management of radioactive waste and spent fuel
  • The convention has already contributed to this, e.g. by the work to produce the national reports that has helped in identifying needs for increasing nuclear safety
  • The need to develop long term plans for waste management and disposal is underlined
  • The need for planning for decommissioning of nuclear facilities is also underlined
  • The need for consultation between stakeholders in the process is underlined.

Nuclear Waste Management in Some Countries SOU 2004:67

1.11.3. The European Commission

In September 2000, responsibility for nuclear safety issues in the European Commission was largely transferred from the Environment Directorate (DG-Env) to the Transport and Energy Directorate (DG-Tren), although radiation protection matters will be unaffected.

Research work on Radioactive Waste Management and Disposal has been part of the European Atomic Energy Community (EURATOM) for more than 25 years, supervised by the Research Directorate. This is part of the general research and technological development (RTD) programme of the EC. The programme covers activities in major fields of science and technology, organised in five-year framework programmes. The programme is performed through ‘shared-cost’ contracts by national laboratories of the Member States of the European Union (EU) with financial support from the EC (normally up to 50 % of the total costs) or through and in conjunction with the Joint Research Centres (JRC).

Since the publication of KASAM’s state-of-the-art report in 2001, the sixth framework programme (2002-2006) has started. The sixth framework programme will contribute to creating a “European Research Area (ERA). The European area for research is a vision of the future of European research, an internal market for science and technology. The aim is to promote state-of-the-art research, competition and innovation through improved co-operation and increased co-ordination between all of the different levels. Economic growth is increasingly dependent on research and individual countries can no longer, on its own, solve many of the problems that industry and society is faced with today or which can be predicted for the future. At a summit meeting Lisbon in March 2000, the heads of states and governments called for a better use of Europe’s research work. This would be achieved through the creation of a European area for research activities. The framework programme

SOU 2004:67 Nuclear Waste Management in Some Countries

is the financial instrument that is to contribute to the realisation of the European area of research.

So far, the framework programmes have almost exclusively been conducted with the help of projects for research cooperation. This was highly effective when the project started, but has two disadvantages:

  • Most often, co-operation in the project consortium ceased when the project was finished.
  • In many cases, the projects were not large enough to achieve a “critical mass” and to have more far-reaching effects from the research standpoint or from the industrial or economic standpoint. In order to remedy this and to contribute to the creation of a European area for research activity, two new instruments have been created which will be applied in the sixth framework programme, namely, the network of excellence and integrated projects.

The principle behind both of these instruments is to finance coherent programmes for research rather than many small projects while, at the same time, the European research consortia will be allowed as much freedom and flexibility as possible.

The aim of the network of excellence is to integrate the activities of the network partners in stages in order to promote virtual research centres. Integrated projects consist of very large projects which will lead to goal-oriented research with clearly defined scientific and technical objectives for the critical mass that is required.

The sixth framework programme will include research on the disposal of radioactive waste in the sub-programme, Fuel Cycle Safety, and the total available budget is EUR 60 million.

Nuclear Waste Management in Some Countries SOU 2004:67

Research priorities for radioactive waste are

1. Research on geological disposal. a. Improvement of basic knowledge and development and testing of technology. b. New and improved tools.

2. Partitioning and Transmutation (P&T) as well as methods that lead to smaller waste quantities in connection with nuclear energy production.

1.12. Conclusion

All countries described in this chapter share the fact that increasing attention has been paid to issues relating to the treatment and disposal of spent nuclear fuel and nuclear waste from the operation of nuclear reactors, by both representatives from society’s institutions (parliament, governments, regulatory authorities) and by the nuclear industry. This applies in countries with a growing nuclear programme (such as Finland, France and Japan) as well as in countries, such as Sweden, which have a more static or declining programme.

In most of these countries, there is a common view to how nuclear waste issues should be solved, even if concrete technical solutions, timetables etc. are different. This joint approach is manifested through the Joint International Convention on Nuclear Waste which most countries with a substantial nuclear power programme as well as countries without their own programmes have ratified. Sweden was one of the first countries to ratify the Convention.

An overall evaluation shows that Finland, Sweden and the USA have come the furthest in realising the disposal of spent nuclear fuel, both with respect to choice of technology and site selection. In France, a highly advanced and extensive research and development programme is underway on methods for the treatment, storage and disposal of radioactive waste. The final

SOU 2004:67 Nuclear Waste Management in Some Countries

report for the programme will be submitted in 2006. Germany, Japan, Canada and Great Britain also have advanced research programmes although much remains to be done before concrete solutions can be presented. In many other countries, research on radioactive waste is also underway. Issues relating to the longterm financing of nuclear waste management and the decommissioning of reactors are attracting increased international interest.

Nuclear Waste Management in Some Countries SOU 2004:67

References

Von Maravic H, Haijtink B, Mc Menamin T: 2000; ”European

Commission R&D-activities on radioactive management and disposal towards the fifth EURATOM Framework Programme (1998

  • Proceedings of Dis Tec 2000, an

International Conference on Radio-active Waste Disposal, September 4

  • 2000, Berlin, Germany. Publ. By KONTEC.

European Commission, EURADWASTE 1999

  • ”Radioactive waste management strategies and issues”, Fifth European Commission Conference on Radioactive Waste Manage- ment and Disposal and Decommissioning, Luxembourg, 15
  • November 1999, EUR 19143 EN, 2000.

Grupa, JB, et al 2000: “Concerted action on retrievability of

long-lived radioactive waste in deep underground laboratories”, EUR 19145 EN. IAEA Board of Governors General Conference, September

2000. Joint Convention on the Safety of Spent Fuel Management and on the Safety of Radioactive Waste Management. First Review Meeting of the Contracting Parties. 3 to 14 November 2003 Vienna, Austria. SUMMARY REPORT. JC/RM.1/06/Final version.

Abbreviations

General AGR, advanced gas-cooled reactor PWR, pressurized water reactor LLW, low level waste ILW, medium level waste HLW, high level waste MOX (mixed oxide fuel), mixed fuel containing both uranium- and plutonium oxide R&D, research and development

SOU 2004:67 Nuclear Waste Management in Some Countries

Canada OPG, Ontario Power Generation Inc. NFWA, Nuclear Fuel Waste Act CNSC, Canadian Nuclear Safety Commission NWMO, Nuclear Waste Management Organisation AECL, Atomic Energy of Canada Limited NRCan, Ministry of Natural Resources Canada

Finland Fortum (earlier IVO, Imatran Voima), state-owned power enterprise VVER, Russian type of reactor TVO, utility, owned by Finnish industry and power enterprises STUK, Radiation safety central (Finnish authority for nuclear safety and radiation protection) ONKALO, the first stage of the deep repository (used for R&D) Posiva, Finnish company (corresponding to SKB in Sweden)

France ANDRA, organisation responsible for disposal (corrresponding to SKB in Sweden) EdF, Electricité de France (state-owned company with a main responsibility for electric energy supply in France) CEA, Commissariat à l'Energie Atomique (a state organisation responsible for the development of nuclear energy) COGEMA, (a state organisation operating the reprocessing facilities in la Hague) DGSNR, Direction Générale de la Sûreté Nucléaire et de la Radioprotection IRSN, Institut de Radioprotection et de Sûreté Nucléaire ICE, Installation Centrale d´Entreposage (a planned central facility for the intermediate storage of spent fuel) CNE, Commité National d'Evaluation (national commission for the evaluation of nuclear waste research activities)

Nuclear Waste Management in Some Countries SOU 2004:67

Germany BfS, the federal radiation protection authority PBT, federal institute for science and technology ERAM, Endlager für Radioaktive Abfälle, Morsleben, final disposal for LLW and ILW BMU, the federal ministry for the environment AKEND, committee responsible for proposing a new procedure for site selection

Japan AEC, Atomic Energy Commission NSC, Nuclear Safety Commission METI, Ministry of economy, trade and industry MECSST, Ministry of education, culture, sport, science and technology NUMO, an organisation responsible for work on site selection, construction, operation etc. of a deep geologic repository JNC, an institute responsible for work related to advanced reactors and nuclear fuel cycle technology and research and development related to disposal of HLW JNFL, Japanese Nuclear Fuel Ltd

Russia Minatom, Atomic power ministry GAN, Gosatomnadzor” (nuclear power authority) RBMK, Russian reactor type VVER-440, VVER-1000, BN-350, BN-600 Russian reactor types IGEM, Institute for Geology, Ores, Petrografy, Mineralogy and Geochemistry CEG , Contact Expert Group (expert group within IAEA) PHARE, a support program financed by EU NPT, Non Proliferation Trust, Inc. (an American enterprise) (NPT, Non-Proliferation Treaty, an international agreement)

SOU 2004:67 Nuclear Waste Management in Some Countries

Switzerland NAGRA, organisation responsible for final disposal of nuclear waste (corresponding to SKB in Sweden) ZWILAG, a company responsible for central intermediate storage of spent fuel AGNEB, Federal advisory group for nuclear waste KSA, Federal commission for nuclear safety HSK, Swiss Federal Nuclear Power Inspectorate EKRA, an expert group for development of a disposal concept for radioactive waste GNW, an organisation corresponding to SKB in Sweden

UK BNFL, British Nuclear Fuels Ltd NII, Nuclear Installations Inspectorate EA, Environment Agency SEPA, Scottish Environmental Protection Agency RAWMAC, Radioactive Waste Management Advisory Committee CoRWM, Committee on Radioactive Waste Management UKAEA, United Kingdom Atomic Energy Authority THORP, Thermal Oxide Reprocessing Plant in Sellafield LMA, Liabilities Management Authority National Decommissioning Agency, a new organisation for issues related to decommissioning and dismantling of nuclear reactors UK Nirex, Nuclear Industry Radioactive Waste Management Executive, works with issues related final disposal of long lived ILW and LLW and for short lived ILW

Nuclear Waste Management in Some Countries SOU 2004:67

USA DOE, Department of Energy OCRWM, Office of Civilian Nuclear Waste Management (part of DOE) NWPA, Nuclear Waste Policy Act NRC, Nuclear Regulatory Commission DOT, Department of Transportation WIPP, Waste Isolation Pilot Plant i New Mexico NWTRB, Nuclear Waste Technical Review Board

OECD/NEA RWMC, Waste Management Committee IGSC, Integration Group for the Safety Case FSC, Forum on Stakeholder Confidence WPDD, Working Party on Decommissioning and Dismantling

International organisations IAEA, International Atomic Energy Agency OECD/NEA, OECD Nuclear Energy Agency EU, European Union

2. The Municipalities – One of the Main Actors in the Nuclear Waste Issue

2.1. Introduction

Disposal of nuclear waste is an issue that deeply affects the local community. In this chapter, KASAM would like to:

  • Direct the Government’s attention to the issues that are of particular importance for the municipalities concerned and which are also of importance for the quality of the entire decision-making process, as well as to KASAM’s views on these issues.
  • Describe how the municipalities concerned – Östhammar,

Oskarshamn and Hultsfred – are handling the issues relating to site investigation and consultation for a planned repository and an encapsulation plant for spent nuclear fuel.

  • Document the sequence of events in these municipalities.

This documentation is a continuation of the report on the municipalities’ work during the Swedish Nuclear Fuel and Waste Management Co’s (SKB) feasibility studies and which is presented in the reports: “A Site for Final Disposal of Nuclear Waste? – Feasibility Studies in Eight Municipalities” (SOU 2002:46) and “Nuclear Waste – Democracy and Science” (SOU 2004:99), both in Swedish.

The Municipalities – One of the Main Actors in the Nuclear Waste Issue SOU 2004:67

2.2. The Nuclear Waste Issue – a Joint Concern for Industry, the State and the Municipalities

In Sweden, issues concerning the disposal of nuclear waste requires co-operation among three main actors: The nuclear industry, the state and the municipalities.

A basic principle of Swedish environmental legislation is that anyone who causes environmental damage is responsible for paying for the measures that are needed to prevent and correct the damage caused (“polluter pays principle”). This is specified in Chapter 2 of the Environmental Code (1998:808). The previous Environmental Protection Act was also based on this principle. According to the same principle, the Act on Nuclear Activities (1984:3) states that the reactor owners are responsible for waste from the activity. The Swedish Nuclear Fuel and Waste Management Co (SKB), which is jointly owned by the reactor owners, fulfils this responsibility in practice.

The state supervises the reactor owners to ensure that they take their responsibility. The state acts through the regulatory authorities (primarily the Swedish Nuclear Power Inspectorate – SKI – and the Swedish Radiation Protection Authority – SSI), and in certain cases, through the Government. The Swedish Riksdag (parliament) has established the laws that apply, for example, with respect to consultation and decision-making processes prior to the construction of nuclear facilities – as is the case with other hazardous activities.

The facilities that are necessary in order to manage the waste will be located in one or more Swedish municipalities. The municipal right of self-determination, which applies to the siting of industries and to the use of land in Sweden, means that the opinion of the municipalities is decisive with respect to the siting of the planned nuclear waste facilities. The municipalities, with their democratically elected representatives and their inhabitants, are therefore the third main actor.

The strong position of the municipalities is expressed in Chapter 17 of the Environmental Code. These regulations mean

SOU 2004:67 The Municipalities – One of the Main Actors in the Nuclear Waste Issue

that a municipality can prevent the Government from allowing the siting of a facility for the interim storage or final disposal of nuclear waste in the municipality (“municipal veto right”. The Government may, under certain circumstances, allow a certain siting of such an activity to take place even if the municipality says no. However, the right to override a municipal veto cannot be used if there is another site within another municipality that can be assumed to accept the repository. Thus, as can be seen, it is hardly practically possible for the other two actors – the industry and the state – to resolve the issue of the final disposal of nuclear waste without the municipality’s permission. Therefore, there are strong reasons for KASAM to follow and take note of how the municipalities concerned act in connection with the site investigations and the different consultations that SKB is now conducting.

2.3. Where Are We in the Siting Process?

With the aim of finding a suitable site for the final disposal of spent nuclear fuel, SKB conducted feasibility studies in the 1990’s in eight municipalities: Storuman, Malå, Älvkarleby, Tierp, Östhammar, Nyköping, Hultsfred and Oskarshamn. These feasibility studies resulted in SKB’s proposal to conduct in-depth site investigations with trial drilling at three sites, namely Forsmark in Östhammar municipality, Simpevarp in Oskarshamn municipality and an area north of the population centre in Tierp municipality. The latter siting alternative also involved Älvkarleby municipality due to the need for transport to Skutskär harbour. SKB also proposed in-depth investigations, without any further trial drilling, with respect to one siting alternative, which has been the subject of previous trial drilling, in Nyköping municipality. (See SKB’s report Integrated Account of Method, Site Selection and Programme prior to the Site Investigation Phase “RD&D Supplement”, December 2001.)

The Municipalities – One of the Main Actors in the Nuclear Waste Issue SOU 2004:67

In late 2001 and early 2002, a broad majority of the municipal councils in Östhammar and Oskarshamn, responding to a request by SKB, voted “yes” to SKB’s proposal to initiate site investigations. On the other hand, Tierp and Nyköping municipalities were opposed to further investigations. Therefore, of the proposal originally put forward by SKB, only the area in Forsmark in Östhammar municipality and the Simpevarp area in Oskarshamn remained as feasible site investigation areas (maps of the areas concerned are provided in Sections 2.5.2 and 2.6.2).

SKB’s investigations at both of these sites started in 2002. Based on the results from the first trial drilling in the initial site investigation phase, SKB proposed an adjustment of the “Simpevarp” site, including the Simpevarp peninsula. The Simpevarp peninsula, which is now of interest for site investigations (actually “the Simpevarp-Laxemar area”), comprises two areas, namely an area around Simpevarp and the neighbouring Laxemar area. The region around the Simpevarp peninsula comprises an area that was included in the original proposal, namely the Simpevarp peninsula, as well as an area that was not included from the beginning, namely the Ävrö and Hålö islands and some of the sea surrounding these areas. Through a decision in September 2003, the municipal council in Oskarshamn voted “yes” to this adjustment of the site to be investigated.

An initial stage of the site investigations at Forsmark and Simpevarp is expected to have been completed during the first half of 2005. SKB expects that further site investigation in these areas will provide information for an application to be submitted at the end of 2008 to the Government for licensing under the Environmental Code and the Act on Nuclear Activities with respect to a repository for spent nuclear fuel.

SKB is also working on preparing a basis for applications for government licensing in accordance with the Environmental Code and the Act on Nuclear Activities, with respect to an encapsulation plant for spent nuclear fuel. SKB is primarily planning to construct this facility adjacent to CLAB (Central Interim Storage Facility for Spent Nuclear Fuel) in Oskarshamn.

SOU 2004:67 The Municipalities – One of the Main Actors in the Nuclear Waste Issue

An alternative siting in the Forsmark area is also being studied at the same time. SKB expects to submit the licence applications for the encapsulation plant in 2006.

SKB’s long-term planning is based on the assumption that the Government will make a decision in 2010 concerning the licences that are needed and that an encapsulation plant and a repository for spent nuclear fuel will be taken into operation in 2017. In such a case, all of the spent nuclear fuel from the current nuclear power programme in Sweden would be deposited in the 2050’s and, once this is done, the repository would be closed.

An overall timetable, which also includes the site investigations that are in progress, is provided in Figure 2.1.

Figure 2.1. Siting: What happens next?

The Municipalities – One of the Main Actors in the Nuclear Waste Issue SOU 2004:67

No site investigations are in progress in Hultsfred municipality, one of the six other municipalities where SKB has conducted feasibility studies, and none have been planned. However, neither SKB nor the municipality has completely rejected the possibility of conducting site investigations at a later stage, depending on the results of the site investigations conducted in the Forsmark and Simpevarp areas. Therefore, it is reasonable to consider Hultsfred municipality as a “reserve candidate” for possible site investigations in the future. This is the reason why Hultsfred municipality is also included in this presentation.

2.4. Expectations and Anxieties in the Municipalities Concerned

To obtain the necessary information for drafting this section, representatives from KASAM visited the Östhammar, Oskarshamn and Hultsfred municipalities in November 2003 to conduct interviews with key individuals in each of these municipalities. These interviews were followed up by informal contacts with politicians and municipal officials. Based on experience from these contacts, the section is divided into three themes.

Firstly, the questions surrounding nuclear waste management that the municipal leaders consider to be particularly important for the phase, which has now been initiated, with site investigations and increased consultation in accordance with the Environmental Code. Views held in the municipalities concerning issues relating to the allocation of responsibilities between the municipality and other actors with respect to nuclear waste issues are then presented. Finally, the views of the municipal leaders, with respect to the impact that the work on nuclear waste issues has had on work within other municipal areas of responsibility, are presented.

SOU 2004:67 The Municipalities – One of the Main Actors in the Nuclear Waste Issue

2.4.1. Important Issues for the Municipal Leaders

The issues that are currently important to municipal leaders differ depending on the municipality – on one hand, Östhammar and Oskarshamn and on the other hand, Hultsfred. However, the pictures that emerge of how the two first-mentioned municipalities are handling the issues are far from identical.

Even if there are certain differences between the municipalities of Östhammar and Oskarshamn, it should be emphasised that the two municipal leaderships have in recent years developed a closer co-operation with each other. There is reason to assume that the aim of this co-operation is to strengthen the position of both municipalities in relation to the proponent.

The initial steps of this co-operation were taken in autumn 2003. The following two factors appear to have been decisive.

  • At this time, both of the municipalities attained a stronger role in the siting and Environmental Impact Assessment (EIA) processes by entering as a party in the expanded consultation on EIA, in accordance with Chapter 6 § 5, initiated by SKB at that time, with respect to the repository and encapsulation plant.
  • After the 2002 election, new individuals in the position of municipal executive board chairman represented both of these municipalities, as of 2003, even though the party affiliation remained the same, namely social democratic, as the previous representatives. These new executive board chairmen seem to have a common view of the value of cooperation in their situation in order to handle the nuclear waste issue.

The budding co-operation between the two municipal management groups was outwardly manifested for the first time at an international conference on nuclear waste that SKB, in cooperation with the International Atomic Energy Agency (IAEA) and the OECD/NEA (OECD’s Nuclear Energy

The Municipalities – One of the Main Actors in the Nuclear Waste Issue SOU 2004:67

Agency) arranged in Stockholm in December 2003. In a speech given by the Chairman of the Oskarshamn municipal executive board, who also expressly spoke on behalf of his colleague in Östhammar, the Chairman summarised the issues that the leading politicians in the site investigation municipalities consider to be most important.

The speech emphasised the similarities between both municipalities with respect to geographical position, size, municipal service, industry structure and experience of nuclear activities. The following joint position statement was given for both municipalities with respect to their involvement in the nuclear waste issue (the points have been slightly reformulated compared with the original and, where relevant, direct quotations are marked).

  • We are two municipalities with extensive experience of cooperation with the nuclear industry.
  • We do not accept the idea that the present interim storage of spent nuclear fuel should take the form of a more permanent solution – we must actively work towards ensuring that a final solution to the nuclear waste issue is found.
  • We have participated in initial feasibility studies, conducted extensive work on local democracy and we have the full support of our inhabitants to now participate in site investigations.
  • Through our strong position in the decision-making process, we have ensured, and will continue to ensure, that the issues that we raise are investigated and that the basis for decisionmaking includes a detailed investigation of the local perspective.

As a “good platform” for work over the next few years, six points were formulated:

  • Safety is the overshadowing issue – for us as decision-makers and for our inhabitants.

SOU 2004:67 The Municipalities – One of the Main Actors in the Nuclear Waste Issue

  • In order for us to contribute to a solution of the nuclear waste issue, the process must be transparent. All information must be “on the table” throughout the process. It is only if we work in this way that we will be able to build confidence for the actors and for the results that are achieved.
  • As municipalities, we must actively take part in and influence this work. Our work cannot be paid for by our taxpayers but must be compensated for – as is now the case – from the Nuclear Waste Fund.
  • Our inhabitants and environmental interest groups who are involved in the nuclear waste issue are a resource in our work. We who live in the municipalities best know our own district and know what we want for our future. Our environmental interest groups raise difficult questions that must be answered.
  • Our competent authorities, the Swedish Radiation Protection Authority (SSI) and the Swedish Nuclear Power Inspectorate (SKI), are our independent experts. It is the authorities that have to evaluate the industry’s proposals and inform us whether or not the proposals meet the requirements regarding safety.
  • Before we know whether the safety requirements have been fulfilled, we cannot speculate regarding compensation or positive effects from the construction of a repository in one of our municipalities. We do not allow such discussions to disturb us in our work of critically evaluating, investigating effects or safeguarding safety. These discussions have to wait until we know the outcome of the industry’s choice and the outcome of the results of the evaluations made by the competent authorities.

Providing that the industry’s timetable is followed, in about five years’ time, we shall have to adopt a position on the final disposal method to be used in Sweden and on where the repository should be located. As municipalities, we see the following “challenges” that lie ahead:

The Municipalities – One of the Main Actors in the Nuclear Waste Issue SOU 2004:67

  • It is “completely decisive” that the industry should be able to show that a safe repository can be built and that the authorities, through competent review work and their own analyses, also reach the same conclusions.
  • Other challenges entail ensuring that:

– The industry’s ambitions to follow its timetable do not

lead to short cuts and data and analyses of a poor quality. – The authorities are given the resources that they need

and that they can obtain the necessary competence to fully review and evaluate the industry’s licence applications – we are “very concerned” that the Government, in its general drive to cut costs, is not giving the Swedish Nuclear Power Inspectorate (SKI) and the Swedish Radiation Protection Authority (SSI) the funds that they need. – We can initiate the investigations and studies necessary

to ensure that our inhabitants and we, as decisionmakers, have an adequate basis for decision-making. – We obtain “full guarantees to ensure that we can never be

forced to receive nuclear waste from other countries against our will”.

The following must occur “before we, the municipalities, can accept a repository”:

  • We must be convinced that the nuclear waste issue can be resolved in a safe manner – we are very dependent on our regulatory authorities.
  • We must prepare a complete and exhaustive basis for decision-making that also contains a municipal perspective for an option to say “yes” or “no”. This basis for decisionmaking must contain an Environmental Impact Statement (EIS), with all of the positive and negative impacts described in detail. This EIS must also contain exhaustive socioeconomic and social scientific investigations.
  • Negative effects must be limited.

SOU 2004:67 The Municipalities – One of the Main Actors in the Nuclear Waste Issue

  • An “overwhelming majority” of our local inhabitants must support a decision.

In a joint press release in February 2004, both municipal executive board chairmen stated that the final disposal issue has many aspects “that for both municipalities are similar at the same time that there are local differences with respect to political traditions as well as natural conditions.” The press release further showed that the representatives of both municipalities had discussed questions relating to the further content of the consultation process, the decision-making process, the resources of the regulatory authorities and the Environmental Impact Assessment (EIA). Furthermore, they had planned to arrange joint seminars on “joint knowledge-related issues for the municipalities concerning final disposal”.

2.4.2. View of the Allocation of Responsibilities among the Municipality and Other Actors

In the conversations held with the municipal leaders, they consistently expressed the view that the nuclear waste issue is given far too low priority among politicians operating at the national level. This criticism is generally directed to both ministers and members of parliament. The leaders also consider that there is a lack of interest in this issue among the members of parliament from their own counties. Furthermore, in the view of the leaders, the media, in any case at the national level, gives the issue far too little attention and neighbouring municipalities ought to show greater interest.

The municipal politicians also stated that the general lack of interest in the nuclear waste issue makes it difficult for them to handle these issues in the municipality. The nuclear waste issue is specifically of national importance. Therefore, in the view of the local politicians, it is not acceptable that, in reality, the response-

The Municipalities – One of the Main Actors in the Nuclear Waste Issue SOU 2004:67

bility for the handling of the issue should be delegated to the local level.

The municipal leaders further explained that the participation of the local politicians is a necessary condition to gain support for the idea of siting a repository somewhere in Sweden. In order for the local politicians to be able to assume such a responsebility, politicians at the national level also need a visible commitment. The municipal leaders reiterated the municipalities’ veto right in connection with forthcoming licensing by the Government. In the view of the councils, the nuclear waste issue must be handled in such a way by industry, the regulatory authorities and politicians at the national level that local opinion is confident in the solutions proposed. The implementation of site investigations is currently considered to be strongly supported by the inhabitants of Oskarshamn and Östhammar municipalities. However, the interviewees pointed out that this current level of support is no guarantee for the state of opinion when the time comes to evaluate a licence application for the construction of a repository at a specific site.

As reported in detail below (Sections 2.5.3 and 2.6.3), Östhammar and Oskarshamn have organised their work during the site investigation phase in different ways. The organisation that has been selected in Oskarshamn could give the impression that the local government leaders consider that the municipality should assume a particularly large responsibility as an actor in the nuclear waste issue. In Section 2.9.1, similarities and differences between the attitudes in both municipalities are discussed in this respect.

Based on an agreement between SKB and Hultsfred municipality concerning a contact programme (see Section 2.7.2), an ambitious programme of seminars on the nuclear waste issue has been conducted since 2003. The seminars target the general public. What expectations does the municipal council in Hultsfred have for the near future?

It can be seen from the above (see Section 2.3) that Hultsfred municipality would not be subjected to a site investigation, in

SOU 2004:67 The Municipalities – One of the Main Actors in the Nuclear Waste Issue

accordance with the proposal put forward by SKB in the RD&D Programme Supplement. However, in the opinion of the local government leaders, if SKB had proposed a site investigation in Hultsfred municipality, a broad majority of the municipal council would have voted “yes”. Nevertheless, the municipality is satisfied to act as a reserve municipality for the time being, since the view is that there are strong reasons why SKB should more closely investigate the type of bedrock, which occurs in the municipality. However, the leaders emphasise that a possible initiative by SKB in this direction would probably require the municipality to provide extensive information to the inhabitants.

2.4.3. Nuclear Waste Issues and Areas of Municipal Responsibility

In connection with the conversations with the municipal leaders in Östhammar, Oskarshamn and Hultsfred municipalities, the question was raised of the impact that the nuclear waste issue had had on the work in other areas of municipal responsibilities. This question can be further divided into two questions as follows:

  • To what extent does one use – or intend to use – the experience from the handling of the nuclear waste issue in the municipality in connection with the handling of other complex issues?
  • Have the efforts that the local politicians have put into the nuclear issue since the mid-1990s detracted from the handling of other municipal issues?

The responses to these questions are related to how the nuclear waste issue is perceived. Formulated somewhat provocatively, it could be said that the choice is between considering the nuclear waste issue to be primarily a technically complex waste management issue or an issue that also includes significantly

The Municipalities – One of the Main Actors in the Nuclear Waste Issue SOU 2004:67

broader aspects. This second view is characterised by the fact that the issue, in addition to its technical complexity, is of such dimensions that finding a satisfactory solution also requires the types of considerations to be made that usually belong to the realms of ethics, morality and democracy.

The interviews conducted give the impression that, Oskarshamn municipality, more than Östhammar, emphasises that experience from the handling of the nuclear waste issue in the municipality can be applied to increasing the involvement of the local community in the handling of other complex issues in the municipality. The municipal leaders in both municipalities considered that their way of handling the nuclear waste issue had led to increased confidence in politicians and in their will/ability to handle other difficult issues as well. The same view is held in Hultsfred. In all of the three municipalities, it was believed that the involvement in the nuclear waste issue had not led to the neglect of any other important issues. During a separate interview with the former municipal executive board chairman in Oskarshamn, the chairman mentioned that he had been criticised to that effect, especially by party colleagues. However, he did not consider that the criticism was justified.

2.5. Sequence of Events 2002

  • in Östhammar

Municipality

2.5.1. Facts about the Municipality

Östhammar municipality is located in Uppsala County, on the coast of the Gulf of Bothnia/northern part of the Åland Sea, and has almost 22,000 inhabitants. About 4,700 people live in the central district of Östhammar and, in four other population centres, about 8,800. In the 1970’s and 1980’s, the number of inhabitants increased in connection with the construction of Forsmark nuclear power plant. The nuclear power plant is located on the coast, about 20 kilometres north of the

SOU 2004:67 The Municipalities – One of the Main Actors in the Nuclear Waste Issue

population centre of Östhammar and about 5 kilometres from the border with Tierp municipality. In recent years, the number of inhabitants has fallen somewhat. In summer, several thousand holiday homeowners and tourists come to the municipality.

The largest employer is the municipality with about 1,800 employees. The dominant industrial company and the next largest employer is Sandvik Coromant in the population centre of Gimo with about 1,600 employees. The only other major industrial company is Forsmark Kraftgrupp AB with about 750 employees. Forsmark nuclear power plant comprises three reactors, of which the last was taken into operation in 1985. SKB’s repository for low and intermediate-level waste (SFR) is also located in the Forsmark industrial site. Radioactive waste from all of the Swedish nuclear power plants is disposed of at the repository.

Östhammar municipality suffered from the closure of a number of industrial activities in the 1980’s and 1990’s. The number of those employed in agriculture, forestry and construction has also decreased considerably. In 2000, about 1,400 people commuted to work in the municipality, while about 2,800 commuted to work in the opposite direction.

The Social Democratic Party has long been the leading political party in the municipality. However, during the 1998 election, the party lost its former majority status but maintained a dominant position. After the 2002 election, a political majority comprising the Social Democratic Party, the Left Party and the Green Party governed the municipality. Since the 2002 election, the distribution of the 49 mandates on the council has been as follows (the distribution of the mandates for the previous period is provided in brackets): Centre Party 9 (8), Liberal Party 3 (2), Christian Democratic Party 2 (2), Green Party 2 (2), Moderate Party 8 (9), Social Democratic Party 21 (22), Left Party 2 (4), a local party called Solidaritet & Samverkan (Solidarity & Cooperation) 2 (-).

The Municipalities – One of the Main Actors in the Nuclear Waste Issue SOU 2004:67

2.5.2. Council Decision to Allow SKB to Conduct Site Investigations in Forsmark

In December 2001, the municipal council decided (with a vote of 43-5, one member abstaining from voting) to allow SKB to conduct the site investigation in Forsmark, providing that an agreement could be reached with SKB regarding the conditions for the investigation. The council handled the issue of the content of the agreement in February 2002. The proposed agreement that the council approved (with one reservation) has been published in a report, SOU 2002:46 p. 146 f.).

The site to be investigated is shown on the map in Figure 2.2.

Candidate area Candidate area

Figure 2.2. Site investigation in the Forsmark area (Swedish Nuclear Fuel and Waste Management Co, SKB).

SOU 2004:67 The Municipalities – One of the Main Actors in the Nuclear Waste Issue

2.5.3. The Municipality’s Organisation for Following the Site Investigation Work

The reference group, which existed in Östhammar during the feasibility study period ,

1

decided, in June 2002, to adopt the

name, Reference Group for the Site Investigation in Forsmark (Östhammar). During autumn 2002, the municipal leaders discussed a change in the organisation. The discussions resulted in a decision, in January 2003, by the municipal executive board. The board decided to create two groups – a reference group and a preparatory group.

The purpose of the preparatory group was to prepare issues to be presented to the municipal executive board for decisionmaking. The group comprises 7 members (chairman, Social Democratic Party and 1 additional member from the Social Democratic Party as well as 1 member each from the Moderate Party, the Centre Party, the Christian Democratic Party, the Green Party and the Left Party). The political majority in the municipality (Social Democratic Party, Left Party and Green Party) have the majority in the group. In addition, one member has been co-opted to the group from Tierp municipality. The group has both members and alternates. The task of the group is to decide on and implement day-to-day matters.

The preparatory group also has the task of preparing matters for the reference group to handle. The reference group is described as “a new interface for the municipal executive board in its contacts with the public and the political organisation” The reference group comprises the members of the preparatory group (7 members and 7 alternates) as well as a representative for each of the parties represented (8 representatives), two representatives for Tierp and Älvkarleby municipalities (4 representatives) as well as currently, 3 representatives from NGOs which are interested in the disposal issue (EFÖ, NSF and

1

For an account of the work carried out by Östhammar municipality during the

feasibility study phase, see the report SOU 2002:46, pp. 133

The Municipalities – One of the Main Actors in the Nuclear Waste Issue SOU 2004:67

OSS)

2

. The t otal number of members is thus currently 29. Both members and alternates have been appointed for Tierp and Älvkarleby municipalities. In April 2003, the preparatory group reported to the executive board that the group was waiting for “detailed terms of reference and clarification from the executive board with respect to its own and the reference group’s activities.” The report outlined future activities. It was also mentioned that both groups “when necessary will use the available expert resources during the site investigation phase”, and that it could be appropriate to arrange one or two seminars per year, together with for example, KASAM, SKB, SKI, SSI and Oskarshamn municipality, and to continue with the previous information work on targeting the Gimo and Forsmark upper secondary schools as well as to publish a brochure on the site investigation in summer 2003. In August 2003, the municipal executive board decided to adopt and establish the “proposal as the goal for activities during the coming year.” In September 2003, the executive board also appointed a local EIA group for SKB’s site investigation in Forsmark. The task of the group is to capture and pass on to the executive board issues that should be taken up during the expanded consultation that SKB had started to implement at that time. This group included the chairmen and vice-chairmen of the municipal executive board, of the preparatory group, of the municipal environmental committee and of the municipal building committee (a total of 8 people), as well as the municipal officials most directly concerned (5 individuals, namely, the administrative head of the municipality, the environmental co-ordinator, the environmental director, the city architect and the municipality’s project manager for nuclear waste issues).

2

The abbreviations mean the following: EFÖ = Energy for Östhammar, SNF = local

chapter of the Swedish Society for Nature Conservation, OSS = Opinion Group for Safe Final Disposal – Östhammar.

SOU 2004:67 The Municipalities – One of the Main Actors in the Nuclear Waste Issue

(EIA=Environmental impact assessment)

Figure 2.3. Organisation of Östhammar municipality to follow the site investigation and participate in increased consultation (Östhammar municipality).

The current municipal organisation for handling the site investigation and the consultation process is illustrated in Figure 2.3.

2.5.4. Examples of Issues relating to the Site Investigation that Have Been Dealt with by the Municipal Organisation of Östhammar

At the beginning of 2003, the municipal executive board of Östhammar had decided how the municipality should be organised in order to follow SKB’s site investigation work (cf. Section 2.5.3). A small preparatory group, consisting exclusively of “politicians” has the task of preparing questions that should

The Municipalities – One of the Main Actors in the Nuclear Waste Issue SOU 2004:67

be put to the executive board for decision-making. The preparatory group also had the task of preparing issues for handling in a reference group of about thirty people, comprising “politicians” and representatives from NGOs interested in the disposal issue. During autumn, a special EIA group was appointed.

In 2003, the preparatory group convened on seven occasions and the reference group, on three. So far, the EIA group has not held any meetings.

A recurrent feature of the reference group’s meetings has been information from SKB on the ongoing work. Information has also been provided concerning measures that the preparatory group has adopted or discussed. The members of the reference group have also received information on seminars and other forms of competence-building that have been considered of interest. Copies of documents given to the preparatory group are also regularly sent to reference group members. The extent to which discussions in the reference group have affected the position adopted by the preparatory group is not evident from the minutes.

Under the auspices of the preparatory group, a seminar was organised, in May 2003, on the following theme: “A Municipal Matter of National Concern in an International Perspective”. Furthermore, a school project was completed, where pupils from Forsmark school prepared information material on the disposal issue for distribution to other pupils at the school. The preparatory group also commissioned an up-to-date version of a brochure that had been previously prepared and that had been distributed to the municipality’s permanent inhabitants and holiday homeowners. The plan of activity that was established for 2004 states that the intention is to provide information to the public in the municipality’s population centres with the participation of environmental NGOs, SKB, SKI and SSI as well as to organise study circles. Specific information will be provided to certain schools. The group also expects to participate in the seminars and conferences arranged during the year by various

SOU 2004:67 The Municipalities – One of the Main Actors in the Nuclear Waste Issue

actors as well as in the expanded consultation that SKB intends to conduct. At the end of 2003, the preparatory group made a decision regarding applications for grants for activities that two local groups (the Opinion Group for Safe Final Disposal, OSS and Energy for Östhammar, EFÖ) intend to conduct in 2004.

The minutes from the preparatory group’s meetings give the impression that, so far it has not been relevant to discuss, within the group, whether the municipality needs to react to the information that SKB has provided about the site investigation. However, it can be noted that the preparatory group has taken the initiative to arrange a training day on EIA-related issues at the beginning of 2004.

In the light of discussions held between the chairmen of the municipal executive boards in Östhammar and Oskarshamn municipalities at the end of 2003 (cf. Section 2.4.1), the members of the preparatory group met with representatives for the site investigation organisation in Oskarshamn municipality. The meeting considered co-operation during the site investigation phase. As has been described above, the meeting resulted in a joint press release. One concrete result was the decision to arrange joint seminars. The first seminar took place in Oskarshamn in April 2004 and dealt with alternatives to the KBS-3 method. A seminar is being planned for autumn in Östhammar on the topic of SKB’s community development programme.

2.6. Sequence of Events 2002-2004 in Oskarshamn Municipality

2.6.1. Facts about the Municipality

Oskarshamn municipality is located in Kalmar County on the Baltic Sea coast parallel to northern Öland and has just over 26,000 inhabitants. 18,500 of these inhabitants live in the town of Oskarshamn. In the 1970’s the population increased

The Municipalities – One of the Main Actors in the Nuclear Waste Issue SOU 2004:67

somewhat in connection with the establishment of nuclear power on the Simpevarp peninsula, about 30 kilometres north of the town of Oskarshamn. Since 1994, the number of inhabitants has decreased by 100-200 people every year, depending on reduced employment in the industrial sector.

The largest employer is the municipality with about 2,400 employees. The dominant company and next largest employer is Scania with about 2,100 employees. The second largest industrial company, with about 900 employees, is OKG AB. The company owns Oskarshamn nuclear power plant, which has three reactors, of which the last was taken into operation in 1985. SKB’s Central Interim Storage Facility for Spent Nuclear Fuel (CLAB), where spent fuel from all of the Swedish nuclear power plants is stored, is also located on the industrial site.

In 2001, about 2,350 people commuted to work in the municipality, while about 1,350 commuted to work in the opposite direction.

The Social Democratic Party has been the leading political party in the municipality for a long time. However, in the 1998 election, the party lost its earlier majority status but maintained a dominant position. Since the 2002 election, a political majority comprising the Social Democratic Party and the Left Party has led the municipality. Since the 2002 election, the distribution of the 49 mandates on the Council (there were 51 mandates in the previous period), has been as follows: Centre Party 3 (2), Liberal Party 3 (1), Christian Democratic Party 6 (6), Green Party 1 (1), Moderate Party 7 (9), Social Democratic Party 23 (22), Left Party 8 (10).

SOU 2004:67 The Municipalities – One of the Main Actors in the Nuclear Waste Issue

2.6.2. Council Decision to Allow SKB to Start Site Investigations on Simpevarp

In March 2002, a practically unanimous municipal council in Oskarshamn

3

to allow SKB to start investigations at the site that

SKB had indicated which comprised the Simpevarp peninsula and an area west of that area. The decision carried thirteen stipulations and clarifications (see SOU 2002:46, p. 232 ff). As described in a previous section (Section 2.3), in September 2003, the council voted “yes” to a minor adjustment to the boundaries of the site.

The site for investigation is shown on the map in Figure 2.4.

2.6.3. The Municipality’s Organisation for Following the Site Investigation Work

The municipality’s work on following the site investigation

4

is

being conducted within the framework of the LKO Local Competence Development in Oskarshamn – Nuclear Waste Project, which was originally started in 1994. The municipal executive board acts as a steering committee for the LKO Project, while the municipal council acts as the “client” of the project and has the task of making decisions on issues of major importance.

The current organisation is based on the situation during the feasibility study phase, where the focus was on a number of working groups, which were attached to the LKO Project. Prior to the site investigation phase, the municipality considered that the organisation that had applied during the feasibility study phase needed to be adapted to the new conditions. In November 2002, the council adopted the current organisation.

3

One member moved to have the matter reviewed once more, but when that motion was

rejected by the council, no other motions were put forward.

4

An account of the municipal organisation in Oskarshamn during the feasibility study is

provided in the report, SOU 2002:46, pp. 209-237.

The Municipalities – One of the Main Actors in the Nuclear Waste Issue SOU 2004:67

Original candidate area Sub candidate areas Laxemar and Simpevarp Interest sphere for a deep repository Original candidate area Sub candidate areas Laxemar and Simpevarp Interest sphere for a deep repository

Figure 2.4. Site investigation in the Simpevarp area (Swedish Nuclear Fuel and Waste Management Co, SKB).

SOU 2004:67 The Municipalities – One of the Main Actors in the Nuclear Waste Issue

The purpose of the LKO Project is to provide an adequate basis so that the council can make a decision in the event that an application is submitted for permission to construct a repository/encapsulation plant. The aim is for all issues of importance to be thoroughly investigated in the information that is provided. This means that the LKO Project should:

  • Continuously follow the safety issues and SKB’s site investigation in Oskarshamn.
  • Ensure that SKB, the authorities and the Government comply with the council’s site investigation stipulations.
  • Initiate investigations into issues that arise during the site investigation phase.
  • Enhance the competence of citizens within the nuclear waste area.
  • Elicit questions and viewpoints from the municipality’s inhabitants and neighbours.
  • Maintain international contacts in order to follow developments within the nuclear waste programmes in other countries, with an emphasis on local participation.

The work is mainly being conducted “within the framework of a developed EIA”. In this process, SKB is responsible for promoting the consultation and for conducting investigations, taking into account the fact that the municipality is one of the most important parties in the consultation. In its description of this work, Oskarshamn municipality states that the co-operation with Östhammar municipality needs to be developed in order to co-ordinate parts of the EIA process, for example, with respect to the description of alternatives.

One official is employed full-time within the LKO Project as project manager. In addition, an official works part-time on supporting the Misterhult group (see below) with a local development programme. Three experts also assist the project on a consultancy basis. Additional experts are hired when necessary.

The Municipalities – One of the Main Actors in the Nuclear Waste Issue SOU 2004:67

Within the framework of the LKO Project, there is a development group and four working groups (see below). The task of the development group is to develop the project work and the “Oskarshamn model”, to co-ordinate activities in the project, to prepare matters to be handled by the municipal executive board etc. The group comprises the chairman and vice-chairman of the municipal executive board, the four chairmen of the working groups, the former chairman of the executive board as well as experts and officials who are connected to the project – a total of 12 people. Therefore, in practice, the work is conducted in close co-operation with the municipal executive board. The chairman of the executive board represents the municipality in the consultation process with concerned parties that SKB must conduct, under the Environmental Code, and which is conducted within the framework of the EIA Forum for Studies of Final Disposal Systems for Spent Nuclear Fuel in Oskarshamn Municipality (see below).

Work in the LKO Project is mainly conducted through the four working groups. The task of each group is to follow three or more of the stipulations in the council decision from March 2002 (Section 2.6.2). Other important tasks of the groups as well as the designations of the groups are presented below.

Safety Group

  • Responsibility for issues concerning safety and radiation protection in connection with encapsulation, transport and final disposal.

Misterhult Group

  • Responsible for ensuring that the Misterhult local programme is defined and also participates in the implementtation and follow-up of the programme.
  • Follows local environmental issues in the EIA.

SOU 2004:67 The Municipalities – One of the Main Actors in the Nuclear Waste Issue

Municipality Group

  • Responsible for issues relating to physical planning, infrastructure and socioeconomic investigations.
  • The group has a responsibility for co-ordinating the EIA.

Community Group

  • Responsible for social scientific issues.
  • Responsible for co-operation with neighbouring municipalities.
  • Responsible for ensuring that regional issues are investigated in the site investigation programme.
  • Follows the results of surveys and conducts its own surveys when necessary.
  • Follows up the national issues.

The municipal executive board appoints all of the members of the groups. The development group proposes members, with the exception of individuals who are “politicians”. Such individuals are directly appointed by the executive board. However, the composition of members of the four working groups is different. The chairman and three members of the safety group represent political parties. The other members are from the Döderhult chapter of the Swedish Society for Nature Conservation, the municipal rescue services and the environmental and health care administration. The Misterhult group focuses on the inhabitants living closest to the investigation site. Members were recruited to the group when the LKO Project advertised a meeting and individuals who were interested in joining the group. The group now comprises about 15 people who are attached to various NGOs and societies in the area that comprises old Misterhult parish. The group has itself proposed its chairman (one of the inhabitants living close to the investigation site). Two of the members represent political parties. The task of the municipality group is to ensure that the municipality’s officials are have a good insight into and understanding of the issues. The administrative

The Municipalities – One of the Main Actors in the Nuclear Waste Issue SOU 2004:67

director of the municipality has been appointed as chairman. The group primarily comprises officials from different municipal administrations. Three members represent political parties. The chairman and two other members of the community group represent political parties. The other members are from the child and youth welfare department, arts and cultural amenities department, Nova higher technical education centre, the Döderhult chapter of the Swedish Society for Nature Conservation and the Regional Council in Kalmar county.

In 2003, the working groups convened a total of just over 30 times. A large number of meetings have also been planned for 2004.

The current organisation for handling the site investigation and consultation process can be illustrated as shown in Figure 2.5.

Figure 2.5. Municipal organisation for following the site investigation and participating in expanded consultation in Oskarshamn (Oskarshamn municipality).

SOU 2004:67 The Municipalities – One of the Main Actors in the Nuclear Waste Issue

2.6.4. Examples of Site Investigation-related Issues that Have Been Discussed in the Framework of the Municipal Organisation in Oskarshamn

The way of working with final disposal issues that has been developed in Oskarshamn municipality means that the issues that, according to Section 2.8.3, have been brought to light in the EIA forum have almost without exception been discussed beforehand in one of the four working groups. The groups prepared work plans for 2004, which also include general descriptions of activities in 2003. Examples of issues that are of concern in the different groups are provided below. It should be added that the work in the LKO Project is reported to the municipal council twice every year.

Safety Group

The group is to specifically monitor eight of the 13 stipulations that the council formulated in its decision of March 2002 to allow the site investigation to be conducted. In 2003, when the group convened on eight occasions, special attention was devoted to SKB’s wishes concerning a certain expansion of the area for the site investigations to also include areas adjacent to the Simpevarp peninsula. This issue led to the group arranging a special, official hearing, in September 2003, of SKB and the authorities with respect to these plans. Other issues dealt with in the hearing included

  • the future responsibility for a repository after closure,
  • the sealing of boreholes near a repository and their importance for the safety assessment,
  • the decision-making process – establishing how the requirements of the Environmental Code and the Act on Nuclear Facilities are interlinked,
  • the meaning of the concepts “best site” and “sufficiently safe site”,
  • retrievability,

The Municipalities – One of the Main Actors in the Nuclear Waste Issue SOU 2004:67

  • the need for the authorities to have adequate resources to satisfy the requirements on competence for regulatory review.

On the group’s initiative, a seminar was conducted in April 2004 together with Östhammar municipality, where the question of alternatives to the KBS-3 method was discussed.

Misterhult Group

In 2003, during which time the group met on 13 occasions, work started on a local development programme for the Misterhult area. The responsibility for conducting this development programme rests with SKB, although the work of the programme is based on a broad participation and commitment from those living close to the investigation site, NGOs and organisations. In autumn 2003, the group arranged a seminar for the inhabitants of old Misterhult parish in order to elicit proposals for developing the community centre.

Municipality Group

The group convened on eight different occasions in 2003. The main focus of work was preparations for increasing information to municipal employees on the nuclear waste issue. Measures included a survey, which was conducted among municipal employees to investigate the need for information.

Community Group

The group has had six meetings in 2003. Work focused on contributing to obtaining a basis for discussion for the social science studies that SKB is planning to undertake. The group’s tasks include specially monitoring the decision-making process and, for this reason, an environmental lawyer has been attached to the group. Before 2004, the group expects to develop the co-

SOU 2004:67 The Municipalities – One of the Main Actors in the Nuclear Waste Issue

operation with lower and upper secondary school pupils, to prepare information material about the LKO Project which is specially adapted to young people as well as to develop contacts with other municipalities in the region.

As reported in Section 2.5.4, a close co-operation has started between the LKO Project in Oskarshamn and the corresponding organisation in Östhammar municipality.

2.7. Sequence of Events, 2002-2004 in Hultsfred Municipality

2.7.1. Facts about the Municipality

Hultsfred municipality (Kalmar county) is located in the interior of Småland, on the border of Oskarshamn municipality to the east and has about 14,700 inhabitants. About 5,400 people live in the population centre of Hultsfred. Since 1994, the number of inhabitants has decreased with just over 2,000 people, due to reduced employment in the industrial sector and to the migration of young people to other areas where higher education is available.

The municipality is the largest employer with about 1,500 employees. The dominant company and next largest employer is OKG with about 360 employees. Apart from these two, only small-scale employers are located in the municipality. The economy of the municipality is strained.

In 2001, about 1,000 people commuted to the municipality while about 1,150 commuted to work in the opposite direction.

Since 1994, the Social Democratic Party has formed a majority, together with the Left Party. Since the 2002 election, the distribution of the 49 mandates on the municipal council has been as follows (the distribution of the mandates for the previous period is provided in brackets): Centre Party 9 (8), Liberal Party 2 (1), Christian Democratic Party 6 (7), Green Party – (-), Moderate Party 4 (5), Social Democratic Party 21

The Municipalities – One of the Main Actors in the Nuclear Waste Issue SOU 2004:67

(19), Left Party 5 (7), a local party called Medborgarpartiet, skola, vård och omsorg (Citizens’ Party, school, health care and welfare) 2 (2).

2.7.2. The Municipality and the Final Disposal Issue

The proposal presented by SKB at the end of 2000 concerning which sites would be included in the site investigations did not include a site in Hultsfred municipality. As has been reported elsewhere

5

, the company’s attitude meant that both the local

government leaders and the municipal feasibility study organisation expressed disappointment that SKB had adopted a position on the matter without awaiting the outcome of the municipality’s handling of the preliminary feasibility study report. In spring 2001, an agreement was signed between the company and the municipality concerning some concluding activities. The agreement stated that if Hultsfred municipality were considered for site investigations in the future, SKB would submit a new request for permission to the municipality and a new political process would then be started.

In June 2001, the municipal executive board approved a plan for the municipality’s further work on the nuclear waste issue in 2001. In a document to the municipality in December 2001, SKB emphasised that “there is no overriding reason to write off any siting alternatives, such as Hultsfred, at present” and stated that, in 2002, the company intended to conduct certain geohydrological investigations in the municipality as well as continue with certain information work.

In January 2002, the executive board’s working committee decided on a plan of activities, budget and organisation for the municipality’s information work on the final disposal issue during the next year. Representatives from the municipality have since participated in various activities that KASAM, SKI, SSI,

5

A detailed account of the sequence of events in Hultsfred municipality during the

feasibility study phase is provided in the report, SOU 2002:46, pp. 239-254.

SOU 2004:67 The Municipalities – One of the Main Actors in the Nuclear Waste Issue

other municipalities as well as SKB arranged on the nuclear waste issues.

In December 2002, SKB presented a “contact programme” for Hultsfred municipality. The programme was based on an agreement with the local government leaders. In the contact programme, SKB emphasised again that there were no important reasons to write off any of the alternatives that were not prioritised for site investigations and continued: “It is important to ensure that SKB continues to have freedom of action if unforeseen events should occur during the site investigation phase. Therefore, SKB would like Hultsfred municipality to remain in the programme even if there are currently no plans to conduct site investigations in the municipality.” The programme meant that SKB would continue to have a local office in the municipality, although with limited opening hours.

Since December 2002 and during 2003, meetings have been arranged regularly (about once a month) under the auspices of the municipality, on different topics relating to the nuclear waste issue. In November 2003, the municipality was the host of an “exchange of opinion between authorities, the company, municipalities and citizens about the society-related process for the deep disposal issue.”

During the feasibility study phase, the municipality created an organisation focussing on a number of working groups, comprising individuals representing political parties as well as private individuals who had voluntarily expressed their interest in the issues. The number and areas of responsibility of the groups gradually changed in 2001-2002. In February 2003, a contact group, in accordance with a decision by the municipal executive board, replaced them. Half of the members (seven people) represent all of the parties that have members on the council. The remaining seven members are people who have shown a particular interest in the issues and have participated in the previous working groups.

At the same time, the municipal executive board established the following guidelines for the activities of the contact group:

The Municipalities – One of the Main Actors in the Nuclear Waste Issue SOU 2004:67

  • The individual members should be able to act as an interface with the citizens.
  • Information work would have a social and democratic focus.
  • The municipal work would be characterised by knowledge, insight and participation.
  • The municipality would choose suitable supplementary training and information in order to develop comprehensive knowledge when alternatives to the information provided by industry and the authorities are required.
  • Local information should be adequately distributed. The citizens and their elected representatives would be mentally well prepared and informed of the content and consequences of a possible siting of a deep repository in the neighbouring municipality (Oskarshamn) and of a possible site investigation in Hultsfred municipality.
  • The environmental NGOs and other local NGOs should be given the opportunity to participate in the municipal process.

2.8. Consultation under the Environmental Code

2.8.1. Requirements on Consultation

The final disposal and encapsulation of spent nuclear fuel requires government licensing under both the Environmental Code and the Act on Nuclear Activities. The requirements on consultation prior to this licensing are presented in the regulations on EIS and other assessments used as a basis for decision making in Chapter 6 of the Environmental Code. The Environmental Code also places requirements on consultation prior to the site investigations. SKB must take the initiative for consultation as described below.

SOU 2004:67 The Municipalities – One of the Main Actors in the Nuclear Waste Issue

2.8.1.1 Consultation Prior to Site Investigations

Consultation prior to the site investigations must be held with the county administrative board in accordance with Chapter 12 § 6 of the Environmental Code. This consultation concerns activities or measures that can essential effect the natural environment. Issues relating to the impact on the cultural environment are also to be dealt with in this context.

The purpose of the site investigations is to ensure that SKB obtains the necessary information in order to submit an application to the Government for permission to establish a repository for spent nuclear fuel at a certain site.

2.8.1.2 Consultation Prior to the Preparation of Licence Applications and EIS

SKB is now conducting investigations at the Forsmark and at Simpevarp sites (see also Sections 2.8.2.2 and 2.8.3.2). In connection with this, the project planning has reached such a degree of detail that SKB has started the consultation in accordance with Chapter 6 of the Environmental Code.

Consultation prior to the preparation of applications for a government licence to construct a repository or an encapsulation plant, along with the required EIS, should be conducted in accordance with Chapter 6 of the Environmental Code. The consultation should be held at an early stage with the competent regulatory authorities, municipalities, the public and organisations. The consultation should be conducted in two phases.

These regulations mean that SKB, as the proponent, must take the initiative to and conduct these consultations with those parties who are in different ways concerned. Therefore, it is SKB that formally “owns” the issue and has the role of providing an impetus for the work within the framework of the existing regulations. The role of the county administrative board is to

The Municipalities – One of the Main Actors in the Nuclear Waste Issue SOU 2004:67

provide advice to SKB prior to various consultations with the ultimate aim of ensuring that the consultation is conducted in the spirit of the regulations. At the same time, the county administrative board’s task is to make the decisions that are necessary to enable SKB’s work.

In the first consultation phase – “early consultation” – SKB must consult with the county administrative board and individuals who it can be assumed are specifically concerned, namely, people living in the vicinity and landowners. Prior to the consultation, SKB must submit information on the siting, scope and design of the planned activity as well as on the anticipated environmental impact.

After this early consultation, and as a result of the compulsory decision of the county administrative board that the activity can be expected to result in a “significant environmental impact”, SKB must hold “an expanded consultation with EIA”. SKB must consult with the other government authorities, the municipalities, general public and organisations that are assumed to be concerned. Furthermore, in addition to the siting, scope, design and environmental impact of the planned activity, the consultation must also include the content and form of the EIS.

In December 2003, SKB invited twenty government authorities to an information meeting on SKB’s planning reports “Scope, Boundaries and Investigations for Environmental Impact Statements (EIS) for an Encapsulation Plant and Repository for Spent Nuclear Fuel. Version 0 – Basis for Expanded Consultation” concerning the repository in Forsmark and Simpevarp (see Sections 2.8.2.4 and 2.8.3.4). The authorities were also invited to comment on the reports.

SOU 2004:67 The Municipalities – One of the Main Actors in the Nuclear Waste Issue

2.8.2. Consultation in Uppsala County

2.8.2.1 Preparatory Consultation in Uppsala County

In connection with SKB starting feasibility studies in Östhammar municipality, an organisation had been created for consultation and exchange of information between the county administrative board, SKB, municipalities concerned and government authorities etc. under the auspices of the county administrative board in Uppsala county. These consultations were based on a government decision in May 1995 where the county administrative boards concerned were given the responsibility of co-ordinating contacts with municipalities and government authorities that were necessary for SKB to be able to prepare a basis for an EIS. They were also given the responsibility of ensuring that the municipalities concerned by the site selection process could follow SKB’s site selection studies etc. closely. The organisation for consultation was called The County Administrative Board’s Reference Group on Issues concerning a Possible Siting of a Repository for Spent Nuclear Fuel in Uppsala County. Up to and including 2002, the reference group convened about twice a year, for regional consultation on the final disposal of spent nuclear fuel

6

.

2.8.2.2 SKB’s Consultation Prior to the Site Investigation in Forsmark

In December 2001, SKB submitted to the county administrative board in Uppsala County an application for a consultation prior to the initial site investigations. This consultation primarily concerned the impact that the site investigation work could have on the natural environment and did not concern issues relating to the risk of environmental impact in connection with the

6

An overview of the work conducted in this reference group and in a working group

attached to this group, is presented in the report, SOU 2002:46, pp. 269-271.

The Municipalities – One of the Main Actors in the Nuclear Waste Issue SOU 2004:67

construction of a repository at the site. In its decision of February 14, 2002, the county administrative board found that SKB’s application contained sufficient information for a consultation on the initial site investigations but not sufficient information for a complete site investigation. The decision meant that SKB was able to start initial site investigations on condition that certain measures were taken.

2.8.2.3 Early Consultation Prior to an Application and Environmental Impact Statement for a Repository and Encapsulation Plant in Forsmark

In 2002, SKB held an early consultation in accordance with Chapter 6 § 4 of the Environmental Code with the county administrative board of Uppsala County and individuals who were assumed to be specifically concerned by a repository in the Forsmark area. A consultation report was prepared by SKB and submitted to the county administrative board in July 2002. Based on this report – as well as statements of opinion on the report from the Swedish Nuclear Power Inspectorate, the Swedish Radiation Protection Authority, the National Board of Housing, Building and Planning, the municipal executive board and the environment and health board in Östhammar municipality – the county administrative board decided in December 2002 that a deep repository in the Forsmark area could be “expected to result in a significant environmental impact”.

In autumn 2003, SKB had also conducted an early consultation concerning a possible encapsulation plant for spent nuclear fuel in Forsmark. Based on the consultation report prepared by SKB, the county administrative board decided in January 2004 – after statements had been issued by the Swedish Nuclear Power Inspectorate, the Swedish Radiation Protection Authority, the National Board of Forestry in Mälardalen, the local safety committee at the nuclear facilities in Forsmark and the environment and health board in Östhammar municipality –

SOU 2004:67 The Municipalities – One of the Main Actors in the Nuclear Waste Issue

that also such a facility could be “expected to result in a significant environmental impact”.

Both of the decisions by the county administrative board in Uppsala meant that SKB would continue to follow the regulations concerning expanded consultation with EIA in accordance with Chapter 6 § 5 of the Environmental Code.

2.8.2.4 Expanded Consultation Prior to Submitting an Application with EIS for a Repository and Encapsulation Plant in Forsmark

SKB currently conducts expanded consultations on EIS in accordance with Chapter 6 § 5 of the Environmental Code, for a repository and an encapsulation plant for spent nuclear fuel with siting in the Forsmark area and in the Simpevarp area.

At the last meeting in November 2002 with the county administrative board’s reference group concerning a possible siting of a repository for spent nuclear fuel in Uppsala county, a working group was given the task of presenting a proposal for work procedures for the continued regional consultation work. The working group comprised representatives for SKB, Östhammar municipality, the Swedish Nuclear Power Inspectorate, the Swedish Radiation Protection Authority and the county administrative board. Based on the group’s proposals, a first meeting was arranged in September 2003 with a body called Forsmark consultation and EIA group. On this occasion, the group decided on work procedures to conduct its activities.

The document regulating the forms of work states that the group “was formed on the basis of the responsibilities of the county administrative board, the most closely concerned central authorities and the municipalities” (primarily in accordance with the Environmental Code and the government decision of May 1995) as well as “SKB’s responsibility in accordance with the regulations in Chapter 6 of the Environmental Code.” The

The Municipalities – One of the Main Actors in the Nuclear Waste Issue SOU 2004:67

subject of the negotiations is an encapsulation plant and repository for spent nuclear fuel in Forsmark, Östhammar municipality.

Representatives from SKB, Östhammar municipality, the Swedish Nuclear Power Inspectorate, the Swedish Radiation Protection Authority and the county administrative board in Uppsala are members of the consultation and EIA group for Forsmark, in accordance with the work procedures and in the same way as with the previous reference group. Representatives from other parties can be co-opted when necessary. The county administrative board in Uppsala is responsible for chairing the group’s meetings and for the final minutes. Joint meetings with the corresponding organisation in Kalmar County can be arranged. The document on the group’s forms of work also states that it is SKB (the proponent) that is responsible for preparing an EIS. The document also states that the group:

  • Consults “on information and consultation issues prior to the construction of a repository for spent nuclear fuel as well as on the scope, design, site adaptation and environmental impact of the planned activity as well as on the content and structure of the EIS to be attached to the licence for the construction and operation of the repository. The consultation should also, in a corresponding manner, deal with the siting of an encapsulation plant at Forsmark.”
  • Is only an advisory body. The participants in the group are not bound to make decisions in accordance with the consultation group’s views. The issues that are dealt with are raised the participants themselves.
  • Must work to ensure that the basis for the EIS for the repository and for the encapsulation facility is adequate in terms of reliability, comprehensibility and relevance.
  • Usually convenes in Uppsala. Some meetings can be public and should take place in Östhammar municipality. What occurs in the meeting should be reported in minutes along with the conclusions reached and justifications that the group has found. The minutes are administered by the

SOU 2004:67 The Municipalities – One of the Main Actors in the Nuclear Waste Issue

county administrative board and adjusted by all of the organisations that have participated in the meeting. Agenda proposals are prepared by SKB, although the participants in the consultation notify SKB of topics to put on the agenda.

In September 2003, SKB presented a preliminary version of a report with the title, “Scope, Boundaries and Investigations for Environmental Impact Statements (EIS) for an Encapsulation Plant and Repository for Spent Nuclear Fuel. Version 0 – Basis for Expanded Consultation.” At the same time, a corresponding report concerning the consultation in Oskarshamn was presented, see Section 2.8.3.4. SKB has asked for views on the content of both documents from a number of authorities, organisations etc., that are assumed to be concerned.

The Forsmark consultation and EIA group has so far convened twice. January 2004 was the most recent meeting. During the first meeting in September 2003, a number of status reports were dealt with, in addition to the issue of work procedures. Furthermore, a working group was set up with the task of presenting a work programme for further work.

During the second meeting with the Forsmark consultation and EIA group, SKB provided information on the ongoing investigations in Östhammar and in Oskarshamn as well as on the planning of forthcoming consultations. Other participants presented status reports on various issues.

2.8.3. Consultation in Kalmar County

2.8.3.1 Preparatory Consultation in Kalmar County

On the initiative of Oskarshamn municipality, a body was created in 1994 for consultation between the municipality, county administrative board in Kalmar county, SKB, the Swedish Nuclear Power Inspectorate and the Swedish Radiation Protection Authority concerning the plans for an expansion of the

The Municipalities – One of the Main Actors in the Nuclear Waste Issue SOU 2004:67

Central Interim Storage Facility for Spent Nuclear Fuel (CLAB), located next to Oskarshamn nuclear power plant’s facilities on the Simpevarp peninsula. In 1996, the consultation also included issues relating to a repository in Oskarshamn municipality. From 1997, this consultative body was called The EIA Forum for Studies of Final Disposal Systems for Spent Nuclear Fuel in Oskarshamn Municipality (commonly referred to as the EIA forum in Kalmar county)

7

. The w ork in the EIA forum has been characterised by the fact that the municipality has seen this body as a forum where the municipality puts questions concerning the plans for the final disposal of nuclear waste to SKB and to the regulatory authorities and where the municipality demands answers to its questions. The objective of the work within the LKO Project has been to obtain a basis for action within the framework of the EIA forum.

2.8.3.2 SKB’s Consultation Prior to the Site Investigation in Simpevarp

In April 2002, an application was submitted to the county administrative board in Kalmar County. In the decision of June 19, 2002, the county administrative board stated that it did not have any objections to SKB conducting initial site investigations on the Simpevarp peninsula. The county administrative board added that the information in the application did not provide a sufficient basis for consultation on a possible complete site investigation and that “a continued process with consultation must be conducted as the site investigation continues in other parts of the candidate site.” This decision also meant that SKB could start the initial site investigations under certain conditions.

7

For an overview of the work conducted in the EIA forum in Oskarshamn, see the

report, SOU 2002:46, pp. 271-272.

SOU 2004:67 The Municipalities – One of the Main Actors in the Nuclear Waste Issue

2.8.3.3 Early Consultation Prior to an Application and EIS for a Repository and Encapsulation Plant in Simpevarp

The early consultation for a possible repository in the Simpevarp area started somewhat differently than that for the Forsmark area. At the request of Oskarshamn municipality, SKB started, as early as in January 2002 – before the municipality in March 2002 decided to “allow” the proposed site investigation – an initial consultation meeting with specifically concerned parties and the county administrative board. A consultation report was prepared by SKB after the meeting and submitted to the county administrative board in Kalmar County. When the municipality, the Swedish Nuclear Power Inspectorate and the Swedish Radiation Protection Authority had submitted statements of opinion on the report, the county administrative board decided, in January 2003, that a deep repository for spent nuclear fuel at the proposed site on Simpevarp could be expected to result in a significant environmental impact.

Early in 2003, SKB also conducted an early consultation with specifically concerned parties and the county administrative board in Kalmar County concerning a possible encapsulation plant for spent nuclear fuel. The intention is to site the encapsulation plant adjacent to CLAB. On the basis of SKB’s consultation report and on the basis of statements of opinion on the report submitted by Oskarshamn municipality, the Swedish Nuclear Power Inspectorate and the Swedish Radiation Protection Authority, the county administrative board decided, in September 2003, that such a facility could also “be expected to result in a significant environmental impact.”

Both decisions of the county administrative board in Kalmar County mean, in the same way as corresponding decisions in Uppsala County that, also with respect a siting in Oskarshamn municipality, SKB will have to follow, in the future, the regulations for expanded consultation with EIA, in accordance with Chapter 6 § 5 of the Environmental Code.

The Municipalities – One of the Main Actors in the Nuclear Waste Issue SOU 2004:67

2.8.3.4 Expanded Consultation Prior to an Application and EIS for a Repository and Encapsulation Plant on Simpevarp

SKB is currently conducting an expanded consultation with EIA in accordance with Chapter 6 § 5 of the Environmental Code, for a repository and an encapsulation plant for spent nuclear fuel to be sited in the Forsmark area and in the Simpevarp area.

In response to a request from Oskarshamn municipality, SKB arranged, already in January 2002 – before the municipality decided to “allow” the proposed site investigation in March 2002 – an initial consultation meeting with specifically concerned parties and the county administrative board. In different contexts, Oskarshamn had emphasised its intention to also continue to work actively on the nuclear waste issues and emphasised the sound experience that had been gained through the work within the framework of “the EIA forum.”

At a meeting with the EIA forum in May 2002, the parties had decided to conduct a review of activities. An evaluation and a proposal for changes in the forms of activity were presented and discussed in a total of three meetings during the period from October 2002 to March 2003. The end product comprised two documents: a “rules of procedure” and a “basic document”.

According to the rules of procedure, representatives from SKB, Oskarshamn municipality, the Swedish Nuclear Power Inspectorate, the Swedish Radiation Protection Authority and the county administrative board in Kalmar county participate in the EIA Forum on Questions Relating to the Final Disposal System for Spent Nuclear Fuel in Oskarshamn Municipality (“EIA forum in Oskarshamn”). When necessary, additional representtatives from authorities, organisations and neighbouring municipalities can be co-opted. Initially, it is established that SKB is responsible for preparing the EIS, which must be attached to an application to construct facilities. The rules of procedure also state that SKB “is to prepare a separate consultation report which provides possible answers to questions asked and possible

SOU 2004:67 The Municipalities – One of the Main Actors in the Nuclear Waste Issue

measures that SKB is adopting and that the consultation has occasioned.” Otherwise, the rules of procedure mainly state that the EIA forum:

  • Consults on the EIS (documents) for the facilities and on the EIA (the process that results in these documents).
  • Is consultative and none of SKB, the municipality or the government authorities is bound to make decisions in accordance with the recommendations of the EIA forum. The participants themselves raise the issues that are dealt with, and they have the right to put forward requests with respect to studies and investigations.
  • Through its composition, is to work towards ensuring that the basis for decision-making for each facility is adequate with respect to reliability, comprehensiveness and relevance.
  • Usually convenes in Oskarshamn. Certain meetings should be open to the public. Initiatives should be taken, at relevant intervals, to arrange a joint meeting with a corresponding organisation in northern Uppland. Minutes should report what has been discussed at the meeting and the conclusions and justifications that the EIA forum has reached. The county administrative board administers the minutes, although SKB “provides secretarial assistance”. The minutes are adjusted by each organisation that is represented. Prior to each consultation occasion, “SKB is to ensure that the representatives submit matters for the agenda.”

The basic document, which is dated May 16, 2003, is a document which, according to the preface, “aims to provide a holistic view of the different consultations that will be held between SKB and different actors, to describe how consultations within the framework of the EIA forum in Oskarshamn municipality will be conducted and co-ordinated with other consultations as well as to provide a view of how the consultations in the EIA forum are linked to Oskarshamn municipality’s activities on the nuclear waste issue”. Furthermore, it is stated that the intention is to

The Municipalities – One of the Main Actors in the Nuclear Waste Issue SOU 2004:67

prepare a scoping report. The scoping report presents “the investigations that the parties request so that the EIS will provide the basis for decision-making that each individual party will need. The scoping report will, therefore, provide SKB with advice on the contents of the EIS…” In September 2003, SKB presented a preliminary version of a “scoping report” entitled “Scope, Boundaries and Investigations for Environmental Impact Statements (EIS) for an Encapsulation Plant and Repository for Spent Nuclear Fuel. Version 0 – Basis for Expanded Consultation in Oskarshamn”). A corresponding report concerning consultation in Forsmark was presented at the same time, see Section 2.8.2.4. SKB has requested viewpoints on the content of both documents from a large number of authorities, organisations etc. that are assumed to be concerned.

The information given in the basic document is provided under the following headings:

  • Repository project
  • Licensing process for nuclear facilities
  • Consultation
  • Municipality’s activities
  • EIA forum in Oskarshamn

The document also contains three appendices. These provide an account of SKB’s consultation process, the meaning of “good EIA practice” as well as an account of the development of Oskarshamn’s LKO Project.

In practice, the EIA forum in Oskarshamn was conducted in accordance with the intentions of the rules of procedure from the beginning of 2003. Up to and including March 2004, five meetings had been held in accordance with the new rules of procedure (March, May, September and December 2003 as well as March 2004). At all of these meetings, SKB and other participants had provided detailed information on current issues. Discussions have also been conducted concerning preliminary versions of the scoping report. In addition, Oskarshamn

SOU 2004:67 The Municipalities – One of the Main Actors in the Nuclear Waste Issue

municipality put detailed questions to SKB and to the authorities. The matters or questions that the municipality initiated at these three meetings are reported below. The choice of topic is a good illustration of how the municipality uses the EIA forum to obtain clarification on various issues.

March 20, 2003

1. Status report from the municipality

2. County administrative board’s decision on expanded consultation

3. The forum’s rules of procedure and basic document

4. Public hearing on the choice of the P2 area in Misterhult

5. SKI and SSI’s information project

6. Earlier question on investigation into health consequences, response from SKB?

7. Planning of the EIA forum meetings, annual plan with different topics

8. Question concerning Claes Thegerström’s (President of SKB) participation in the county administrative board’s board

May 26, 2003

1. International solutions to the nuclear waste issue

2. Is the timetable for the encapsulation plant realistic?

3. Results from the well inventories

4. Traffic on the Laxemar-Kråkelund road

5. Information: municipality - SKB

September 30, 2003 No list of questions from the municipality is included in the minutes. However, from the municipality’s status report it can be seen that further explanations were required from SKB regarding the question of expanding the investigation area and that the municipality wished to include some municipality-specific questions in the survey questionnaire directed to municipality inhabitants that SKB conducts each year.

December 11, 2003

1. Siting work for canister fabrication

2. SR-can – request for report in Swedish

The Municipalities – One of the Main Actors in the Nuclear Waste Issue SOU 2004:67

3. Expanded consultation – How does SKB intend to give insight into the expanded consultation?

4. EIA forum meetings – are all meetings open?

5. Consultation reports for previous meetings in the EIA forum. When will they be published?

6. Question to the county administrative board: the municipality’s report with a request for limiting the speed limit at the junction between the Kråkelund road and the coastal road. How much progress has been made in the handling of the matter?

7. Question to SSI: Request for a report on the results from the work on general recommendations, feedback from the focus groups etc.

March 24, 2004 No questions from the municipality at this time.

2.9. KASAM’s Comments

The previous sections show how the municipalities deal with questions in connection with SKB’s site investigations and consultation on the final disposal issue. Site investigations are being conducted in the Forsmark area (Östhammar municipality) and in the Simpevarp area (“the Simpevarp-Laxemar area”) (Oskarshamn municipality).

In this section, KASAM comments on what has occurred in the contacts with representatives from Östhammar, Oskarshamn and Hultsfred municipalities. Finally, some conclusions that KASAM believes should be drawn from these comments are presented.

2.9.1. Östhammar and Oskarshamn – Different but Similar?

In Östhammar and Oskarshamn, different organisational models have been developed for how each municipality participates in the expanded consultation and for how each municipality follows SKB’s site investigations. In both cases, these models are

SOU 2004:67 The Municipalities – One of the Main Actors in the Nuclear Waste Issue

based on how each municipality had organised its work to follow SKB’s feasibility studies. The question is whether these different organisational solutions reflect differences in terms of each municipality’s view of how active it should be as an actor in the final disposal issue. KASAM’s perceptions are presented below.

Up to autumn 2003, the municipal politicians in Östhammar, to a greater extent that in Oskarshamn, seemed to have put their trust in the assumption that the site selection process and allocation of roles among important actors (SKB, central and regional authorities and the municipality) would function well. The municipality’s representatives acted on the basis of the assumption that it was SKB that “owned” the issue and, therefore, there was no reason for the municipality to become more active until the company presented different proposals. There was – and there still is – basic confidence in SKB among the majority of the municipal politicians. These politicians mean that the company listens closely and takes into account the views that the municipality’s representatives present in different contexts. The municipal politicians consider that the inhabitants have a good understanding of the issues and that the citizens of the municipality have considerable confidence in SKB. Furthermore, in their opinion, a large majority of the inhabitants also have confidence in their elected representatives. Taken as a whole, this has resulted in the view that the municipality should act in a “reactive” manner.

During the feasibility study phase in Oskarshamn, the prevailing approach towards SKB was more “proactive”. This was not due to a lack of basic confidence in SKB. However, the view held – and still held – by the municipal leaders is that the municipality is in a unique situation with respect to the disposal issue. The unique aspect is that spent nuclear fuel from all of the nuclear power plants since 1985 is successively being transported to the Central Interim Storage Facility for Spent Nuclear Fuel (CLAB), which is located next to Oskarshamn nuclear power plant. The municipality has been positive to the establishment of this facility for interim storage for a limited period of time,

The Municipalities – One of the Main Actors in the Nuclear Waste Issue SOU 2004:67

about 40 years. However, at the same time, the very establishment of CLAB means that the municipality has the problem inside its boundaries. When SKB, in the early 1990’s raised the question of expanding CLAB and of constructing an encapsulation plant next to CLAB, the municipal leaders reached the conclusion that they could not settle for allowing other actors to have the responsibility of reaching a satisfactory solution to the final disposal question.

From the mid-1990’s, the municipal leaders placed the question of feasibility studies high on the agenda and gave impetus to the work of establishing forms for consultation between the important actors. On the initiative of the municipality, “the EIA Forum for Studies of Final Disposal Systems for Spent Nuclear Fuel in Oskarshamn Municipality” was created. The discussions in this forum were based on the ideas behind the regulations on consultation concerning the preparation of EIS, which were successively introduced in the 1990’s. However, it was only when the Environmental Code was introduced in 1999 that a well-thought out system was created for consultation and for the preparation of EIS prior to major industrial facility siting projects.

The municipality developed its own extensive project organisation and sought to bring about the broad participation in this organisation by both elected politicians and representatives for various interest groups in the municipality. The costs were covered by funds that the Government made available from the Nuclear Waste Fund. The purpose of this project organisation was to ensure, at an early stage in the process, that different aspects of the project would actually be investigated satisfactorily. Another purpose of the project organisation was to promote and pursue different issues in the “EIA forum”. Thus, the consultations in the framework of this forum did not occur as a result of formal requirements in accordance with the regulations of the Environmental Code, not even when the Code had entered into force. However, the municipality considered that the idea behind consultation on EIS provided an

SOU 2004:67 The Municipalities – One of the Main Actors in the Nuclear Waste Issue

opportunity to be an active actor. The expression “EIA – our platform” eventually came to be one of the mottos used by the municipal representatives when describing their activities.

When SKB initiated site investigations in Forsmark and Simpevarp, the planning of the project reached such a level of implementation that the regulations of the Environmental Code on different types of consultation could be applied. An agreement has been reached with respect to new forms of consultation, co-ordinated by the two counties, to replace the previous consultation bodies at county level. These agreements show that SKB has the responsibility to conduct an expanded consultation in accordance with the Environmental Code and to obtain a basis for the EIS. Each county administrative board concerned is responsible for chairing the consultation. In the regional consultation forums participate, along with SKB, the county administrative board and the municipality, the Swedish Nuclear Power Inspectorate and the Swedish Radiation Protection Authority. There is a desire, primarily from both county administrative boards, for the discussions in both of these to be conducted somewhat in parallel and to result in similar approaches, if possible.

In Oskarshamn municipality, the type of project organisation that was established during the feasibility study phase has been kept, although it has been adapted to the issues that are now of interest (cf Section 2.6.3). Questions and proposals are directed to SKB to a significant degree. A number of working groups work intensively to penetrate different issues. The viewpoints of the groups then provide a basis for the municipality’s stance in the discussions that are continuously conducted with SKB within the framework of the “EIA forum in Oskarshamn”, which was created in 2003. Requirements are placed on SKB to conduct investigations on different issues. The work is resulting in an extensive documentation which is also made available to citizens via the municipality’s website. The fact that SKB formally “owns” the issue during the consultation phase does

The Municipalities – One of the Main Actors in the Nuclear Waste Issue SOU 2004:67

not mean that the municipality has in any way renounced its ambitions to exercise a major influence over SKB’s work.

In Östhammar municipality, less extensive preparations were initially made, compared with Oskarshamn, prior to the meetings with “the Forsmark consultation and EIA group”, which was created in 2003. Nevertheless, the municipal leaders and other elected politicians in Östhammar have shown considerable commitment to the regional consultation. However, the approach is different from Oskarshamn’s, which is something that may perhaps lie behind the wording of a previously mentioned joint press release from both municipalities in February 2004 (Section 2.4.1), where “differences … in political traditions” are mentioned.

The co-operation and common approach shared by Oskarshamn and Östhammar municipalities gives the overall impression that the similarities between both municipalities now outweigh the differences. The differences that exist are more a matter of form than content.

2.9.2. Site Selection in Certain Possible Scenarios

The strategy behind the site investigations now being conducted by SKB seems to be that the results should lead to the conclusion that one of the sites is more suitable than the other and that the company will propose the more suitable site as a site for the repository, while the other will be regarded as an alternative. Representatives from SKB have expressed the view, on different occasions, that the company will propose two sites in any event, although it will also state a preference for one of the two sites. SKB has promised that two complete site investigations will be conducted.

However, KASAM lacks – a view which has also been put forward during conversations with the municipal leaders concerned – an in-depth discussion, on SKB’s part, regarding how the company should act if the results of the ongoing site

SOU 2004:67 The Municipalities – One of the Main Actors in the Nuclear Waste Issue

investigation show that one of the two areas currently being investigated does not appear to be suitable. Questions can be raised on the basis of a number of scenarios.

Scenario 1 The Forsmark site proves not to be suitable. Should SKB then primarily conduct a site investigation within a suitable site in Östhammar municipality, possibly within the Hargshamn area, which has been identified by SKB in its study as a potential site for investigation? Or should SKB look for new site to conduct site investigations, outside the boundaries of the municipality? Perhaps in Hultsfred, where at least one site was identified during the feasibility study? Or in another part of Oskarshamn than the current site investigation (the feasibility study identified three candidate sites in Oskarshamn for investigation)? Or in another municipality with different geological conditions (cf KASAM’s statement of June 2001 on the desirability of greater geological breadth in connection with site selection for site investigations

8

)?

Scenario 2

Investigations in the Simpevarp area (“Simpevarp-Laxemar site”) show that this site is not suitable. Should SKB then, primarily focus on conducting a site investigation further west in Oskarshamn municipality, within the two other sites in the municipality identified in the feasibility study or should SKB go outside the municipality boundaries? Perhaps to Hultsfred? Or to the Hargshamn site in Östhammar municipality? Or to some other municipality with other geological conditions?

8

See pp. 14-16 of KASAM’s statement to the Government on June 14, 2001 on SKB’s

Supplement to RD&D Programme 1998 – Integrated Account of Method, Site Selection and Programme Prior to the Site Investigation Phase (RD&D Supplement).

The Municipalities – One of the Main Actors in the Nuclear Waste Issue SOU 2004:67

Scenario 3

None of the two ongoing site investigations results in the conclusion that a repository should be constructed at these sites. Should SKB, under such circumstances, primarily attempt to conduct site investigations at other sites identified in the feasibility studies in the three municipalities, Östhammar, Oskarshamn and Hultsfred? Or should some other municipality with other geological conditions be investigated?

2.9.3. Availability of the Necessary Competence at the Regulatory Authorities

One of the issues that often recurred during the conversations with the municipal representatives was the concern that the government authorities are not being given adequate resources to fulfil their task in terms of a competent regulatory review of SKB’s proposals. The municipalities take the view that they are dependent, and must be dependent, on the expertise of the regulatory authorities. Using their own expertise to review and evaluate SKB’s proposals is not possible – the municipalities and their citizens are quite simply entitled to depend on the regulatory authorities conducting a competent review and evaluation of the proposals submitted by the nuclear industry.

The concern for the availability of competence in the future does not only apply to the authorities. The municipalities also make demands on the Government, the cabinet office and ministries. The municipalities’ representatives expect that the members of the Government, to a greater extent than has been the case so far, will allocate time to be briefed on the issues before they are forced to make decisions with far-reaching consequences. As far as the cabinet office and ministries are concerned, there is considerable concern over the relatively large turnover of the few officials that handle issues relating to the final disposal of nuclear waste.

SOU 2004:67 The Municipalities – One of the Main Actors in the Nuclear Waste Issue

The review of the application for a licence to construct a repository for spent nuclear fuel and the review of the attached EIS is an important step in the decision-making process. The review aims to show that the repository can be considered to comply with the requirements on safety, that the EIS complies with the requirements of the Environmental Code and that the basis for decision-making is credible and adequate. The necessary foundation for a qualitatively adequate basis for decision-making is laid through the consultation and investigation process that SKB is now leading. Past Swedish, Nordic and international experience of decision-making processes and EIAs with respect to major and technically advanced projects indicates that there is a very great need for a quality assessment of the basis for decision-making as a whole and that this quality assessment is an important part of the decision-making process.

2.9.4. Competition between the Municipalities?

An interesting question is whether there is any type of competition between the two municipalities where the site investigations are currently underway. Does either of the municipal leaderships see the establishment of a repository for spent nuclear fuel within the municipality as something desirable – providing that they can be convinced that the safety issue has been resolved?

The chairmen of the municipal executive boards have emphasised, on different occasions, that there is no competition in the relationship between the two municipalities. However, as an outside observer, it is difficult to completely shake off the impression that there are, or could be, aspects of competition. Each of the municipal leaderships seems to be of the opinion that SKB should select a new site for investigation, primarily within their own respective municipalities, if it should be found that the sites currently under investigation are unsuitable. However, at the same time, the management groups of both

The Municipalities – One of the Main Actors in the Nuclear Waste Issue SOU 2004:67

municipalities seem firmly determined to act in such a way that SKB cannot play one municipality off against the other. According to the municipalities’ representatives, it is the requirements of principle regarding the selection of a site, in accordance with Chapter 2 of the Environmental Code, which is the determining factor.

2.9.5. Consultation under the Environmental Code

KASAM has the impression that SKB has a high level of ambition for the expanded consultation. The company is demonstrating considerable openness and will to receive and thoroughly consider the viewpoints that other consultation participants put forward. Such an attitude is probably also a prerequisite for the general public and the representatives of the municipalities concerned to have the necessary confidence in the activity. Otherwise, it would probably not be possible to realise “the nuclear waste project” within a reasonable period of time.

However, in KASAM’s view, it must be emphasised that the EIA and consultation processes are time-consuming. It is important for the high level of ambition to be sustained, even if the process takes a long time. KASAM assumes that the county administrative boards concerned feel responsible for assisting SKB – although the responsibility for an adequate consultation ultimately rests with the company. If the company, at suitable time intervals, allows an independent party to assess the quality of and to evaluate the ongoing consultation process, the possibility of sustaining the current high level of ambition will probably increase. Achieving an independent review and evaluation is also in the interests of the two site investigation municipalities.

SOU 2004:67 The Municipalities – One of the Main Actors in the Nuclear Waste Issue

2.9.6. Conclusions

The comments from the municipalities concerned, which have been reported in Sections 2.9.1-2.9.5, have led KASAM to draw the following conclusions:

  • The Government should, in good time, ensure that the competent authorities (SKI, SSI, county administrative boards etc.) have adequate resources prior to the further consultations and reviews of SKB’s applications for a repository and an encapsulation plant for spent nuclear fuel. The municipalities do not have the necessary resources to evaluate the type of comprehensive and advanced applications that are expected to be submitted on this issue. The municipalities and the Government will be completely dependent on the competence that SKB and that the regulatory authorities, primarily SKI, SSI and the county administrative boards have on this matter (Section 2.9.3).
  • There is cause for SKB to conduct a more in-depth discussion on how it should act if the results of the ongoing site investigations are not favourable, in one or both site investigation municipalities (Section 2.9.2).
  • The consultation process is a decisive factor for the EIS instrument to fulfil its purpose, both from the standpoint of the environment and democracy. The purpose of the consultations is to decide what the EIA will cover and to provide a basis for the evaluation of forthcoming licences along with EIS, safety assessments etc. In order to sustain the current high level of ambition in the expanded consultation, SKB can allow an independent party to assess the quality of and to evaluate the ongoing consultation process (Section 2.9.5).
  • In order to be successful, the ongoing consultation process, in accordance with Chapter 6 of the Environmental Code assumes a strong commitment of the municipalities involved. An active participation in the site investigation process will

The Municipalities – One of the Main Actors in the Nuclear Waste Issue SOU 2004:67

contribute to developing this commitment. Such a commitment currently exists among the municipality’s elected representatives and among the inhabitants that choose to concern themselves with these issues (Section 2.9.1).

  • A repository and an encapsulation plant will contribute to increasing employment, which is naturally of interest to the municipalities. The establishment of the nuclear power plants in Forsmark and Simpevarp between the 1960’s and 1980’s is a clear example of what the establishment of major industries can mean for the development of the municipality concerned. Therefore, it cannot be excluded that some sort of competition could arise between the municipal leaderships of Östhammar and Oskarshamn, even if they are firmly determined to act in such a way that SKB cannot play one off against the other (Section 2.9.4).

SOU 2004:67 The Municipalities – One of the Main Actors in the Nuclear Waste Issue

Sources and literature

9

Översikter

Plats för slutförvaring av kärnavfall – förstudier i åtta kommuner.

Rapport av Särskilde rådgivaren på kärnavfallsområdet, SOU 2002:46 Förstudiekommuner i dialog med allmänheten: exemplen Ny-

köping, Oskarshamn och Tierp (i Kunskapsläget på kärnavfallsområdet 2001, rapport av Statens råd för kärnavfallsfrågor, SOU 2001:35) Kärnavfall

demokrati och vetenskap. Rapport från ett

seminarium om beslutsfattande inför anläggande av ett slutförvar för använt kärnbränsle, Gimo 7

  • april 2003.

Statens råd för kärnavfallsfrågor (SOU 2004:99)

SKB:s FUD-program, granskningsyttranden och regeringsbeslut

Samlad redovisning av metod, platsval och program inför plats-

undersökningsskedet, FUD-K. SKB December 2000 (Komplettering av FUD-program 98) KASAM:s yttrande 2001-06-14 till regeringen över FUD-K

(Dnr KASAM 14/00) Regeringsbeslut 2001-11-01 (Miljödepartementet): Komplettering

av program för forskning, utveckling och demonstration för kärnavfallets behandling och slutförvaring, FUD-program 98 (Dnr M2001/2840Mk, m.m.) FUD-program 2001 Program för forskning, utveckling och demon-

stration av metoder för hantering och slutförvaring av kärnavfall. SKB September 2001

These references are only provided in Swedish. The report A site for final disposal of nuclear waste? – Feasibility studies in Eight municipalities (presented in 2002 by the Special Advisor to the Government for Nuclear Waste Disposal, SOU 2002:46) contains a more comprehensive list of references (also only in Swedish).

The Municipalities – One of the Main Actors in the Nuclear Waste Issue SOU 2004:67

Kärnavfall

forskning och teknikutveckling. KASAM:s yttrande

till regeringen över SKB:s FUD-program 2001, SOU 2002:63 Regeringsbeslut 2002-12-12 (Miljödepartementet): Program för

forskning, utveckling och demonstration av metoder för hantering och slutförvaring av kärnavfall, FUD-program 2001 (Dnr M2002/1287Mk, m.m.)

Kommuner

Östhammar:

Kommunstyrelsens, referensgruppens och beredningsgruppens proto-

koll perioden 2002

april 2004.

Muntlig information vid sammanträffande november 2003 med

kommunstyrelsens ordförande m.fl.

Oskarshamn: Kommunstyrelsens och arbetsgruppers inom ramen för projekt

Lokal Kompetensuppbyggnad protokoll perioden 2002

april

2004 jämte verksamhetsberättelser från projektet Muntlig information vid sammanträffande november 2003 med

kommunstyrelsens ordförande m.fl. Anförande av kommunstyrelsens ordförande vid Stockholm Inter-

national Conference on Geological, Repositories: Political and Technical Progess, December 7

10, 2003 in Stockholm (Pro-

ceedings finns som CD-skiva, som kan tillhandahållas av SKB).

Hultsfred: Muntlig information vid sammanträffande november 2003 med

kommunstyrelsens ordförande m.fl.

SOU 2004:67 The Municipalities – One of the Main Actors in the Nuclear Waste Issue

Diverse SKB-publikationer

Platsundersökning Oskarshamn. Årsrapporter 2002 och 2003 Platsundersökning Forsmark. Årsrapporter 2002 och 2003

Samråd

Beslut 2002-02-14 av Länsstyrelsen i Uppsala län: Anmälan för

samråd enligt 12 kap. 6 § miljöbalken (1998:808) inför platsundersökningar i Forsmark, Östhammars kommun (Dnr 2421-14060-01) Beslut 2002-12-30 av Länsstyrelsen i Uppsala län: Tidigt samråd

och fråga om betydande miljöpåverkan enligt 6 kap. 4 § miljöbalken (1998:808) inför tillståndsprövning enligt miljöbalken och lagen (1984:3) om kärnteknisk verksamhet avseende ett eventuellt djupförvar för använt kärnbränsle vid Forsmark, Östhammars kommun (Dnr 2420-6907-02) Beslut 2004-01-19 av Länsstyrelsen i Uppsala län: Tidigt samråd

och fråga om betydande miljöpåverkan enligt 6 kap. 4 § miljöbalken (1998:808) inför tillståndsprövning enligt miljöbalken och lagen (1984:3) om kärnteknisk verksamhet avseende en eventuell inkapslingsanläggning för använt kärnbränsle vid Forsmark, Östhammars kommun (Dnr 525-14371-03) Samrådsyttrande 2002-06-19 av Länsstyrelsen i Kalmar län:

Anmälan för samråd enligt 12 kap. 6 § miljöbalken (1998:808) inför platsundersökningar i Simpevarp, Oskarshamns kommun (Dnr 525-4380-02) Beslut 2003-01-10 av Länsstyrelsen i Kalmar län: Tidigt samråd

och fråga om betydande miljöpåverkan enligt 6 kap. 4 § miljöbalken (1998:808) inför tillståndsprövning enligt miljöbalken och lagen (1984:3) om kärnteknisk verksamhet avseende ett eventuellt djupförvar för använt kärnbränsle vid Simpevarp, Oskarshamns kommun (Dnr 551-6359-01) Beslut 2003-09-24 av Länsstyrelsen i Kalmar län: Tidigt samråd

och fråga om betydande miljöpåverkan enligt 6 kap. 4 § miljö-

The Municipalities – One of the Main Actors in the Nuclear Waste Issue SOU 2004:67

balken (1998:808) inför tillståndsprövning enligt miljöbalken och lagen (1984:3) om kärnteknisk verksamhet avseende en eventuell inkapslingsanläggning för använt kärnbränsle vid CLAB, Oskarshamns kommun (Dnr 551-2362-03, m.fl.) Miljökonsekvensbeskrivning och samråd för djupförvaret

SKB:s

översiktliga planering. September 2001, Rapport R-01-46 Djupförvar och inkapslingsanläggning för använt kärnbränsle.

Samråd och miljökonsekvensbeskrivning enligt miljöbalken och kärntekniklagen. November 2002, Rapport R-02-39 Omfattning, avgränsningar och utredningar för miljökonsekvens-

beskrivningar (MKB) för inkapslingsanläggning och slutförvar för använt kärnbränsle

Version 0, underlag för utökat samråd

i Forsmark. September 2003, preliminär (inget rapportnummer) Omfattning, avgränsningar och utredningar för miljökonsekvens-

beskrivningar (MKB) för inkapslingsanläggning och slutförvar för använt kärnbränsle

Version 0, underlag för utökat samråd

i Oskarshamn. September 2003, preliminär (inget rapportnummer) Protokoll Länsstyrelsens referensgrupp i fråga om en eventuell

lokalisering av ett slutförvar för använt kärnbränsle i Uppsala län 2002 Protokoll Samråds- och MKB-grupp Forsmark 2003

januari

2004 Protokoll MKB-forum för studier av slutförvarssystem för använt kärnbränsle i Oskarshamns kommun 2002

2003

Forskningsrapporter

Bjarnadottir, Homfridur and Hilding-Rydevik, Tuija, Final

disposal of spent nuclear fuel in Sweden. Some unresolved issues and challenges in the design and implementation of the forthcoming planning and EIA-process. June 2001, SKI Report 01:24

Section II Handling the Risks of Nuclear Waste. An Overview of

Methods, Problems and Possibilities

3. Some Geological, Geodynamic and Geophysical Investigation Methods Used for the Siting of a Repository in Hard Rock

3.1. Introduction

The purpose of this chapter is to

  • Provide an overview of important geoscientific investigation methods,
  • Through a critical review, show whether one or more investigation stages or important information is missing in connection with site selection and whether additional investigation methods may have to be developed for the future siting work or in the forthcoming detailed characterisation phase for a repository for spent nuclear fuel.

This review will focus on geological, geodynamic and geophysical investigation methods that are considered to be of particular importance. A systematic review of evaluation methodology and modelling is not included. Furthermore, investigation methods based on Quaternary geology and pure chemical methods are not included in this review.

An important requirement in physical planning today and in the future is that the siting, engineering design and construction of facilities in rock, for example, for the disposal of spent nuclear fuel, should be performed in an environmentally sound and safe manner. This requires comprehensive and accurate information on the properties of the rock. Knowledge is also necessary to

Some Geological, Geodynamic and Geophysical Investigation … SOU 2004:67

ensure an optimum design is achieved and that the construction work can be conducted in a manner that is technically and economically adequate, taking into account the environment and safety. The facility must be able to perform as intended throughout its envisaged “lifetime”, namely, for about 100,000 years in the case of a repository for spent nuclear fuel.

The primary task of the rock in a repository for radioactive waste is to ensure stable mechanical, hydraulic and chemical conditions that are favourable to the durability of the canister and clay barrier. Leaching of radionuclides from the spent fuel must be prevented and delayed as far as possible. The siting of a deep repository in suitable bedrock that fulfils these mechanical and chemical conditions is therefore crucial. To be able to evaluate mechanical stability, knowledge must be acquired of the bedrock and of its ancient and most recent geological history. In order to evaluate the chemical stability, knowledge of existing natural conditions and of the substances in the water that affect the stability of the buffer and canister. Furthermore, knowledge is required of the parameters that affect the evolution of water chemistry such as different groundwater types and their origin and of important reactive processes in the bedrock, in the soil cover and in the biosphere. Geological methodology, in the broad sense of the term, is therefore necessary in order to site the repository in a location that meets the safety objectives.

In the report Site Investigations Investigation Methods and General Execution Programme TR-01-29 (SKB 2001), a system is described for collecting information on geoscientific conditions during different phases of the site selection work. An overview is provided with a flow chart for soils, rock type distribution, structure, hydrology and geochemistry.

The mapping approach involves direct geological investigation methods, such as observations on exposed rock surfaces (outcrops), excavation and drilling. These methods are highly limited in the vertical direction and the investigation depth cannot be greater than the drilling depth. Problems also occur in the horizontal direction when observations from scattered drill

SOU 2004:67 Some Geological, Geodynamic and Geophysical Investigation …

holes must be linked. Fracture zones are often associated with movements in the Earth’s crust. These displacement zones have been active during different geological periods. It can be assumed that individual zones are also active today. A characteristic of displacement zones is the patterns that can be seen in different types of data and which have arisen from intensive and lengthy shearing between large blocks of the Earth’s crust.

The direct or indirect methods used to describe the geology are static in the sense that the conditions and properties of the bedrock are characterised in the present time. The dynamic aspect of geology, namely the evolution over time, requires geodynamic investigation methods in order to observe changes in specific natural reference structures or reference systems that are established for this purpose. This is of particular importance in the Swedish geological environment with very young sedimenttary deposits (soils) that were formed during and after the ice age, directly on top of very old crystalline bedrock types, which were formed over one billion years ago. The geological evolution, as can be seen in the soils, therefore encompasses a very short timescale (a few ten thousands of years at most) while the evolution that can be seen in the crystalline basement occurred an extremely long time ago. In spite of the fact that the soil stratification only contains traces from a short geological timeperiod, it is the only medium in which recent geological evolution can be observed. In order to predict the geological evolution during the lifetime of a planned nuclear waste repository, the geodynamic investigations must cover a timescale that is sufficiently long. For such studies, more tools exist today than were available when the question of nuclear waste disposal in bedrock was first discussed.

Due to erosion, fracture zones are mostly located in soilcovered depressions in the terrain and are therefore difficult to access for direct observations. Furthermore, the displacement indicators that can sometimes be observed are often very old and indicate the characteristics of the zone under completely different conditions than those that currently exist. Therefore,

Some Geological, Geodynamic and Geophysical Investigation … SOU 2004:67

indirect mapping must also be made, based on the interpretation of aerial photography and geophysical investigation methods. These methods are sensitive to contrasts in physical properties which characterise the transition from soil to rock or from one rock mass to another, such as in a fracture zone, but are also related to different water contents and water chemistry. Under favourable circumstances, the geophysical methods provide a systematic depth penetration, down to a depth of several kilometres, which is considerably deeper than can usually be achieved by direct observation. Furthermore, they reflect characteristics in conditions that are undisturbed by the investigation. The mapping methods for fracture zones also include the analysis of digital elevation data and aerial photographs. The bedrock in fracture zones is often disintegrated and can therefore be dispersed by weathering or be easily removed (for example by glacial erosion during an ice age) compared with unaffected bedrock. Depressions in the terrain and topographical escarpments can therefore represent the visible traces of fracture zones and they should be investigated by geophysical measurements in order to confirm whether the extent is significant.

However, there is a difference with respect to what geophysics and geology represent. Both approaches are applied to observe the same material in the same state and at the same time. However, each investigation method is limited to what can actually be measured although this is not necessarily what needs to be measured. Measurements require an analysis by which measurement values are transferred to models. These models are characterised by existing concepts, desired results and, above all, by assumptions concerning what it has not been possible to measure.

SOU 2004:67 Some Geological, Geodynamic and Geophysical Investigation …

3.2. Geological Methods

3.2.1. Structural and Rock Mechanical Studies

The mechanical stability of the rock types is determined by the different mineral components and by the structural-geological history of the region. Rock structure can be plastic (for example, folding and foliation) or brittle (for example, joints, faults and crushed zones) (Berglund and Stigh 1998). These phenomena are usually included in the concept of tectonics and are a result of the geological evolution of the bedrock and of the original composition of the tectonically deformed material. Tectonic impact is therefore important from a repository perspective and the fracture pattern of the bedrock determines the ultimate design of the repository.

Studies of block tectonic patterns in areas of crystalline bedrock show that two types of bedrock blocks are common. Shear lenses are delimited by meandering shear zones and are formed in connection with horizontal block movements at depth. Figures 3.1 and 3.2 show examples of lens-formed bedrock blocks. It is typical to find a meandering sequence of individual zones connected in a network with shear lenses located in between. The entire network can be hundreds of kilometres long and several tens of kilometres wide.

In addition more regular block patterns occur in the uppermost part of the Earth’s crust due to the proximity to the free ground surface. Plinths are bordered by straight lineaments and are formed by fracturing and block movements in the uppermost part of the Earth’s crust (an example of such blocks is shown in Figure 3.4). The analysis of seismic surface waves shows that the uppermost 1-2 kilometres of the crystalline crust has a lower seismic wave velocity, which can be explained by the occurrence of fractured and crushed zones (Åström & Lund, 1994). These patterns often overprint older deformations (for example, foliation and folding). The overprint can be discordant (cutting through older directions) although in large fracture

Some Geological, Geodynamic and Geophysical Investigation … SOU 2004:67

zones, the new movements preferably follow the older zones of weakness in the crust. This causes a very complicated pattern which is also difficult to observe in the field since these parts of the zones that are most crushed have been eroded.

It is also difficult to drill through these zones and to obtain a sufficient number of drill cores to study the movement patterns in detail since crushed parts of the rock often result in drill core losses. The better-preserved parts of a shear zone are relatively older and the reference structures, which can be used to determine the movement are normally very old.

SOU 2004:67 Some Geological, Geodynamic and Geophysical Investigation …

Figure 3.1. Part of the topographic map of northeastern Uppland. The topographically visible Forsmark lens has been interpreted from elevation data. The lens is down-warped in the terrain and goes diagonally across the map view. The clear transverse step in the terrain in the middle of the lens is supposedly a fault with the southeastern block down-faulted. The Forsmark lens is 10 km long and 2 km wide (from Terrängkartan ©, Lantmäteriet Gävle 2004, permission M 2004/3790).

The mapping of major fracture zones, shear zones and block shapes is conducted mainly by interpretation of digital elevation data and gravity, aeromagnetic, aero-VLF (Very Low Frequency) data. The mapping can be done, both on a regional scale and on a local scale. For small areas, the resolution is increased by the measurements in grids with a 10 or 20-metre point distance. In good conditions, such data allows the dip of the individual zones

Some Geological, Geodynamic and Geophysical Investigation … SOU 2004:67

and the accumulated displacement with time and the direction of the block movements to be calculated.

Figure 3.2. Part of the aeromagnetic map of the inner part of Norrbotten. Shear zones are visible as low magnetic (light red) zones. The Murjek lens in the western part of the map area is interpreted from magnetic data. The transverse low magnetic zone in the middle of the lens is most likely a fault with the southeastern block thrusted over the northwestern block. The Murjek lens is 25 km long and 7 km wide (aeromagnetic measurement, data from Sveriges Geologiska Undersökning, (SGU), permission 30-915/ 2004).

SOU 2004:67 Some Geological, Geodynamic and Geophysical Investigation …

Facts Fracture zone

  • region (1 m – 10 km) through the bedrock with a large frequency of fractures (0.1 mm – 0.1 m), Crush zone – region with crushed rock caused by strong deformation, Shear zone – region in bedrock (1 m – 20 km) with intense deformation caused by shearing, Movement zone (fault zone) – region in the bedrock where rock blocks have been dislocated, Shear lens rock block surrounded by shear zones, Plinth – rock block surrounded by straight lineaments.

Facts Movement zones in the bedrock described with respect to the relative displacement of blocks in the vertical and or in the horizontal direction: Normal fault – one block is down-faulted, Reverse fault – one block is pushed over the other, Thrust – reverse fault at low angle with the horizontal plane, Horizontal fault (strike-slip fault) – the opposite block has moved to the right (dextral) or to the left (sinistral).

Deformation zones around a rock body (a tectonic lens) can cause the tectonic lens to be less deformed than the surrounding bedrock and future deformation can be taken up in these zones. This requires a major difference in the deformability (competence) of the material in and around the lens. However, in crystalline bedrock, there is usually not a great difference in competence. With further deformation in the surrounding movement zones, the lens can become compressed or pulled apart with a risk of fragmentation. Figures 3.1 and 3.2 show examples of lenses that have been intersected by fault zones. In certain cases, the lens can be favourable as a repository site if its vertical and horizontal range is adequate. However, rock stresses in such a tectonic lens can be high and this is a disadvantage

Some Geological, Geodynamic and Geophysical Investigation … SOU 2004:67

from the siting perspective. Rock stress measurements are performed to investigate these stresses. Geodetic observation networks make it possible to determine the way in which the zones around the lens are active.

The orientation of stress in the bedrock in three dimensions (the stress field) can be calculated from registrations of major earthquakes and from measuring the shapes in deep boreholes. There is a considerable difference in depth between earthquakes (usually, deeper than 10 km) and drill hole data (usually less than 2 km deep). The results from such investigations have been compiled in a Neotectonic Map of Norway and Adjacent Areas (Dehls et al. 2000). The orientation of the stress field in Norway is different in coastal areas compared with inland areas. Blocks that have a similar stress field have a lateral length of about 250 km. This segmentation follows the coast and the large-scale morphology and the extension towards the northwest of major shear zones with a southeast-northwest orientation. In Sweden, a horizontal principal stress dominates in the southeastnorthwest orientation although local deviations occur both horizontally and vertically (Amadei & Stephansson 1997). This orientation is suggested to be related to the pressure from the Mid-Atlantic spreading zone where the North American lithosphere plate separates from the Eurasian plate by about 2 cm per year. There is probably a similar segmentation in large present-day tectonic blocks in Sweden as in Norway. However, data from major earthquakes, which can be used to map this segmentation is lacking. Knowledge of the natural orientation of the stress field is decisive for forecasts of the tectonic evolution in an investigation area. In addition to the natural stress field, rock stresses will occur due to the repository itself and the increase in temperature around the repository that is generated by the radioactive waste. The long-term impact of the natural stress field on the site investigation areas should therefore be modelled together with the induced stress fields that arise as a result of the repository.

SOU 2004:67 Some Geological, Geodynamic and Geophysical Investigation …

3.2.2. Drilling Methods, Borehole Measurements and Drillcore Analysis

The investigation of the properties of the bedrock is made by studying the available outcrops of the rock, with geophysical investigations and drilling. Normal hammer and core drilling is used for investigations in crystalline bedrock. Hammer drilling is carried out using bits with a diameter from 45 to 86 mm. The drilled rock is washed out of the borehole by air or water. The drilling process is logged and a diagram of the sinking of the drill hole is made. The diagram does not provide unambiguous information about the rock quality, especially when the rock is weathered or fragmented. Core drilling is made with rotation drilling and water flushing. The core drilling allows cylindrical drill cores to be recovered from the rock. Mineralogical and petrographical investigations are conducted at the site and on samples and microscope specimens (thin sections prepared by grinding and polishing) in the laboratory. More detailed studies of isotopes, physical properties and mineral composition are made on material from the drill cores. For projects in hard rock at depths greater than a couple of hundred meters, core drilling is the only drilling method used. Results from drill core mapping allow the fracture density of the bedrock to be estimated in several different ways.

The drill hole walls can be examined by TV camera. The camera can be lowered to great depth into water-filled holes. Several methods of measuring different conditions in boreholes are performed with borehole logging methods developed by various prospecting companies.

3.2.3. Rock Mechanics Testing and Rock Materials Testing

It is important to differentiate between rock types at a certain site or in a restricted area and the surrounding bedrock as a whole when the mechanical strength properties of the rock are

Some Geological, Geodynamic and Geophysical Investigation … SOU 2004:67

analysed. The dimension of a rock sample or a small rock volume that is investigated has a considerable impact on the analysis results. The mechanical strength values for a large rock volume may be one-hundredth or less of the corresponding value of a small rock sample. When determining the mechanical strength values, existing stresses and moisture contents as well as the time-dependency that is so vital for deformation must be taken into account (Janelid 1965). Rock engineering leads to changes in stress, which can be of decisive importance for the stability in the short and long term. It is vital to know the state of stress of the undisturbed rock for planning activities. In order to achieve stability in the long term, the changes in stress and deformations that occur in connection with the construction of the repository must also be taken into account. If the factors that from a rock mechanical point of view affect planning are known, the influence of these factors must be determined, by measurements and modelling. The determination of the uni-axial compressive strength of the rock can be tested in the field on drill cores by uni-axial compression tests where the sample is pressed against a blade until a crack occurs (Andersson et al. 1984). Laboratories can also test the compressive strength under different load conditions (uni-axial, biaxial and tri-axial), different moisture contents and temperatures. The time factor is of importance since the deformation and creep properties of the rock are of decisive importance for the long-term stability. The stress state of the rock can be determined by analysis of major earthquakes, deformation measurements in large rock volumes or in drill holes. Measurement cells of different designs – from compliant deformation measuring cells (strain gauges) to stiff stress measuring – can be used for this purpose. Modelling can provide invaluable information for planning, for example, by optical stress investigations and load testing on scaled models under known or assumed conditions.

A field method for the determination of the stress state in the bedrock is hydraulic fracturing which is based on the measurement of the pressure that is required to create new or

SOU 2004:67 Some Geological, Geodynamic and Geophysical Investigation …

reactivate existing fractures. The orientation of the stress field is obtained from an investigation of the orientation of the fractures, which have been activated. In a recently conducted fracturing test in highly fractured crystalline bedrock at the Björkö island in Lake Mälaren, the horizontal stress field was less than previously found in crystalline bedrock areas in Sweden. The largest horizontal principal stress was in the northwestern-southeastern orientation, which is in agreement with other investigations (Ask 2003). Experiments show that the stress field has a local variation, which has also been noted in connection with the classification into tectonic blocks, based on earthquake analysis.

The bedrock characteristics are different in different directions. It is inhomogeneous with discontinuities. The rock varies from hard, massive rock types to rock types that have been weakened by different geological processes and by blasting. The characteristics of some rock material vary from being almost elastic to plastic. In view of this, statistic data must be obtained that is as representative as possible. The mathematical treatment of rock mechanical problems does not only include static stresses and related mechanical strength problems but also dynamic stresses which the rock takes up in connection with different types of deformations (Janelid 1965). If the mechanical strength and stability of the rock is initially inadequate, a certain improvement can be achieved by grouting, rock bolting and concrete injection.

3.2.4. Dating and Evolution Studies

With modern dating, important geological events can be dated. The crystallisation ages of magmatic rock types and the age of metamorphic events can be determined by measurement of isotopes from radioactive decay chains, such as uranium-lead. Zirconium is a suitable mineral for age determination, since it often has a core (which represents the crystallisation age) and an

Some Geological, Geodynamic and Geophysical Investigation … SOU 2004:67

accretion zone around this core (which represents the metamorphic age).

By studying the formation sequence of fracture minerals, a relative age distribution can be obtained (Figure 3.3). It is also possible to determine the absolute age of certain fracture minerals with the help of radioactive isotopes and thereby increase the understanding of the tectonic evolution of the area. It is also possible to derive the pressure and temperature conditions under which the fracture minerals have crystallised.

The datable minerals are often considerably older than the intended repository lifetime. Processes that have occurred over the past 100,000 years do not leave any clear measurable traces in the materials that can be investigated. This condition underlines the importance of using geophysical and geodynamic observation networks in connection with site selection and of ensuring that more attention is paid to the youngest geological formations.

SOU 2004:67 Some Geological, Geodynamic and Geophysical Investigation …

Figure 3.3. Example of relative ages of healed fractures. (micro photograph). The thin section shows three different fracture minerals. The first generation (prehnite) is broken and the new fractures are filled with the mineral magnesium chlorite (Mg-chl). The youngest generation with iron chlorite (Fe-chl) as fracture fill mineral cuts the older patterns.

3.3. Geodynamic Methods

Geodynamic processes are reflected in changes in the large-scale topography, the occurrence of land uplift, earthquakes and fault zones. The mapping of the range and intensity of geodynamic processes requires observations of deformations in reference structures or in grids over a longer timescale. However, currently, no measurement data are available which can determine the changes in large-scale topography. In order to

Some Geological, Geodynamic and Geophysical Investigation … SOU 2004:67

achieve these, observations of the land surface and sea bottom changes over long timescales are required, probably for a several decades. Such observations are made in geodetic networks which are nationwide and where continuous measurements in comparison with satellites in the Global Positioning System (GPS) are applied. Information about land rise is also nowadays obtained with the same measurement system. Small-scale topography (for example elevated or depressed shear lenses) can indicate geodynamic processes. To study such changes, local geodetic GPS networks must be set up.

The brittle upper part of the Earth’s crust is dissected by zones of movement. When adjacent bedrock blocks are displaced, this is referred to as a fault (see Berglund & Stigh 1998). Some of these zones were active just after the deglaciation. However, the movement must have displaced a datable geological structure, for example, an esker or a moraine ridge, a measurable distance in order to be able to observe the movement.

The major deformation zones are characterised by deviant topography, deviant land uplift, and the occurrence of earthquakes and systematic displacements of large blocks in the lithosphere. These different characteristics and how they can be studied are treated in greater detail in an appendix on geodynamic processes.

3.3.1. Measurement of the Change in Gravity

Gravity can be measured with very great accuracy. By repeated measurements at the same sites, slow changes in gravity over time can be studied. The national land surveys in Norway, Sweden and Finland co-operate with measurements that follow the 63

rd

latitude (Ekman & Mäkinen 1996). The change in

gravity is caused by the rising land surface and by the redistribution of masses that occurs at the same time in the lithosphere. This mass flow is controlled by the processes that

SOU 2004:67 Some Geological, Geodynamic and Geophysical Investigation …

operate. Measurements of both the land uplift and the change in gravity is an example of how it is possible to acquire better knowledge of geodynamic conditions with several independent methods.

3.3.2. Geodetic Networks

With the Global Positioning System (GPS), positions can accurately be determined in three dimensions. The system is therefore used in networks with GPS stations that register data continuously. If this is conducted over a long period, it is possible to determine how the site with the station has moved (relative to a reference point) due to various geodynamic processes. When the movements of the entire lithosphere plate are excluded from the data set, the differential movements caused by more local displacements can be studied. In Sweden, such a GPS network with 25 stations has been in operation since 1993. Measurement data are compiled at the Onsala Space Observatory. Co-operation is also in progress with nearby Norwegian and Finnish networks. The locations of the stations are determined taking into account land surveying applications. Certain areas may need to be supplemented (for example the Lake Vänern subsidence region and Kvarken) in order to make these data useful for geological applications.

GPS networks can also be designed for local surveys in order to monitor the movement of suspected fault zones or to study how individual tectonic blocks move in three dimensions in, for example, the Oskarshamn region (Figure 3.4). The measurement points must then be located on outcropping rock based on a tectonic analysis of the area. Furthermore, the measurement points must be designed so that the antennae can be placed on the point in a unique way (vertically and horizontally) and so that a large part of the horizon is visible. Values are registered for more than about 24 hours. Such local networks exist in Scania (about 50 km between the points), Norrbotten (over a

Some Geological, Geodynamic and Geophysical Investigation … SOU 2004:67

number of shear zones with a distance of a few km between the points) and in the Stockholm area (with 3 points in a number of well-defined tectonic blocks). Personnel from the Royal Institute of Technology (KTH) measure them at intervals of a few years. The results that have been obtained so far are only preliminary. The large data sets mean that special computer codes must be used for the analysis and this is expensive. It is important to maintain the networks and to conduct measurements for as long a time period as possible in order to ensure that clear results are obtained. Figure 3.5 shows the layout of a local GPS network. Figure 3.6 shows the national GPS network, SWEPOS, and the change in the Scandinavian land surface.

Figure 3.4. The detailed GPS network in the Oskarshamn region for determination of block movements. The observation points have been given shortened place names. Fault zones are marked with a thick line. Arrows mark the displacement velocity in mm per year that have occurred during the observation period (from Sjöberg et al. 2002).

SOU 2004:67 Some Geological, Geodynamic and Geophysical Investigation …

Figure 3.5. Block movements along a shear zone result in the formation of shear lenses. During compression (when the upper block is displaced towards the left), the free ground surface is elevated and during tension (when the upper block is displaced to the left), it is down-warped. The diagonal fracture is a normal fault in tension and a reverse fault in compression. The diagram also shows how a local GPS network can be designed across a shear zone and a shear lens. With three observation points (small squares) in every tectonic unit, the rotation and displacement in three dimensions can be calculated. With one observation point in every unit, only the horizontal movement relative to an external point can be determined.

Some Geological, Geodynamic and Geophysical Investigation … SOU 2004:67

Figure 3.6. Change of the land surface derived from the GPS network SWEPOS in Sweden and Finland. The map shows the land rise with coloured contour intervals. Arrows indicate the lateral direction and the velocity of movement of the different GPS stations. (The ellipses mark the uncertainty range). With longer observation time a gradually more precise determination of the pattern of movement is obtained. (Scherneck et al. 2002).

SOU 2004:67 Some Geological, Geodynamic and Geophysical Investigation …

3.3.3. Seismic Networks

Earthquakes occur when the Earth’s crust is broken up by the sudden release of stress that has built up for a long period of time. Such stresses accumulate due to differential movement between crustal blocks along shear zones. The earthquakes are registered in national networks with seismograph stations.

In Sweden, a sparse network with seismograph stations has existed for a long time. These stations have mostly been used to register and analyse major earthquakes, which have occurred at remote sites. At the same time, the considerably smaller earthquakes in Scandinavia have also been registered. The long observation period means that there is an extensive catalogue of Swedish earthquakes to analyse. Furthermore, old observations exist which have been compiled from historical sources. This material shows that earthquakes in Sweden occur in two distinct areas: Lake Vänern depression and along the Swedish coast of the Bothnian Sea and Bay (especially around Luleå). During a few time-periods, seismograph networks have been established in small regions and a network in the coastal area of Norrland is currently being operated. From the registered data from these various sources, important information has been obtained concerning the position of the earthquakes in the crust and, in the case of large earthquakes, the orientation of the movement surface and stress field as well as the size and direction of the displacement. Seismic observation networks can, like GPS networks, be designed on a more local scale to monitor motions in the bedrock. A new seismic network has been established in 2000 focusing on the shore region of the Bothnian Sea and Bay, SNSN (2003), Figure 3.7. So far, over 1,000 earthquakes were registered in this network. A seismic observation network was previously located around the seismically active Lake Vänern depression. It is important to make the seismic observation network comprehensive and to ensure that the co-operation between adjacent countries is further developed. Together with

Some Geological, Geodynamic and Geophysical Investigation … SOU 2004:67

GPS networks, seismic networks are the only tools for monitoring the effects of the ongoing geodynamic processes.

Figure 3.7. The Swedish National Seismic Network (SNSN). The squares indicate geophone stations. (SNSN, Uppsala University, Department of Earth Sciences).

3.4. Geophysical Methods

3.4.1. Problems and Objectives

Knowledge of deep conditions, without having to excavate or drill down to the area of interest, is necessary in order to solve a geological investigation problem. This can be achieved by the use

SOU 2004:67 Some Geological, Geodynamic and Geophysical Investigation …

of geophysical methods, which can indirectly provide such knowledge. The purpose of geophysical investigation methods is therefore to conduct systematic measurements of the conditions that cannot be directly observed, to present results in an informative manner and, guided by the measurement results, to construct models of the geological situation. Geophysical measurements are very accurate. However, the measurement results do not always have a unique geological cause, which leads to uncertainty in interpretation and modelling. For a calculated model to be able to reflect reality, several independent measurement data most often have to be combined in the same model. For this reason, several geophysical methods should be combined in an investigation to limit the interpretation alternatives. Furthermore, the physical characteristics of the geomaterials should be measured and used as boundary conditions for modelling. Boreholes and borehole investigations should be planned so that they can be used to calibrate and verify the models that have been created. In SKB (2001), the use of geophysical methods for site investigations has been indicated on the different flow diagrams. During the analysis stage, different structures are qualitatively and quantitatively determined. A quantitative determination should contain measures of a structure’s horizontal and vertical extension.

3.4.2. Processing and Presentation of Geophysical Data

During the last decade, considerable progress has been made in geophysics, primarily with respect to data processing and presentation. Measurement data from the different methods are treated with different forms of modelling techniques. Inverse modelling is often used, which means that the subsurface structure and characteristics are theoretically varied until they agree with the data obtained. A number of computer codes have been developed for these purposes. Ground penetration radar technology uses advanced signal processing. Even if data from

Some Geological, Geodynamic and Geophysical Investigation … SOU 2004:67

several different methods are currently often combined, a method for co-processing is lacking. In certain cases, methods involving neural networks have been tested for these purposes.

Geographic Information Technology (GIT) has developed rapidly and is now a standard tool for the analysis of complex geoscientific data. Several Geographical Information Systems (GIS) are available on the market and they can now be run on PCs, as can 3D presentation programs such as CAD programs. The major breakthrough is due to the development of computer capacity, advanced visualisation technology and a multitude of tools for a combination of data, calculations and analyses as well as methods for decision support. Large data sets can be stored on CDs/DVDs. The increased 3D capacity means that data from, for example, borehole investigations, can be illustrated in three dimensions. It is of interest to present repeated or continuous geophysical measurements and take into account the time factor. Such 4D processing and presentation can be used in monitoring programs during the construction and operation stages to study the groundwater conditions and thermal conditions. It can also be used during the pre-investigation stage, for example, to study groundwater changes in heterogeneous environments during hydraulic testing or for the analysis of tracer experiments.

For model calculations, there is a need for knowledge of the physical properties, (i.e. petrophysics) of the geological materials (minerals, soils and rock types). The importance of knowledge of petrophysics is described by the following simplified formula for the relationship between measurement (anomaly A), cause (volume and orientation V, O), distance (d) as well as the contrast in the petrophysical property (K):

A = (1 / d) K f (V, O)

The measurement of A is determined by traditional geophysics and the description of volume and orientation by traditional geology. The relationship also includes a distance-dependent

SOU 2004:67 Some Geological, Geodynamic and Geophysical Investigation …

factor (1/d) which shows another typical condition in geophysics, namely the anomaly’s or signal’s decrease with increasing distance. The relationship shows that if the distance is great and the volume small, the anomaly will rapidly become so small that it can no longer be measured. The petrophysical contrast, K, is included in the relationship as a factor of great importance. The function of f of volume and orientation is not analytical and must therefore be approximated with mathematical methods.

Facts The connection between geophysical method and characteristic property in crystalline rock: Gravity – density – varies from 2.5 to 3.3 Mgm

-3

,

Magnetic field – magnetic susceptibility – varies from 10

-6

to 10 SI,

Seismic – velocity of sound waves – varies from 5 to 8 kms

-1

,

Radar – dielectric property – varies from 1 to 80, Gamma radiation – radioactive decay of uranium, potassium or thorium, VES, VLF, slingram, MT, VLF-R – electric resistivity – varies from 10 to 10

5

Ωm,

IP (Induced Polarisation) – chargeability – varies from 0 to 20 %.

3.4.3. Measurements of the Physical Properties of Rock and Soil Materials

The physical properties of geological materials must be known in order to make it possible to interpret geophysical measurements. The measurements can be conducted in situ, directly on the soil or rock type, although in many cases, they are based on samples taken from the geological material. Such sampling must be based on statistical principles, which means that the number of samples is in relation to the variance of the property. It is not enough to have a single representative sample. The sampling of the bedrock is best done on rock cuts or drill cores to avoid the effects of weathering which affect the characteristics of the near surface.

Some Geological, Geodynamic and Geophysical Investigation … SOU 2004:67

The characteristics that are of interest to study relate to the geophysical method that will be used. Furthermore, the selection of a method is dependent on the geological question to be investigated. A short description of some important petrophysical parameters, the units in which they are expressed and how they can be determined, are presented below.

The density of geological materials is dependent on the mineral composition and porosity. The density of composite geological material is the sum of the densities of the components in proportion to their quantities. The density is determined by weighing and determining the volume of samples of the material or indirectly, by borehole logging. Knowledge of the density of the geological materials is required in order to calculate geological models based on gravity measurements. The unit for density is Mgm

-3

.

The magnetisation of geological materials is the sum of induced magnetisation and the material’s permanent magnetisation. It is also dependent on the occurrence of highly magnetic minerals. In Swedish crystalline bedrock, this mineral is usually magnetite and, in certain areas, pyrrhotite. The induced magnetisation is dependent on the magnetic susceptibility of the geomaterial and the intensity of the local geomagnetic field. The magnetic susceptibility can be measured directly on the geological materials in situ while the determination of permanent magnetisation requires sampling in the field and measurements in the laboratory. The calculation of geological models based on magnetic measurements requires knowledge of the combined magnetisation of the involved materials. Magnetic susceptibility is a dimensionless property and can be expressed as µSI.

The electrical conductivity (or the inverse – electrical resistivity) of geomaterials depends on the occurrence of electrically conductive minerals (graphite, magnetite and sulphides) and porosity (and the water that fills the pores). The conductivity can be measured in situ using electromagnetic or electrical methods, on drill cores or in boreholes with different types of logging. The interpretation of geophysical models based on

SOU 2004:67 Some Geological, Geodynamic and Geophysical Investigation …

electrical or electromagnetic measurements requires knowledge of the electrical conductivity of the materials. The resistivity is expressed in Ωm.

Geological materials can be electrically charged and this ability to be polarised is dependent on the occurrence of the electrically conductive minerals graphite, magnetite and sulphides. The induced polarisation can be measured in the field on drill cores or in boreholes with logging. It is an important method for determining the occurrence of electrically conductive minerals in the near field of the measurement and is therefore used in ore prospecting. The polarisation is dimensionless and is expressed as a percentage.

The capacitance per metre of different materials is called the dielectric constant (also called permittivity). It is important for the analysis of electromagnetic measurements in radiofrequency ranges and is to a large degree controlled by the water content of different geomaterials. The dielectric constant is often specified as relative to the conditions in a vacuum and is therefore dimensionless.

The velocity of propagation of electromagnetic waves varies with different geomaterials. Knowledge of this velocity is necessary in order to analyse radar measurements. Above all, it is dependent on the occurrence of water in the geomaterials.

The velocity of propagation of sound waves varies with different geomaterials. It can be measured directly in the field or in drill cores. There is a positive correlation between seismic wave velocity and density. The difference in wave velocity between crustal rock types and the upper mantle is so great that it is used as a criterion for the boundary between the crust and the mantle. Knowledge of seismic wave velocity is necessary in order to analyse seismic recordings. The unit used is ms

-1

.

The thermal properties comprise heat production, thermal capacity and thermal conductivity. Crustal heat production is considerable due to the decay of naturally radioactive isotopes. This heat production varies from 2 to 20 µWm

-3

.

Some Geological, Geodynamic and Geophysical Investigation … SOU 2004:67

Different geomaterials also have different thermal conductivity. This, and the crustal heat production and the heat flux from the mantle, determine how the temperature increases with depth in the upper crust. The heat flux from the mantle is about 60 mWm

-2

and the temperature gradient in crystalline rock is

15-20 Kkm

-1

. Areas with sedimentary rocks have a somewhat higher temperature gradient (the sediments function as insulation) and areas with bedrock rich in quartz have a somewhat lower temperature gradient due to differences in heat conductivity. Knowledge of the heat conductivity of geomaterials is important for forecasting the propagation of the temperature pulse that occurs during the storage of spent, but still radioactive, nuclear fuel. The thermal capacity indicates how much thermal energy can be stored in a material in order to obtain a certain temperature increase. Water has a high thermal capacity, which is therefore much greater in water-saturated soils than in crystalline rock. This knowledge is important for the modelling of the thermal conditions surrounding the nuclear fuel and for the modelling of the temperature exchange with the biosphere. The thermal capacity is expressed as WK

-1

m

-3

.

The gamma radiation emitted from the ground depends on the content of radioactive minerals, with the components uranium, thorium and potassium. The content of radioactive minerals varies with the formation and age of the rock types. Measurements can be made from the air, on the ground, in boreholes or directly on samples. The radiation is often expressed as the calculated quantity (in ppm for uranium and thorium and as a percentage for potassium) of the different isotopes at the ground surface.

3.4.4. Strategies in Site Selection

Geophysical investigations for site selection start with an analysis of the site in question in relation to regional geological

SOU 2004:67 Some Geological, Geodynamic and Geophysical Investigation …

structures. At this stage, literature studies and map information that cover a large part of the country are required. The sites in relation to areas where geodynamic processes (see appendix on geodynamic processes) can be expected to affect the crust are an equally important and early part of site selection. In order to obtain knowledge of these conditions, geodetic and seismic observation networks are established in and around the area. Since it takes a long time to obtain data on changes, the networks should be set up at an early stage.

In the next step, the local conditions of the area are investigated, with the help of geological and geophysical mapping based on the databases (for example, airborne geophysical measurements), which already exist, and by supplementary investigations on the ground and from the air. At this stage, a large enough environment must be taken into account and the petrophysical properties of rock and soil material must be mapped. The extension of the investigation area must be at least 3 times as large as the extent of the area of interest in different directions. This means that an area that is about 10 times greater than a candidate site should be investigated with relevant measurements in order to understand the structural context of the area in relation to its environment.

Important structures are identified and followed up by more detailed ground geophysical measurements in a grid or in profiles. The methods for studying the bedrock are selected from among those that have suitable depth penetration and can cover the supposed investigation depth with a good margin. The methods to study the soil cover and the location of the upper surface of the bedrock beneath the soil cover are selected among those methods that have less depth resolution, see Table 3.1.

Based on these data, investigation drilling is ultimately required in order to do measurements and sampling in the boreholes. The depth of at least one borehole must extend into the saline groundwater region in order to enable the calibration of the electromagnetic methods used to map the transition to saline groundwater. When structures that are important for the

Some Geological, Geodynamic and Geophysical Investigation … SOU 2004:67

stability of the area have been mapped, calculations are conducted of how displacement zones and the rock in between are affected by continued geodynamics and changes in rock stresses. Knowledge from geodetic and seismic observation networks and the existing rock stresses is necessary for these calculations.

The characterisation of soil types and the shape of the rock surface are important input parameters for the study of groundwater flows and groundwater recharge. Therefore, the methods that are applied for site selection cover a wide spectrum and it is an advantage if several methods are used in order to limit the possible interpretations. The selection of methods is also determined by the petrophysical properties that exist in the rock and soil material in an investigation area and by different types of natural or artificial constraints (for example, power lines).

3.4.5. Geophysical Measurement Systems

The various geophysical measurement methods can be classified in different ways. However, the measurement systems and the design of the measurements are similar within methods where measurements are taken from the air, directly on the ground, or underground in boreholes. For each measurement method, the measurement point distance is related to the size of the object. The measurement point distance should therefore be less than half of the size of the object. Corresponding data collection principles also apply to the selection of measurement data from a large database. Methods with a large-scale range are suitable both for general regional surveys and very detailed characterisations. Methods with limited depth penetration are suitable for investigating the soil cover and rock surface.

In order to establish the existence of a contrast, the object’s surroundings must also be included in the measurement to an adequate extent. The surroundings included in a measurement

SOU 2004:67 Some Geological, Geodynamic and Geophysical Investigation …

should be as large as the specific area of interest. The measurement point distance and the area that is to be measured are directly related to the cost of the measurements.

Table 3.1 below provides an overview of geophysical methods and their applications, depth penetration and scale range. All of the methods are applicable in connection with site selection for nuclear waste disposal. The methods that are best combined partly depend on the geological conditions and, above all, on the petrophysical properties of the rock. Therefore, the starting point should always be the existing regional and local databases that occur in an investigation area in order to design methods and new investigations. If knowledge of the petrophysical properties is lacking, they should be measured at an early, initial stage of an investigation.

Some Geological, Geodynamic and Geophysical Investigation … SOU 2004:67

Table 3.1. Various geophysical methods and their fields of application.

METHOD (scale range in parenthesis)

FIELDS OF APPLICATION

DEPTH PENETRA-TION

Ground based geophysical measurements (1-100 km): Gravity (a) Rock composition, large block movements

10 m – 10 km

Magnetic field (a) Large fracture- and movement zones in magnetic rocks, block movements, bedrock mapping

10 m – 1 km

Electromagnetic methods (1 – 10 km): Slingram Occurrence of conductive minerals

1 – 50 m

Radar (GPR) Depth to bedrock and groundwater level 0.1 – 50 m IP Occurrence of conductive minerals 1 – 50 m MT (a) Vertical distribution of electric resistivity to large depth, level of salt groundwater

10 m – 10 km

VLF Occurrence of fracture zones and their approximate dip

10 m – 1 km

VLF-R Determination of soil and bedrock resistivity

10 m – 600 m

Electric methods (0.1 - 10 km): VES (a) Determination of groundwater level,

depth to bedrock, soil layering, level of salt groundwater

1 m – 1 km

Seismic methods (50 m – 1,000 km): Refraction (a) Depth to bedrock and groundwater level, occurrence of steep fracture zones

1 m – 50 km

Reflection (a) Depth to bedrock and groundwater level, layering in sediments, location of low angle fracture zones

0.1 m – 50 km

SOU 2004:67 Some Geological, Geodynamic and Geophysical Investigation …

METHOD (scale range in parenthesis)

FIELDS OF APPLICATION

DEPTH PENETRA-TION

Airborne geophysical measurements (1 – 100 km): Magnetic field (a) Orientation of large fracture zones in 3-dimensions, block movements, characterization of bedrock

10 m – 1 km

VLF (*) Steeply inclined water containing fracture zones

10 – 100 m

Drill hole geophysical loggings (0.1 – 10 m): Water flow Water flow in sections of the bedrock Electric resistivity Porosity and occurrence of fractures IP Occurrence of conductive minerals TV camera Orientation of fractures in 3-dimensions Radar Orientation of fractures in 3-dimensions Shape of drill hole Orientation of the horizontal stress field Observation networks (1 – 2,000 km): Seismic Location and orientation of displacements in the bedrock, orientation of the stress field

1 – 30 km

Geodetic (GPS) Displacement and rotation of bedrock units in 3-dimensions in the uppermost crust, land rise Hydrological Precipitation, run off, changes in groundwater level

(a) Methods with great depth penetration, > 500 m. (*) The airborne VLF method is direction selective depending on which transmitter that is used for the measurements.

Some Geological, Geodynamic and Geophysical Investigation … SOU 2004:67

3.4.6. Limitations Due to Terrain and Artificial Objects

All geophysical measurements are dependent on terrain variations. The more variable the terrain is, the greater the effects will be. This is taken into account when planning the measurements as well as in the analysis. With certain methods, the effect of the terrain can be reduced by applying corrections or by inclusion in the model. It is always suitable to study altitude data in parallel with the analysis of measurement data. This can be accomplished particularly efficiently by using digital data and Geographic Information Technology (GIT). Geophysical measurements can be performed on ice over water-covered areas. However, the increased distance to the soil cover or bedrock under the water reduces the signals to some extent. For certain measurements, constant altitude and the absence of topography over the measurement surface is an advantage. Geophysical measurements over water-covered areas make it possible to obtain more continuous information about rock structures. With methods based on electrical conductivity, water (especially seawater) and electrically conductive parts of the soil cover (such as clay) have a strong shielding effect.

Certain geophysical methods are sensitive to artificial (anthropogenic) objects. This particularly applies to electromagnetic measurements where secondary fields from power lines, telephone lines, large fences, pipes and telephone transmitters predominate the natural variations in the area close to such objects. In the case of large power lines, this can extend over several kilometres. Similarly, the environment around active telephone transmitters is severely disturbed. By using electromagnetic methods with controlled signal formation, these disturbances can be avoided in connection with measurements or they can be filtered out during data processing.

With magnetic measurements, it is large iron structures (such as power line poles and sheet metal roofs) instead that disturb the measurements in their proximity. Furthermore, direct current power lines result in magnetic fields that cause local

SOU 2004:67 Some Geological, Geodynamic and Geophysical Investigation …

disturbances. When conducting airborne measurements at low altitudes, large power lines and populated areas are avoided by flying at a higher altitude and the natural signals are thus weakened due to the increase in distance. Broad corridors can therefore occur around anthropogenic objects where the use of electromagnetic measurement methods is rendered difficult or impossible.

3.4.7. Airborne Geophysics

Airborne geophysical measurements are performed from satellites, aeroplanes or helicopters and, on the same measurement occasion, several different types of measurements can be performed simultaneously. The measurements rapidly cover large areas and, today, many countries have comprehensive airborne geophysical databases. Satellite-based measurements are internationally available and have global coverage. In Sweden the Geological Survey of Sweden is responsible for the design, processing and storage of airborne geophysical measurements. The compromise between cost and measurement point distance has so far favoured quite detailed measurements, which can be used for many issues. The measurements are also performed at a low altitude, about 50 metres, i.e. at a short distance to the geological structures in the bedrock. The measurement point distance is 20 metres along the flight lines but there are about 200 metres between the flight lines. For the analysis of measurement data, it is therefore important to know where the flight lines are situated, especially since modern interpolation techniques normally cannot reproduce the context of structures at a small angle to the flying direction. The measurement data are presented on maps in the scale 1:50,000, which follow the map sheet division of Sweden. Digital extracts of an optional geographical area can also be obtained from the database.

The measurements performed from airborne surveys in Sweden comprise magnetic total intensity, gamma radiation

Some Geological, Geodynamic and Geophysical Investigation … SOU 2004:67

(represented as the equivalent content at the ground surface of the natural radioactive isotopes, potassium, uranium and thorium) and electromagnetic secondary fields from long-wave (VLF) transmitters. These measurements can be used for many purposes, including mapping of the extent of the rock types under the soil cover and under water, the mapping of large fracture zones in the bedrock, the investigation of radon risk (in soils, the bedrock and groundwater) as well as for prospecting for mineral deposits.

Radar measurements that are conducted from satellites and aircraft can be considered to be geophysical measurements. They are usually very detailed and are conducted in several frequency ranges. The direct geological use is for the mapping of fracture zones as well as the determination of soil water content. In areas with heavy vegetation and intensive forestry, the geological information is hidden by the traces left by the methods of land cultivation (like property boundaries and ploughing grooves) that are clearly visible in the radar measurements. The measurements are not dependent on cloud cover and the effects that occur from cloud and shadow on the ground in connection with aerial photography or satellite scanning in the visible wavelength spectrum can thereby be avoided.

Facts Measurement direction, measurement spacing, measurement altitude Airborne measurements – in east-west or north-south direction, 200 m distance between flight lines and about 20 m between measurements, elevation about 50 m above the terrain, Ground based measurements – selected direction, distance between measurements and measured lines 5 – 20 m, Regional gravity measurements – irregular net of measurements with 0.8 – 5 km spacing, Profile measurements – oriented at right angle to the direction of the structure, measurement spacing 1 – 20 m.

SOU 2004:67 Some Geological, Geodynamic and Geophysical Investigation …

3.4.8. Ground Geophysics

Purpose and Access to Data

Geophysical ground surveys have been carried out in connection with the prospecting of ore and industrial minerals and the mapping of gravel deposits as well as for specific investigations within the regular soil and rock type mapping at the Geological Survey of Sweden. From an early stage, ground geophysical surveys have been conducted for groundwater prospecting in Sweden and abroad. In recent decades, ground surveys have had an increased importance within different types of environmental studies.

Geophysical ground surveys, in connection with underground construction, such as for a repository for spent nuclear fuel, aim at developing a geological-tectonic model of the studied soil and rock volume. Furthermore, the aim is to increase knowledge of the composition and thickness of the soil cover, the physical properties, fracturing, water content and boundaries between different rock types. The ground surveys are non-destructive, but require considerable interpretation. In general, the resolution decreases with increased depth penetration. To study conditions at a depth of 500 metres, considerable changes in the physical properties (or large structures) are therefore required in order for them to be detected at the ground surface. Also near surface changes in the horizontal direction must be less than those in the vertical direction.

The measurements are performed on the ground, either in an irregular grid over large areas, in a systematic grid over a limited area or as profiles. The measurement point distance is determined by the purpose of the measurement and can vary between 1 metre (detailed profiles) and 5 kilometres (regional nationwide surveys). Measurement data are presented on maps or in profiles. For certain types of measurements, national databases exist that are managed by the Geological Survey of Sweden.

Some Geological, Geodynamic and Geophysical Investigation … SOU 2004:67

Regional, nationwide surveys currently exist for gravity, with point distances that vary between 0.8 and 5 kilometres. The measurements usually follow the road network. On large lakes and near-coastal sea areas, measurements have been conducted on ice.

Seismic surveys are sometimes conducted on a regional scale, especially in sediment-covered areas and for special projects. No complete overview exists of where such measurements have been conducted or of which company or institution that is holding the results.

Measurement Methods

The most important geophysical methods for investigations of structural conditions of the bedrock in the form of fractures and fracture zones are seismic, magnetic, electrical and electromagnetic measurements. Some of these measurement methods also provide information on rock types and rock type boundaries. All methods are sensitive to horizontal near surface variations while changes at depth are much more difficult to detect. It is also easier to detect steeply dipping structures and rock type boundaries than to map horizontal fracture zones and boundaries. In the case of refraction seismic and electrical methods, depth penetration also requires that instruments be arranged over long distances. Figure 3.8 shows a series of measurements with different methods over a large shear zone in Norrbotten and how the results of the magnetic measurement can be used to determine the dip of the zone (Figure 3.9).

Seismic surveys are used to detect structures in the bedrock. The surface structures, for example the occurrence of fractured bedrock, especially steeply dipping fracture zones, can be interpreted from refraction seismic surveys, where the refracting part of the sound wave is followed by registering the time until it reaches the geophones that have been set up. The seismic signal velocity is considerably reduced in crushed rock. It is difficult to

SOU 2004:67 Some Geological, Geodynamic and Geophysical Investigation …

detect horizontal low velocity zones with refraction seismics. On the other hand, refraction seismics can be used to advantage to determine the depth to the bedrock under the soil cover. This has been carried out in connection with many large construction projects, for example, along the Bolmen tunnel where more than 200 km of refraction seismic profiles were evaluated (Stanfors 1987). With reflection seismics the part of the sound wave that is reflected at the interface to a material with a deviating sound velocity is measured. The method requires heavy equipment and more powerful computer processing. Therefore, it is more suitable for local surveys. A major advantage of reflection seismics is that the method is one of the few that can be used to identify rock structures with low angle to the horizontal at great depths, for example, horizontal fracture zones (Andersson 1993, Cosma et al. 1994). This is of decisive importance for the siting of a repository since it must be possible to take into account low angle structures when determining the position for the rock volume that can be taken into consideration. Seismic methods have also been used during the construction of underground facilities (Tunnel Seismic Predition, TSP) to predict the conditions and determine the need for reinforcement (Sattel et al. 1996).

Some Geological, Geodynamic and Geophysical Investigation … SOU 2004:67

Figure 3.8. Example of the geophysical response from a large shear zone (marked with grey shading) in Norrbotten. The different methods show a clear response above the zone. From top: Magnetic (MAGN) low anomaly over the zone due to oxidation of magnetite, VLF horizontal component giving a typical anomaly over the zone, Slingram (SLING) gives a negative anomaly, VLF resistivity (RES) shows low resistivity, the phase angle (FASV) varies very little over the zone, and at the bottom a high conductivity (KOND) anomaly is seen. (from Henkel 1988).

SOU 2004:67 Some Geological, Geodynamic and Geophysical Investigation …

Figure 3.9. The magnetic anomaly seen on top in the previous figure has been used to determine the dip of the zone, which is 73 degrees towards the southwest (from Henkel 1988).

Ground Penetrating Radar (GPR) utilises similar reflection principles as reflection seismics but is based on the propagation of the electromagnetic waves through the ground. A reflection is obtained when the radar wave hits an object with deviant electrical properties. Today, pulse radar systems are often used, whereby electromagnetic pulses are directed by a transmitter antenna into the ground and a receiver antenna registers the reflected signals. The time delay for the reflected signals is measured in nanoseconds, 10

-9

s. In recent decades, the method

has become increasingly important for the mapping of superficial soil and rock layers and has been used for studies of soil layer

Some Geological, Geodynamic and Geophysical Investigation … SOU 2004:67

conditions and geological evolution (Widén 2001, O’Neal & McGeary 2002, Helle 2004). GPR has also been used to study tectonic zones, both active (Rashed et al. 2003, Slater & Niemi 2003) and older neotectonic zones (Dehls et al. 2000, Tirén et al. 2001). Like with reflection seismics, the method can be used to identify low angle tectonic structures and is therefore of importance for studies of the near surface, generally more fractured rock, Figures 3.10 and 3.11. In soil-covered areas, the depth to the bedrock and flow-promoting structures in the soilrock contact zone, that are important for groundwater recharge, can be mapped, Figure 3.12. GPR can also be used continuously during the construction phase, directly from the underground facility, to predict fractures, rock boundaries and other rock structures in order to establish reinforcement needs and to map the effectiveness of pre-grouting (Cardarelli et al. 2003).

Figure 3.10. Example of an interpretation of fractures in the near surface bedrock using GPR measurements (Grasmück 1994). From the time scale, the depth to the reflecting structures can be calculated if the velocity of the signal in different geomaterials is known.

SOU 2004:67 Some Geological, Geodynamic and Geophysical Investigation …

Figure 3.11. Example of a low angle fracture zone in the Forsmark area. Such fracture zones can be detected in near surface locations with ground penetrating radar and at larger depth with reflection seismic measurements (photograph by Kaj Ahlbom 2003).

If the crystalline bedrock is magnetic, magnetic measurements from the ground (or from an aeroplane) can be used to map large fracture zones. These zones are always low magnetic due to mineral alterations and can also be mapped beneath the soil cover and in water-covered areas. Through model calculations and with knowledge of the magnetisation of the surrounding bedrock, the dip of the zones can be established.

Some Geological, Geodynamic and Geophysical Investigation … SOU 2004:67

Figure 3.12. Example of interpretation of the depth to the bedrock based on GPR measurements in an area in southeastern Sweden (Olofsson et al. 2004).

Electrical measurements are based on electrical fields created in the subsurface between two current electrodes. The extent of the current field depends on the distance between the electrodes but is also affected by the conductivity of the soil cover. By measuring the voltage with potential electrodes, the apparent resistivity can be calculated. The resistivity depends on how the electrodes are arranged as well as on lateral and vertical changes in the electrical properties of the subsurface. Through inverse modelling, where the electrical properties of the subsurface and the thickness of the soil cover are varied until an agreement is

SOU 2004:67 Some Geological, Geodynamic and Geophysical Investigation …

reached with the measured values, an interpretation of the structure of the subsurface and its electrical properties is obtained. Most often, a multi-electrode system (Continuous Vertical Electrical Sounding, CVES) is used today with a large number of electrodes arranged along lines or in a network together with a computer that determines which electrodes are to be current and which are to be potential electrodes. Through inverse modelling, the resistivity distribution of the ground can then be two- or three-dimensionally calculated. Electrical measurements have become important for the mapping of soil and rock stratification and in determining groundwater surfaces. Other important applications are for environment-related investigations and for environmental control (Bernstone & Dahlin 1998, Aaltonen 2001), Figure 3.13. If fixed electrodes are set up in the ground, the method can be used for long-term monitoring, for example, around landfills where pollutants often have a high salinity (Aaltonen & Olofsson 2001) or for the monitoring of climate-related ground moisture conditions and groundwater levels.

Most of the multi-electrode systems occurring on the market only allow sensing to a depth of about one hundred metres. An interesting application of geoelectrical surveys is to map the occurrence of saline water at great depths with a several kilometre-long electrode separation. This is an excellent complement to deep drilling. However, in coastal areas, it may be difficult to avoid the short-circuiting effect of seawater on the measurements.

The chargeability of the ground can be measured by induced polarisation (IP). The method is based on a current field created over the ground that causes polarisation to occur in the subsurface. When the field is turned off, this polarisation continues for a certain time and can be measured. The method has a considerable potential for studies of polluted soils, like dispersed salt pollutants or oil spills (Dahlin & Leroux 2002, Sjögren 2004). Even without external current fields, a weak polarisation occurs due to the mineral content in the ground and

Some Geological, Geodynamic and Geophysical Investigation … SOU 2004:67

the electrolyte properties of the ground fluid. The measurement of this natural self potential (SP) with sensitive non-polarising electrodes can, in the same way, be used in connection with ore prospecting and pollutant mapping. The method has also been used in connection with near-surface tracer experiments in rock (Nimmer & Osiensky 2002).

Figure 3.13. Resistivity measurements for analysis of leacheates spreading from a waste deposit. The measurements are made with CVES technique and are modelled two and three-dimensionally, respectively. The results are presented as profiles (left), horizontal sections in the near surface bedrock about 12 m below the ground (upper right), and as three-dimensional low resistivity zones (lower right) (Olofsson et al. 2004).

SOU 2004:67 Some Geological, Geodynamic and Geophysical Investigation …

Electromagnetic induction means that a current field is created in electric conductors in the ground with the help of an external electromagnetic field. The secondary electromagnetic field, which occurs, can be measured at the ground surface. There are several frequency-controlled methods that either use natural electrical currents (MT measurements), in the frequency range from 10

-4

to 1 kHz, or currents induced by radio signals (VLF

measurements) in the frequency range from 15 to 25 kHz. Electromagnetic methods are also designed for fields created by a mobile transmitter (slingram) in the frequency range from 5 to 15 kHz. In general, the depth penetration is determined by the frequency of the electromagnetic field and the conductivity of the ground. There is always a high contrast in resistivity between unaffected bedrock and fracture zones in crystalline bedrock. VLF measurements are therefore an effective method of mapping fracture zones on land areas (but not over watercovered areas).

In recent years, electromagnetic measurement methods have been developed to describe the distribution of electrical resistivity down to a depth of several kilometres in the bedrock. A summary of VLF and MT methods is provided in Oskooi & Pederson (2004). With magnetotelluric measurements (MT), natural electrical currents occurring in the bedrock are used, Figure 3.14. Penetration depth is up to 10 kilometres and the measurement is conducted so that anisotropic conditions also can be investigated. The observation times are up to 12 hours. Interference from transmitters for mobile telecommunication and power lines can, in most cases, be filtered out. With measurements in a coarse network, three-dimensional electrically conductive structures can be identified. With this method, the depth at which the transition to saline groundwater occurs can be determined.

Electromagnetic measurement methods have been used for ore prospecting, investigations of water-bearing fracture zones in the rock and for studies of pollutant dispersion. The methods are based on complex theory. New instruments are developed

Some Geological, Geodynamic and Geophysical Investigation … SOU 2004:67

for environmental applications, for example, EnviroMT (Bastani 2000).

Figure 3.14. Two models of the resistivity variation with depth based on MT measurements (from the islands Midsommar and Björkö in Lake Mälaren). (From Oskooi and Pedersen 2004).

SOU 2004:67 Some Geological, Geodynamic and Geophysical Investigation …

3.4.9. Borehole Geophysics

In most deep boreholes in Sweden, measurements have been conducted with different types of geophysical logging in order to determine the variation of the measured characteristic property with depth. Such measurements can be conducted at intervals that vary from 0.1 to tens of metres. Accurate methods have been developed to correlate the depth values obtained in connection with different measurements. However, in Sweden, there are very few boreholes with a depth exceeding 1 kilometre. Consequently, knowledge is lacking of where the transition to saline groundwater occurs in the bedrock and how deep the fracture zones extend into the upper part of the Earth’s crust. Boreholes that are deeper than 2 kilometres in crystalline bedrock only exist in the central part of the Siljan structure in Sweden. In borehole measurements, the sensing distance in the horizontal direction is very small, from decimetres for certain methods and, under favourable conditions, up to tens of metres, in the case of borehole radar for example. The measurement of resistivity in boreholes only gives relative values and calibration is required to obtain values that are representative for rock types. This problem is treated in Löfgren & Neretnieks (2002).

The following types of borehole measurements are common and can be used in connection with site selection:

Methods that characterise rock types and rock type boundaries Gravity measurements Measurements of magnetisation Induced polarisation (IP) Gamma radiation (several different methods)

Some Geological, Geodynamic and Geophysical Investigation … SOU 2004:67

Methods that identify fracture zones and the occurrence of water Measurement of electrical resistivity (several different methods) Radar measurements Water flow measurements Measurement of borehole shape (calliper) Temperature measurements Video photography

Methods that identify stress and temperature conditions Response to pressure changes Measurement of borehole shape Temperature measurements Gamma radiation measurements (several different methods)

The methods are often used in combination and several sophisticated measurement probes have been developed for the electrical methods including a choice of different electrode configurations, Figure 3.15. Measurements involving radar, borehole shape and photography also provide information on the orientation of structures that have been detected. Water flow measurements are performed in limited sections, in response to pressure changes. The response in the bedrock displacement is measured and identified during the test period with the help of local seismograph networks. The connection between borehole data, which is very detailed (dm-scale) and continuous, with surface data that are dispersed (1 metre to 10 metre scale) and incomplete, is a difficult problem. The difficulty is related to how local phenomena can be distinguished from those that cover a large area. The distance dependence of the measurement method implies that the spatial resolution rapidly decreases with distance from the borehole and with depth in ground based surveys. The problem cannot be resolved with more frequent or more sensitive measurements – instead, more boreholes are needed – which however change the properties of the bedrock in an unfavourable manner.

SOU 2004:67 Some Geological, Geodynamic and Geophysical Investigation …

Figure 3.15. Example of logging data from a 900 m deep drill hole (on Björkö in Lake Mälaren) with electric resistivity (two methods, short normal and long normal), water flow, and induced polarization (IP) generalised over 10 m intervals. (Sträng 2003). The variation in resistivity reflects the fracture frequency. Higher water flow indicates open fractures and increased IP effect indicates sections where electrically conductive minerals occur.

Some Geological, Geodynamic and Geophysical Investigation … SOU 2004:67

3.4.10. Databases at SGU and the Swedish Maritime Administration

The Geological Survey of Sweden (SGU) holds a large number of databases with digital and analogue geoscientific information. They are available for research, prospecting, geotechnical and environmental investigations. A licence is required and fee must be paid to use the data. Digital data can be obtained for an optional geographical area and they are often directly suitable for analysis with Geographical Information Technology (GIT). Furthermore, geoscientific maps with different degree of detail occur all over the country.

Regional surveys are conducted systematically by SGU while detailed surveys are conducted by geological consulting companies, prospecting companies and geoscientific departments.

Queries about seismic measurements should be primarily directed to SGU. Several international projects, with the aim of determining the structure and thickness of the Earth’s crust, have been based on seismic investigations covering many 100 kilometres.

In connection with prospecting for ore, large areas in Västerbotten and Norrbotten have been mapped in great detail with several types of ground geophysical measurements. These are documented at SGU.

The Swedish Maritime Administration handles bathymetric data, often with a high degree of detail, over coastal areas and inland lakes where shipping occurs. These bathymetric data can be used in the same way and in combination with altitude data to study the occurrence of fracture zones in water areas (or their extension from land to water areas). Such a combined study has, for example, been conducted for the Lake Vänern basin (Isaac 1992) and southern Björkfjärden (Chuang 2003).

SOU 2004:67 Some Geological, Geodynamic and Geophysical Investigation …

3.5. Conclusions

Geological Methods

Swedish crystalline bedrock is a complex heterogeneous medium, formed by geological processes during more than 2,000 million years. Many of these processes are ancient but affect the stability and safety of a repository for radioactive waste. Other processes are active and gradually change the geological conditions. The geological situation in the shield with a very young soil cover over a considerably older crystalline bedrock means that the time-period during which ongoing geological changes can be studied is much less than the planned lifetime of the repository. Therefore, it is important to conduct systematic studies in the young geological deposits with respect to the effects from land uplift, earthquakes and fault movements. Many of these dynamic processes will probably continue for a foreseeable time in the future.

Geodynamic Methods

Much research has been conducted on the induced geodynamic changes that will occur locally through the construction of a repository for spent nuclear fuel, also coupled to the heat exchange that will occur between the repository and the environment. However, natural geodynamics has not attracted the same interest. Nevertheless, several indicators show that systematic movements between crustal blocks occur continuously. Such movements have been quantified in some cases with geological methods, with measurements in the Global Positioning System (GPS) and by analysing major earthquakes. The movements are located in limited areas or zones. These zones can be mapped geographically and in terms of depth using geological and geophysical methods. The movements along the

Some Geological, Geodynamic and Geophysical Investigation … SOU 2004:67

zones are relatively small and, therefore, long observation periods are required in order to determine them with certainty.

The displacement zones function as part of a larger regional context and, at present, there is insufficient information on the way in which they function locally. Consequently, local systems must be built up and measured for a long time. The ongoing deformation is one of the key problems in making forecasts of the bedrock stability. Therefore, knowledge of the position and extent of the zones (horizontal and vertical), the velocity and direction of the motion, the function of the zones in time and their function in the regional and plate tectonic deformation is necessary. How plinths and shear lenses react to changes in the stress field should therefore be modelled. Such modelling can be made for observed structures in the investigation areas and their regional context.

The methods that must be further developed to provide such knowledge are both direct and indirect, for example measurement techniques with GPS and seismograph networks, age determinations of minerals and geological observations, in order to provide increased knowledge of the structure and performance of the lithosphere. The existing geodetic and seismic networks should be nationwide and co-operation over national boundaries should be developed to create databases that can be used for several geoscientific purposes. The GPS networks which were previously set up should also be measured in the future in order to obtain time series that are as long as possible. This also applies to measurements of the change in gravity.

Geophysical Methods

A large number of geophysical surveys have been conducted so far or are planned in connection with site investigations prior to the construction of a repository for spent nuclear fuel. The measurements have had different purposes and scales, from general airborne surveys to detailed characterisations in bore-

SOU 2004:67 Some Geological, Geodynamic and Geophysical Investigation …

holes. In many cases, the aim has been to build up a geological/tectonic model over the area or to predict geological and tectonic changes during the construction phase, such as during the construction of the Äspö tunnel. A limited amount of research work has been conducted on the possibilities of transforming measurements to input variables for chemical dispersion models. Certain development efforts have been made, for example, resistivity measurements for determination of diffusion in massive rock (Löfgren & Neretnieks 2002).

Geophysical surveys are a very valuable tool since, in principle, they are the only methods that provide non-destructive measurements of the rock volume where the repository will be constructed. Therefore, it is of great importance that surfacebased geophysical surveys should be conducted at an early stage. A combination of several methods with high data point density and determination of the physical properties of the geomaterials and control drilling is necessary in order to reduce uncertainty when interpreting the measurements.

A combination of magnetotelluric (MT) measurements, which have great depth penetration capabilities, and reflection seismic measurements are tools to determine the depth to saline groundwater and the occurrence of deep fracture zones. Such measurements must be made systematically and with sufficient coverage of the investigation area and its surroundings. Ground geophysical surveys are of particular importance, such as surfacecovering measurements with ground penetrating radar in order to map the soil stratigraphy, the soil thickness, the contact zone between soil and rock and the fracture conditions of the near surface rock, as a basis for calculating groundwater recharge in the bedrock.

In the case of geological and geophysical investigations, the extent of the measurements must be large enough to include an adequate environment outside the actual area of interest is included. This also applies to water-covered areas. The extent should be about 3 times greater than the area of interest in all directions. The total investigation area should thereby be about

Some Geological, Geodynamic and Geophysical Investigation … SOU 2004:67

10 times greater than the area of interest. Reflection seismic and radar investigations should be conducted in a systematic manner in the entire investigation area in order to map the occurrence of low angle fracture zones since these can not normally be observed in outcrops or with other geophysical methods.

3.6. Appendix: Geodynamic Processes

The mapping of the extent and intensity of geodynamic processes requires observations of deformations in reference structures or in observation networks over a long time-period. The deformation of the crust over the past million years and the ongoing deformation of the crust are referred to as neotectonics. In Sweden, this particularly refers to the deformation that occurred after the last glaciation. The deformation that is currently in progress is almost unnoticeable over short timescales (decades). However, it can accumulate to a considerable size during geological time periods (millions of years). Due to the constant movement of the global lithosphere plates, all parts of the crust are affected all over the Earth. Along the plate boundaries, the deformation is very great and causes severe earthquakes and volcano eruptions. Inside a lithosphere plate, the deformation is considerably less, hardly noticeable and does not cause catastrophes. The boundaries of our lithosphere plate (the Eurasian plate) are located in the middle of the North Atlantic (Figure 3.16), in the Arctic Ocean, along the Japanese island chain, Indonesia, the Himalayas, Anatolia, the Alps and the Atlas mountains. The Eurasian plate largely comprises continents and moves due to the growth of the Atlantic ocean crust by about 1 centimetre per year (i.e. the same order of magnitude horizontally as the land uplift). Several active deformation zones are located in this plate, for example, the graben system that stretches from the North Sea via the Rhine valley to the Rhone valley. Areas also exist in our vicinity that can be suspected, on good grounds, to be active deformation

SOU 2004:67 Some Geological, Geodynamic and Geophysical Investigation …

zones, such as the mountain belt, Lake Vänern and the Bothnian Sea and Bothnian Bay. The deformation zones are characterised by anomalous topography, anomalous land uplift, the occurrence of earthquakes and the systematic displacements of large crustal blocks. These characteristics, as well as how they can be studied, are treated briefly below.

Some Geological, Geodynamic and Geophysical Investigation … SOU 2004:67

Figure 3.16. The plate tectonic situation of Sweden. The Mid-Atlantic ridge is our nearest plate boundary between the North American (dark grey) and the Eurasian (light grey) lithosphere plate. The large-scale geomorphic regions are the rising area in the Scandian mountain belt (red lines) and the parallel, about 400 km to the east located, areas of down warping (blue lines) around Lake Vänern and the Bothnian Sea and Bay. Generalised areas with earthquakes are outlined green. The first order shear zones are marked with purple lines (Henkel & Roslund 1994).

On a more detailed scale, neotectonics manifests itself by the occurrence of fault escarpments with varying height (from less

SOU 2004:67 Some Geological, Geodynamic and Geophysical Investigation …

than 1 metre to over 20 metres), landslides, slumping and liquefaction structures in soil layers, boulder fields and caves, and as displacements of glacially shaped outcrops. Some of these phenomena can also occur due to other geological processes and the connection between occurrence and cause requires extensive mapping over large areas. The terrain shapes that are associated with young fault zones were first discovered by studies of aerial photography in areas located over the highest shoreline and which, therefore, have not been exposed to seashore erosion. Landslides can be detected in the same way (and run the risk of erosion if they have been exposed to shore erosion). Therefore, these neotectonic indicators have so far mostly been found in northwestern Norrbotten and it is still unclear whether they indicate an anomalous neotectonic active area or whether they have also occurred in areas below the highest shoreline. Considerable new road construction work has created road cuts with sections that are suitable for detailed studies of disturbances in the soil stratification. These are common phenomena in mobile sedimentary environments and a determination of the boundaries of tectonically caused structures requires regional mapping and dating of the sediment stratification. Boulder fields and caves can be related to earthquakes but also occur through frost heaving and frost erosion. Minor displacements of glacially shaped rock outcrops across fractures are a clear indication of block movements that have occurred after the formation of the surface. An interruption in such surfaces, where one block is missing, occurs when the missing part is transported away by ice. In Mörner (2003), a thorough neotectonic interpretation of a large number of observations is made, which is connected to paleoseismic activity. Many of the observed phenomena are located in time to the deglaciation phase, which was a period of relatively major changes in the stress field.

Knowledge of the ongoing geodynamic processes is important for judging the long-term stability of a nuclear waste repository. Without actual measurements of geodynamic changes and

Some Geological, Geodynamic and Geophysical Investigation … SOU 2004:67

knowledge of the underlying processes, predictions of future changes are based on assumptions.

3.6.1. Topography

Tectonic processes and erosion primarily cause the variation in the large-scale topography in Scandinavia. Elevated areas cannot last for long geological time-periods due to continuous erosion. In the same way, sinks cannot last for long periods of time due to continuous sedimentation. On the other hand, areas without significant topographical variation are relatively stable (for example, the Småland highlands and Finland). By studying elevation data (in the form of topographical maps or digital elevation data), older erosion surfaces can be reconstructed (Lidmar-Bergström 1988). However, only exceptionally can the age of these be determined. The large-scale topography in Scandinavia is young. Studies of sedimentation in the sea areas off the coast of Norway indicate increased sedimentation starting about 5 to 10 million years ago and distinct uplift areas have been identified in the mountain belt (Riis & Fjedskaar 1992). In Lake Vänern and the southern and northern parts of the Bothnian Sea and Bay, there is still no occurrence of thick young sediments despite ongoing mountain belt erosion and the fact that materials are being transported to these sinks by rivers. The cause of the young topography is not yet known. However, due to the large dimensions, it is likely to be related to plate tectonic processes. The natural evolution of the young oceanic lithosphere in the North Atlantic is gradually leading to the formation of a subduction zone at the edge of the continental lithosphere where the oceanic lithosphere is being submerged below the continental lithosphere. At a distance and in parallel with the subduction zone, a subsiding region would develop, as the lithosphere is dragged apart by an opposing current in the upper mantle. However, at present, no measurement data are available for determining changes in the large-scale topography.

SOU 2004:67 Some Geological, Geodynamic and Geophysical Investigation …

In order to obtain such data, observations of the land surface and sea bottom changes are required over long periods of time, probably decades. Such observations are conducted in nationwide geodetic networks where continuous measurements are used against the satellites in the GPS system. Small-scale topography (such as elevated or depressed shear lenses) can also indicate geodynamic processes. Figure 3.17 shows a cross-section of the Earth’s crust from northwest Lofoten to central Finland (Henkel & Lund 2004). Figure 3.18 shows a profile over a major shear zone in Värmland.

Figure 3.17. Section through the Earth’s crust from northwest of Lofoten to central Finland. The model is based on a combination of refraction seismic and gravity data. To the northwest, the change from the oceanic crust to the continental shelf is seen. The thickness of the crust is larger under the mountain belt and increases to its largest value in Finland. The number of earthquakes, which occur in three distinct zones (delineated by vertical lines), is presented with numbers in their approximate depth location. (The gravity anomaly is in gu (= 0.1 mgal). The small numbers mark areas of different density.

Some Geological, Geodynamic and Geophysical Investigation … SOU 2004:67

Figure 3.18. Profile across one of the first order shear zones in Värmland (marked as PZ), which cuts through the entire crust (here about 40 km thick) (Henkel 1992). In the upper part of the diagram magnetic measurements are shown which are the basis for calculations of the near surface dip of the zone. In the lower part of the diagram gravity measurements are shown which are the basis for calculations of the extent of the zone through the Earth’s crust. It also shows down warping of different layers in the crust from west towards the zone, which dips steeply towards the east.

SOU 2004:67 Some Geological, Geodynamic and Geophysical Investigation …

Facts Plate tectonics

  • the deformation of the lithosphere due to heat convection from the Earth’s mantle, Lithosphere – the uppermost shell of the Earth, which is displaced as a unit in plate tectonic processes. Its thickness is about 250 km in central Scandinavia, Mantle – the region between the lithosphere and the Earth’s core, about 3,000 km thick, Earths crust – the uppermost part of the lithosphere outside the mantle, the thickness in central Scandinavia is about 50 km, The boundary between the crust and the mantle is the Moho (the Mohorovicic discontinuity).

3.6.2. Land Uplift

In Scandinavia, land uplift is well-known, has been measured for centuries and can be seen in the young geological deposits that are reshaped in shore zones and which have gradually ended up at increasingly higher levels above the present sea surface. Land uplift is currently the greatest, about 9 mm per year, in the vicinity of Umeå. It is zero close to the boundary of the crystalline shield against the surrounding sediment covered areas. In the area just south and east of the shield (i.e. in northern Germany, Denmark, the southernmost part of Scania, the Gulf of Riga and around Lake Ladoga) a slight land subsidence occurs. The cause of the land uplift is attributed to the deglaciation that occurred over 10,000 years ago. However, there are several indications that other forces are active. The extent of the land uplift is not compatible with the extent of the ice. Local deviations in the land uplift also exist (known as differential land rise) and there is a considerable difference in the land uplift gradient between the western and eastern part of the land uplift area. Areas with a significant deviation from the general land uplift (which can be connected to the deglaciation) show relative rising areas by more than 1.5 mm/year in the mountain belt and relative subsiding areas with corresponding

Some Geological, Geodynamic and Geophysical Investigation … SOU 2004:67

deviations in the southern part of the Bothnian Bay and Sea (see Figure 3.16, areas within the red and blue lines respectively). The subsiding area extends further towards the northeast beyond the northern part of the Bay of Bothnia. It also includes northern Uppland (Fjeldskaar et al. 2000). Investigations of shoreline displacements in northeastern Uppland (Hedenström & Risberg 2003) show that the exponentially decreasing land uplift has turned into a linear trend about 5 500 years ago. This is a strong indication that other processes besides isostatic compensation after deglaciation are active.

The land uplift can be measured by recurring levelling of fixed points and such measurements provide the basis for knowledge of the present land uplift. However, since 1993, traditional levelling measurements have been replaced by data obtained from 25 permanent GPS reference stations placed all over Sweden, known as the SWEPOS network. After a long observation period, the relative movement of the observation points, horizontally and vertically, can be calculated from the measurement data.

3.6.3. Earthquakes

Earthquakes occur when the Earth’s crust breaks apart due to the sudden release of stresses that have built up over a long period of time. Such stresses accumulate due to differential movements between crustal blocks along shear zones. In Scandinavia, only mild earthquakes occur and earthquakes with a magnitude of 5 or larger (on the Richter scale) are rare. The earthquakes occur in the brittle part of the crust at an average depth of about 18 kilometres along certain zones and in a few limited areas. The present-day seismic active areas in Sweden are especially the Lake Vänern depression and the Swedish coast along the Bothnian Sea and Bay (see map in Figure 3.19). The earthquakes are registered in a network of seismograph stations, which operate over a long period of time. The more dense the

SOU 2004:67 Some Geological, Geodynamic and Geophysical Investigation …

network, the better it is to locate and characterise also minor earthquakes. Registered data from average and large earthquakes can be evaluated with regard to the orientation of the stress field and the movement surface, its area and the displacement that has occurred. Such evaluations are conducted by the seismology division (Department of Earth Sciences) at the University of Uppsala, which also since the year of 2000 operates the new seismograph network, SNSN. So far, over 1,000 earthquakes have been registered in this network, Figures 3.19 and 3.20.

Some Geological, Geodynamic and Geophysical Investigation … SOU 2004:67

Figure 3.19. The occurrence of earthquakes in Scandinavia. The increased number of earthquakes in the four regions marked green in Fig. 3.16 is clearly visible (from Sveriges Nationalatlas ©, Lantmäteriet Gävle 2004, permission M 2004/3790).

SOU 2004:67 Some Geological, Geodynamic and Geophysical Investigation …

Figure 3.20. The distribution of earthquakes in the Vänern region shows an accumulation of earthquakes (map view A) and their distribution projected onto a west-east (section B) and a southnorth section (profile C). (from Isaac 1992).

Some Geological, Geodynamic and Geophysical Investigation … SOU 2004:67

Traces of earthquakes can also be found in sediment stratification and in the bedrock. In the former case, the time of the earthquake can often be identified, while the age of the traces in the bedrock can seldom be determined. In the sediment stratification, the occurrence of landslides and liquefaction indicate earthquakes. In the bedrock, the occurrence of friction melting indicates the position and extent of fossil earthquakes. It has also been suggested that bedrock caves are caused by earthquakes.

3.6.4. Fault Movements

The brittle uppermost part of the Earth’s crust is dissected by movement zones. When adjacent bedrock blocks are displaced, this is called a fault (see Berglund & Stigh 1998). Some of these zones have been active just after the deglaciation (Figures 3.21 and 3.22). However, the movement must displace a geological structure that can be dated, for example an esker or a moraine ridge, a measurable distance in order for the movement to be observable. If the movement has occurred in a completely homogeneous environment or is only very small, the movement cannot be determined. The geological environment must also be so stable that the displacements can be preserved. In recent years, methods have been developed that allow all systematic bedrock movements to be measured, for example, with repeated GPS measurements of fixed points positioned strategically with respect to the zones that are to be investigated (see Figures 3.4 and 3.5). The measurement series must be conducted over a period of at least 6 years in order to obtain interpretable results. Investigations so far conducted with GPS measurements show that lateral movements that are a few mm per year occur along the Tornquist zone in Scania (one of the first order shear zones – see Figure 3.16) (Pan et al. 2001). In the network in Norrbotten, where the observation time is only 5 years, it has not been possible to prove any movements with certainty

SOU 2004:67 Some Geological, Geodynamic and Geophysical Investigation …

(Ågren 2001) and in that region, the measurements should be repeated several times. Information on deformations that have occurred very long ago has been compiled in Milnes (1998). However, their present function is still unclear. It is not well understood where, how and why present-day movements occur since this requires both detailed local investigations and a good knowledge of the movement pattern in the plate tectonic unit to which Sweden belongs. Furthermore, the problem would require a three-dimensional approach, which is difficult to achieve since the distribution of horizontal fractures are often unknown.

Some Geological, Geodynamic and Geophysical Investigation … SOU 2004:67

Figure 3.21. Post-glacial faults in northern Scandinavia (red dashed lines), (from Lagerbäck (1988).

SOU 2004:67 Some Geological, Geodynamic and Geophysical Investigation …

Figure 3.22. The Pärve fault – one of the large post-glacial fault zones in Scandinavia, view towards north (from Lindström et al. 2000), (photograph by J. Lundquist 1975).

When the position and movements of fracture zones have been established, questions arise concerning the future function of the zones. For example, which changes in the strength and orientation of the stress field can activate a certain fracture direction as well as how the stress field will change due to the plate tectonic evolution or due to future glaciations. In LaPointe et al. (2000), model calculations describe how earthquakes that occur in the vicinity of a repository affect the repository through the activation of existing fracture zones. With the same technology, it is possible to model the size of the change in the stress field that is needed to activate the fracture and shear zones mapped in the investigation area.

Some Geological, Geodynamic and Geophysical Investigation … SOU 2004:67

References (some references are in Swedish)

Aaltonen, J., 2001: Ground monitoring using resistivity

measurements in glaciated terrains. Doktorsavhandling, KTH, Institutionen för Mark- och Vattenteknik, TRITA-AMI PHD 1042. Aaltonen, J. & Olofsson, B., 2001: Direct current (DC)

resistivity measurements in long-term groundwater monitoring programmes. Environmental Geology 41:662

Amadei, B., & Stephansson, O., 1997: Rock stress and its

measurements. Chapman and Hall, London. Andersson, O., Bergdahl, U., Nemeth, T., Nyberg, I., Stille, H.,

Svesson, P.L., Tenne, M. & Viberg, L.,1984: Fältundersökningsmetoder – Kapitel G08. Handboken bygg. Liber -Förlag. Ask, D., 2003: Hydraulic rock stress measurements in borehole

BJO01, Björkö Island, Lake Mälaren, Sweden. KTH, Department of Land and Water Resources Engineering. TRITA-LWR. Report 3003. Bastani, M., 2001: EnviroMT – a new controlled source/radio

magnetotelluric system. Acta Universitatis Upsaliensis. Uppsala Dissertations from the Faculty of Science and Technology 32. Berglund, J. & Stigh, J., 1998: Sprickor i berg. Kunskapsläget på

kärnavfallsområdet. SOU 1998:68. Bernstone, C. & Dahlin, T., 1998: DC resistivity mapping of old

landfills: Two case studies. European Journal of Environmental and Engineering Geophysics 2:121

Cardarelli, E., Marrone, C. & Orlando, L., 2003: Evaluation of

tunnel stability using integrated geophysical methods. Journal of Applied Geophysics 52:93

Dehls, J.F., et al. 2000: Neotectonic map of Norway and adjacent

areas. In Olesen et al., NGU Report 2000.002.

SOU 2004:67 Some Geological, Geodynamic and Geophysical Investigation …

Dehls, J.F., Olesen, O., Olsen, L. & Blikra, L.H., 2000: Neo-

tectonic faulting in northern Norway; the Stuoragurra and Nordmannvikdalen postglacial faults. Quaternary Science Reviews 19:1447

Fjeldskaard, W., Lindholm, C. & Fjeldskaard I., 2000: Geo-

dynamic modeling regional and local. In Olesen et al. 2000: Neotectonics in Norway. NGU Report 2000.002:74

Grasmück, M., (1994): Application of seismic processing

techniques to discontinuity mapping with ground-penetrating radar in crystalline rock of the Gotthard Massif, Switzerland. Proc. of the fifth international conference on ground penetrating radar, June 12

  • 1994, Ontario, Canada,

pp. 1135

Hedenström, A. & Risberg, J., 2003: Shore line displacement in

northern Uppland during the last 6500 calendar years. SKB TR 03-17. Helle, S.K., 2004: Sequence stratigraphy in a marine moraine at

the head of Hardangerfjorden, western Norway: evidence for a high-frequency relative sea-level cycle. Sedimentary Geology (in press). Henkel, H., 1988: Tectonic studies in the Lansjärv region. SKB

TR 88-07. Henkel, H., 1992: Geophysical aspects of the Protogine Zone in

three traverses. GFF 114:344

Henkel, H. & Lund, C-E., 2004: Integrated gravity and

refraction seismic model along the Blue Road traverse and its extensions. The 26th Nordic Geological Winter Meeting, GFF 126:90. Henkel, H. & Roslund, M., 1994: Första ordningens branta

skjuvzoner i Sverige. SKB AR 94-56. Isaac, E, 1992: An integrated study of the Vänern lens with a

GIS. MSc thesis, Univ. of Washington, Seattle USA. Janelid, I., 1965: Bergmekaniken och dess betydelse vid planering

av gruvor och bergrum. Bergmekanik. Ingeniörsvetenskapsakademiens (IVA) meddelande 142:7

Some Geological, Geodynamic and Geophysical Investigation … SOU 2004:67

Lagerbäck, R., 1988: Postglacial faulting and peleoseismicity in

the Lansjärv area, northern Sweden. SKB TR 88-25. LaPointe, P.R., Outters, N. & Folin, S., 2000: Evaluation of the

conservativeness of the methodology for estimating earthquake-induced movements of fractures intersecting canisters. SKB Tr 00-08. Lidmar-Bergström, K., 1988: Denudation surfaces of a shield

area in south Sweden. Geogr. Ann. 70 A:337

Lindström, M., Lundqvist, J. & Lundquist, T., 2000: Sveriges

geologi från urtid till nutid. Studentlitteratur ISBN 91-44-090875-9. Löfgren, M. & Neretnieks, I., 2002: Formation factor logging in-

situ by electrical methods. Background and methodology. SKB Tr 02-27. Milnes, G., 1998: Crustal structure and regional tectonics of SE

Sweden and the Baltic Sea. SKB TR 98-21. Nimmer, R. & Osiensky, J., 2002: Direct current and self-poten-

tial monitoring of an evolving plume in partially saturated fractured rock. Journal of Hydrology 267:258

Olofsson, B., Jernberg, H., & Rosenqvist, A., 2004: Tracing

leachates at waste sites using geophysical and geochemical modelling (manuscript). O´Neal, M. & McGeary, S., 2002: Late Quaternary stratigraphy

and sea-level history of the northern Delaware Bay margin, southern New Jersey, USA – a ground penetrating radar analysis of composite Quaternary coastal terraces. Quaternary Science Reviews 21:929

Oskooi, B., & Pedersen, L.B., 2004: Magnetotelluric studies on

Björkö impact structure, west of Stockholm. Report, Department of Earth Sciences, Geophysics, Uppsala University. Pan, M., Sjöberg, L.E. & Talbot, C., 2001: Crustal movements in

Scania, between 1992 and 1998 as observed by GPS. J. of Geodynamics 31:311

Rashed, M., Kawamura, D., Nemoto, H., Miyata, T. &

SOU 2004:67 Some Geological, Geodynamic and Geophysical Investigation …

Nakagawa, K., 2003: Ground penetrating radar investigations

across the Uemachi fault, Osaka, Japan. Journal of Applied Geophysics vol. 53, pp. 63

Sattel, G, Sander, B.K., Amberg, F. & Kashiwa, T, 1996: Tunnel

Seismic Prediction, TSP – some case studies. Technical article, Amberg Measuring Technique Ltd, Regensdorf-Watt, Switzerland. Scherneck, H.-G. et al.,: Observing the Three-Dimensional

Deformation of Fennoscandia. In: /Glacial Isostatic Adjustment and the Earth System, /edited by J.X. Mitrovica and B.L.A. Vermeersen, pp. 69

  • Geodynamics Series, Volyme

29, American Geophysical Union, Washington, D.C., 2002. Sjöberg, L.E., Pan, M., & Asenjo, E., 2002: An analysis of the

Äspö crustal motion monitoring network observed by GPS in 2000, 2001, and 2002. SKB R 02-33. SKB 2001: First TRUE Stage – Transport of solutes in an inter-

preted single fracture. Proceedings from the 4th International Seminar Äspö, September 9

  • 2000, SKB Technical Report

TR-01.24. Slater, L., & Niemi, T.M., 2003: Ground-penetrating radar

investigation of active faults along the Dead Sea Transform and implications for seismic hazards within the city of Aqaba, Jordan. Tectonophysics, vol. 368, pp. 33

SNA 1994: Sveriges Nationalatlas, Berg och Jord. ISBN 91-

87760-27-4. Sträng, T., 2003: Geofysisk borrhålsloggning i borrhål BJO 01 på

Björkö och MID 01 på Midsommar. Geosigma AB. 15. SWEPOS 2003: Displacement rates. http.//www.oso.chalmers.se. Tirén, S., Wänstedt, S. & Sträng, T., 2001: Moredalen – a canyon

in the Fennoscandian Shield and its implication on site selection for radioactive waste disposal in south-eastern Sweden. Engineering Geology 61:99

Widén, E., 2001: Groundwater flow into and out of two lakes

partly surrounded by peatland. MSc thesis, KTH, Institutionen för Mark- och Vattenteknik.

Some Geological, Geodynamic and Geophysical Investigation … SOU 2004:67

Ågren, J., 2001: Processing the 1992, 1994 and 1997 campaign on

the northern GPS deformation traverse. Licentiate thesis, KTH, Department of Geodesy. Åström, K., & Lund, C-E., 1994: Thin superficial layer and

lateral heterogeneities in southern Sweden using short-period Rayleigh-wave dispersion. Geoph. J. Int. 118:231

Recommended reading

Lindsröm, M., Lundqvist, J. & Lundquist, T., 2000: Sveriges

geologi från urtid till nutid. Studentlitteratur ISBN 91-44-090875-9. Lundqvist, J., 2001: Geologi. Processer – utveckling – tillämp-

ning. Studentlitteratur. Mazor, E., 2004: Chemical and isotopic groundwater hydrology.

Third Edition. Marcel Dekker, New York. Basel. Milsom, J., 2003: Field Geophysics. Third Edition. John Wiley &

Sons, Chichester. SNA 1994: Berg och jord. Sveriges Nationalatlas. Stanfors, R., Triumf, C-A., & Emmelin, A., 2001: Geofysik för

bergbyggare. SveBeFo K 15.

4. Some Hydrogeological Methods for Determining Groundwater Recharge and Groundwater Flow

4.1. Introduction

The occurrence of groundwater, groundwater flow and the chemical composition of groundwater are of central importance for the siting and design of underground rock facilities, especially for the disposal of spent nuclear fuel. A high hydraulic conductivity makes rock engineering and disposal difficult. The groundwater can also attack barriers and waste containers, especially if the salinity is high, and can dissolve and transport hazardous components. The aim of this chapter is to present a few hydrogeological investigation methods used for determining groundwater recharge (quantity, spatial and temporal distribution) and its impact on groundwater chemistry as well as for studying groundwater flowpaths and their transport properties. Hydrological, hydraulical and chemical investigation methods and modelling methodology are not discussed here.

4.2. Hydrometeorological and Hydrological Data

Purpose

Hydrometeorological data are important in order to correctly calculate groundwater recharge in the ground and rock and to thereby provide general input data for flow potentials, for

Some Hydrogeological Methods for Determining Groundwater … SOU 2004:67

example, for numerical flow models. Hydrochemical data are also important for providing a basis for the calculation of chemical equilibrium reactions, mixing, groundwater age and flow patterns. In particular, isotope determination can be of importance for tracer studies, see Section 4.5. Hydrometeorological and hydrological data provide boundary conditions for modelling based on present-day conditions. For long-term, retrospective climate trends, geological and biological studies are required, for example dendrochronological studies (studies of tree rings), sediment studies with pollen and diatom analysis as well as studies of natural isotopes (for example, oxygen) in polar ice. These paleoclimatic studies can also provide valuable information on natural climate variations which provide input data for climate forecasts. Advanced computer models are currently used to calculate future climate conditions where anthropogenic effects (human impact) are of particularly great significance.

Data Access and Measurement Techniques

Hydrometeorological data series comprise temperature, precipitation, precipitation chemistry, relative moisture content, air pressure, wind direction, wind spred and global radiation. There are a large number of meteorological stations operating in Sweden from which data can be obtained. Most of these stations are run by the Swedish Meteorological and Hydrological Institute (SMHI). Furthermore, weather stations exist at airports, military air bases and other military facilities as well as along public roads for the purpose of road maintenance control. In addition, measurements (of precipitation, temperature and wind etc.) are conducted at nuclear facilities, for example, at Forsmark and Simpevarp, as well as at the Äspö Hard Rock Laboratory, southeastern Sweden. The frequency of measurement data collection and the parameters registered vary considerably. Major weather stations at SMHI are currently often completely automated. Information on suitable climate stations

SOU 2004:67 Some hydrogeological Methods for Determining Groundwater …

for regional and local investigations is provided by SMHI where data is currently stored digitally in several different large databases, Svenskt klimatarkiv (KLAR), Svenskt vattenarkiv (SVAR) and for sea and oceanographic data, Svenskt Havsarkiv (SHARK). Hydrometeorological data for Östhammar, Tierp and Oskarshamn have been compiled by SMHI on behalf of SKB (Larsson-McCann et al. 2002a, 2002b).

The air temperature, which is important for the calculation of evapotranspiration, is measured by mercury or resistance thermometers; the latter is preferable from the environmental standpoint. They are positioned protected from solar radiation, often about 1.5 metre above ground and at a distance from surrounding objects. The measurements are usually presented as weighted average values at different times of the day (Alexandersson 2002). In SMHI’s assessment, error sources are small.

One of the most important and most common parameters which is necessary to provide input data for balance calculations and flow modelling is precipitation. The measurements are often conducted using a wind-protected precipitation gauge with a collection surface of 200 cm

2

, placed 1.5 metres above the

ground. In general, SMHI’s stations perform measurements 1 to 2 times a day (at 07

00

h and 19

00

h, respectively). Precipitation

collection is associated with significant uncertainty that is mainly due to turbulence around the gauge which causes the precipitation to miss the gauge. Significant measurement problems are associated with snowfall since the precipitation also has to melt. The losses vary with the wind strength and wind direction as well as with evaporation and adsorption on the walls of the vessel (Eriksson 1983). The measurements are often 10 to 25 % lower than the actual figures. Therefore, it is important for the precipitation values to be adjusted before use in, for example, water balance calculations. Statistical processing of long series of precipitation data is required to provide knowledge of the frequency of dry years and wet years. Since precipitation quantities can vary locally, it is important that several

Some Hydrogeological Methods for Determining Groundwater … SOU 2004:67

representative measurement stations are located in the areas under investigation.

Wind direction and velocity are measured and specified as a matter of principle at a height of 10 metres. Since the height and speed constantly vary, an average value is given as a rule, such as during 10 minutes. The wind is used to correct other data, including precipitation, although it also has considerable significance in other contexts, for example, for the calculation of airborne pollutants, including the spreading of salt to the environment around roads (Blomqvist 2001).

Air pressure is measured using different types of barometers and this is conducted at a large number of SMHI’s weather stations as well as at airports and military air bases. The air pressure is important for the interpretation of surface and groundwater levels and other parameters and should therefore be taken into account in accurate calculations of small level changes. The combined effects of air pressure and wind can often have a considerable impact on surface water levels in lakes and seas. The effects can also be reproduced in the form of distinct level changes in groundwater levels where hydraulic connections exist. This should be taken into account in connection with groundwater level measurements in coastal areas.

Evapotranspiration is an important factor for the calculation of groundwater recharge. In practice, it is very difficult to measure, since it is dependent on many different factors, such as radiation balance, air temperature, air humidity, wind, type of ground, soil water and type of vegetation. Potential evapotranspiration can be calculated on the basis of climate parameters using Penman’s formula or can be measured as evaporation from an open, waterfilled vessel. However, since actual evapotranspiration is considerably less and is strongly affected by soil water and vegetation, it is difficult to measure. It should therefore be calculated, either as a loss item, if measurements of surface water runoff and precipitation are conducted, or be based on potential evapotranspiration and soil water content (Brandt et al. 1994).

SOU 2004:67 Some hydrogeological Methods for Determining Groundwater …

Runoff is generally determined on the basis of data from the runoff stations operated by SMHI, among others. The mainland of Sweden is divided into 119 main catchment areas which, in turn, are divided into more than 13,000 sub-catchment areas (SMHI 2004). The water level in large lakes and runoff into many large watercourses are measured manually one or more times per day or, which is more common today, are continuously registered. On the other hand, information on runoff into minor watercourses is often lacking. Therefore, it is necessary to start measurements, as early as possible, of representative, small catchment areas in order to obtain a basis for local water-balance studies. The flow in watercourses can generally be calculated directly from the water level in a measuring weir, for example a V-shaped Thomson overflow.

Measurements of precipitation and atmospheric chemistry are conducted by SMHI and IVL Swedish Environmental Research Institute Ltd. Together with Statistics Sweden (SCB), they have formed a consortium for the collection of emission data and for the development of a national database. Deposition data are very important for groundwater chemistry modelling and can also be used to study infiltration and water transport to the groundwater (percolation). Previously, isotopes in the water were also determined in precipitation samples from several sites in the country. Since the isotope laboratory at the Department of Hydrology, Uppsala University, was closed down, such measurements are no longer conducted, which is a major disadvantage for studies of groundwater recharge (see Section 4.4).

4.3. Measurement of Surface and Groundwater Levels

Purpose

The measurement of surface and groundwater levels is an important part of hydrogeological investigations. The measure-

Some Hydrogeological Methods for Determining Groundwater … SOU 2004:67

ments can have many different purposes, including long-term measurements to determine long-term trends and seasonal patterns in the level fluctuations. They can also be conducted as general difference measurements to determine flow potentials and flow directions or as specific difference measurements to determine hydraulic relationships, for example, in connection with pump tests and other investigations that aim at determining the hydraulic properties of the ground. The measurements are often used within an environmental control programme, for example, in connection with underground construction in order to prevent environmental effects in the form of ground settlement and damage to constructions, groundwater supply and vegetation. The measurements are sometimes conducted for several purposes and this involves different requirements with respect to measurement frequency, accuracy and the length of the measurement series. Prior to the construction of a repository for spent nuclear fuel, level measurements that fill many simultaneous purposes are necessary. It is important that regular measurements in different types of geology and in different terrains are started as early as possible in the site investigation areas, in order to obtain long time series and to describe undisturbed conditions. Regular level measurements in observation tubes and boreholes are going on at Forsmark and in the region of Oskarshamn.

Data Access and Measurement Techniques

Long-term measurements of the groundwater level are regularly conducted within the Geological Survey of Sweden’s (SGU) groundwater network, which comprises about twenty-five measurement areas spread over Sweden. In each measurement area, there are one or more specific measurement points that represent different aquifers, both tubes in soil as well as boreholes in rock. For groundwater monitoring, 82 areas with 120 stations also exist in the form of tubes, boreholes and springs for

SOU 2004:67 Some hydrogeological Methods for Determining Groundwater …

controlling groundwater quality. The size of the groundwater fluctuation and its temporal variation provide good information on the aquifers’ properties, limitations, heterogeneity and hydraulic relationships. SGU’s level measurements are generally conducted twice a month, and this is considered to be the minimum to obtain a clear reflection of the seasonal variations. High-resolution level measurements at som stations can be used to calculate the size of the groundwater recharge, see Section 4.4 (Johansson 1987, Healy & Cook 2002). Therefore, the evaluation requires a sufficiently high measurement frequency and, for aquifers with a small variation (for example, large aquifers or groundwater discharge areas), a high measurement accuracy is necessary.

In connection with major construction projects, separate control programmes are conducted for existing as well as newly installed measurement points. For example, major tunnel projects, such as the Bolmen tunnel which, during construction, involved measurements in more than 400 wells, tubes and boreholes as well as the Hallandsås tunnel, where the number of measurement points was close to 1,000 (Banverket 2000). However, for many of these measurement points, the measurements have only been conducted very occasionally or the measurement series are very short. Furthermore, in major cities, such as Stockholm and Gothenburg, specific monitoring programmes exist with a very large number of measurement points (almost 1,000 in Stockholm) which are, however, only measured a few times a year.

It has quite often been found that the length of the measurement series before the start of an underground construction project has been far too short for reliable assessments of groundwater impact to be made. The Swedish Environmental Protection Agency (1999) specifies an absolute minimum period of 6 months of measurement before construction start. Studies of non-equivalent measurement series (=unequal measurement frequencies) show that the measurement series should preferably be 15 to 18 months (Lundmark & Olofsson 2002) in order to

Some Hydrogeological Methods for Determining Groundwater … SOU 2004:67

determine minor deviations (<1 dm) from natural fluctuations. The length of the measurement series over several hydrological years and the use of equidistant measurements allow statistical time-series analyses to be used. If measurement points are used where groundwater abstraction occurs, for example, dug and drilled wells, the size of the groundwater abstraction must also be taken into account when evaluating the measurement series.

The measurements are either performed manually through sounding or continuously through, for example, pressure sensors and data logs. Continuous measurements are naturally preferable although they often result in large data sets. At present, there is a possibility of automating measurements from many points and of sending information via links to a data processing centre through which information can be obtained in real time from the measurement points. There is a considerable value in obtaining real-time information during the construction phase in order to allow for rapid measures and thereby prevent damage to buildings and vegetation. This approach has been successfully used in connection with underground construction in Norway in order to determine the need for leakage-mitigation measures in the underground facility (Randolph-Lund et al. 2003). It is also important that methods for analysis of groundwater level data are available in order to distinguish construction-related effects on the levels from natural variations. Systems for such statistical computer processing have been developed (such as GCP – Groundwater Control Programme) and have been used in connection with different underground projects, for example the Ormen tunnel in Stockholm (Cesano & Olofsson 1997), the Bolmen tunnel and the Hallandsås tunnel (Banverket 2000), see examples in Figure 4.1. Groundwater data are routinely collected in many construction projects, although this is often done without a structured analysis methodology. In this way, deviations have not been observed at all or have been detected at such a late stage that it has not been possible to prevent effects on the soil and vegetation.

SOU 2004:67 Some hydrogeological Methods for Determining Groundwater …

D iff er en ce (m )

D iff er en ce (m ) m .a .s. l

Figure 4.1. Examples of how statistical calculations can be conducted on groundwater levels in order to obtain deviations from natural level variations in connection with underground construction. The uppermost diagram shows unprocessed groundwater level measurements. The middle curve shows deviations from natural level variations obtained using stepwise regression and the last curve shows deviations calculated using a modified double mass analysis. The vertical line shows the time when a tunnel was constructed close to the measurement point (taken from Olofsson in Knutsson & Morfeldt, 2002).

The number of measurement points and their position are naturally very important for the usability of the groundwater data. Existing wells in rock and soil as well as springs are

Some Hydrogeological Methods for Determining Groundwater … SOU 2004:67

naturally used as measurement points which is particularly important in the initial stage as well as to investigate possible impacts during a later construction phase. The determination of the number of boreholes in rock that is necessary and the positioning of these boreholes in connection with construction projects, for example, during the construction of the Hallandsås tunnel and prior to the construction of the repository, is generally conducted on the basis of geological and geophysical investigations as well as the tectonic and geological models which are set up on the basis of these investigations. The borehole configuration is therefore highly dependent on the heterogeneity of the rock and the need to investigate specific geological rock structures. The number and positioning of soil tubes for investigation are similarly determined by the variation of the soil cover and topographical conditions. In order to capture the typical long-term level variations in an investigation area, soil tubes and boreholes must be located in different geological and topographical environments and the levels must be registered in recharge and discharge areas for different groundwater systems and at different depths (if the stratification involves several groundwater systems). Therefore, this is different from the siting of control and investigation holes that primarily aim at providing construction-related data or at investigating specific structures. In order to design a long-term control programme for groundwater levels, a good knowledge of the geology of the area is required. The more heterogeneous and geologically fragmented an area is, the more observation points are required for a good control of the level changes. It is very difficult to obtain an adequate control in crystalline bedrock, since two adjacent boreholes can demonstrate completely different or temporally displaced level variations. In construction projects, it is usual to underestimate the area of impact, especially along major conductive zones in the rock (Olofsson 1991, Banverket 2000). Existing measurement programmes can be made more efficient as measurement data are obtained, through different statistical methods, for example principal

SOU 2004:67 Some hydrogeological Methods for Determining Groundwater …

component analysis (PCA, Pearson 1901), from which the covariation between different points can be determined. The methodology is independent of the spatial distribution of the points and only explores linear trends in the data set. For points with hydraulic connections, different variations of geostatistic methodology can be used, for example, kriging, in order to render the position and number of measurement points more efficient (Ackerberg 2002).

The measurement of surface water levels is important, as has been described above, for the determination of runoff in small watercourses and for the calculation of water balances and the interaction between the surface water and groundwater. In many cases, high-resolution registration is of considerable importance, with respect to time and level, and this can provide knowledge of the lake’s or watercourse’s hydraulic conditions. High-resolution pressure and temperature registration have been conducted in a few lakes in the Forsmark area and show that lakes in the same area can function very differently in hydrodynamic terms with respect to recharge and discharge conditions as well as with respect to hydraulic connections with the surrounding groundwater (Widén 2001).

4.4. Groundwater Recharge – Measurement Methods and Calculations

Background and Problems

Groundwater is the underground part of the water cycle and, thereby, the most difficult part to measure and investigate. Groundwater recharge is defined as the downward water flow that reaches the groundwater system in question. Knowledge of the quantity of the recharge and of its spatial and temporal distribution is of greatest importance, for example, in connection with siting, design and construction of underground facilities below the groundwater table as well as in connection

Some Hydrogeological Methods for Determining Groundwater … SOU 2004:67

with the siting and design of waste deposits and water supply wells. The impact of groundwater recharge on the groundwater chemistry (for example, through acid rain or pollutants) must also be taken into account, for example, by conducting a vulnerability analysis for existing or planned water supply wells.

Groundwater recharge can be direct, namely, the precipitation directly infiltrates through the ground to an open aquifer (aquifer=a permeable geological formation capable of yielding groundwater to wells and springs) or indirect through the inflow of water from surrounding elevated areas to a closed aquifer or through contact with other aquifers. Another indirect process is induced infiltration, namely leakage from adjacent lakes or watercourses to an open aquifer as well as infiltration in dry river beds which is common in arid climate areas after heavy rain. The infiltration conditions are very different in different rock and soil strata depending on their permeability and moisture content. The size of the infiltration naturally also depends on the weather conditions, primarily the nature, quantity and temporal distribution of the precipitation as well as the size of the evapotranspiration. In this way, the conditions for groundwater recharge are very different from year to year or from time-period to time-period depending on the changes in weather and climate, especially in an arid climate (Knutsson 1988). Therefore, it is very important to collect and process hydrometeorological and hydrological data (see above), also statistically, so that the frequency of “dry” years and “wet” years is determined as well as more long-term climate changes.

In connection with direct groundwater recharge, inflitration into the ground takes place within the elevated areas of the terrain, also known as recharge areas, from which the water flows all the way from small, superficial, local systems to large, deep regional systems (Figure 4.2). Through topographical variations as well as variations in the geology, such as the occurrence of horizontal or flat structures with considerable water permeability, such as sand and gravel layers in till, superficial, open fractures in the bedrock (such as in Forsmark, see Figure 3.11 in

SOU 2004:67 Some hydrogeological Methods for Determining Groundwater …

Chapter 3) or fracture zones at greater depths (such as at Finnsjön in Uppland, Sweden), the groundwater is then step by step linked to springs, wetlands, surface watercourses and lakes, also known as discharge areas at different levels in the landscape. In this way, only a small part of the water reaches deeper parts of the bedrock and flows to the regional systems. The small-scale topography which dominates both southeastern Sweden and northeastern Uppland is favourable for the occurrence of local flow systems and superficial groundwater recharge, although not for regional systems and groundwater recharge at deeper levels (Follin & Svensson 2003, SKB 2003). One difficult complication is if human intrusion should disturb the natural groundwater recharge, for example, by leading water away in connection with tunnel construction. This causes the groundwater levels to sink and the recharge area changes and this can lead to increased recharge, faster turnover and changes in the groundwater chemistry. In agricultural areas with irrigation, a small addition of (surplus) infiltrating water can be expected, as is the case in densely populated areas with leaking sewage and clean water pipes followed by subsequent changes in groundwater chemistry.

Some Hydrogeological Methods for Determining Groundwater … SOU 2004:67

Rock Soil Water Fracture zone

Fracture

Theoretic flow lines Real groundwater flow

Figure 4.2. Recharge and discharge areas as well as groundwater flow patterns in a valley with varying topography and thin soil cover on fractured, hard rock. The actual flow pattern deviates considerably from the theoretical depending on fractures and fracture zones (Olofsson et al. 2001).

Important questions relating to groundwater recharge include the following:

  • How and where does groundwater recharge occur? How is the chemistry affected?
  • How great is the groundwater recharge in different aquifers and at different depths and what kind of hydraulic connection occurs with the surface water and between different aquifers?

SOU 2004:67 Some hydrogeological Methods for Determining Groundwater …

  • How does groundwater recharge occur in time with different weather conditions and climate changes?
  • What kind of human intrusion can disturb groundwater recharge and change the chemistry?

Methods and Calculations

Overall assessments of groundwater recharge in a large area can be conducted in the form of a water-balance study based on precipitation and evapotranspiration data and taking into account geology, hydrology, topography and vegetation. The amount of groundwater recharge in a certain aquifer can be calculated using infiltration coefficients (the relationship between the quantity of infiltrated water and precipitation in a recharge area) for different rock types and soils if the geological and topographical conditions are very homogeneous and largescale. However, this is seldom the case in Swedish terrain and consequently the method cannot be recommended.

Area and site-specific information on the size of groundwater recharge, its spatial distribution and temporal evolution requires detailed knowledge of geology, hydrogeology, land use and topography in the area as well as extensive measurements and calculations. Up-to-date information on precipitation and evapotranspiration is needed in the form of long series of or forecastes of climate data.

Different methods, based on different principles, exist for measuring and calculating groundwater recharge. Method selection should be conducted taking into account the purpose, time-scale, type of information desired (point or area data) as well as access to background information and resources. The use of the different methods must be based on good knowledge of the groundwater recharge processes and the existing geological and hydrogeological conditions. Therefore, it is important to initiate the study by setting up a conceptual model of the area of investigation. This entails a simplified, generalised description

Some Hydrogeological Methods for Determining Groundwater … SOU 2004:67

with a principle diagram (block diagram, cross section) of how the entire groundwater system functions as a whole (Figure 4.3). The conceptual model is based on the water-balance calculations and on existing data on the geology, size and limits of the groundwater system as well as on where and how groundwater recharge occurs and flows and on whether human intrusion can be expected to disturb the natural processes. Based on the model and the criteria specified above, the most suitable investigation methods and computer models can be selected. However, remarkably few good examples exist of conceptual models that are openly described in the literature, especially for groundwater conditions in hard rock.

In principle, the methods can be classified according to where in the system the movement and quantity of the water is being studied:

  • Recharge, for example, using tracers.
  • Response within the system, for example using groundwater level analysis.
  • Discharge, for example runoff measurements.

Preferably, several independent methods should be tested. The uncertainties in the calculations must be specified for each specific method.

SOU 2004:67 Some hydrogeological Methods for Determining Groundwater …

Figure 4.3. Conceptual model for the groundwater conditions in the Nybro esker and its surroundings in a profile from the esker to the sea. E=Evaporation + T=Transpiration (350 mm/year), I=Irrigation, P=Precipitation (510 mm/year), P

0

=Natural

groundwater recharge (160 mm/year), Q

AR

=Artificial recharge

from basins (40 mm/year), Q

GF

=Groundwater inflow and

outflow, Q

SF

=Outflow of groundwater from sandstone aquifer to

the Baltic Sea. Q

W

=Abstraction wells (60 mm/year),

Q

WS

=Abstraction of water from sandstone aquifer, R

G

=Runoff in

streams and drainage from groundwater, S=Sublimation and infiltration from snow. Note that the diagram is not to scale. The length of the profile is about 5 km and the maximum thickness is about 50 m (from Eliasson 2001).

Recharge Methods

Groundwater recharge can be studied with the help of tracers and through modelling. Added tracers and natural tracers (see Section 4.5) have both been used to follow the path of the precipitation, such as snow melt water with a certain oxygen isotope composition through the unsaturated zone down to

Some Hydrogeological Methods for Determining Groundwater … SOU 2004:67

different depths below the groundwater surface for a couple or several years. Based on the average velocity of the water particles and the water content in an observed stretch, the size of the groundwater recharge is determined at 280 mm/year in sandy soil in the Uppsala district, south central Sweden (Saxena 1987). In Scania, south Sweden, and Denmark, tritium pulses have been followed for several years down through the thick soil cover to considerable depths in the bedrock. This has made it possible to determine parameters such as the time sequence for groundwater recharge to limestone at a depth of 150 metres on the Kristianstad plain to about 5 years (Engqvist 1991, see Section 4.5). Isotope data (deuterium, oxygen-18, carbon-14 and tritium) on the water from different depths at the Äspö Hard Rock Laboratory have provided important information on the origin of different types of groundwater, for example, that a low oxygen-18 content indicates that water from land ice melting has contributed to groundwater recharge deep in the bedrock (Laaksoharju 1999). These methods are of great interest for the development and evaluation of possible future scenarios for how a repository for spent nuclear fuel can be affected in connection with deglaciation after an expected, future ice age (see SKB 2003). It has also been possible to follow the changes in the original composition of the groundwater during the construction of the access tunnel to the Äspö Hard Rock Laboratory (see SKB 2003).

Experiments with added tracers result in pointwise measurements which can be difficult to transfer to larger areas or deeper levels. Furthermore, several of the mathematic models used are not suitable for determining groundwater recharge at depths since they have been developed for soil water studies. One complication in the use of recharge methods is if infiltration is affected by particularly permeable zones, for example, macropores in the soil cover or fracture zones in the rock. However, the results provide information on the quantity of water that is added to the surface groundwater system, namely the greatest possible groundwater recharge, which is of

SOU 2004:67 Some hydrogeological Methods for Determining Groundwater …

interest for further calculations using groundwater models (Olsson 2000). What are needed are methods to determine the groundwater flow from the soil cover to the bedrock on the basis of existing hydraulic heterogeneity, for example, for the determination of the flow from till to underlying fractured rock. This could be achieved using a combination of geophysical measurements for mapping conductive soil and rock structures as well as measurements of groundwater pressure levels and groundwater chemistry (including isotope analysis) in different geological environments.

Response Methods

The methods involve studies of how different parts of the groundwater system, for example groundwater levels, groundwater flow and groundwater chemistry, react to changes in the form of added water and chemical substances, in this case, through groundwater recharge or discharge/abstraction of water, which is compensated for by subsequent recharge. The latter continuous abstraction method has been tested at water supply wells with long-term abstraction, which often entails a change in natural groundwater recharge. The response methods provide information on the actual groundwater recharge to the system or to the level in question.

The analysis of groundwater level changes is the most immediately suitable method since groundwater levels are easy to measure and are often included in long measurement series, such as with respect to many municipal water supply wells, and in different control programmes and as a reference in similar groundwater environments in SGU’s groundwater network since the mid-sixties. A detailed description of the method with its different variations, for example, to calculate reservoir changes, is provided by Fealy & Cook (2002). The most common analysis involves transforming the groundwater level fluctuations in a number of representative observation tubes, wells or boreholes

Some Hydrogeological Methods for Determining Groundwater … SOU 2004:67

in an open groundwater reservoir to corresponding water quantities with the help of a value for the storage coefficient, also known as the specific yield of water. The storage coefficient is the quantity of water that is removed or added to the reservoir per unit area (for example, 1 m

2

) in connection with the lowering

or the raising of the groundwater level by one unit (for example 1 m). It is primarily determined by pump tests but can also be established on soil or rock samples in the laboratory. It should be known for different parts of the groundwater reservoir, which can be a demanding task, especially in fractured, hard rock. The groundwater level analysis method is otherwise best suited to groundwater levels that are fast-reacting and relatively deeply located, such as in the bedrock, where the level fluctuations are not affected by capillary transport and evapotranspiration (Johansson 1987) or ground frost. Important information which is also obtained through this method, includes knowledge of the temporal processes in groundwater recharge in relation to precipitation and climate changes and the effects of different activities that affect groundwater recharge.

The chloride balance or chloride concentration method is based on the relationship between wet and dry precipitation of chloride from the atmosphere and the chloride content in the groundwater. The chloride content usually increases with the infiltration of the water due to evapotranspiration but is then not changed in the groundwater zone. The method appears to be simple and inexpensive but has been found to contain significant uncertainties, particulary in the determination of dry precipitation and through the fact that the chloride content in the groundwater can be affected by both relict saltwater and pollutants. It is probably most suitable for rough estimates of groundwater recharge in large areas and over long periods of time. Gustafson (1988) has carried out such a calculation for crystalline bedrock in Sweden, divided into six regions with the support of existing data from SGU and SMHI. The results are interesting and show regional differences which appear to be reasonable, namely low values (24-28 mm/year) in eastern

SOU 2004:67 Some hydrogeological Methods for Determining Groundwater …

Götaland and Svealand with a low net precipitation and high values in Scania (114 mm/year, compare with Hallandsås below) and in western Sweden (250 mm/year). The values correspond to groundwater recharge in relatively superficial parts of the bedrock since the calculation is based on data from local water supply wells which are usually 100 m deep, at most. The method has been much used in dry areas, where it is expected to be a useable supplement to other methods (Lloyd 1999).

The groundwater flow method is a more demanding method which applies both to input data on hydraulic parameters and boundary conditions and to calculations with analytical and numerical solutions, or nowadays, primarily with numerical modelling. An early use of a finite element model for twodimensional flow was conducted in the sedimentary bedrock on Gotland in the Water Planning Official Report (Berggren et al. 1980). The groundwater recharge was calculated at between 10 mm/year in an area with low hydraulic conductivity and 80 mm/year in another area with higher hydraulic conductivity. The development of mathematical models has since then been extensive, including three-dimensional (3-D) flow, at the same time that increased computer capacity has speeded up calculations. In a 3-D model of northeastern Uppland, groundwater recharge at a depth of 500 m in crystalline rock is estimated at between 1.6 mm/year and 5.7 mm/year for different cases with a net precipitation of 250 mm/year (Holmén et al. 2003). In this case, it would be suitable to attempt to calibrate this modelling by measurements and calculations with other methods. Previously, groundwater recharge at Äspö has been estimated at 150 mm/year on the surface and 5 mm/year at great depth. In general, it is stated that a turnover of only 1-2 % of the surface groundwater recharge occurs in the deeper parts of the bedrock (SKB 2003). However, a disturbance in the form of construction work with subsequent groundwater lowering can essentially increase groundwater recharge. On the tunnel level in Hallandsåsen, the increase has been calculated at 25 % in connection with

Some Hydrogeological Methods for Determining Groundwater … SOU 2004:67

a maximum groundwater lowering of 100 metres (Anderberg 2000).

Discharge Methods

The methods are based on obtaining data on the quantity of water leaving the groundwater system either by direct measurements or by model calculations. The most simple method is flow measurements from springs on condition that the catchment area for the spring is well-defined and that no water passes by or below the spring. The method has been tested with great success in superficial systems, for example, springs in moraine areas (Johansson 1987) and is useable in sedimentary bedrock, above all in karst formations. On the other hand, it is difficult to apply to deep groundwater systems in fractured rock. Runoff measurements in surface water which drain a certain area and at the same time isotope analysis of oxygen-18 and deuterium in rainwater, groundwater and surface water from the same area have, however, been found to provide very valuable information, above all that the amount of groundwater in the runoff is much greater than previously assumed also at flood peaks in connection with snow melting or heavy rain (Rodhe 1987, Figure 4.4). However, the quantity of groundwater is probably dominated by superficial groundwater and it should be an important task to investigate, through additional isotope determination, whether the groundwater supplied from greater depths, for example from well-defined bedrock areas, can be separated.

Runoff models have been used to determine groundwater recharge in areas with consistent geology, such as the moraine areas and large glaciofluvial deposits in southeastern Sweden (Johansson 1987 and Eliasson 2001). In the first study, several different models and methods were compared. In both studies, different variations of the HBV model, developed by SMHI, which is based on easily available weather data, were used. The model gave reasonable results on the average, annual ground-

SOU 2004:67 Some hydrogeological Methods for Determining Groundwater …

water recharge for each area. In the second study, it was also possible to obtain a value for groundwater recharge in the sandstone aquifer situated below the glaciofluvial deposits (15 mm/year compared with 160 mm/year in the superficial layers, see Figure 4.3). Unfortunately, the study did not include the underlying hard rock, although the groundwater recharge can be estimated at only a few mm/year.

Some Hydrogeological Methods for Determining Groundwater … SOU 2004:67

runoff (l/s)

total

ground water

rain water

June

June

rain mm/h

rain

runoff (l/s)

total

ground water

rain water

June

June

rain mm/h

rain

stream

Figure 4.4. Diagram of runoff in a stream, the rain intensity and oxygen-18 content in rainwater at different precipitation times and in the stream water for the entire period. The low oxygen-18 content in the heavy rain does not have any particular impact on the oxygen-18 content in the stream water due to the fact that most of the runoff comprises “old” groundwater with a higher oxygen-18 content. It is forced out of the discharge areas near the stream of the infiltrating water upstream through the piston flow principle (based on Grip & Rodhe 1988 in Knutsson & Morfeldt 2002).

SOU 2004:67 Some hydrogeological Methods for Determining Groundwater …

4.5. Tracer Methods and Isotope Techniques

Background and Problems

It is often of great interest to study groundwater flowpaths, flow velocities and transport pathways for pollutants or sorption of pollutants in the groundwater zone in connection with different types of groundwater investigations. The least controversial method to do so is to follow the path of the groundwater or pollutant through experiments and measurements of very small quantities of specific substances or isotopes that occur naturally or that are added to the soil and groundwater, namely, to conduct a tracer experiment. The results can then be used to determine hydraulic contexts and safety distances to sources of pollutants as well as to evaluate the results of modelling of for example, the transport and sorption of different radioactive substances. The usual problems that are studied are:

A. The groundwater

  • flow between boreholes and wells, in boreholes in connection with packer tests and sampling or, for example, between sink holes and springs in a karst system
  • flow direction and flow patterns in the bedrock fracture system or in soil layers
  • flow rate between two points or, for example, within a protection area of a water supply well
  • recharge, origin and age

B. The soil and ground

  • dispersion properties, such as the dispersion plume of a pollutant
  • hydraulic properties, primarily permeability/hydraulic conductivity
  • sorption and ion-exchange properties, such as sorption of a pollutant

Some Hydrogeological Methods for Determining Groundwater … SOU 2004:67

Requirements on Artificial Tracers

It is not difficult to find suitable tracers for investigations to determine a hydraulic connection between two points, since the behaviour of the tracer in the ground is not of decisive importance for the interpretation of results. The only important factor is to be able to detect the arrival of the tracer. In order to determine the flow direction of the groundwater, tracers, that to a certain extent are retained in the bedrock, can be used. The sorption of certain pollutants or ion-exchange in different rock or soil types, for example, fractured rock, can also be studied. This is the concept for a series of tracer experiments that are conducted in different parts of the world, such as at the Äspö Hard Rock Laboratory, prior to the disposal of spent nuclear waste.

For investigations to determine the actual flow rate of the groundwater and to determine hydraulic properties, there are major difficulties in finding suitable tracers. The ideal artificial tracer must fulfil certain requirements:

  • It should follow the groundwater movement without being sorbed or delayed in the ground by ion-exchange.
  • It may not react, for example, with microorganisms, or be affected by pH changes.
  • It should be possible to detect the tracer in very low concentrations so that the physical and chemical conditions of the water are not changed.
  • It may not be hazardous or damage plant or animal life, for example, in discharge areas and springs.
  • It should be easy to acquire at a reasonable cost and should not entail high analysis and measurement costs.

The first two requirements mean that the difficulty of finding an ideal tracer is greatest in porous rock and soil types, where the contact surfaces between the particles in the rock or soil types and tracers are very large and, thereby, the sorption and ion-

SOU 2004:67 Some hydrogeological Methods for Determining Groundwater …

exchange processes are very active. The more fine-grained the rock or soil type, the greater is the effective contact surface for these processes. The mineral composition in the rock or soil types also play an important role for the scope of the processes as does the content of organic material as well as precipitation and weathering on particle or fracture surfaces. Quartz particles have the least impact, clay minerals and organic minerals have the greatest impact. This means that in the “cleanest” sandstones and sand deposits and in open fractures and channels in the bedrock, certain types of tracers are slightly or not at all affected, while the impact is great, for example in humus and clayey soil types, in clay-weathered zones and in fractures with precipitation in the bedrock (Knutsson 1971). The occurrence and role of the microorganism can have considerable importance for the decomposition of organic dyes, some of which are also sensitive to pH- and temperature changes as well as light.

The third requirement means that a tracer which must be added in large quantities to be detectable cannot be selected. Large quantities of sodium chloride have, for example, been added in karst areas, and a heavy saltwater stream has penetrated into deep cavities and thereby not participated in the natural flow process. In porous rock and soil layers, density stratification can occur. However, the problem has decreased as analysis techniques have evolved, which has also had a favourable impact on the fourth requirement which, during a period when radioactive tracers were preferable from the detection standpoint entails considerable limitations near to water supply wells. The fifth requirement can usually be fulfilled, even if the analysis costs for isotope determination are considerable. However, the dominant costs are often the experiment costs themselves since extensive drilling, measurements and sampling at the experiment site are required. Groundwater level measurements on a large number of points are therefore necessary both for the planning and performance of tracer experiments and for the interpretation of the results.

Some Hydrogeological Methods for Determining Groundwater … SOU 2004:67

Different Types of Tracers

The following tracers have been used:

  • Organic dyes with fluorescence, for example, Rhodamine,

Sulforhodamine B, C, WT and Uranine.

  • Salts, above all anions such as bromide, iodide, chloride and nitrate.
  • Complex compounds such as fluorinated benzoates and stable metal complexes such as chromium-EDTA.
  • Radioactive isotopes, primarily tritium and radioactive isotopes of anions and metal complexes (see above).
  • Organisms, primarily bacteria, bacteriophagues and spores.
  • Diverse chemical substances in the form of pollutants such as detergents, pesticides and chlororganic compounds (such as CFCs).

Organic dyes have been successfully used for a long time in karst areas and, recently, also in fractured crystalline bedrock, especially in connection with tracer experiments in the TRUE programme in the Äspö Hard Rock Laboratory (SKB 2001). In spite of the occurrence of both weathered feldspar on the fracture surfaces and mylonite, Uranine had the same transport rate as the anions, bromide and iodide as well as tritiated water, which indicates open fractures. However, the transport paths in this initial experiment were very moderate, about 5 m (SKB 2001). Therefore, it was not surprising that, in connection with the continued block-scale experiments on a 100-metre scale, which corresponds to the safety distance from a nuclear waste landfill to a major fracture zone, Uranine was significantly retarded in relation to bromide when in contact with different sorbing materials (Andersson et al. 2002). Similar results were obtained in connection with tracer experiments in a large fracture zone in hard rock in Germany in connection with a 295metre flow path (Maloszewski et al. 1999). Normally since dye tracers undergo sorption and degradation in the soil cover, they

SOU 2004:67 Some hydrogeological Methods for Determining Groundwater …

cannot be recommended in such environments. Furthermore, they can probably not be recommended in porous sediment rock types. According to Table 4.1, it is on the whole difficult to identify a dye tracer which is not adsorbed, degraded or changed. It is remarkable that SKB has considered Uranine to be a tracer that is conservative (that cannot be affected), since it is pH and temperature-dependent and is easily adsorbed on humus and clay minerals.

Table 4.1. Comparison between the properties of different fluorescing dyes (based on Tilly et al. 1999).

Detection

limit, µg/1

Tempe- rature dependent

pHdependent pH 6

8

Photochemical degradation

Adsorption on humus

Adsorption on kaolinite

Cost

BLUE Amino G Acid

0,51 little little moderate big relative little

high

Photine CU 0,36 little yes strong very big relative little

high

GREEN Uranine 0,29 moderate yes strong very big rather big high

Lissamine FF 0,29 little no little big rather big very high

Pyranine 0,087 little yes strong big relative

little

high

ORANGE Rhodamine B 0,010 big no little extremely big

extremely big

low

Rhodamine WT 0,013 big no little very big big

rather high

Sulpho Rhodamine

0,061 big no little big very big rather

high

BLUE-GREEN Na-Naphthionate no strong

Some Hydrogeological Methods for Determining Groundwater … SOU 2004:67

As far as salts are concerned, most cations can be excluded due to sorption and retardation by ion-exchange processes (although lithium has been used with a certain success). On the other hand, anions are only sorbed to a negligible extent or not at all, since the mineral particles are also negatively charged, as a rule. Bromide, iodide and chloride ions have been largely successfully used in a large number of experiments. Bromide and iodide have advantages since the natural concentrations are very low as a rule and, consequently, only very small quantities need to be added. However, they also have certain disadvantages, for example, the risk of sorption at low pH values, when the mineral particles are positively charged. Similarly, problems can occur in contact with iron precipitation in the B-horizon and below the groundwater table at low pH values (Tilly et al. 1999). Chloride appears to have given the consistently best results and is considered to be a conservative tracer which follows the water flow without being retarded. It has been used in a large number of experiments at municipal water supply plants in Sweden in order to determine residence times for water between infiltration basins and abstraction wells. In these contexts, it is significant transport distances (up to 2,000 metres) and long residence times (weeks to months), although on the other hand, the deposits are often very coarse-grained (Hansson 2000). However, sometimes chloride is less suitable, bearing in mind the fact that chloride can occur in varying amounts in certain geological environments and in places due to pollutants, for example from landfills and roads. Therefore, chloride is directly unsuitable for use at great depths in the bedrock where the chloride concentrations are often high. The use of chloride is also dubious in low-lying areas, below the highest seawater-line in Sweden with relict salt, which requires that large quantities of salt have to be added to obtain reliable results. However, the disadvantages are most often outweighed by the fact that chloride in the form of common sodium chloride is inexpensive and easy to handle and through the fact that detection in the field is simple. The conductivity is measured directly in boreholes, wells or springs or even from the

SOU 2004:67 Some hydrogeological Methods for Determining Groundwater …

ground surface using geoelectrical methods (see Section 3.4.8) as well as the fact that chloride analyses can be inexpensively conducted in laboratories.

Stable metal complexes have also been found to be very useful as tracers. Suitable complexes exist among the metal chelates, of which the best known is ethylenediaminetetraacetic acid (EDTA). A chromium-EDTA complex has been tested in a very large number of laboratory experiments with different mineral mixtures, including different clay minerals, as well as several field experiments in rock and in the soil (Knutsson & Forsberg 1967). The chromium complex in dilution down to 0.0001 ppm is not sorbed or retarded in common minerals or in rock and soil types made of these minerals if complexation is complete. However, in contact with high concentrations of iron-bearing minerals and precipitation, for example, goethite and the B-horizon, certain iron and manganese-bearing silicates as well as clay minerals and clay mineral-rich rock and soil types, a certain retardation of the chromium complex occurs (Knutsson 1971). Other EDTA complexes and metal complexes have also been tested with favourable results (Knutsson 1970).

However, tritium, the radioactive hydrogen isotope, is the least controversial tracer since a small quantity of tritium is included in ordinary water (HTO) and tritium must be considered to follow the path of the water without sorption or retardation in most situations. Tritium has therefore been used extensively in a large number of experiments, especially in the Äspö Hard Rock Laboratory, as well as a reference tracer in connection with the testing of other tracers. However, in connection with such testing, with a 10 % addition of watersaturated bentonite (with montmorillonite as the main component) in quartz sand, tritium was found to be absorbed to these swelling clay minerals and tritium was retarded in relation to chromium-51-EDTA. Similar effects were not obtained in experiments with other clay minerals or other mineral mixtures. Furthermore, this was not the case in field experiments in different rock and soil types (Knutsson 1970).

Some Hydrogeological Methods for Determining Groundwater … SOU 2004:67

By adding tritium, or previously, through the fluctuations in tritium content which occurred through hydrogen bomb experiments, it has been possible to follow a “pulse” of tritium from infiltration by water through the soil layers down to deep rock layers. In this way, the transport velocity of the water, or the time that it takes for the groundwater to reach a certain level in the bedrock, can be demonstrated. This has been studied in deep bedrock aquifers in Scania, south Sweden (Engqvist 1991) as well as in connection with nuclear waste disposal investigations. However, investigations conducted at the same time with other tracers have shown that a mixture of water of various origins can occur at great depths. A new modelling concept has therefore been developed within projects at SKB, the M3 model, through which it is possible to investigate the proportions in water of various origins (Laaksoharju 1999, Figure 4.5).

Added tracers can primarily be used to determine the groundwater flow velocity between boreholes, in fracture zones or around water supply wells in order to determine the layout of the protection areas (particularly complicated in fractured bedrock) as well as to determine the residence time of the water in connection with artificial groundwater recharge as well as to map groundwater flowpaths from planned waste landfills. Investigations with added tracers are thus most suitable for small or medium scale experiments, where the residence times are moderate and the experiment times reasonable. On a regional scale, natural tracers should be used in the first instance or analyses of possible pollutants dispersed by man, such as freons and pesticides, should be tried, see below.

SOU 2004:67 Some hydrogeological Methods for Determining Groundwater …

a)

Seawater

Continental ice

Non-saline

Brackish

Saline

Injection of glacial melt water

Penetration of Seawater by density overturn

Up-flow of saline water

Seawater

Continental ice

Non-saline

Brackish

Saline

Injection of glacial melt water

Penetration of Seawater by density overturn

Up-flow of saline water

Some Hydrogeological Methods for Determining Groundwater … SOU 2004:67

b)

Glacial

Brine Marine

Meteoric

Short term reactions e.g: Redox, Organic decomposition, Calcite dissolution/precipitation, Ion exchange

% 100%

Mixing proportions

Short term reactions e.g: Microbial sulphate reduction, Ion exchange

Long-term/short term reactions e.g: Mineral alteration, Ion exchange, Redox, Calcite precipitation

Long-term reactions: Water rock interaction

100%

0%

50%

50%

0

Figure 4.5. a) Conceptual model of different events in geological evolution since the ice age, which have affected groundwater chemistry at Äspö. b) The calculation of mixing portions between different types of water at Äspö as well as dominant mass balance reactions with the help of the M3 model (from Laaksoharju, 1999).

A special application of added tracers is to use the conservative tracer elements such as bromide, iodide and HTO together with a number of sorbing elements, common cations, such as sodium and calcium, and radioactive cations such as cesium and strontium. In this way, flow conditions and hydraulic parameters can be reliably determined through measurements of the

SOU 2004:67 Some hydrogeological Methods for Determining Groundwater …

conservative tracers and sorption and delay (through ionexchange and diffusion) of different cations can be studied under controlled forms. The methodology has been tested in a large number of experiments conducted in a number of SKB projects, previously in Stripa and Finnsjön and, in recent years, at the Äspö Hard Rock Laboratory, where several tens of experiments have been conducted with highly interesting results (SKB 2001, Figure 4.6).

A new type of tracer which enables groundwater dating and groundwater recharge determination to be conducted is to measure the content of chemical products which started to be manufactured in recent years and which are used in liquid form, such as for agricultural purposes (pesticides) or released as gases in the atmosphere (freons, namely chlorofluorocarbons /CFCs/). The assumption is that they are not degraded or that the decomposition products can be measured. Freons appear to be the most useful. Freon manufacturing started in the 1940’s and, since then, they have accumulated in the atmosphere. They are water soluble, are added through precipitation and act as tracers. The determination of the Freon content in groundwater at varying depths can therefore show with great accuracy when the water in question came into contact with the atmosphere. The method was developed in the USA in the 1970’s and has been used in Germany and Denmark and other countries as well as on the Kristianstad plain and in southern Scania (Barmen 2001).

A group of researchers in Uppsala has started to use the method to determine the age of the groundwater in fractured rock (Bockgård 2000). The concentrations of CFC-12 and tritium at different depths in three boreholes at Finnsjön show an increasing age with depth and a mixture of water of different ages (Bockgård et al. 2004). As the use of freons ceases, the method will become less useful. Pesticides have been found in deep aquifers in Denmark as well as in some wells drilled in the rock in Sweden. The difficulty often lies in determining when the pesticides were brought to the surface.

Some Hydrogeological Methods for Determining Groundwater … SOU 2004:67

1

10

100

1000

10000

Elapsed time (h)

1E-008 1E-007 1E-006 1E-005 0.0001

0.001

No rm al is ed m a ss fl u x (1 /h )

Br-82 C-1 I-131 C-4 Na-24 C-1 Ca-47 C-1 Ca-47 C-4 K-42 C-1 Ba-131 C-4 Rb-86 C-1 Mn-54 C-4 Cs-134 C-1 Co-58 C-4

Flow path I (KI0025F03:P5 - KI0023B:P6) Injections C1 and C4

Figure 4.6. Normalised breakthrough curves for all tracers in the C1 and C3 tests in the TRUE block-scale experiments at Äspö. Note the difference in recovery and transport time between the conservative tracers, Br-82 (bromide) and I-131 (iodide) and the sorbing tracers Cs-134 (cesium) and Co-58 (cobalt), which are retained and retarded to a large extent (from Andersson et al. 2002).

Natural Tracers

The following natural tracers can be used:

  • Radioactive isotopes, above all tritium, carbon-14 and chloride-36.
  • Stable isotopes, above all deuterium, oxygen-18/oxygen-16 as well as sulphur-34/sulphur-32.
  • Noble gases such as argon, helium and radon (primarily radon-222).

SOU 2004:67 Some hydrogeological Methods for Determining Groundwater …

Tritium and carbon-14, which are produced in the atmosphere through cosmic radiation, are the most important radioactive isotopes for determining the age of the groundwater. This can vary from a few weeks to many thousands of years and is of interest to know in several practical contexts, for example, in order to determine whether groundwater at great depth is fossilbased and without turnover occurring in connection with present-day conditions which can be favourable for the disposal of hazardous pollutants but unfavourable if groundwater abstraction for water supply is planned. Before the first hydrogen bomb explosion, it was possible to determine the actual age of the groundwater to a certain level, although certain complications arose due to the mixture conditions between different types of groundwater. At that time, precipitation had a certain concentration of tritium (4 to 20 tritium units /TU/ depending on the season) and no additional tritium was supplied during infiltration. The knowledge that tritium has a half-life of 12.3 years meant that the age of the groundwater could be calculated fairly accurately. After the hydrogen bomb tests, the tritium concentrations in the precipitation increased very rapidly with the highest values at about 10,000 TU for 1963 and 1964 in certain locations in Europe. This was like an enormous tracer experiment in the whole of the northern hemisphere. Since then, the concentrations have successively decreased so that they are now at natural levels apart from in some fairly old groundwater with residues of bomb tritium and where local sources of pollutants occur (IAEA 2000). In spite of pollutants in the groundwater system, one way of determining the actual age is to determine the relationship between the concentrations of tritium and its daughter, helium-3. Helium starts to accumulate in the groundwater zone when tritium-bearing groundwater reaches the zone. The method is expensive and so far little used (Bockgård 2000).

Tritium determination can also be used to determine whether the groundwater at different depths is of the same origin and whether the groundwater at a certain depth is fed by ground-

Some Hydrogeological Methods for Determining Groundwater … SOU 2004:67

water from another area or is connected to the surface water. This has been successfully utilised for practical purposes, in a large Swedish mine in order to trace the origin of large flows of mine water, partly in connection with tunnel engineering in the Gothenburg area to determine whether the water in lakes could be connected to the groundwater in bedrock where tunnels would be built (Knutsson & Morfeldt 2002).

The determination of the age of very old water can be conducted with the help of carbon-14 which has a half-life of 5,730 years or chlorine-36 with a half-life of about 300,000 years. The determination of carbon-14 in groundwater carbon dioxide has been used since the 1950’s in many parts of the world, and very high ages have been measured in groundwater in deep aquifers, for example, in Florida and in Nubian sandstone beneath the Sahara desert as well as at great depths in Swedish crystalline bedrock within the SKB projects and at great depths in the Kristianstad plain where mineral water is abstracted which, according to the carbon-14 determination, was formed during the bronze age. However, the use of carbon-14 is problematic and complex due to the fact that the carbon dioxide content of groundwater can have different origins: from the atmosphere, from fossil organic material as well as from carbonate minerals. Major progress in resolving this problem has been made in a SKB project through the development of a method of measuring the carbon-14 concentration in groundwater in the very small occurrences of humus in groundwater at great depths by enrichment in ion-exchange columns (Petersson & Allard 1991). The deep groundwater ages calculated by previously used methods in Swedish crystalline bedrock were found to be too high.

Deuterium (D) and oxygen-18, which in very low concentrations are included in the water molecule, are of great interest in order to determine the residence time and origin of the water. The possibility of using these stable isotopes arises from the fact that an isotope fractionation (see Chapter 5) occurs in water through the fact that during each evaporation process, the

SOU 2004:67 Some hydrogeological Methods for Determining Groundwater …

enrichment of the lighter oxygen-16 isotope occurs in relation to the remaining liquid phase. The vapour that forms over the sea therefore has a lower oxygen-18 content and deuterium content than the seawater. The fractionation process is affected to a high degree by the temperature conditions prevailing during evaporation and condensation which leads to seasonal variations in temperate climates and with increasing altitudes over the sea. Norwegian investigations have found very small variations on the coast but major seasonal variations in upland areas in the interior of the country. It has been possible to determine residence times for water infiltrating into different groundwater systems (Haldorsen 1994) as well as the amount of induced surface water in connection with the pumping of groundwater in crystalline bedrock (Figure 4.7). In Greece, the geographical origin of groundwater recharge for different springs and boreholes in a rock area is identified through differences in the oxygen-18 concentration due to the effect of altitude (Leontiades and Nikolau 1999). The method has also been used to obtain data for the previously mentioned modelling conducted at Äspö (Figure 4.5) as well as in connection with experiments with added tracers at Äspö.

Helium has started to be used to study diffusion in the bedrock matrix (Andersson et al. 2002).

Radon has been successfully tested to study the exchange between surface water and groundwater.

4.6. Conclusions and Recommendations

Hydrometeorological and hydrological data series are necessary for the calculation of the water balance and groundwater recharge in an area where underground facilities are to be sited in the rock. Statistical processing of long data series is necessary in order to obtain the frequency of, for example, “dry years”, which is the design basis for the removal of groundwater, bearing in

Some Hydrogeological Methods for Determining Groundwater … SOU 2004:67

mind the environmental consequences to fauna and flora as well as for the local water supply.

Lake Honningen

Extraction

well

Reference well

in the area

Lake Honningen

Extraction

well

Reference well

in the area

O-content (δ

O

SMOW

%)

SMOW=Standard Mean Ocean Water

Figure 4.7. Variations in the concentration of oxygen-18 in a well in hard rock and in lake water in Rakkestad, Norway, which shows induced infiltration in rock with a residence time of 2.5 months and 77 % mixing of lake water (based on Hansson 2000).

The local variations in, for example, precipitation and temperature can, however, be considerably dependent on, for example, altitude effects and location, in relation to the coast. Therefore, it is necessary to supplement the national measurement stations by local and regional measurement stations for

SOU 2004:67 Some hydrogeological Methods for Determining Groundwater …

hydrometeorology and hydrology as well as extensive networks of measurement stations for groundwater level/groundwater pressure and groundwater chemistry in different hydrogeological environments and at different depths. The data are successively processed statistically and correlated with the data series from the national measurement stations.

Conceptual models of the groundwater conditions on a regional and local scale must be set up and reported openly for each investigation area to provide a basis for method selection and for computer models. There are several investigation methods that can be used to determine groundwater recharge and considerable knowledge has been obtained in the past few decades, although unfortunately, not much has been obtained regarding the size of groundwater recharge at large depths in hard rock. Knowledge must therefore be improved by testing of several independent methods on the same area, for example, response methods in combination with natural isotopes and freons as well as computer models. By using different methods, results can be checked and compared and different types of information can be obtained on groundwater recharge in time and space. This has been found in an analysis of ten different methods which were tested at Yucca Mountain in the USA (Flint et al. 2002). It is also of great importance to develop methods for the measurement of the groundwater flow from the soil layer to the bedrock, which can, for example, be achieved by combinations of geophysics, the measurement of groundwater pressure and groundwater chemistry including isotopes. In this, and in most other contexts, it is a disadvantage that the determination of natural isotopes in the water and certain other isotopes is no longer conducted in Sweden. The use of natural isotopes has decreased in Sweden unlike, for example, Norway, with its “domestic” laboratory.

Large-scale tracer experiments (safety distance to regional fracture zone) with several different conservative tracers (not dyes) are necessary in order to characterise the groundwater flow, not only in fracture zones but also in the entire bedrock.

Some Hydrogeological Methods for Determining Groundwater … SOU 2004:67

Experiments to determine the sorption and retardation of different radioactive substances should be conducted in parallel as should diffusion experiments.

Calculations using different computer models must naturally continue, in order to predict relevant groundwater recharge and groundwater chemistry conditions in the site investigations and to explore different future scenarios, such as different climate situations (greenhouse effect, glaciation) in these contexts during the repository construction phase and during long-term disposal.

SOU 2004:67 Some hydrogeological Methods for Determining Groundwater …

References (some of the references are in Swedish)

Ackerberg, B., 2002: Application of some statistical methods for

evaluation of groundwater observations – design and optimisation of a groundwater level network. Licentiatavhandling, KTH, Institutionen för Mark- och Vattenteknik, TRITA-LWR-LIC 2006. Alexandersson, H., 2002: Temperatur och nederbörd i Sverige

1860

  • SMHI, Rapport Meteorologi nr 104.

Anderberg, J., 2000: The Hallandsås railway tunnel – geology

and groundwater. In Knutsson (ed) Hardrock hydrogeology of the Fennoscandian shield. Proceedings of the Workshop on Hardrock Hydrogeology, Äspö, Sweden, May 26

1998. NHP Report 45:5

  • Stockholm.

Anderssson, P., Byegård, J. & Winberg, A., 2002: Final report of

the TRUE Block Scale project, 2 Tracer tests in the block scale. SKB Technical Report TR-02–14. Banverket, 2000: Projekt Utredning Hallandsås. Miljökon-

sekvensbeskrivning, Rapport, november 2000. Barmen, G., 2001: Nybildning i grundvattensystem med flera

akvifersenheter – i perspektiv av sårbarhet och hållbar utveckling. Avdelningen för Teknisk Geologi, LTH, Lund. Opublicerat material. Berggren, R., Falkenmark, M. & Knutsson, G., 1980: Några

metoder för bedömning av grundvattenbildningens storlek. Vattenplanering, Bilaga 4, SOU 1980: 40, Stockholm. Blomqvist, G., 2001: De-icing salt and the roadside environment.

Air-borne exposure, damage to Norway spruce and system monitoring. Doctoral thesis. KTH, Department of Land and Water Resources. TRITA-AMI-PHD 1041. Bockgård, N., 2000: Environmental tracer methods for dating of

young groundwaters. NHP Report 46-2, Uppsala. Bockgård, N., Rodhe, A. & Olsson, K.A., 2004: Accuracy of

CFC groundwater dating in a crystalline bedrock aquifer. Data from a site in southern Sweden. Hydrogeology Journal 12-2:171

Some Hydrogeological Methods for Determining Groundwater … SOU 2004:67

Brandt, M., Jutman, T. & Alexandersson, H., 1994: Sveriges

Vattenbalans. Årsmedelvärden 1961

  • av nederbörd, avdunstning och avrinning. SMHI Rapport Hydrologi nr 49. Cesano, D. & Olofsson, B., 1997: Impact on groundwater levels when tunnelling in urban areas. In Chilton et al. (eds) Groundwater in the Urban Environment. Proceedings of the XXVII IAH Congress, Nottingham, UK, 21-27 September 1997. Eliasson, Å., 2001: Groundwater impact assessment and protection – predictive simulation for decision aid. Licentiate thesis, KTH, Department of Land and Water Resources, TRITA-AMI-LIC 2066, Stockholm, ISBN 91-7283-050-6. Engqvist, P., 1991: Hur gammalt är grundvattnet? Grundvatten,

1. SGU, Uppsala. Eriksson, B., 1983: Data rörande Sveriges nederbördsklimat. Normalvärden för perioden 1951

  • SMHI, Klimatsek-

tionen. Rapport 1938:28. Flint, A.L., Flint, L.E., Kwicklis, E.M., Fabryka-Martin, J.T. &

Bodvarsson, G.S., 2002: Estimating recharge at Yucca Mountain, Nevada, USA: comparison of methods. Hydrogeology Journal 10-1:180-204. Follin, S. & Svensson, U., 2003: On the role of mesh discre-

tisation and salinity for the occurrence of local flow cells, SKB Rapport R-03-23, Stockholm. Grip, H. & Rodhe, A., 1988: Vattnets väg från regn till bäck.

Hallgren & Fallgren, Uppsala. Gustafson, G., 1988: Groundwater in crystalline rocks – some

ideas. In Englund et al. In (eds) Studies on Groundwater Recharge in Finland, Norway and Sweden. Proceedings of a workshop, Mariehamn, Åland, Finland 25

  • September

1986, pp. 91

  • Helsinki.

Haldorsen, S., 1994: Oksygenisotoper og grunnvann. Institutt

for jord- og vannfag. Norges Landbrukshögskole, Rapport 13, Ås.

SOU 2004:67 Some hydrogeological Methods for Determining Groundwater …

Hansson, G. 2000: Konstgjord grundvattenbildning, 100-årig

teknik inom svensk dricksvattenförsörjning. VAV AB, VA-FORSK Rapport 2000:5, Stockholm. Healy, R.W. & Cook, P.G., 2002: Using groundwater levels to

estimate recharge. Hydrogeology Journal 10-1:91

IAEA, 2000: Global network for isotopes in precipitation.

Hydrology Web Site. Johansson, P-O., 1987: Methods for estimation of direct natural

groundwater recharge in humid climates. Institutionen för Kulturteknik, KTH, Meddelande TRITA-KUT 1045. Knutsson, G., 1970: Spårämnen som hjälpmedel vid grund-

vattenundersökningar. Grundvatten, Norstedts, Stockholm, pp. 147

Knutsson, G., 1971: Studies of groundwater flow in various

aquifers using tracers. Doctoral thesis. Kvartärgeologiska avdelningen, Geologiska institutionen, Lunds Universitet, Lund. Knutsson, G., 1988: Humid and arid zone groundwater recharge

– a comparative analysis. In Simmers(ed) Estimation of Natural Groundwater Recharge, D.Reidel. pp. 493

Knutsson, G. & Forsberg, H., 1967: Laboratory evaluation of

51Cr-EDTA as a tracer for groundwater flow. Isotopes in Hydrology, IAEA, Vienna, pp. 629

Knutsson, G. & Morfeldt, C-O., 2002: Grundvatten – teori och

tillämpning. Svensk Byggtjänst, Stockholm. Laaksoharju, M., 1999: Groundwater characterisation and

modelling: problems, facts and possibilities. Doctoral thesis, KTH, Department of Land and Water Resources, TRITA-AMI-PHD 1031, Stockholm. Larsson-McCann, S., Karlsson, A., Nord, M., Sjögren, J.,

Johansson, L., Ivarsson, M. & Kindell, S., 2002a: Meteorological, hydrological and oceanographical information and data for the site investigation program in the communities of Östhammar and Tierp in the northern part of Uppland. SKB Technical Report TR-02-02.

Some Hydrogeological Methods for Determining Groundwater … SOU 2004:67

Larsson-McCann, S., Karlsson, A., Nord, M., Sjögren, J.,

Johansson, L., Ivarsson, M. & Kindell, S., 2002b: Meteorological, hydrological and oceanographical information and data for the site investigation program in the community of Oskarshamn. SKB Technical Report TR-02-03. Leontiadis, I.L. & Nikolaou, E., 1999: Environmental isotopes in

determining groundwater flow systems, northern part of Epirus, Greece. Hydrogeology Journal 7-2:219

Lloyd, J.W., (ed) 1999: Water resources of hard rock aquifers in

arid and semi-arid zones. Unesco Studies and reports in hydrology 58 Unesco Publishing, Paris. Lundmark, A. & Olofsson, B., 2002: Analysis of groundwater

levels in urban areas. In Killingtveit, Å.(ed) Nordic Hydrological Conference, Röros, Norge 4

  • augusti 2002, NHP

Report 47, pp. 849

Maloszewski,P., Herrman, A. & Zuber, A., 1999: Interpretation

of tracer tests performed in fractured rock of the Lange Bramke basin, Germany. Hydrogeology Journal 7-2:209

Naturvårdsverket, 1999: Grundvatten – bedömningsgrunder för

miljökvalitet. Naturvårdsverket Rapport 4915. Olofsson, B., 1991: Groundwater conditions when tunnelling in

hard crystalline rocks

  • a study of water flow and water chemistry at Staverhult, the Bolmen tunnel, S Sweden. BeFo, forskningsrapport, 160:4/91. Olofsson, B., Jacks, G., Knutsson, G., & Thunvik, R., 2001:

Grundvatten i hårt berg – analys av kunskapsläget I: SOU 2001:35. Olsson, T., 2000: Bedömning av grundvattenpåverkan. Resultat

av genomförda utredningar. Banverket Södra Banregionen. Rapport till Projekt Utredning Hallandsås. Pettersson, C. & Allard, B., 1991: Dating of groundwaters by

14C-analysis of dissolved humic substances. In Allard et al (eds) Humic substances in the aquatic and terrestrial environment, Springer Verlag, Berlin.

SOU 2004:67 Some hydrogeological Methods for Determining Groundwater …

Rodhe, A., 1987: The origin of streamwater traced by oxygen-18.

Doctoral thesis, Uppsala University, Div. of Hydrology, Rep. Ser. A No. 41, Uppsala. Rudolph-Lund, K., Skurtveit, E., Engene, B. & Mykland, J.,

2003: Active groundwater monitoring and remediation during tunnelling through fractured bedrock in urban areas. In Krasny, J., Hrkal, Z, Bruthans, J., (eds) International Conference on Groundwater in Fractured Rock, 15

  • September

2003, Prague, Czech Republic. Saxena, R., 1987: Oxygen-18 fractionation in nature and estima-

tion of groundwater recharge. Doctoral thesis, Uppsala University, Div. of Hydrology, Rep. Ser. A No. 40, Uppsala. SKB 2001: First TRUE Stage – Transport of solutes in an inter-

preted single fracture. Proceedings from the 4

th

International

Seminar Äspö, September 9

  • 2000, SKB Technical Report

TR-01.24. SKB 2003: Grundvattnets regionala flödesmönster och samman-

sättning – betydelse för lokalisering av djupförvaret. SKB Rapport R-03-01. SMHI 2004: GIS och GIS-databaser 2004. SMHI Faktablad

nr 19. Tilly, L., Maxe, L. & Johansson, P-O., 1999: Spårämnesförsök

som undersökningsmetodik vid konstgjord grundvattenbildning. VAV AB, VA-FORSK rapport 1999:14, Stockholm. Widén, E., 2001: Groundwater flow into and out of two lakes

partly surrounded by peatland. MSc thesis, KTH, Institutionen för Mark- och Vattenteknik.

Recommended Reading

Englund, J-O., Knutsson, G. & Soveri, J., (eds) 1988: Studies on

Groundwater Recharge in Finland, Norway and Sweden. Proceedings of a workshop, Mariehamn, Åland, Finland, 25

  • September 1986. NHP Report No 23, Helsinki.

Some Hydrogeological Methods for Determining Groundwater … SOU 2004:67

Gustafsson, G., 1986: Geohydrologiska förundersökningar i

berg. Bakgrund-metodik-användning. BeFo 84:1. Hydrogeology Journal, 2002: Theme Issue: Groundwater

Recharge Volume 10. Knutsson, G. & Morfeldt, C-O., 2002: Grundvatten – teori och

tillämpning. Svensk Byggtjänst, Stockholm. Käss, W., 1998: Tracing Technique in Geohydrology. Balkema,

Rotterdam. Lerner, D.N., Issar, A.S. & Simmers, I., 1990: Groundwater

recharge- a guide to understanding and estimating natural recharge. Internat. Ass. Hydrogeologists Volume 8. Heise, Hannover. Lloyd, J.W., (ed) 1999: Water resources of hard rock aquifers in

arid and semi-arid zones. Unesco Studies and reports in hydrology 58, Unesco Publishing, Paris. Mazor, E., 2004: Chemical and isotopic groundwater hydrology.

Third Edition. Marcel Dekker, New York. Basel. Sanders, L., 1988: A manual of field hydrogeology. Prentice

Hall, New Jersey.

5. Analysis and Fractionation of Isotopes

5.1. Introduction

The ability to measure extremely low concentrations of ions and other dissolved substances in the groundwater around a deep repository for used nuclear fuel is an essential requirement for future safety analysis. This concerns not only the measurement of total concentrations, but also the speciation and transport through the natural and technical barriers that will surround the copper capsules deposited in accordance with the KBS-3 concept. Of particular concern in these respects are the radionuclides, which are isotopes of the elements that decay, emitting electromagnetic or particulate radiation, and thus may be hazardous to the environment. Although many such isotopes occur naturally, it is quite conceivable that they could be released from nuclear waste deposits should the protective barriers fail to function as planned.

Since most radionuclides are more or less soluble in water, transport pathways will be dependent on the presence and the characteristics of the water in the repository environment.

Freely flowing water should, of course, be avoided, as this would facilitate rapid transport of dissolved species, as well as colloids. Colloids may consist of precipitated radionuclides or particles from the bentonite barrier together with adsorbed species.

Analysis and Fractionation of Isotopes SOU 2004:67

However, transport of ions and neutral species will even occur in stagnant water, as a result of, e.g., diffusion. One of the driving forces for the latter process is known as chemical potential, which strives to eliminate differences in concentration. Consequently, ions or other mobile species flow from regions of high concentration to regions of low concentration. Capsule breach, followed by dissolution of exposed radionuclide compounds, presents such a scenario where diffusion would become operative.

There is also an additional array of chemical processes that affect transport, e.g., precipitation, dissolution, complex formation, oxidation/reduction and adsorption on surfaces in the local environment. All of these processes can interact with transport, the dominating mechanism depending on the chemical characteristics of the species, as well as water parameters such as pH, ionic strength, redox conditions and the presence of other dissolved substances or bacteria. Investigations concerning the analysis and transport of radionuclides therefore constitute prioritised areas of research for the Swedish Nuclear Fuel and Waste Management Company (SKB).

For these purposes, a variety of analytical techniques have been applied, ranging from simple measurements of electrical conductivity to diverse chromatographic methods. Atomic absorption spectrometry, as well as the more modern and more advanced technique of inductively coupled plasma mass spectrometry (ICP-MS), has also found application. The latter technique offers the distinct advantage of furnishing isotope-specific information. This enables its use in, e.g., determining the age and origin of groundwater, or tracing the sources of possible heavy metal and radioactive substance contamination.

Such measurements often assume that isotope ratios are constant, which has proven to be a rule with many exceptions. In fact, it has been observed that many, if not all, of the aforementioned processes lead to changes in the original isotopic composition, an effect termed fractionation. This is an important reason for KASAM to give an account of the current state of

SOU 2004:67 Analysis and Fractionation of Isotopes

knowledge about isotope analyses, and to give examples of processes leading to fractionation.

This chapter will begin with a general introduction to the elements and their isotopes, as well as a description of certain characteristics of the latter.

5.2. The elements, isotopes and mass numbers

Atoms of any given element are characterised by a specific number of protons in their nuclei, defining the atomic number, normally denoted by the letter Z. For example, pure copper consists entirely of atoms of atomic number 29. Each element has been assigned a name and a defined place in the periodic table; all atoms of the element have essentially identical properties.

Even though all atoms of a given element have a defined number of protons, the number of neutrons can vary, within certain limits. This leads to the occurrence of isotopes. One example is element 1, hydrogen, which besides containing a single proton in its nucleus, may also possess 0, 1 or 2 neutrons, i.e., hydrogen has three isotopes with atomic masses of 1, 2 or 3, denoted by the symbols H, D (or

2

H) and T (

3

H), respectively.

Several important properties of the isotopes are, on closer inspection, dependent on mass number, which is the sum of the numbers of protons and neutrons, denoted A. The mass number gives an approximate value of the atomic mass of an isotope, whereas the atomic weight of an element is determined by the composition of the isotopic mixture in question.

To specify a certain isotope of an element, the quantities A and Z, in addition to the chemical symbol, are written in a defined fashion. As examples, the following notations

correspond to three specific isotopes of the elements copper,

63

Cu,

235

U,

1

H

29 92 1

Analysis and Fractionation of Isotopes SOU 2004:67

uranium and hydrogen, namely copper-63, uranium-235 and hydrogen-1, or simply hydrogen.

5.2.1. What is fractionation?

Two different isotopes of the same element therefore have distinct mass numbers but essentially identical chemical properties since these are determined by the number of electrons. Certain chemical effects can, however, arise because of differentces in mass number. Different isotopes may exhibit slightly different equilibrium constants for a given chemical reaction, which can result in so-called fractionation. The extent of this effect can be expressed in terms of the fractionation factor,

α

,

also known as the separation factor or enrichment factor.

α

is

defined by the quotient between isotope ratios describing the compositions of two different chemical compounds or phases, i.e.,

( ) ( )

2 1

/ /

N N

N N

l

h

l

h

=

α

where

h

N and

l

N are the abundances of the light and heavy

isotopes, respectively, present in the two forms denoted by the subscripts 1 and 2.

To obtain more convenient numbers (with fewer decimal places) the following relationship is often used. The fractionations given in the rest of this chapter have been calculated using

( )

( )

‰ 1000 1

/

/

standard

sample

,

⋅    

   

  • =

N N

N N

N

l

h

l

h

l h

δ

yielding the relative change in an isotope ratio between two forms, in this case a sample and a reference, expressed in per mil units (‰). An example of an equilibrium reaction that results in

SOU 2004:67 Analysis and Fractionation of Isotopes

fractionation is the precipitation of calcium carbonate (CaCO

3

)

from an aqueous solution.

18

O is enriched, relative to the most

common isotope,

16

O, in the precipitate by 25‰ (2.5% or

α

=

1.025). The magnitude of the fractionation factor is temperature dependent, permitting measurement of oxygen isotope ratios in CaCO

3

to be used to determine the temperature of the water at

the time of precipitation. This is the principle for the oxygen isotope geothermometer.

Photosynthesis is an example of a process where the lighter isotope, in this case

12

C, is enriched relative to the heavier

13

C.

Cellulose and lignin in wood have in this way been enriched in

12

C by somewhere in the region of 2.5% (or

δ

13,12

C = –25‰).

This is actually an example where kinetic effects lead to fractionation, since the lighter carbon-12 isotope moves more rapidly through the processes of cellulose or lignin formation, thereby becoming enriched in the final products of the reactions.

Physical processes such as evaporation, condensation and diffusion can also result in pronounced fractionation. In this way the lighter oxygen isotope,

16

O, becomes enriched in water

vapour from the oceans. At the same time, since the heavier

17

O

and

18

O containing water molecules are enriched by conden-

sation, atmospheric water vapour becomes even more depleted in these heavier isotopes. Through evaporation and condensation processes at the equator and poles, water deposited in Polar Regions is enriched in

16

O by up to about 5%.

The fissionable uranium isotope,

235

U, can be separated and

enriched relative to the more abundant, non-fissile isotope

238

U,

by virtue of minor differences in transport rates arising when gaseous

235

UF

6

and

238

UF

6

diffuse through porous barriers (see

section 5.5).

5.2.2. Radioactive isotopes

Only a small fraction of all known isotopes are stable, whereas the vast majority changes spontaneously by radioactive decay. A

Analysis and Fractionation of Isotopes SOU 2004:67

radionuclide decays ultimately to one or more stable isotopes with the release of energy. This may be exemplified by the radionuclide tritium (

3

H or T, as mentioned previously), which

always converts to helium-3,

3

He, by release of a β-particle,

which is nothing more than an energy-rich electron.

Under normal conditions, each type of radioactive isotope decays at a well-defined and characteristic rate. This means that, in the absence of any new source of formation, it is only a matter of time until all radionuclides disappear. However, certain isotopes decay so slowly that they still persist on Earth some 4500 million years after their formation. Examples of long-lived radioactive isotopes are potassium-40,

40

K, rubidium-87,

87

Rb,

neodymium-144,

144

Nd, thorium-232,

232

Th, uranium-235,

235

U,

and uranium-238,

238

U.

It might therefore seem surprising that short-lived isotopes, such as radon-222,

222

Rn, and carbon-14,

14

C, are so common on

Earth. The reason is that the amounts of these isotopes are continuously renewed by special nuclear reactions,

222

Rn by

radioactive decay of uranium and

14

C by cosmic radiation.

Nuclear weapons testing and nuclear power plants also give rise to a multitude of radioactive isotopes.

5.2.3. The isotopic composition of the elements

Since the end of the 1930’s, geochemists, astrophysicists and nuclear physicists have combined talents in an attempt to explain the observed isotopic composition of different elements. Hydrogen and helium, the two lightest elements are now assumed to have been formed in the “Big Bang”. The relatively rare isotopes with mass numbers 6-11 (lithium, beryllium and boron) have partly originated from the influence of cosmic radiation. The heavier elements are believed to derive from nuclear reactions occurring in stars, resulting in the isotopic composition of the elements known today. Consequently, practically all iron on

SOU 2004:67 Analysis and Fractionation of Isotopes

Earth and in meteorites has been shown to contain about 5.85%

54

Fe, 91.75%

56

Fe, 2.12%

57

Fe and 0.28%

58

Fe.

The fact that the isotopic composition of different elements is relatively constant has enabled the tabulation of average atomic weights. Atomic weights are of the utmost importance in all chemical calculations.

5.2.4. The properties of isotopes

Generally speaking, all differences between the properties of different isotopes of the same elements can be related to two factors – differences in mass or differences in nuclear structure. The first is usually called the isotope effect, whereas the second has various names depending on the nature of its effect.

Helium consists of two stable isotopes,

3

He and

4

He, both of

which exist as gaseous atoms under normal conditions. At given temperature and pressure,

4

He will have 33% greater mass than

the same volume of

3

He, thus conferring a greater density. If the

hydrogen isotopes (H) are completely replaced by deuterium in water, the result is so called heavy water, with a density some 10% greater than that of normal water.

A further difference in properties, which also depends on isotopic mass, concerns the mobility of atoms. Gaseous

3

He

atoms move with an average velocity some 15% greater than

4

He

at the same temperature. Additional properties that depend on average velocities, and hence mass, include thermal conductivity and gaseous viscosity.

As mentioned above, certain properties are dependent on nuclear structure. Radioactivity is one of these, and is the result of an interaction between the forces acting on protons, neutrons and electrons. For example,

6

He is radioactive whereas

4

He is

stable.

Nuclear spin is another property of the isotopes that depends on the number and structural arrangement of neutrons and protons in the atomic nucleus. This means that atomic nuclei

Analysis and Fractionation of Isotopes SOU 2004:67

behave like minute magnets, which can, e.g., interact with electromagnetic radiation. This property is exploited in nuclear magnetic resonance (NMR) spectroscopy, which is employed in research, medicine and a range of technical applications.

The distribution of neutrons and protons in the nucleus also affects the surrounding electrons. The presence of an extra neutron in a certain isotope changes the distribution of protons and thus the shape of the atomic nucleus, in turn affecting the energies of electromagnetic radiation that can be absorbed or emitted by the electrons.

5.2.5. Fissionable isotopes

None of the elements with atomic numbers greater than 83 (bismuth), i.e., Z>83, possess stable isotopes, and therefore are subject to radioactive decay. Those elements primarily of interest for application in the nuclear power industry are the actinides with Z≥90, since some of their isotopes are fissile.

Among the actinides are the only known fissionable isotopes with their enormous potential for energy production, but also with attendant, long-term risks for the environment. Uranium, with atomic number 92, has a pair of fissile isotopes,

233

U and

235

U. Plutonium, Z=94, also has two such isotopes of considerable importance, namely

239

Pu and

241

Pu. These are formed

as unwanted bi-products in nuclear reactors from

238

U, itself

non-fissile, via the capture of neutrons released during

235

U

fission.

235

U is present at a relative abundance of only about

0.7 % in naturally occurring uranium ores, and must be enriched to concentrations in the vicinity of 2.8 % before a nuclear reaction can be initiated (Spiro & Stigliana, 2003a).

Heavier actinides, Z>94, are mostly of scientific interest, although they have found some, albeit limited, application in cancer therapy.

232

Th has great potential economic value since it

can be converted to

233

U, which is in turn fissionable.

SOU 2004:67 Analysis and Fractionation of Isotopes

Even though relatively few isotopes are actually fissile, considerably more are instable and radioactive. As a matter of fact, all elements have at least one radioactive isotope. As mentioned previously, the lightest of all elements, hydrogen, has three isotopes, of which the heaviest, tritium, is radioactive. More than 1,000 radioactive isotopes are currently known, about 50 being found naturally and the rest artificially synthesised. In excess of 500 radionuclides are produced in nuclear reactors.

Radioactive isotopes are utilised in a range of applications in medicine and technology: radioactive tracers for imaging and functional diagnostics, e.g. technetium (

99

Tc) phosphate com-

plexes for skeletal scintillography; further

99

Tc labelled sub-

stances for the diagnosis of heart, kidney, lung, etc. conditions; and

18

F labelled glucose for tumour diagnosis. Radioactive formulations are also used for localised radiation therapy, e.g.,

125

I and

192

Ir for tumour treatment.

60

Co is em-

ployed as a radiation source for cancer therapy and

131

I to locate

brain tumours, whereas

14

C is utilised for studies of diabetes,

gout, anaemia, etc.

241

Am has found application in fire alarms,

3

H in luminous

evacuation signs, and both

210

Po and

238

Pu in batteries for the

space industry.

5.3. Analytical methods and their limitations

5.3.1. Mass spectrometry

Mass spectrometry (MS) is the technique that has provided most of the experimental evidence on which our understanding of the nature and, indeed, the very existence of isotopes is based.

J. J. Thomson is credited with constructing the earliest form of instrument designed to separate atoms on the basis of their mass-to-charge ratios. Experiments with this instrument led to the discovery of the first two isotopes of any element,

20

Ne and

22

Ne of the noble gas neon in 1913 (Rouessac & Rouessac,

Analysis and Fractionation of Isotopes SOU 2004:67

2000b). This work followed Thomson’s receipt of the 1906 Nobel Prize in physics, for studies demonstrating the particulate properties of the electron.

A colleague of Thomson, F. W. Aston continued this pioneering work and discovered over 200 of the naturally occurring isotopes, including a third minor isotope of neon,

21

Ne. For his outstanding achievements, Aston was awarded the Nobel Prize for chemistry in 1922. Platzner (1997; Chapter 1) gives a brief historical account of the early development of MS in a recent book, which is also a good source of literature on the subject of isotope measurement in general.

Over the century since its conception, a plethora of instruments for MS has been designed (Platzner, 1997), certainly too numerous to describe in detail here. Therefore, we will confine ourselves at this point to a discussion of the magnetic sector type of instrument, as used in the original device constructed by Thomson, and still in use today. The basic premise in MS is that the motion of charged particles in a vacuum can be manipulated by application of magnetic or electric fields. As illustrated in Figure 5.1, ions having different mass-to-charge ratios will subscribe circular trajectories of differing radii in a magnetic field. Another important feature is that ions of different mass-to-charge ratios will be brought to focus along a plane. By positioning an array of detectors along this focal plane, it is therefore possible to simultaneously monitor a suite of ions and thus measure isotope ratios with very high levels of precision.

Once ions have been generated in a suitable source, vide infra, they are sampled by applying a large potential gradient, of opposite sign to the ionic charge, between the source and the mass spectrometer. In this way, the ions are accelerated to high velocities, preventing them from simply diffusing to surfaces inside the instrument where they would be neutralised.

A prerequisite for the technique is that the ions survive transport from the source of their production to the detector. Operating the mass spectrometer under vacuum conditions

SOU 2004:67 Analysis and Fractionation of Isotopes

facilitates their survival. As the pressure is lowered, collisions between particles become less and less frequent. Collisions are undesirable for two reasons, the first being that the ion may lose its charge by abstracting an electron from its collision partner. Uncharged particles cannot be detected and so collisions resulting in charge transfer will result in a reduction in the number of ions surviving transport to the detector. The second effect of collisions is to scatter ions, diverting them from the trajectory that leads to the detector, again resulting in losses before detection. (This latter effect can be visualised as a billiard ball grazing another ball on its way to the pocket. The collision will obviously cause the moving ball to change direction and the shot will be missed.) Scattered ions tend to collide with parts of the instrument, such as the magnet poles, where they are neutralised.

Most of the residual pressure in a mass spectrometer results from leakage of atmospheric gases into the instrument. These gases, mainly oxygen (O

2

), nitrogen (N

2

) and argon (Ar), are

very light, i.e., have relatively low masses, and therefore tend to scatter lighter ions to a greater degree than heavier ions. (A stationary billiard ball will scatter a moving ping-pong ball much more effectively than a moving bowling ball.) Consequently, heavier ions are more likely to survive transport through a mass spectrometer than lighter ions, which means that the detection efficiency increases with mass. It should be noted that there are also other effects that tend to accentuate this problem, which is termed instrumental mass discrimination or mass bias. The result of this effect is that, when an isotope ratio is measured experimentally, it will not correspond to the true value actually present in the studied material. Experimental MS data must therefore always be corrected for instrumental mass discrimination. Correction is based on experimental measurement of the mass discrimination using a sample of known isotopic composition. However, herein lies the dilemma, since isotopic compositions are determined using MS! The key to overcoming this problem is to use synthetically prepared mixtures of pure isotopes.

Analysis and Fractionation of Isotopes SOU 2004:67

Although more efficient means for the isolation of pure isotopes are now available, MS itself can be used for this purpose. Historically, large sized mass spectrometers, known as calutrons, were developed for the electromagnetic separation of

235

U, the uranium isotope employed in the manufacture of the first atomic bomb in the Manhattan project (Rouessac & Rouessac, 2000b). Assuming that sufficiently pure samples of two or more isotopes are available, mixtures of known composition can be prepared. Comparison of measured (R

meas

) with

known or true (R

true

) isotope ratios can then be used to calibrate

the mass spectrometer, i.e., determine the instrumental mass discrimination correction factor (K):

R

true

= R

meas

×K ; K = R

true

/R

meas

It should be mentioned that K is dependent on mass, and must therefore be determined for each element, and perhaps even for each pair of isotopes under study (Woodhead, 2002). The functional form of the correction factor has also been the object of considerable investigation (Russell et al., 1978).

Since a complete mathematical treatment of mass discrimination awaits a more thorough understanding of the underlying physical phenomena, K remains a purely empirical correction factor, despite widespread reference to various “laws” in the literature. For this reason, there is a growing need to ensure that isotope ratios measured and corrected in one laboratory, can be reproduced elsewhere. This necessitates the availability of reference materials that can be used as international standards for the calibration of mass spectrometric measurements. Reference materials with certified isotopic compositions may be obtained from such authorities as the Institute for Reference Materials and Measurements, Geel, Belgium, and the National Institute of Standards and Technology, Gaithersburg, USA.

SOU 2004:67 Analysis and Fractionation of Isotopes

(a)

(b) (c)

V

q r B z m

e

⋅ ⋅ =

2

/

2

2

m = mass of isotope (kg) z = ionic charge (dimensionless) B = magnetic field strength (T) r = magnetic sector radius of curvature (m) q

e

= electronic charge (1.60×10

-19

C)

V = accelerating potential (V)

Figure 5.1. Schematic diagram showing: (a) The lay-out of a mass spectrometer; (b) The governing equation showing how mass separation is achieved. Ions generated in the ion source have characteristic mass to charge ratios (m/z). The ions are accelerated by a potential applied across the ion optics, and injected into the mass analyser. Since the magnetic sector has a fixed radius of curvature (r), ions of different m/z are brought to focus by varying either the accelerating potential (V) or the magnetic field strength (B). Increasing B or decreasing V will bring heavier ions to focus at a given point on the focal plane shown in (c); (c) A detail of the magnetic sector mass analyser, showing how ions of differing m/z are focused at different positions. The left (blue) beam represents the path of the lightest ions; the right (red) beam is that of the heaviest ions. Moveable detectors are positioned at intervals along the focal plane to permit simultaneous collection of several ion beams and determine isotope ratios.

Analysis and Fractionation of Isotopes SOU 2004:67

5.3.2. Infrared spectroscopy

Although MS is undoubtedly the first choice of technique to use for the measurement of isotopic abundances, it is not the only one. The major advantage of MS in its various forms is that it is applicable to essentially all elements and compounds. On the other hand, as noted in the preceding paragraphs, mass discrimination can be a source of considerable error if not adequately corrected for. Thus there is an incentive to be able to measure isotope ratios by other techniques, as this provides an independent means of checking the data. One such independent technique is infrared (IR) spectroscopy.

As far as the measurement of isotopes is concerned, IR spectroscopy is still very much in its infancy. Unlike MS, which can measure isotopic compositions for samples in almost any form, IR spectroscopy is, at least at present, only applicable to compounds that can be introduced to the instrument as gases. Consequently, isotope ratio measurements by IR spectroscopy have found greatest application in the study of atmospheric gases, carbon dioxide (CO

2

) being a popular choice (Becker et

al., 1992; Esler et al., 2000). The greatest advantage of IR spectroscopy over MS, other than the lack of mass discrimination problems, is that the instrumentation is less expensive, simpler and portable. Therefore, atmospheric monitoring probably comprises the most important area of potential application.

Esler et al. (2000) have remarked that IR spectroscopy is capable of resolving the symmetry isotopomers of gases such as ozone (O

3

) and nitrous oxide (N

2

O) – a gas implicated in the

environmental issues of global warming and the destruction of the stratospheric ozone layer (Spiro & Stigliani, 2003b). [Isotopomers are chemical compounds in which one or more of the constituent atoms may exist as a mixture of isotopes. Since there are two stable hydrogen isotopes,

1

H and

2

H, the simple

molecular species hydrogen (H

2

) exists in three isotopomeric

forms (

1

H–

1

H,

1

H–

2

H and

2

H–

2

H) representing all the possible

SOU 2004:67 Analysis and Fractionation of Isotopes

combinations of two hydrogen atoms.] In the case of N

2

O, two

such isotopomers,

14

N

15

N

16

O and

15

N

14

N

16

O, have identical

molecular weights, since they contain equivalent isotopes, and thus cannot be distinguished by MS (Yung & Miller, 1997).

Considering how the atoms are connected provides the key to the resolution of this and other pairs of equal mass isotopomers by IR spectroscopy. Although mass discrimination is not of direct concern, IR spectroscopy still requires calibration in order to be able to convert instrumental signals to concentrations of isotopomers. For this reason, gas standards with known composition must be available for calibration purposes. Such standards are often analysed by MS (Esler et al., 2000). Fortunately, synthetic standards can also be prepared using isotopically enriched starting materials and purified products, thus relaxing the reliance on complementary measurements by MS.

It may come as some surprise to note that most car owners will unwittingly come into contact with IR spectroscopy, sooner or later (Rouessac & Rouessac, 2000a). Such instruments are namely used routinely to measure exhaust gas emissions of atmospheric pollutants such as carbon monoxide, unburnt fuel in the form of hydrocarbons, etc.

5.4. Applications of isotope ratio measurements

Isotope ratio measurements have numerous areas of application in a variety of scientific disciplines (Platzner, 1997). Two particularly relevant fields of study concern the dating of groundwater and the isotopic analysis of the actinides, especially uranium (U) and plutonium (Pu), as exemplified in the following paragraphs.

Analysis and Fractionation of Isotopes SOU 2004:67

5.4.1. Dating of groundwater

Mass spectrometry has an important role to play in the selection of sites for nuclear waste storage.

One important criterion for the selection is that, in the event of leakage from the deposited capsules, the released radioactive material will be isolated by geological barriers and hindered from entering the biosphere (KASAM, 2001a). In effect, contaminated depository water should not be able to flow unrestricted into neighbouring water bodies. Injecting stable isotopes or long-lived, radioactive isotopic tracers and monitoring their progress through geological barriers and appearance in recipient water bodies can be used to investigate water flow patterns in boreholes. Changes in isotopic composition can then be employed to infer rates of transport through the bedrock. Such experiments have recently been initiated at the Äspö laboratory.

A more traditional and non-invasive means to assess the efficiency of the bedrock as a barrier to radioactive waste dispersion is provided by dating techniques. These are performed by measuring specific isotopes in water samples collected from boreholes at prospective repository sites. Certain radioactive isotopes are naturally produced by the interaction of cosmic rays with atoms present in the Earth’s atmosphere. Such so-called cosmogenic radionuclides are distributed in the atmosphere, gradually being removed by rain and show, thus entering water bodies at the Earth’s surface. One chlorine radionuclide,

36

Cl, shows particular promise for groundwater dating (Faure, 1986). This isotope has a half-life of 3.08 × 10

5

years, and the

chemical properties of the chloride ion largely ensure that deposited

36

Cl will remain dissolved. Therefore, losses of

36

Cl are

only by radioactive decay (and not by precipitation reactions as may affect other cosmogenic radionuclides), the time-scale of which allows water that may be millions of years old to be dated.

SOU 2004:67 Analysis and Fractionation of Isotopes

Measurements of

36

Cl in modern Antarctic ice samples have

shown that the concentration is about 2.5 × 10

6

atoms kg

-1

ice.

If a volume of water, or a block of ice, is isolated from further input of recently formed

36

Cl, the concentration will decay

exponentially, as shown in Figure 5.2. From the known initial concentration present in water, and measurement of the current level in a sample collected from, e.g., a borehole, the age of the water can be calculated. For example, if the measured

36

Cl

concentration is 1.25 × 10

6

atoms kg

-1

(1.25 mega atoms per kg

= 1.25 Matoms kg

-1

), then one half-life has expired in the

sample, i.e., the water is about 0.3 million years (0.3 Myear) old. If water sampled at a site has been isolated from the in-flow of younger, fresher water for extensive periods of time, then it is likely that the geological formations will also be able to limit the out-flow of any accidentally released radioactive material in the event of any of the capsules being breached.

Further examples of the use of radioactive isotopes in connection with the dating of groundwater and groundwater flows are given in Chapter 4.

Analysis and Fractionation of Isotopes SOU 2004:67

0 1 2 3

0

2

4

6

8

10

Time (half-lives)

Conc (Matom kg

-1

)

0 1 2 3

0

1

2

3

Time (Myear)

Figure 5.2. Change in the concentration of the cosmogenic radionuclide

36

Cl in groundwater as a function of time. It is

assumed that the initial concentration is 2.5 × 10

6

atoms kg

-1

, as has

been measured in recent samples of Antarctic ice (Faure, 1986). After 3.08 × 10

5

years (one half-life), the initial concentration will

have halved. Measurement of the

36

Cl concentration in

groundwater by mass spectrometry therefore allows the age of the sample to be determined.

5.4.2. Tracing radioactive sources

The uranium found in all naturally occurring minerals has an essentially invariant isotopic composition, consisting of 0.005%

234

U, 0.720%

235

U and 99.275%

238

U (Richter et al., 1999;

Desideri et al., 2002; Cobb et al., 2003).

The resultant ratio,

235

U/

238

U ≈ 7.25 × 10

-3

, is therefore that

expected in, e.g., biological tissues and body fluids collected from flora and fauna exposed only to natural, environmental sources of uranium. However, the isotopic composition is radically altered by industrial processes geared to the production

SOU 2004:67 Analysis and Fractionation of Isotopes

of enriched uranium suitable for nuclear-fuel or -weapons manufacture. Both applications require enrichment in the abundance of

235

U, although to rather different extents. For use

as fuel in light-water nuclear reactors (the kind used in Sweden), the atomic abundance of

235

U must be at least 2.8%, whereas

enrichment to some 93% is necessary to produce weapons-grade uranium (Spiro & Stigliani, 2003a). A by-product of the enrichment process is the infamous depleted uranium (DU).

In the wake of the Gulf War and the more recent Balkan conflict, concerns grew that exposure to DU-containing debris from spent armour-piercing ammunition could constitute a health hazard (Sandström, 2002). Some soil samples collected from Kosovo in the aftermath of the conflict revealed altered uranium isotope ratios, providing evidence for the contamination of the region by DU originating from munitions (Boulyga et al., 2001). Urine samples collected from inhabitants of a suspected DU contaminated urban area, on the other hand, exhibited uranium isotope ratios consistent with natural sources (Tresl et al., 2004), as illustrated in Figure 5.3(a).

In 2001 a study was conducted on participants of the Swedish peace keeping force. Before departure for Kosovo, and again after six months of service, urine samples were acquired and analysed by MS. It was observed that the concentrations of uranium in urine were, on average, 10 times lower at the later date, as evident in Figure 5.3(b) (Sandström, 2002). Thus the application of MS contributed to dispelling fears concerning the exposure of Swedish servicemen to DU in Kosovo.

Analysis and Fractionation of Isotopes SOU 2004:67

(a)

6.5 7.0 7.5 8.0 8.5

0 5 10 15 20 25 30 35

Volunteer

235

U/

238

U x 1000

(b)

0 40 80 120 160

1 3 5 7 9 11 13 15 17 19 21

Volunteer

U (ng g

-1

creatinine)

Figure 5.3. (a) Uranium isotope ratios measured in the urine of local inhabitants of an urban area suspected of being contaminated with depleted uranium. Uncertainty bars are drawn at a 95% confidence level; data have been gleaned from Tresl et al. (2004). (b) Uranium concentrations present in the urine of KFOR personnel before leaving Sweden (shaded bars) and after six months service in Kosovo (open bars). The data have been extracted from Sandström (2002).

SOU 2004:67 Analysis and Fractionation of Isotopes

It should be mentioned that spent fuel from nuclear reactors still contains

235

U. By reprocessing, this

235

U can be re-enriched up to

about 4% and used to fuel a reactor (Desideri et al., 2002). However, during the chemical reprocessing of spent fuel, both the enriched uranium and the DU by-product are contaminated with artificial isotopes including

236

U,

239

Pu and

240

Pu.

Mass spectrometric analyses have provided irrefutable proof that the armour-piercing ammunition employed in the Balkans contained at least some DU derived from re-processed nuclear fuel, and thus spread artificial radioactive isotopes in the environment. On the other hand, the amounts of radionuclides actually released are considered to be insignificant in comparison to other sources, such as fallout from Chernobyl, and consequently, their toxicological effects are deemed negligible (Desideri et al., 2002).

Mass spectrometry also has an important roll to play in differentiating the sources of nuclear contamination in the environment. During the latter half of the 20th century, nuclear weapons detonations in the stratosphere, conducted by the United States and the former Soviet Union, spread radioactive material across the face of the Earth, deposition reaching a maximum in the period 1963-1964.

This resulted in global fallout inventories in the range 50-100 Bq m

-2

, expressed as the sum of the most prevalent isotopes,

239

Pu and

240

Pu, and denoted

239+240

Pu. This may be augmented by

local or regional sources, such as leakages or authorised discharges from nuclear power plants and fuel reprocessing facilities, as well as reactor or satellite accidents (Warneke et al., 2002). Although a local or regional source might conceivably be detectable on the basis of an elevated

239+240

Pu inventory, more

definitive evidence can be obtained from isotope ratios, each source having a characteristic isotopic composition (Kelley et al., 1999; Warneke et al., 2002; Ketterer et al., 2004).

Note that the use of

239+240

Pu results from the common

application of a-spectrometry to measure plutonium inventories in the environment. For most instruments, the energies of the

α

-

Analysis and Fractionation of Isotopes SOU 2004:67

particles emitted by decay of

239

Pu and

240

Pu are too similar to be

resolved, and so, in effect, the sum of the activities of both isotopes is measured (Mitchell et al., 1997).

Data for the plutonium isotopes are collected in Table 5.1, where it can be seen the

240

Pu/

239

Pu ratio differs greatly between

sources, thus providing an excellent means of revealing the origins of environmental contamination. This possibility is exemplified by the data shown in Figure 5.4 (adapted from Ketterer et al., 2004), where soil sampled from southern Poland is seen to be contaminated with plutonium from northern hemisphere fallout. Samples collected in north-eastern Poland, on the other hand, have also been subjected to pollution from the Chernobyl accident. The plutonium present in the latter samples therefore represents a mixture of material derived from these two different sources.

It is important to realise that isotope ratios will be altered over the projected time scale for nuclear waste storage in the deep repository, because of differences in the half-lives of the radionuclides, such as

239

Pu and

240

Pu, as evident from Table

5.1(a). Nevertheless, differences between the isotopic signatures of the sources will be preserved, and thus isotope ratio measurements will continue to provide a means of identifying the origins of radionuclides in the environment, far into the future. However, in about 65,000 years time, i.e., after 10 halflives of

240

Pu, the concentration of

240

Pu will be only 0.1% of the

current level, and therefore extremely difficult to detect, at least with today’s technology.

SOU 2004:67 Analysis and Fractionation of Isotopes

Table 5.1. (a) Half-lives (Kelley et al., 1999; Ketterer et al., 2002) and abundance ranges of Pu isotopes in weapons-grade plutonium (Mitchell et al., 1997). (b) Atomic abundance ratios of the two most common Pu isotopes originating from various sources.

(a) Isotope Half-life (year) Abundance (atom %)

238

Pu

87.74 <0.005 – 0.04

239

Pu 24 119 ± 27 93.3 – 97.0

240

Pu 6 564 ± 11 2.9 – 6.0

241

Pu 14.33 ± 0.02 0.12 – 0.58

242

Pu

376 000

(b) Source of Pu

240

Pu/

239

Pu Reference

Global fallout 0.166 – 0.194 Kelley et al., 1999 (northern hemisphere) Weapon production 0.01 – 0.07 Warneke et al., 2002 DU from nuclear fuel 0.12 Desideri et al., 2002 reprocessing Chernobyl accident 0.

37 – 0.41

Muramatsu et al., 2000, Boulyga & Becker, 2002

5.5. Processes leading to isotopic fractionation

In the so called LTDE (long term diffusion experiment) project, SKB is currently assessing the extent of diffusion of radioactive species through bedrock. In the parallel LOT (long term test of buffer material) project, SKB is also studying the diffusion of radionuclides through the bentonite buffer material.

These projects, to study the transport of radionuclides through the bedrock at Äspö and bentonite, raise two potentially complicating factors for the interpretation of the results. As the groundwater flow rate through the bedrock at any finally selected site must be essentially zero, to prevent the spreading of any accidental radioactive waste leakage, transport of material will be driven by diffusion.

Analysis and Fractionation of Isotopes SOU 2004:67

0,1 0,2 0,3 0,4 0,5

0 1 2 3 4 5 6 7 8 9 10

Sample number

240

Pu/

239

Pu

Figure 5.4. Plutonium isotope ratios in soil samples collected in Poland, illustrating the ability to discriminate between sources. The lower shaded region covers the range of

240

Pu/

239

Pu typically found

in northern hemisphere fallout. The Pu present in samples 1-3 collected in southern Poland (filled circles) clearly originates from this source. The upper shaded region encompasses the composition interval of Chernobyl-derived Pu. Samples 4-9, acquired in northeastern Poland, exhibit isotope ratios that are characteristic of twocomponent mixing between northern hemisphere fallout and Chernobyl Pu. Data adapted from Ketterer et al. (2004).

The first question that follows is whether diffusion transports different isotopes of the same element in groundwater at the same rate or not. The second concerns the extent to which chemical reactions, such as precipitation and complex formation, might induce fractionation of isotopes in the deep repository environment.

It is well known that, in the gas phase, lighter atoms and molecules diffuse faster, this principle being exploited for the enrichment of fissionable

235

U, as mentioned above. This process

requires that uranium be converted into the volatile compound,

SOU 2004:67 Analysis and Fractionation of Isotopes

UF

6

. On passing through each of a series of porous diffusion barriers, the gas becomes enriched in the lighter isotopomer,

235

UF

6

, by a factor equal to the square root of the

238

UF

6

/

235

UF

6

mass ratio. As each fluorine atom has a mass of 19, the factor is equal to √[(238 + 6 × 19)/(235 + 6 × 19)] ≈ 1.004, so literally hundreds of diffusion barriers are required to enrich natural uranium, containing 0.720%

235

U, to fuel-grade uranium, with at

least 2.8%

235

U (Spiro & Stigliani, 2003a).

Although isotopic separation by gas phase diffusion is a wellunderstood process, the question of whether similar effects might be observed in solution has only recently been addressed (Rodushkin et al., 2004).

As shown schematically in Figure 5.5(a), when a solution containing dissolved iron (Fe

2+

ions) is brought into contact

with another, iron-free solution, Fe

2+

will diffuse into the pure

medium. Gradually, Fe

2+

migrates deeper into the initially pure

solution, causing a concentration gradient to develop, as illustrated in Figure 5.5(b). The concentration of iron in the solution drops by factors of 10 and 100 at distances (x) of about 2.7 cm and 4.2 cm, respectively, from the boundary between the two solutions, located at x = 0. These observations are in perfect agreement with the behaviour expected according to theory (Noggle, 1996).

In Figure 5.5(c), the effect of diffusion on the isotopic composition of the iron sampled at various distances from the initial boundary is depicted. After 72 h and about 5 cm from the initial boundary, a

δ

56,54

Fe-value of –0.4‰ (–0.04%) is observed,

i.e., the solution has become enriched in the lighter isotope, consistent with

54

Fe-species diffusing more rapidly than the

corresponding

56

Fe-containing ones. Figure 5.5(d) demonstrates

that consistent behaviour is also obtained for a third iron isotope,

57

Fe.

Analysis and Fractionation of Isotopes SOU 2004:67

(b)

0.001

0.01

0.1

1

0 1 2 3 4 5

x (cm)

c

/c

f

SOU 2004:67 Analysis and Fractionation of Isotopes

Analysis and Fractionation of Isotopes SOU 2004:67

Figure 5.5. Effect of diffusion in solution on the concentration and isotopic composition of iron. (a) Experimental set-up with 1 ml iron solution covered by quartz sand to provide a mechanical barrier. After careful addition of 9 ml of pure, iron-free solution, the set-up was allowed to stand undisturbed for 72 h. Then the solution was removed, from the top, in portions of 0.5 to 1.0 ml. (b) With increasing distance (x) from the source of dissolved iron, the concentration drops in accordance with a pure diffusion model, illustrated by the solid line. The data are given as measured concentrations (c) divided by the final concentration (c

f

) that

would be reached once all iron has been uniformly distributed throughout the solution volume. (c) Changes in the isotopic composition of the iron measured at various distances from the source. The solid horizontal line shows the initial isotopic composition, the parallel dotted lines representing the range of uncertainty in the

56,54

Fe ratio. The data points (diamonds) with

uncertainty bars trace the change in isotopic composition with distance. After about 1.5 cm, the isotopic composition has changed significantly from that of the iron source. The solid curve is a mathematical model of the effect of diffusion on the isotopic composition. (d) Three-isotope plot showing that the change in isotopic composition is dependent on the masses of the diffusing isotopes. As the mass differences between the isotope pairs

57

Fe –

54

Fe

and

56

Fe –

54

Fe are 3 and 2 atomic mass units, respectively, the data

points should plot on a line with a slope of about 3/2. Clearly, all but one of the data points fit the theoretical slope (solid line).

SOU 2004:67 Analysis and Fractionation of Isotopes

The latter is known as a three-isotope plot (Zhu et al., 2001), and provides a useful check on the consistency of experimental data. Considering the isotope pairs

57

Fe –

54

Fe and

56

Fe –

54

Fe, the

mass differences are 3 and 2 atomic mass units, respectively. Any mass-dependent process causing fractionation between

56

Fe –

54

Fe (Figure 5.5(c)) would be expected to induce a proportionately greater effect on the

57

Fe –

54

Fe isotope pair, by

virtue of the greater mass difference. In the simplest terms, we expect that the ratio of

δ

-values, (

δ

57,54

Fe)/(

δ

56,54

Fe), should be

roughly equal to the ratio of the mass differences, 3/2, as verified by the results shown in Figure 5.5(d). Analogous results have also been obtained for zinc isotopes in the same experimental set-up.

Clearly then, diffusion will cause fractionation of dissolved species in any environment, representing a potential source of error in the interpretation of isotopic measurements. On the other hand, the magnitude of the observed effect is very small as shown by Figure 5.5(c), and thus should not have any significant effect on the safety analyses performed on the deep repository for nuclear waste. Pescatore (2002) has called for more careful consideration of the potential isotope fractionation effects that may occur in the setting of radioactive waste disposal. To this end, a new model accounting for the effects of chemical potential gradients as well as Brownian motion has been proposed (Pescatore, 2002).

It should be noted that based on the theory of Brownian motion, there is a simple relationship between the diffusion coefficient (D/cm

2

s

-1

) and the distance (x/cm) that an isotope

(or any other diffusing species) will travel in a given time (t/s), as expressed by the Einstein-Smoluchowski equation (Atkins, 1990): D = x

2

/(2 t). If we assume a diffusion coefficient of

1.0×10

-5

cm

2

s

-1

, which corresponds to a somewhat lighter and

faster moving species than iron (D ≈ 0.6×10

-5

cm

2

s

-1

), the

Einstein-Smoluchowski equation tells us that travelling average distances of 1, 10 and 1,000 m by diffusion alone would take 16, 1600 and 16 million years, respectively. Diffusion in solution is

Analysis and Fractionation of Isotopes SOU 2004:67

evidently an extremely slow process, which is why you must stir your coffee or tea after adding a lump of sugar!

Regarding the second concern alluded to above, there is a growing body of evidence that fractionation is a rather commonplace accompaniment to chemical reactions in a diverse range of settings. Therefore, the discussion will be confined to some preliminary experimental results obtained following the addition of individual, transition metal solutions to fresh, powdered samples of bentonite clay (Forsling et al., 2004).

After standing overnight, samples of solution remaining above the swollen bentonite were taken for concentration measurement and isotopic analysis. The results are summarised in Table 5.2, and indicate that bentonite efficiently removes most of the dissolved metal ions from solution. This is one of the attractive features of bentonite as a technical barrier in the KBS-3 concept for nuclear waste storage (KASAM, 1998).

One interesting observation made during these experiments was that, during water (and metal ion) uptake, the degree of bentonite swelling was noticeably diminished by the presence of copper ions (Cu

2+

) in solution. A similar effect has previously

been noted for calcium ions (Ca

2+

), i.e., the degree of swelling

for sodium-bentonite is significantly greater than that of calcium-bentonite (Abdullah et al., 1999; Hoeks et al., 1987). During the repository lifetime, sodium-bentonite (the preferred barrier material in the KBS-3 concept) would be converted to the calcium form by ion exchange processes occurring following the influx of Ca

2+

-rich groundwater (KASAM, 2001b).

Calcium-bentonite cannot adsorb as much water as the sodium form, and will therefore contract, possibly creating fissures in the material. This could potentially impair the efficiency of bentonite as a barrier to the dispersion of radioactive waste in the event of capsule damage. Corrosion of the copper cladding, and subsequent uptake of Cu

2+

by the clay,

might similarly compromise the integrity of the bentonite layer.

The % sorption results in Table 5.2 show that the efficiency of copper uptake is lowered at the higher initial concentration,

SOU 2004:67 Analysis and Fractionation of Isotopes

suggesting that the bentonite buffers capacity to take up Cu

2+

has been exceeded. This indicates that Cu

2+

is very strongly

bound to the surfaces of negatively charged bentonite particles, in turn causing inter-particle attraction and aggregation of the clay, effectively limiting the space available for water molecules to be accommodated (KASAM, 2001b). This interpretation explains the observation that dissolved copper reduces the degree of bentonite swelling, and is supported by the isotopic data presented in Table 5.2, as will become apparent below.

Table 5.2. Uptake of cadmium, copper and zinc from solution during the swelling of initially dry, powdered bentonite. The

δ

-

values are expressed as average values per atomic mass unit to facilitate comparison between isotopic pairs for different elements. The isotope ratios measured were

111

Cd/

110

Cd,

112

Cd/

110

Cd,

113

Cd/

110

Cd and

114

Cd/

110

Cd for cadmium

, 65

Cu/

63

Cu for copper

and

66

Zn/

64

Zn,

67

Zn/

64

Zn and

68

Zn/

64

Zn for zinc.

Concentration (mg I

-1

)

Element Initial Final Sorption (%)

δ (‰ per amu)

Cadmium 500 18.9

96.2 +0.02 ± 0.04

Cadmium 50 2.0

96.1 +0.13 ± 0.04

Copper 500 55.1

89.0 –0.06 ± 0.10

Copper 50 0.2

99.6 –1.64 ± 0.09

Zinc

50 0.35

99.3 +0.52 ± 0.14

First though, we must consider the processes occurring during hydration of bentonite clay. During water uptake, water molecules and dissolved metal ions interact with surfaces and diffuse into pores in the clay mineral particles. If diffusion to particle surfaces and within pores were the only processes taking place, then we would expect that the fraction of ions remaining in solution would be over-represented by heavier isotopes. As shown in Figure 5.5(c), diffusion favours the lighter isotopes,

Analysis and Fractionation of Isotopes SOU 2004:67

which would thus be able to migrate into pores more readily than their heavier counterparts, leaving the latter behind. This is what appears to happen in the cases of cadmium and zinc (Table 5.2). At both initial cadmium concentrations, the fractions sorbed are statistically identical. While this demonstrates that the capacity of bentonite for cadmium uptake has not been exceeded, it also indicates that the Cd

2+

resides within water

channels inside, and between particles, and is not strongly bound to surfaces like copper ions.

Other than transport phenomena, chemical reactions may occur during the hydration process. The products of reactions are the most stable compounds that can be formed from the given starting materials. Heavier isotopes form more stable bonds than lighter isotopes (Fujii et al., 2002; Schauble et al., 2001; Weston, 1999), thus chemical reactions may be an important source of fractionation. As copper is suspected of being strongly bound to bentonite particles, the reaction should lead to preferential removal of the heavier isotope (

65

Cu) from

solution. In other words, the δ

65,63

Cu-value measured for the

copper remaining in solution should be negative, as indeed is observed (Table 5.2). Isotopic measurements can therefore be used to shed light on processes occurring in the deep repository.

5.6. Conclusions

There are a variety of processes with the potential to disturb the natural isotopic compositions of different elements. Such changes, which can be documented by measuring isotope ratios, are termed fractionation effects.

Many of the processes inducing isotopic fractionation have been known for decades, such as those observed for oxygen and carbon in natural cycles or caused by radioactive decay. The fractionation occurring during natural cycling of the elements is, to a large extent, a result of differences in diffusion rates between isotopes in the gas phase.

SOU 2004:67 Analysis and Fractionation of Isotopes

This chapter demonstrates that there are additional chemical and physical processes that may cause fractionation, e.g., in aqueous solutions, and thereby affect the transport of radionuclides through natural and technical barriers in the deep repository. These processes include diffusion in solution, which favours transport of the lighter isotopes of a given element, whereas many chemical reactions, such as precipitation, complex formation and possibly adsorption as well, lead to enrichment of the heavier isotopes.

Measurements of the isotopic composition of a specific element have traditionally been used to trace pollution sources, but the fact that many chemical reactions along transport pathways may alter isotope ratios, suggests that such methods may provide ambiguous results.

As illustrated by our own experiments, changes in isotopic compositions resulting from various chemical and physical processes can be exploited in different ways. Clearly, careful measurements of isotope ratios can provide important information on the underlying mechanisms for transport of various elements in the deep repository.

This is a field that SKB should investigate further in the future.

Analysis and Fractionation of Isotopes SOU 2004:67

References

Abdullah, W.S., Alshibli, K.A. & Al-Zoúbi, M.S. (1999) Applied

Clay Science, 15, 447-462.

Atkins, P.W. (1990) Physical Chemistry, 4

th

Edn., Oxford

University Press, Oxford, Chapter 25, pp. 748-776.

Becker, J. F., Sauke, T. B. & Loewnstein, M. (1992) Applied

Optics, 31, 1921-1927.

Boulyga, S.F., Testa, C., Desideri, D. & Becker, J.S. (2001)

Journal of Analytical Atomic Spectrometry, 16, 1283-1289.

Cobb, K.M., Charles, C.D., Cheng, H., Kastner, M. & Edwards,

R.L. (2003) Earth and Planetary Science Letters, 210, 91-103.

Desideri, D., Meli, M.A., Roselli, C., Testa, C., Boulyga, S.F. &

Becker, J.S. (2002) Analytical and Bioanalytical Chemistry, 374, 1091-1095.

Esler, M.B., Griffith, D.W.T., Wilson, S.R. & Steele, L.P. (2000)

Analytical Chemistry, 72, 216-221.

Faure, G. (1986) Principles of Isotope Geology, 2

nd

Edn., Wiley,

New York, Chapter 23, pp 405-428.

Forsling, W., Stenberg, A., Ranheimer, M. & Baxter, D.C. To be

published.

Fujii, Y., Nomura M., & Ban, Y. (2002) Journal of Nuclear

Science and Technology, 39, 413-418.

Hoeks, J., Glas, H, Hofkamp J. & Ryhiner, A.H. (1987) Waste

Management and Research, 5, 93-105.

KASAM (1998) “Safety analysis of the final disposal system”, in

Nuclear Waste, State-of-the-Art Reports 1998, KASAM (Swedish Council for Nuclear Waste), SOU1998:68, Fritzes, Stockholm, Chapter 5, pp. 95-119.

KASAM (2001a) “Groundwater in hard rock” in Nuclear Waste

State-of-the-art Reports 2001, KASAM (Swedish Council for Nuclear Waste), SOU 2001:35, Fritzes, Stockholm, Chapter 4.

SOU 2004:67 Analysis and Fractionation of Isotopes

KASAM (2001b) “The function of bentonite as a barrier in the

deep repository for spent nuclear fuel”, Nuclear Waste, State-of-the-Art Reports 2001, KASAM (Swedish Council for Nuclear Waste), SOU2001:35, Fritzes, Stockholm, Chapter 5.

Kelley J.M., Bond, L.A. & Beasley, T.M. (1999) Science of the

Total Environment, 237/238, 483-500.

Ketterer, M.E., Watson, B.R., Matisoff, G. & Wilson, C.G.

(2002) Environmental Science and Technology, 36, 1307-1311.

Ketterer, M.E., Hafer, K.M., Link, C.L., Kolwaite, D., Wilson, J.

& Mietelski, J.W. (2004) Journal of Analytical Atomic Spectrometry, 19, 241-245.

Mitchell, P.I., León Vintró, L., Dahlgaard, H., Gascó, C. &

Sánchez-Cabeza, J.A. (1997) Science of the Total Environment, 202, 147-153.

Muramatsu, Y., Ruhm, W., Yoshida, S., Tagami, K., Uchida, S. &

Wirth, E. (2000) Environmental Science and Technology, 34, 2913-2917.

Noggle, J. H. (1996) Physical Chemistry, 2

nd

Edn., Harper-

Collins, New York, Chapter 9, pp. 459-502.

Pescatore, C. (2002) “Discordance in understanding of isotope

solute diffusion and elements for resolution”, in Radionuclide Retention in Geologic Media, OECD/NEA, pp. 247-255.

Platzner, I. T. (1997) Modern Isotope Ratio Mass Spectrometry,

Wiley, New York.

Richter, S., Alonso, A., De Bolle, W., Wellum, R. & Taylor,

P.D.P. (1999) International Journal of Mass Spectrometry, 193, 9-14.

Rodushkin, I., Stenberg, A., Andrén, H., Malinovsky, D. &

Baxter, D.C. (2004) Analytical Chemistry, 76, 2148-2151.

Rouessac, F.F. & Rouessac, A. (2000a) Chemical Analysis:

Modern Instrumental Methods and Techniques, English Edn., Wiley, New York, Chapter 10, pp. 161-187.

Analysis and Fractionation of Isotopes SOU 2004:67

Rouessac, F.F. & Rouessac, A. (2000b) Chemical Analysis:

Modern Instrumental Methods and Techniques, English Edn., Wiley, New York, Chapter 16, pp. 289-327.

Russell, W.A., Papanatassiou, D.A. & Tombrello, T.A. (1978)

Geochimica et Cosmochimica Acta, 42, 1075-1090.

Sandström, B. (2002) Levels of uranium in urine from Swedish

personnel that have been serving or will serve in the Swedish KFOR contingent. Part II. Follow-up. User Report FOI-R-0581-SE, Swedish Defence Research Agency, Umeå (in Swedish, English abstract).

Schauble, E.A., Rossman, G.R. & Taylor, H.P. (2001) Geo-

chimica et Cosmochimica Acta, 65, 2487-2497.

Spiro, T.G. & Stiglian, W.M. (2003a) Chemistry of the

Environment, 2

nd

edn., Prentice Hall, Upper Saddle River,

Chapter 3, pp. 44-73.

Spiro, T.G. & Stiglian, W.M. (2003b) Chemistry of the Environ-

ment, 2

nd

edn., Prentice Hall, Upper Saddle River,

Chapters 6 and 8, pp. 145-179, 194-215.

Tresl, I., De Wannemacker, G., Quétel, C.R., Petrov, I.,

Vanhaecke, F., Moens, L. & Taylor, P.D.P. (2004) Environmental Science and Technology, 38, 581-586.

Warneke, T., Croudace, I.W., Warwick, P.E. & Taylor, R.N.

(2002) Earth and Planetary Science Letters, 203, 1047-1057.

Weston, R.E. (1999) Chemical Reviews, 99, 2115-2136. Woodhead, J. (2002) Journal of Analytical Atomic Spectrometry,

17, 1381-1385.

Yung, Y.L. & Miller, C.E. (1997) Science, 278, 1778-1780. Zhu, X.K., Guo, Y., O’Nions, R.K., Young, E.D. & Ash, R.D.

(2001) Nature, 412, 311-313.

6. Copper Canisters – Fabrication, Sealing, Durability

6.1. Introduction 6.1 Introduction

Based on available information on canister fabrication methods, strategies and industrial experience, this chapter provides an account of the fabrication processes, methods and techniques which are generally known in the industry and which are reliable with a broad base of experience. Processes, methods and techniques that are new or customised for this application will also be examined. A comparison between this fabrication project and other similar industrial manufacturing projects is conducted, particularly with respect to design, welding and residual stresses. Furthermore, requirements on methods for Non-Destructive Testing (NDT) are compared with other industrial applications. Metallurgical characteristics that arise as a result of varied manufacturing techniques are evaluated and the impact of these characteristics on the long-term properties of the repository is examined.

The sealing of the repository is examined by evaluating its long-term properties and by posing the question of whether there are any canister fabrication processes that could degrade mechanical properties or cause long-term corrosion. Methods, procedures and models that are usually applied in the industry to evaluate long-term corrosion or creep are discussed in a longterm perspective. Furthermore, the extent to which different models can predict phenomena such as corrosion and creep over very long timescales is treated.

Copper Canisters – Fabrication, Sealing, Durability SOU 2004:67

According to the KBS-3 method, the canister, which comprises different parts (Figure 6.1), is an important barrier inside the repository, since the canister prevents groundwater from coming into contact with the radioactive spent nuclear fuel. The outside of the canister is a copper shell which covers a nodular cast iron insert – combining external resistance to corrosion with internal load bearing capacity. Both of these components are therefore important for isolating the spent nuclear fuel from the groundwater over very long timescales (>100,000 years), which is much longer than the lifetime of any other industrially fabricated product. To prevent radioactive substances from leaking out of the canister, the fabrication methods must allow a defect-free canister to be manufactured where the materials properties of the copper and cast iron are guaranteed and optimised against all relevant damage mechanisms, such as forms of corrosion, creep, rupture etc.

Figure 6.1. Dimensions and weights for canisters with wall thicknesses of 50 mm and 30 mm (RD&D Programme 2001).The

SOU 2004:67 Copper Canisters – Fabrication, Sealing, Durability

fuel from both boiling water reactors (BWRs) and pressurised water reactors (PWRs) will be deposited in the repository. The total quantity of spent nuclear fuel to be deposited depends on the total number of reactor operating years. For example, in a scenario with 40 years of reactor operation, the quantity of BWR fuel from Swedish reactors is estimated at about 7,000 tonnes and the quantity of PWR fuel at about 2,300 tonnes. In addition to this, 23 tonnes of MOX fuel and 20 tonnes of fuel from the Ågesta reactor will be deposited. The hypothetical repository is designed for 8,000 tonnes of BWR fuel, which corresponds to 4,000 canisters in Sweden. The canisters weigh about 25 tonnes each when filled with four PWR or twelve BWR fuel elements. This means that one canister can hold about two tonnes of spent fuel. (RD&D Programme 2001)

In Finland, three different canister models are needed, one each for BWR fuel, VVER 440 fuel and OL3 fuel. After 50 to 60 years of reactor operation, the quantity of spent BWR and VVER 440 fuel is estimated at 6,000 tonnes, which corresponds to 3,000 canisters in Finland. The current estimate of spent OL3 fuel is about 2,000 tonnes, which corresponds to 1,000 canisters. (TKS-2003)

The copper shell (50 mm wall thickness) protects the spent nuclear fuel against corrosion. From the standpoint of fabrication, a thinner wall thickness (30 mm) would be better, but the wall thickness must be acceptable from the corrosion standpoint, especially from the perspective of local corrosion. A 30 mm wall thickness facilitates Non-Destructive Testing (NDT). With thinner material, finer grain sizes are also achieved and the canister microstructure is easier to control.

It is expected that the canister will be fabricated either from drawn seamless tubes or by welding together two tube halves of rolled plate. A bottom will be welded to the copper tube either through electron beam welding or Friction Stir Welding (FSW).

Copper Canisters – Fabrication, Sealing, Durability SOU 2004:67

Figure 6.2. Example of fabricated canister components and objects (RD&D Programme 2001).

After the fuel has been placed in the canister, the insert is sealed with a lid that is screwed. The lid is then welded onto the copper shell and leaktightness testing is then conducted using NDT methods. The quantity of copper needed for the finished canisters is about 40,000 – 60,000 tonnes in Sweden and about 25,000-30,000 tonnes in Finland.

The copper material must first and foremost meet the requirements in accordance with the ASM UNS C101000 (Cu-OFE) or EN133/63:1994 Cu-OF1 standards. Other requirements besides these are: O<5 ppm, P 40-60 ppm (in the future, possibly 30-70 ppm), H<0.6 ppm, S<8 ppm and the grain size <360 µm in all conditions after fabrication. See Table 6.1 for the quality requirements for copper (Andersson, 2002).

The fuel channels in the insert are fabricated in the form of an array (cassette) of square tubes. The walls and bottom of the

SOU 2004:67 Copper Canisters – Fabrication, Sealing, Durability

insert are then manufactured by casting nodular cast iron around the channel array. The cast iron must comply with the requirements of the EN-GJS-400-15U standard. The insert is the heaviest component of the canister.

Table 6.1. Requirements on materials composition and comments on different properties of the copper canister material (Andersson, 2002; Appendix 2, Technical Specification no. KTS001).

Three methods of NDT are used for the canister. X-ray radiography allows pore defects to be detected while ultrasound inspection allows defects that do not occupy volume to be detected, such as incomplete penetration, and eddy-current testing allows near-surface defects to be detected. Since the weld surface must withstand corrosion, it is important that the

Copper Canisters – Fabrication, Sealing, Durability SOU 2004:67

finished canister should not have any surface defects. Acceptance criteria will be established in the future for all of the parts of the canister, including the welds. The other destructive test methods make it possible to determine whether the test criteria are fulfilled by the NDT methods.

6.2. Fabrication

6.2.1. Copper Shell

Forging

The forging of copper tubes is a possible alternative to canister manufacturing. However, this process has not been completely investigated and developed. A large number of lids and copper bottoms have been manufactured through hot forging of continuous cast parent material. Homogeneous and defect-free material has been obtained for the finished components. The structure of the material is more coarse-grained than the material in extruded or pierce and draw processed copper tubes but meets the grain size requirement of the Swedish Nuclear Fuel and Waste Management Co’s (SKB) specification (360 µm), see Table 6.1. Further development work is needed to optimise the forging process with respect to materials microstructure and usage.

Roll Forming

By roll forming 12 full-scale copper tubes have been longitudinally welded with electron beam welding for SKB. The weld technique has been improved and the weld quality has increased with time. Consequently, the method can probably be further developed, especially for thinner (30 mm) wall thicknesses, as a suitable alternative for tube manufacturing.

SOU 2004:67 Copper Canisters – Fabrication, Sealing, Durability

Extrusion and Pierce and Draw Processing

Extrusion and pierce and draw processing are two different methods for the manufacturing of drawn or seamless tubes. Both methods are currently suitable for canister fabrication. At least 14 seamless tubes have been manufactured, 11 by extrusion and three by pierce and draw processing, for SKB. 5 tubes have been fabricated for Posiva in Finland.

Hot Isostatic Pressing (HIP)

The HIP process is currently only a theoretical possibility since the largest HIP furnaces are only 3 m high. The HIP process can provide a small and even grain size compared with the other manufacturing methods, although the properties can only be moderately improved due to the absorption of oxygen during the process.

6.2.2. Cast Iron Insert

Many attempts (over 20 in Sweden and two in Finland) have been made to cast full-scale inserts. Since the mechanical properties of the cast iron are highly dependent on the dimensions of the body of casting, the materials testing must be conducted on the finished inserts. So far, these studies have shown a wide scatter in tensile testing results. This has been caused by both casting defects and microstructural inhomogeneity. The probability of obtaining a defect of a critical size increases with the size of the component and under the assumption that the greatest defect determines the canister’s load-bearing capacity, the maximum permitted load – the size effect – in large components decreases. The casting process and the specification of the cast iron, EN-GJS-400-15U (EN 1563), (see also Andersson, 2001), must be optimised due to the above

Copper Canisters – Fabrication, Sealing, Durability SOU 2004:67

investigations of inserts. For the cast iron insert, reliable materials data are required as input data in connection with final mechanical strength calculations.

The canister with its cast iron insert must withstand considerable stresses under the hydrostatic pressure that can occur in a deep repository, for example, the groundwater pressure at a depth of more than 500 m in the rock, the pressure from the swollen bentonite buffer surrounding the canister and from a 3 km thick ice sheet (glaciation). Altogether, there might be a maximum pressure of about 45 MPa (450 bar) on the canister. In a recently conducted test, the model canister – with a cast iron insert with defects – managed a hydrostatic pressure that was three times as high, 130 MPa. Investigations of deformations and possible canister cracking are underway. On the basis of these studies, it will be possible to state, with a high degree of certainty, whether the canister will meet the requirements with an adequate margin (Nilsson and Burström, 2004).

The cast iron insert must be manufactured with high tolerance requirements as must the copper tube for the canister. Copper tubes manufactured by roll forming and longitudinal welding require more material for the final machining than the other manufacturing methods.

6.2.3. Lid Welding

Electron Beam Welding

Electron beam welding is a fusion welding method which in a vacuum (or under low pressure) with a strong electron beam melts the material through local heating. The method has several advantages: thick objects can be welded without consumables and weld parameters are programmable and reproducible. The weld has the same composition as the parent metal, but the oxygen concentration in the copper, in particular, has a negative impact on the weldability and the oxygen concentration must

SOU 2004:67 Copper Canisters – Fabrication, Sealing, Durability

therefore be controlled. Even with a high-energy method, such as electron beam welding, the welding of copper is difficult to conduct due to the high thermal conductivity of the material and the low viscosity of the melt. Therefore, the electron beam welding method needs to be further developed with respect to equipment and welding parameters in order to achieve a stable process with high reliability (Claesson & Ronnetag, 2003). In particular, the seal weld must meet the requirements on longterm properties and durability.

Friction Stir Welding (FSW)

The principle for Friction Stir Welding is relatively simple. A rotating tool is pressed into the joint between the parts that are to be welded. The copper around the tool is heated up by the friction to over 800 ºC and becomes soft. The tool is then moved in the direction of the joint and the two metal parts are joined together. The fundamental difference, compared with electron beam welding is that the material does not melt during welding. A new large welding machine for FSW has been taken into operation at SKB’s Canister Laboratory in Oskarshamn in 2003. The design is such that the welding head rotates during the process around the stationary canister. When the FSW technique is developed, both the lid and the base are welded to the tube and the copper tube can also be manufactured of two halves of rollformed plate, especially if 30 mm thick copper is to be used. The development of the tool, together with the optimisation of the design is particularly necessary in order for the technique to function reliably. When full-scale welding is conducted on a 50 mm thick copper canister (3.3 m long weld) with a welding speed of about 100 mm/min, the welding time is up to an hour for the entire canister circumference. The welding temperature can be up to 950 ºC and the welding forces are high (Andersson et al., 1999; 2000; Cederquist, 2003).

Copper Canisters – Fabrication, Sealing, Durability SOU 2004:67

Narrow Gap (NG) Welding

Narrow Gap (NG) TIG welding is currently used to a large extent for the manufacturing of nuclear power components of steel. For several different reasons, for example, the fact that the thermal diffusivity of the copper is 10 to 100 times higher compared with steel and nickel-based alloys, this technique cannot be applied to thick-walled copper products since the heat transfer must be very high and the welding speed becomes slow (Pohja et.al., 2003).

6.2.4. Residual Stresses

After all manufacturing stages, with forming, machining and welding, residual stresses will occur in the material. These residual stresses must be measured and modelled. The residual stresses have a major impact on creep and stress corrosion. The highest permitted value for the residual stresses, which should be below half of the yield point, must be determined. Furthermore, the need for different techniques to reduce the residual stresses, for example, through stress relief annealing or mechanical surface treatment methods, must be evaluated.

6.2.5. Non-Destructive Testing (NDT)

The copper canister has defects after manufacturing, but only a few (0.1 %) of the canisters are allowed to have greater defects than those allowed by the acceptance criteria for the NDT (RD&D Programme 2001). The acceptance criteria have not yet been specified. One assumption is that these unacceptable defects can cause water leaks in the canister in 100,000 years’ time. Bowyer (2000) has compiled an overview of all possible materials or manufacturing related defects and residual stresses that can occur in copper canisters and in cast iron inserts. Above

SOU 2004:67 Copper Canisters – Fabrication, Sealing, Durability

all, defects in the canister lid weld are important. From the standpoint of corrosion, it is important to minimise the occurrence of fabrication-related defects. Therefore, it is essential that the size and form of various initial defects can be measured as accurately as possible. The requirements on the maximum grain size are important to facilitate ultrasonic testing. The acceptance criteria for initial defects must be based on the best available NDT methods. The sensitivity of the NDT methods must be verified with the help of metallography and microscopic investigations of defects and POD (probability of detection) diagrams for defects of different sizes, forms and positions must be generated. Further qualification of the NDT methods that will be used in the final process during the manufacturing and sealing of canisters must be conducted.

6.2.6. Encapsulation Plant

Trial manufacturing of thirteen full-scale canisters with cast iron inserts has so far been completed (Andersson, 2002). Five of these have already been used in different research projects.

The layout of the canister manufacturing plant was planned in Sweden (Andersson, 2001). The plant is expected to produce more than 200 canisters per year and contains equipment for machining canister shells and lids, welding of copper bottoms, machining of cast iron inserts, quality control and the final assembly of canisters. Finally, the finished canisters are delivered to the encapsulation plant. The handling of the canisters during manufacturing, transport and emplacement in the repository is critical for the subsequent corrosion behaviour of the canisters. Manufacturing methods, equipment and organisation still have to be established in order for canister manufacturing to be conducted as required to achieve a high level of productivity and quality in manufacturing. Further investigations concerning choice of method are needed with respect to welding processes and copper cylinder machining, in particular.

Copper Canisters – Fabrication, Sealing, Durability SOU 2004:67

6.3. Durability

6.3.1. Corrosion Properties

The copper canisters will be affected by both general and different types of local corrosion in the complex chemical, microbial and mechanical environment of the repository, which varies in time and space. The probability of corrosion penetration in the canister should be very low in a 100,000-year perspective. During the first hundred or two hundred years, the copper shell will be deformed under compression. During the same time, oxidising corrosion conditions will occur in the repository. The risk of stress corrosion during this stage must be thoroughly evaluated. The threshold for the initiation and crack propagation of stress corrosion in copper must be measured in the repository environment under different modes of loading. There is a considerably better understanding of other corrosion mechanisms, both with respect to general and local corrosion (pitting and crevice corrosion), due to laboratory investigations and experience from marine and archeological copper discoveries. Considerable progress has also been made with respect to the modelling of these corrosion forms. However, a fundamental problem is the fact that the corrosion rates are based on shortterm experiments. Therefore, it is uncertain whether these results are relevant to very long timescales. All known corrosion mechanisms with respect to copper have been summarised in a state-of-the-art report (King et al., 2002). The corrosion properties of weld metals, where the microstructures vary and are quite different compared with the base metal, have been investigated to a limited extent.

When the copper shell has been penetrated due to some corrosion and rupture mechanism, the water will penetrate into the damaged canister and into the gap between the copper shell and the cast iron insert. The copper and cast iron are in contact with each other and galvanic corrosion occurs in the cast iron which causes hydrogen gas to form and leads to increased

SOU 2004:67 Copper Canisters – Fabrication, Sealing, Durability

pressure inside the canister. Under anaerobic conditions, the rate of cast iron corrosion is still very low, less than 1 µm/year. The galvanic contact with copper in oxygen-free water will only cause a marginal increase in the corrosion rate. Verified experiments should still be conducted to show that galvanic corrosion is not probable in a repository environment for the canister configuration in question. After some time, water will come into contact with the spent nuclear fuel and tube material of zirconium and the actual fuel material will also be attacked by corrosion. At this stage, a number of corrosion mechanisms are active and modelling must be based on many different assumptions (e.g. Shoesmith, 2000). Due to the complexity and the possible interaction between different mechanisms, in order to better model how corrosion damage evolves in the damaged canister, empirical studies must also be conducted under realistic conditions in the future.

6.3.2. Creep Properties

After manufacturing, there is a gap of about two mm between the copper shell and the cast iron insert (depending on tolerances). This means that the copper must be capable of deforming about 4-5 % in the repository. Slow deformation, in the temperature range of 75 to 90 ºC, which occurs in the repository under residual stresses together with the hydrostatic pressure and the pressure caused by the swelling of the bentonite buffer, generates creep in the copper shell. The copper which is used must have a creep ductility (maximum strain before rupture) of at least 10 % even after long timescales, both in the base metal and the weld metal. The importance of the phosphorus alloying (50 ppm) in the base metal for the creeprupture strength and creep ductility of pure copper must be explained mechanistically. Information is also needed about the mechanisms for the long-term extrapolation of available data. It is important to explain the creep properties of weld metals, both

Copper Canisters – Fabrication, Sealing, Durability SOU 2004:67

for the electron beam and FSW welding, which have very different creep properties compared with the parent metal due to their highly variable grain size, which is of importance to creep. When the creep data for all of the canister materials is available, it is possible to carry out a Finite Element Modelling of the deformation of the entire canister.

6.4. Summary

The canister design has already been specified with high precision and the design principles can be considered to be good. However, flexibility must be maintained when ultimately selecting the manufacturing methods, such as lid welding. Full-scale manufacturing is probably easier with extrusion and draw and pierce processing compared with roll forming and longitudinal welding, which cause greater residual stresses in the canister. When selecting the manufacturing method, economic factors should not only be taken into account but also, for example, the long-term properties of the canister. The above-mentioned methods are known in the steel industry on a large scale, but have not been previously used for copper products. As a result, a very small number of companies are expected to be adept at these techniques on a large scale for copper.

The insert, which is of nodular cast iron, has not yet shown such acceptable mechanical properties and, therefore, the casting process must be analysed and better controlled or some other type of cast iron must be used. Casting defects must be more thoroughly analysed. Casting simulation can be a support when planning improvements in casting processes and for the design of different forms of casting. Also, a more accurate specification of the casting process (downhill or uphill) and requirements for the insert are necessary.

Welding methods, electron beam welding and FSW are potentially acceptable for high quality welding of canisters. Both methods, especially FSW, should be further developed. Electron

SOU 2004:67 Copper Canisters – Fabrication, Sealing, Durability

beam welding is known to be suitable for steel products on a large scale and FSW has been previously applied to thick aluminium structures. FSW is a completely new technique which has never before been used for welding 50 mm thick copper. These methods should be further studied since both methods may be needed, especially for repair welding. Under all circumstances, a very deep understanding of the mechanisms that cause weld defects must be developed and the planning of repair welding must be started at an early stage. For this, different NDT methods are required in order to detect defects and to verify the quality of the canisters. It is also very important that no macrodefects, which can rapidly penetrate the canister, should occur during manufacturing and remain undetected. It is necessary to thoroughly follow the development of new NDT methods and to determine their limitations for different defects (Stepinski et al. 2004).

More research work, focusing on the long-term properties of the copper canisters with different manufacturing methods and conditions, is required to better predict future scenarios. More corrosion research is necessary, especially focusing on stress corrosion and microbial corrosion of the copper canister; at an initial stage, under laboratory conditions but also over a longer timescale and, if possible, also in situ in the actual repository.

To guarantee reliability throughout the canister manufacturing process and the final disposal period, acceptance criteria for all of the components of the canister, including welds, must be developed. These criteria should take into account material properties and defects, both surface defects and defects inside the material, in the copper shell and in the cast iron insert. Altogether, consequence analyses must be performed in order to predict possible processes when the canister does not meet the requirements that have been established. It is also important that the acceptance criteria can be verified by NDT methods and that a quality system for canister fabrication will be formulated.

Copper Canisters – Fabrication, Sealing, Durability SOU 2004:67

References (some references are in Swedish)

FUD-program 2001, Program för forskning, utveckling och

demonstration av metoder för hantering och slutförvaring av kärnavfall. SKB, September 2001. TKS-2003, Nuclear Waste Management of the Olkiluoto and

Loviisa Power Plants: Programme for Research, Development and Technical Design for 2004

  • Posiva Oy, December

2003. C.-G. Andersson, Development of Fabrication Technology for Copper Canisters with Cast Inserts. Status Report in August 2001. Technical Report TR-02-07, SKB, April 2002. S. Claesson, U. Ronnetag, Electron Beam Welding of Copper Lids, Status Report up to 2001-12-31. R-03-25, SKB. C.-G. Andersson, R.E., Andrews, Fabrication of Containment Canisters for Nuclear Waste by Friction Stir Welding. 1

st

Int.

Symposium on Friction Stir Welding, Thousand Oaks, CA, USA, 1999. C.G. Andersson, R.E., Andrews, B.G.I. Dance, M.J. Russel, E.J.

Olden, R.M. Sanderson, A Comparison of Copper Canister Fabrication by Electron Beam and Friction Stir Processes. 2

nd

Int. Symposium of Friction Stir Welding, Gothenburg, Sweden, 2000. L. Cederqvist, R.E. Andrews, A Weld Lasts for 100,000 Years:

FSW of Copper Canisters. 4

th

Int. Symposium on Friction

Stir Welding, Park City, Utah, USA, 2003. R. Pohja, H. Vestman, P. Jauhiainen, H. Hänninen, Narrow Gap

Arc Welding Experiments of Thick Copper Sections. Posiva 2003-09, October 2003. W.H. Bowyer, Defects Which Might Occur in the Copper-Iron

Canister Classified According to their Likely Effect on Canister Integrity. SKI Report 00:21, June 2000.

SOU 2004:67 Copper Canisters – Fabrication, Sealing, Durability

F. King, L. Ahonen, C. Taxen, U. Vuorinen, L. Werme, Copper

Corrosion under Expected Conditions in a Deep Geologic Repository. Posiva 2002-01, January 2002. D.W. Shoesmith, Fuel Corrosion Processes under Waste

Disposal Conditions. J. of Nuclear Materials 282(2000)1-31. K-F Nilsson, M. Buström, Pressure Test of KBS-3 Canister

Mock-up. European Commission, DG-JRC, Institute for Energy, NSU/KN/04.01.02. T. Stepinski (editor) et al., Inspection of Copper Canisters for

Spent Nuclear Fuel by Means of Ultrasound, NDE of Friction Stir Welds, Nonlinear Acoustics, Ultrasonic Imaging. Technical Report TR-04-03, January 2004.

7. An Attempt at a Comparable Classification of Radioactive Waste and Hazardous Chemical Waste

7.1. Introduction

The quantification and classification of risks are currently being conducted in different ways for different activities. This means that the risks to which human beings are exposed are difficult to compare and the overall situation is difficult to evaluate. From the standpoint of society, it is desirable to obtain as many comparable assessments as possible. This chapter attempts to compare the risks of radioactive waste with the risks of hazardous chemical waste.

Waste is material that is considered to have too low a value to justify further use and must therefore be disposed of in some way. Waste therefore imposes an economic burden on the producer and society. However, it cannot be excluded that the waste could have a value in some other application than that where it was produced or in a future activity. Waste, which contains toxic substances, either in the form of radionuclides (radioactive substances) or toxic chemicals, is created by many human activities. Waste can arise as a result of the increased availability and concentration of natural substances and materials (mining activities, petroleum extraction, uranium extraction), industrial activities (melting facilities, metal industry, chemical industry, pharmaceutical industry), agriculture (weed killers, plant protection agents) or in households (batteries, fire detectors, electronics, medicines).

Many of the most important radioactive substances, from the standpoint of waste, are heavy metals and have chemical pro-

SOU 2004:67 An Attempt at a Comparable Classification of Radioactive Waste …

perties that are similar to those of non-radioactive (stable) heavy metals. They are non-volatile and less soluble in water than several other pollutants. It is also important to remember that radioactive substances with long physical half-lives can be more chemically toxic than radiotoxic. This applies, for example, to natural uranium in human beings and, probably also to radioactive iodine,

129

I, in soil.

Unlike organic pollutants – and like metals – radionuclides cannot be destroyed or degraded. Therefore, waste management is based on methods such as separation, concentration, volume reduction, fixation and isolation.

Radionuclides have the advantage over stable heavy metals that the amount of a radioactive substance is reduced through radioactive decay, even if the process occurs slowly in some cases.

Over the years, radioactive and chemical waste have come to be viewed differently. Classification systems and regulations are currently strongly associated with the source of the waste.

The difference in views has meant that the public often judges radioactive waste as hazardous while planners often have the view that safety margins are large with respect to radioactive substances. Similar risk-based classification systems and regulations for radioactive substances and chemically toxic substances would simplify environmental impact statements. For environmental and economic reasons, society would gain from a harmonised view based on evaluations that are made on principles that are as similar as possible. Such an approach would also broaden the perspective in the debate on a repository for spent nuclear fuel and would bring to the fore the need for a corresponding repository for heavy metals, such as mercury (SOU, 2001).

SOU 2004:67 An Attempt at a Comparable Classification of Radioactive Waste …

7.2. Proposal for a Comparable Classification of Radioactive and Chemical Waste

The National Council on Radiation Protection (NCRP, 2002) in the USA has recently proposed a system for classifying all types of waste containing either radioactive or chemically toxic substances. This chapter describes the proposal and discusses it in the light of the current system, which is different for radioactive substances and toxic chemicals. The proposed system is interesting in principle, since it provides the necessary basis for making the above-described similar evaluations of different types of waste.

In Europe, limited activities are conducted in the area within the OECD/NEA and within the European Union’s Fifth Framework Programme (www.riskgov.org).

The system proposed by NCRP:

  • can be used for each type of waste that contains radionuclides, hazardous chemicals or a mixture of these,
  • has a classification that is based on a determination of the health hazards to the population resulting from the waste,
  • has an exemption class for waste that involves such a low risk that it can be handled as non-hazardous waste.

The system comprises 3 waste classes:

High-level hazardous waste Low-level hazardous waste Non-hazardous waste

The system is based on the following principles:

  • A linear dose-effect relationship without a threshold for cancer-inducing substances and with a threshold for non- cancer-inducing substances.
  • The term “dose” should be given a uniform meaning. “Dose” currently means different things for radioactive substances

SOU 2004:67 An Attempt at a Comparable Classification of Radioactive Waste …

and for hazardous chemicals. In the case of radiation and radioactive substances, the “dose” is the absorbed dose (often average absorbed dose to the entire specified organ or tissue) or effective dose. The biological effect can be assessed from such dose data. The “dose” in the case of toxic chemicals (as for pharmaceuticals) is the amount of substance taken in.

  • A uniform risk concept. The risk figures that have so far been used for ionising radiation and radioactive substances refers to the number of cancer fatalities while, for chemically carcinogenic substances, the number of cancer cases (incidence) is usually cited.
  • The way of estimating health hazards is also different in the case of radionuclides and hazardous chemicals through the varying degree of caution that is incorporated into the postulated probabilities for undesirable health effects per dose unit and through taking into account different numbers of risk organs in the body.
  • A number of exposure scenarios are assumed when estimating the risk that human beings are exposed to (exposure situations that can be used for each waste repository).

7.3. Designations for Risks to Individuals

For ionising radiation, the following risk assessments are often made

  • Unacceptable risk, which must be reduced, regardless of cost or other conditions. This assessment is made if the radiation caused the extra risk of dying of cancer during the rest of the individual’s life to be greater than an “acceptable” level (often a value in the range of 0.1-0.001 or greater or, in other words, between 10 % and 0.1 % or greater; where in the range it is, often depends on the exposure situation).

SOU 2004:67 An Attempt at a Comparable Classification of Radioactive Waste …

  • Acceptable risk (risks under unacceptable levels as well as

ALARA – “as low as reasonably achievable”). Risks just below unacceptable levels are considered to be just about acceptable and should be considerably reduced by applying the ALARA principle.

  • Negligible risk is considered to be so low that further effort to reduce the risk (in accordance with ALARA) is not justified. This risk usually comprises an extra fatal cancer risk of 0.0001-0.000001 (0.01-0.0001 %) or less for the rest of the individual’s life.

What we currently call “acceptable” risks or doses in the case of toxic chemicals corresponds to what is called “negligible” risk in the case of radionuclides, while “acceptable” risks or doses in the case of radionuclides may be far above negligible levels, providing that they are ALARA. In the case of hazardous chemicals, “unacceptable” is essentially the same as “non-hazardous”. In the case of radionuclides, “unacceptable” refers to doses and risks that are far above negligible levels that cannot be tolerated under normal conditions.

Table 7.1. Differences in the interpretation of “acceptable” and “unacceptable” risk (dose) for radionuclides and hazardous chemicals

Risk description Interpretation for radionuclides Interpretation for hazardous chemicals

”Unacceptable” Intolerable risk. This risk must be reduced, regardless of cost.

The risk exceeds negligible levels. Risk reduction must be considered but is only required to an appropriate extent.

”Acceptable” Risk below intolerable levels and ALARA.

The risk is negligible. Further risk reduction is not necessary.

SOU 2004:67 An Attempt at a Comparable Classification of Radioactive Waste …

Risk, in the case of radioactive substances, is considered to be unacceptable even if it is below unacceptable levels, but not ALARA. This difference in interpretation between toxic chemicals and radioactive substances in risk assessment causes considerable difficulties for decision-makers and the general public as well as for those who have to provide information to these groups.

7.4. Proposed Risk Index for Waste Classification (NCRP)

“Risk” generally refers to the probability of damage occurring combined with the degree of severity of the damage (for example, death, reduced life expectancy, reduced kidney, liver or thyroid function).

For waste, the NCRP normally states the risk as the probability that something will happen to an individual or as the frequency of events in a population group. The following are required in order to calculate the risk

1. The probability of events resulting in a radioactive release

2. The probability that the individual or population group will be exposed to the release

3. The probability that exposure will result in damage

The risk from a repository/landfill can be expressed as a dimensionless risk index (RI). The risk index for the ith hazardous substance (R

i

) is defined as the risk that arises from the

disposal of the substance in question relative to a determined allowable risk for an assumed waste system.

(risk due to disposal)

RI

i

= F

i

(allowable risk)

SOU 2004:67 An Attempt at a Comparable Classification of Radioactive Waste …

F

i

is a modifying factor for substance i and may depend on the design of the waste facility, the packaging of the waste, the uncertainty in the risk assessment etc.

For each substance where the risk can be assumed to be proportional to the dose (substance quantity/activity quantity) without a threshold, RI

i

can be written as follows:

(dose due to disposal)

RI

i

= F

i

(allowable dose)

The difference in the meaning of “dose” for radionuclides and chemicals is uninteresting as long as the same meaning is applied to a given substance in the numerator and the denominator.

If we assume that the risk from an individual source is additive, the following is required

ΣRI

i

< 1

i

namely, that the sum of all contributions may not exceed the permissible dose (or risk).

Adding the risks for non-carcinogenic substances requires caution, bearing in mind the fact that the dose-effect relationship does not have to be linear and that interacting (multiplicative) factors between different chemical substances cannot be excluded.

The advantage of the proposed risk index is that all toxic substances are treated in a similar manner.

7.5. A Risk-based Waste Classification System

The NCRP proposes that all types of waste should be classified into three classes.

SOU 2004:67 An Attempt at a Comparable Classification of Radioactive Waste …

I Waste Excluded from the Regulations

For non-carcinogenic toxic chemicals, the NCRP recommends that a negligible dose should be defined as a small fraction (for example, 10 %) of a certain threshold value for deterministic (predictable) effects in human beings. For radionuclides, it is recommended that an annual effective dose of 0.01 mSv should be considered to be a negligible individual dose. This dose corresponds to an estimated lifetime risk of cancer mortality of about 4*10

-5

(0.004 %) for an assumed exposure time of 70 years

(5 % per Sv). This dose is also the dose that the IAEA uses to define an exemption class for radioactive waste.

What is meant by negligible risks or doses for radionuclides and chemical carcinogens can also be discussed in relation to risks from natural background radiation (1 mSv/year) that cannot be avoided. Since the lifetime risk from exposure to natural background radiation and the natural occurrence of chemical cancer-inducing substances is about 1 %, a negligible risk could be determined as a part of this average background risk (for example 1 % of 1 %). In the long-term, such a “negligible risk” would be less than the variation in background risk, which arises as a result of differences in living habits.

II Low Risk Waste

Low risk waste can be deposited in a special landfill for hazardous waste. It should be possible to derive the limit for concentrations of hazardous substances by establishing that the risk or dose for an unintentional intrusion should not exceed acceptable (just tolerable) levels.

SOU 2004:67 An Attempt at a Comparable Classification of Radioactive Waste …

Acceptable (barely Tolerable) Risks or Doses

For non-carcinogenic toxic chemicals, an acceptable dose should be established at the threshold for the deterministic effect on humans or just below the threshold (for example, by a factor of 2 or 3) if an additional safety margin is desired.

For radionuclides, the limit for the annual effective dose to individuals among the general public is 1 mSv, which corresponds to an estimated risk of dying of cancer during the remaining lifetime of about 4x10

-3

or 0.4 % (for an assumed

exposure time of 70 years). This can be compared to the risk of dying of cancer from causes other than radiation which is just over 20 % or a little more than one out of every five people. Acceptable risk or doses can, as above, also be related to the unavoidable risk from the natural background.

III High-risk Waste

This waste cannot be deposited in landfills but must be deposited beneath the surface of the earth. Geological repositories have so far been the solution for high-level radioactive waste. This type of disposal is also now recommended for mercury (SOU, 2001).

7.6. Risk Estimates and Risk Comparisons

It is possible to, at least theoretically, estimate the risk from low radiation doses (ICRP, 1991). It is of course necessary to discuss this risk in the light of the risk that we accept, without further thought, in our daily lives, for example, risk from natural background radiation. On the other hand, the existence of other risks does not entitle exposure to additional radiation. However, the risk that we have previously accepted provides a framework

SOU 2004:67 An Attempt at a Comparable Classification of Radioactive Waste …

for gaining a perspective on the risk of an additional exposure to radiation from radioactive waste.

Another way of gaining a perspective on the radiation doses to which we are exposed is to compare the hazards of radionuclides with the hazards of chemicals. There is a basic difference between radioactive substances (ionising radiation) and chemicals with respect to dose-response calculations. The doseresponse calculations for radiation can be based on an estimated absorbed dose to organs and tissue in the body. Furthermore, the relationship between the dose and the response which was obtained from studies of groups of individuals exposed to radiation is applied to all radionuclides and most exposure situations. Thus, separate studies do not have to be conducted for each individual radionuclide as is required for each individual chemical. In the case of chemicals, the situation becomes more complex because there are about 30,000 substances, of which perhaps 20-25 % may cause cancer, damage to the embryo/ foetus and genetic effects (Bengtsson, 2002). For toxic chemicals, no units have yet been defined that correspond to the absorbed dose or equivalent dose, even if much work is currently being done to develop a “dose measure” (Törnqvist and Ehrenberg, 2001). The dose response relationship for specific toxic chemicals must therefore be based on studies of the specific substance.

Predictable (Deterministic) Tissue Effects

A basic principle in protection work is to prevent predictable (deterministic) tissue effects (for radiation: skin damage, cataracts; for chemicals: kidney and liver damage, neurological effects etc.) occur both as a result of radioactive substances and chemicals. For chemicals and radiation, the dose-effect curve is expected to have a threshold for deterministic effects. For each substance, the assumed threshold value is based on data for the most sensitive organ or tissue. However, there are important

SOU 2004:67 An Attempt at a Comparable Classification of Radioactive Waste …

differences between radioactive substances and toxic chemicals in the way these threshold values are calculated and then applied for radiation protection work.

In radiation protection, dose limits for predictable effects (skin damage, cataracts) are only based on data from human beings and are normally established at a factor of 10 below the assumed threshold values. This safety factor is intended to ensure that deterministic effects are excluded for practically all individuals, including those who could be unusually sensitive to radiation. With respect to toxic chemicals, an even more conservative approach (which probably overestimates rather than underestimates the risk) is used. This is partly due to the fact that the toxicity of the substances has only been studied in animal experiments. Limits for acceptable doses are often defined by “reference doses”, which are usually derived from the lower value of the uncertainty range for the assumed threshold values in the way that they are represented by the NOAELS (No Observed Adverse Effect Level) or lower confidence limits, for the benchmark dose (the dose where 10 % of the tested animals show an effect) by adding a great number of safety and uncertainty factors, most often of a minimum of a factor of 100, in order to obtain a reference dose. These safety factors can be as high as 5000 for some substances.

The reference doses for toxic chemicals therefore probably most often give a significantly greater safety margin than the dose limits for radiation-induced predictable effects.

Random (Stochastic) Effects

The basic principle for protection against both radioactive substances and toxic chemicals is that the probability for random effects, primarily cancer, should be limited to an acceptable level for the individual and society, seen in the light of the advantages that the activity generates or has generated. For each substance that causes random effects, a linear dose-response relationship

SOU 2004:67 An Attempt at a Comparable Classification of Radioactive Waste …

without a threshold is generally postulated for health effects. This approach is well established in radiation protection and is gaining increasing acceptance with respect to estimating the risk of cancer from carcinogenic chemicals in the environment (Bengtsson, 1998; Granath and Ehrenberg, 1997; Duggan and Lambert, 1998; Granath et al., 1998; Törnquist and Ehrenberg, 2001).

The specified probability values for radioactive substances and chemicals that result in stochastic effects differ in two important respects. Firstly, the dose-response relationship for radiation and associated probability coefficients is based on the best possible estimates. On the other hand, as far as chemicals causing stochastic effects are concerned, the corresponding data are often intended to provide an upper boundary (the upper boundary in the uncertainty interval). In animal data, such a value can be 5 to 100 times greater than the best estimate. Secondly, the primary measure of random effects of exposure to radiation and radioactive substances has been the number of fatalities for the rest of life. On the other hand, in the case of chemicals, the measure has been the incidence, namely the proportion of those becoming ill or injured in a population as a result of exposure to a carcinogenic substance, which is explained by the fact that, in the latter case, the estimate is based on animal testing.

There is another difference between radiation and chemicals. Radiation is a more general carcinogen which can result in cancer in many more organs and tissues than chemicals. In radiation protection, the effective dose measure takes this into consideration. In the case of most of the toxic chemicals, only a single risk organ or tissue is taken into consideration and the rest of the body is ignored. The development of biokinetic models for toxic chemicals provides a corresponding possibility. However, such models have not yet been prepared to any great extent.

SOU 2004:67 An Attempt at a Comparable Classification of Radioactive Waste …

7.7. Calculation of Risk Figures

Different measures of cancer risk are established for radionuclides/radiation and chemicals. In order to classify radioactive waste, the risk figure of 0.05 per Sv (5 % per Sv) can be used, which is the figure that is normally used for the radiation protection of the public (ICRP, 1991). This figure has been derived from the best adaptation to epidemiological data for high doses, above all from Hiroshima and Nagasaki, and has then been further adapted for low radiation doses and dose rates (factor: 0.5). For chemical carcinogenic substances, the risk figures come from the upper value of the uncertainty interval for observed effects at high doses (mainly from animal studies). In several studies, the adjustment at the upper boundary of the uncertainty interval is 10 times higher than that obtained with the best possible adjustment.

For risk estimates, the risk figure mentioned above is applied to the effective dose. The risk figures for chemical carcinogenic substances are based on the observed effects on an individual organ or on a special tissue (often in animals). Attention is seldom paid to the possibility of effects on several organs. Risk figures for low doses of carcinogenic chemicals are more conservative (it is more probable that the risk is overestimated) than the risk figures for radioactive substances.

For radionuclides, the dose constraint at an effective dose of 1 mSv limits the deterministic effects. In the case of toxic noncarcinogenic chemicals the threshold for deterministic effects on humans is estimated from benchmark doses which, to an increasing extent, are used to obtain values for permissible doses of non-carcinogens. A benchmark dose is, as has already been mentioned, a dose that belongs to a specified effect level in a population that is studied (for example, a 10 % increase in the effect). The lower boundary of the uncertainty interval for the benchmark dose (which belongs to the 10 % increase) is then used as a basis for obtaining the permissible dose. In order to obtain a dose that will provide a safe protection for all human

SOU 2004:67 An Attempt at a Comparable Classification of Radioactive Waste …

beings, it is recommended that a dose that is 10 times lower than the lower confidence level should be used for the “benchmark” dose which is obtained in connection with a well-conducted study of human beings and 100 times lower than the lower confidence level for a benchmark dose that is obtained in connection with a well-conducted study on animals.

In order for the proposed standardised classification system to be usable, risk figures for a very large number of chemicals must be obtained. The limited availability of such risk figures currently limits the applicability of the proposed system.

7.8. Examples of Comparative Limits for Radiation, Asbestos and Nickel

In this section, the limits that have been obtained for exposure to radiation, asbestos fibres and nickel compounds are compared (Schneider et al., 2000). Both epidemiological studies and animal experiments have clearly shown that asbestos fibres and certain nickel compounds can cause cancer in the same way as radiation. Epidemiological studies have shown that there is a relationship between relatively high exposure levels and an extra incidence of cancer. There is also cause for a linear, no-threshold relationship to be assumed between exposure and risk. The comparison between risk and permissible levels is based on the rules applied in France (which, at least with respect to radiation, are the same as in Sweden) and are illustrated in Table 7.2.

SOU 2004:67 An Attempt at a Comparable Classification of Radioactive Waste …

Table 7.2. Comparisons between risk estimates and permissible exposure levels for ionising radiation, asbestos and nickel. In this comparison, an exposure time of 40 years has been used.

Extra risk of mortality during the expected remaining lifetime

Permissible exposure level

Risk in connection with permissible exposure level for 40 years

Ionising radiation, occupationally exposed persons

4 % per Sv 100 mSv/5 years 3 %

Asbestos, occupationally exposed persons

0.04 % per fibre/ml years

0.1 fibre/ml 0.16 %

Ionising radiation, public 5 % per Sv 1 mSv/year

0.2 %

Nickel, public

14 % 10

-6

per

ng/m

year

Tens of ng/m

3

0.01 %

The dose limits for ionising radiation, asbestos and nickel are based on extrapolations from known dose-risk relations at high exposure levels. In order to arrive at permissible exposure levels, a comparison with the risk of mortality in other occupations considered to be safe has been conducted for occupationally exposed persons. For the public, comparisons with natural background radiation have been conducted.

7.9. Consequences of the Proposed Classification System

The proposed classification system is applicable to every type of waste containing radioactive substances, toxic chemicals or a mixture of these two types of waste. The system is based on an assessment of the health risks to the public as a result of waste disposal. The system contains an exemption class, which contains waste which entails a very low risk and which can be

SOU 2004:67 An Attempt at a Comparable Classification of Radioactive Waste …

handled as non-hazardous material. The other two classes are low-risk waste (can be stored in near surface facilities) and highrisk waste (requires an underground repository in bedrock).

In future work, the limits between the different waste classes can be quantified in terms of limits for concentrations of different substances so that the exemption group will contain such as low concentrations that the substances do not entail more than a negligible risk for a hypothetical “intruder” into a waste repository. The low-risk facility may not cause more than an acceptable risk for an intruder. Waste with a higher content than can be dealt with the two types of near surface facilities mentioned are classified as high-risk waste and need to be deposited in the bedrock.

The fact that considerable quantities of waste that contain small amounts of radionuclides or toxic chemicals can be excluded from the regulations simplifies handling and makes it cheaper. The high-risk waste will mostly comprise high-level radioactive waste, transuranic waste and long-lived radioactive waste with a lower activity. Chemical waste containing high concentrations of heavy metals (lead, cadmium, mercury) belongs to the same group. The current classification system for chemical waste does not contain such a class. It is assumed that the proposed system will be advantageous compared to the current system. It is simple and easy to understand. The clear connection between the classification and the requirements of protecting the public health will hopefully increase public confidence in waste management and disposal. The system has obvious advantages when it comes to handling mixed waste. The system provides the necessary conditions for a more just assessment of the hazard of different types of waste than the current system.

SOU 2004:67 An Attempt at a Comparable Classification of Radioactive Waste …

References (some references are in Swedish)

Bengtsson G. Comparison of radiation and chemical risks. SSI-

rapport 88

  • Swedish radiation protection authority,

Stockholm, 1988. Duggan M J, Lambert B E Standards for environmental, non-

threshold, carcinogens: A comparison of the approaches used for radiation and for chemicals. Ann occup hyg 42(5), 315

  • 1998.

Granath F, Ehrenberg L. Cancer risks at low doses of ionizing

radiation and chemicals. In: New risk frontiers, Proceedings of 10

th

anniversary conference of the society of risk analysis-

Europe, Stockholm 1997 (Ed by B-M Sjöberg) Center for risk research, Stockholm, Sweden) 1997. Granath F, Vaca C E, Ehrenberg L, Törnqvist M A. Cancer risk

estimation of genotoxic chemicals based on target dose and a multiplicative model. Risk analysis 19, 309

  • 1999.

ICRP, International commission on radiological protection.

1990 recommendations of the international commission of radiological protection. ICRP Publication 60. Annals of the ICRP 21 (1

  • 1991.

NCRP, National Council on Radiation Protection and

Measurements (USA). Risk-based classification of radioactive and hazardous chemical wastes. NCRP Report No. 139, 2002. Schneider T, Lepicard S, Oudiz A, Gadbois S, Hériard-Dubreuil.

A comparison of the carcinogenic risk assessment and management of asbestos, nickel and ionising radiation. Report NEA/CRPPH(2000)11, November 2000, Nuclear Energy Agency. SOU. Kvicksilver i säkert förvar. Betänkande av Utredningen

om slutförvaring av kvicksilver. Statens offentliga utredningar, SOU 2001:58.

SOU 2004:67 An Attempt at a Comparable Classification of Radioactive Waste …

Törnqvist M, Ehrenberg, L. Estimation of cancer risk caused by

environmental chemicals based on in vivo dose measurements. J Env Pathol Toxicol Oncol 20, 263

  • 2001.

Section III The Nuclear Waste Issue and the Future

8. Partitioning and Transmutation – An Alternative to Final Disposal. An Issue in Focus

8.1. Introduction

In research circles, the possibility of radically reducing the radiotoxicity of spent nuclear fuel through a method known as partitioning and transmutation (P&T) has already been discussed for several decades. The technology comprises complex scientific and technical issues. How is it possible that also politicians and the public pay so much attention to such an issue?

The Swedish Act on Nuclear Activities requires that anyone who has a licence to conduct nuclear activities should be responsible for ensuring that the necessary measures should be adopted to ensure that nuclear waste generated by the activities is handled and disposed of in a safe manner. The Swedish strategy for the handling of spent nuclear fuel is that the fuel should be directly disposed of. The main work in the area therefore focuses on developing and constructing a geological repository where the spent nuclear fuel can be kept isolated from the biosphere (the environment of human beings and other living creatures) for hundreds of thousands of years, namely, until the hazardous radioactivity has decayed. This is the basis of the Swedish KBS-3 concept.

Early in the disposal development process, it became evident that alternatives would be necessary if the KBS-3 concept, for some reason, could not be realised. In its decision on SKB’s research programme, the Government established that development work should be conducted on P&T as a possible alternative

Partitioning and Transmutation – An Alternative to Final Disposal … SOU 2004:67

solution. Furthermore, the Environmental Code expressly requires alternative methods to be investigated and reported in the environmental impact statement, which is to be attached to an application for permission under the Environmental Code and the Act on Nuclear Activities.

The bodies reviewing SKB’s research programme (authorities, municipalities, universities, NGOs etc.) have agreed that SKB must study alternatives to the KBS-3 concept. The reasons given in support of this view are both formal (for example requirements on alternative accounts under the Environmental Code) and general expressions of uncertainty regarding whether it would be possible to realise the KBS-3 method. Although the details and the line of reasoning are different, the conclusion is that SKB must describe alternatives to KBS-3 and that P&T is considered to be an alternative.

In its most perfect form, transmutation may mean that the parts of the fuel that remain radioactive for a very long time are completely eliminated. The technology that is necessary for the application of the method has been developed by researchers within several essential areas. However, major technical problems still have to be resolved and these issues have generated research programmes in the EU, the USA, Russia, Japan, Korea and other nations. National programmes in several European countries were also created. All parts of the technology must also be tested in demonstration plants before operating characteristics, safety issues, operating economy etc. can be evaluated.

If successful, it is expected that P&T will lead to a reduction in the volume and in the radioactivity of the remaining fuel by one hundred times. After treatment, the fuel radioactivity would decay to a non-hazardous level in 500 to 1,000 years. A small part of very long-lived substances (a few tenths of a per cent of the same long-lived substances as in the spent nuclear fuel) must still be deposited in a repository due to the fact that the different substances cannot be completely separated. The repository would be considerably smaller and would not need to function

SOU 2004:67 Partitioning and Transmutation – An Alternative to Final Disposal …

for as extensive a period of time as a conventional, direct disposal repository for spent nuclear fuel.

There are also advocates of P&T among groups and individuals who are opposed to the final disposal of spent nuclear fuel. In some accounts, P&T is presented as a present-day method of completely getting rid of hazardous waste. However, this is not the case.

In the Swedish debate about P&T, the technical and other problems associated with the separation (partitioning) of substances in spent nuclear fuel, have been eclipsed. It is also well known that radioactive releases to the environment can be significant in connection with the type of separation processes required in connection with P&T.

P&T technology assumes that there will be a continued and extensive nuclear programme in Sweden. Estimates of P&T technology made in the USA and the EU show that 20 to 30 years of research will be necessary in order to realise the technology. This means that sustainable, long-term research and development programmes are required.

Section 8.2 provides a description of P&T and the types of plants required to implement the process. Section 8.3 summarises the state-of-the-art concerning P&T and Section 8.4 provides an overview of ongoing and planned international research. Three scenarios are presented in Section 8.5 which illustrate what the technology would mean for Sweden. In Section 8.6, the entire chapter is summarised. Sections 8.5 and 8.6 can be read independently of Sections 8.3 and 8.4. From Section 8.2, the reader can therefore proceed directly to Section 8.5.

8.2. Basic Principles of P&T

Obviously, it would be very valuable if, in some way, spent nuclear fuel could be treated so that the long-lived radioactivity could be rendered harmless. Much would therefore be gained if

Partitioning and Transmutation – An Alternative to Final Disposal … SOU 2004:67

the radioactive substances with long half-lives – with respect to both fission products and transuranic elements (substances that are heavier than uranium) – could be converted into short-lived or stable isotopes of different elements. This would then radically reduce the quantity of radioactivity which would have to be deposited in a repository as well as the length of the time that the repository would have to isolate the deposited material.

To understand what P&T is about, it is necessary to know what spent nuclear fuel contains.

8.2.1. The Fuel in the Reactor Core

Uranium Fuel

All of the nuclear reactors in Sweden are light water reactors. Three of the units at Ringhals are pressurized water reactors (PWRs) while the other Swedish reactors are boiling water reactors (BWRs)

1

.

Uranium, in the form in which it occurs in nature (natural uranium) is not suitable as light water reactor fuel. The concentration of fissile, and thereby energy-generating, uranium-235 in natural uranium is only about 0.7 %. The rest predominately comprises uranium-238, which is not fissionable in a light water reactor.

Swedish reactor fuel is therefore enriched. This means that the proportion of uranium-235 in the uranium is increased in an enrichment facility (abroad). The residual product from this process is uranium with a lower concentration than that of natural uranium, also known as depleted uranium.

In Västerås in Sweden, a fabrication plant has existed for a long time which manufactures fuel for Swedish reactors and for some foreign reactors. The fuel is fabricated from enriched uranium purchased from abroad.

1

After the close down of the two BWRs at Barsebäck, there are still seven BWRs in

operation.

SOU 2004:67 Partitioning and Transmutation – An Alternative to Final Disposal …

Fresh enriched fuel for a light water reactor has a uranium-235 concentration of about three per cent. The fuel stays three to five years in the reactor core, often being moved to different core positions during that time. When about two-thirds of the uranium-235 that was in the fuel when it was first inserted into the core is used up, the fuel can no longer be used. The spent fuel is then removed from the reactor and first transferred to a spent fuel pool at the nuclear power plant and – after a couple of years of radioactive decay – the fuel is taken by the M/S Sigyn ship to the Central Interim Storage Facility for Spent Nuclear Fuel (CLAB), located on the Simpevarp peninsula in Oskarshamn municipality.

MOX Fuel

Plutonium-enriched fuel can also be used as an alternative to enriched uranium. Fissile plutonium-239 is formed in the reactor fuel when neutrons are captured by non-fissile uranium-238. By reprocessing spent nuclear fuel, the plutonium can be chemically separated. The plutonium can then be mixed with natural or depleted uranium to produce new reactor fuel, called Mixed Oxide (MOX) fuel. Typically, fresh MOX fuel contains three to four per cent of plutonium-239 and, also in this case, about twothirds of the fissile material are used up before the fuel is removed from the core. The spent MOX fuel can then once again be reprocessed. However, the concentration of heavy plutonium isotopes (heavier than 239) increases with each reprocessing, which means that the plutonium that is extracted during each reprocessing becomes less and less useful for fresh fuel fabrication.

As far as we know, MOX fuel has not been manufactured in Sweden. However, the method is well developed and, in principle, it would be possible to use the method in Sweden.

Partitioning and Transmutation – An Alternative to Final Disposal … SOU 2004:67

Spent Nuclear Fuel

The spent nuclear fuel stored in CLAB predominately comprises uranium fuel from Swedish boiling water reactors and pressurised water reactors. A small quantity of spent MOX fuel is also stored in CLAB.

While the fuel is in the core, a number of chain reactions occur resulting in the formation of radioactive products. The production of radioactive substances in the reactor fuel during reactor operation occurs in two ways – through fission and through neutron capture.

During the fission of uranium-235, the nucleus divides into two fission fragments. The exact way in which the nucleus divides varies and a large number of elements are represented among the fission products. Most of these have short half-lives or are stable. However, there are also some radioactive substances with very long lifetimes. All of the atoms of the fission products are naturally lighter than the uranium atom that undergoes fission.

During neutron capture, a free neutron is captured, for example, by a uranium-238 nucleus. Uranium-239 is first formed, but this soon decays in a couple of steps into plutonium-239 which has a long half-life (24,000 years). Many other elements that are heavier than uranium – transuranic elements – are also formed in the reactor and several of these also have a long half-life.

SOU 2004:67 Partitioning and Transmutation – An Alternative to Final Disposal …

Figure 8.1. Radioactive decay of spent nuclear fuel over time, showing contributions from transuranic elements (TRU) and fission products (FP). The radiotoxicity is compared with that of uranium ore which is present in nature.

About 95 % of the spent nuclear fuel comprises unaffected uranium, while 1.2 % comprises transuranic elements and 4.2 % are fission products.

The largest share of transuranic elements in the waste comprises plutonium (87 %). Besides the fact that plutonium is radiotoxic, it can also be used to make nuclear weapons. However, the composition of the plutonium formed in light water reactor fuel (reactor plutonium) is not suitable for weapons manufacturing. Nevertheless, after separation from the other substances in the spent nuclear fuel, the material can still be used to make primitive nuclear explosives which, if they fall into the hands of a terrorist organisation, could represent a real threat in a blackmail situation. It should also be mentioned that the reactor plutonium which is contained in the spent nuclear fuel

Partitioning and Transmutation – An Alternative to Final Disposal … SOU 2004:67

deposited in a geological repository will gradually become a better weapons-grade material over a period of 1,000 years since the plutonium-239 becomes enriched as a result of shorter lifetimes for several of the other plutonium isotopes.

8.2.2. The Basic Principle of P&T

The purpose of P&T is to render the radioactive substances less hazardous in the sense that they are converted (transmuted) into more harmless radioactive products that are radioactive for a short period of time or are completely stable. This can be achieved by irradiating the radioactive substances in the spent nuclear fuel so that these substances (the nuclei of the elements) are converted into other elements (nuclei) with the desired properties. This transmutation is achieved through nuclear reactions between the atoms of the radioactive elements and the particles with which they are irradiated. The radiation, which it is intended to use for the P&T of radioactive substances, is the same as that in our reactors, namely, neutron radiation. However, in order to achieve the desired effect, the intensity and energy distribution of the radiation may need to be different in a transmutation facility than in a conventional nuclear power reactor.

The neutron irradiation mainly causes two types of nuclear reactions, fission and neutron capture, namely, the same type of reactions that occur in uranium-235 and uranium-238 during reactor fuel burning. To render the transuranic elements harmless, irradiation conditions must be created that cause the elements to mainly undergo fission and to form fission products. Energy, which can be used, is also generated during this process. The long-lived fission products, those that are already present in the spent nuclear fuel and the new products that arise from burning transuranic elements, are then transmuted by adding a neutron to the fission product nuclei during irradiation (neutron capture). This nuclear reaction gives rise to elements with other

SOU 2004:67 Partitioning and Transmutation – An Alternative to Final Disposal …

properties, often with shorter half-lives than the original (longlived) fission products.

Figure 8.2. An illustration of the fission process. A neutron is captured by a uranium nucleus which becomes excited and undergoes fission, splitting into two fission products and emitting neutrons.

8.2.3. Thermal or Fast Neutrons

The probability of the desired nuclear reactions occurring depends on the energy of the neutrons used to irradiate a certain element. Two types of irradiation occur where the neutrons have different energy distributions (or velocity distributions), namely thermal and fast neutrons. With thermal neutrons, the energy of the neutrons is in equilibrium with the energy of the surrounding atoms in motion. Fast neutrons have a much higher velocity than the thermal energy of the surrounding atoms.

In general, in the case of transuranic elements, the ratio between the probability of nuclear fission and neutron capture (neutron absorption) is greatest in the case of fast neutrons. This means that if the aim is to split transuranic elements, they must be irradiated with fast neutrons.

Partitioning and Transmutation – An Alternative to Final Disposal … SOU 2004:67

On the other hand, the probability of a neutron being captured by a fission product is much greater in a thermal neutron flux than in a fast neutron flux. In certain P&T techniques, the fact that the neutron capture process is highly likely to occur for some energies (resonance energies) in a relatively narrow energy range above the thermal energy range has also been exploited.

8.2.4. Partitioning

If P&T is to lead to a substantial reduction of the radiotoxicity of the radioactive waste (a reduction of one hundredfold or more), the spent nuclear fuel must be irradiated in several cycles with an intermediate separation of the elements in the fuel. Material that has been transmuted must be removed so that it does not become radioactive again through further irradiation. Non-transmuted material must be added to fresh fuel for the P&T facility. The elements to be separated depend on the transmutation method that is to be used.

Two different partitioning methods are being studied. In both cases, the aim is to achieve a maximum separation efficiency in order to thereby reduce the quantity of waste to be deposited in a geological repository. A separation efficiency of 99.9 % has been reached for uranium and plutonium, while for other transuranic elements and fission products, the efficiency is between 98 % and 99.9 %.

One method is a refinement of an existing method based on hydrochemical processes (or aqueous processes) and which is used at the existing reprocessing plants, for example in France (La Hague) and Great Britain (Sellafield). At these facilities, plutonium is extracted from spent nuclear fuel by dissolving the fuel in a strong acid. Subsequently, the various components of the fuel are chemically separated for the fabrication of new nuclear fuel (MOX fuel) for commercial thermal nuclear reactors.

SOU 2004:67 Partitioning and Transmutation – An Alternative to Final Disposal …

The first stage is a refinement of the process used for plutonium extraction (PUREX) where uranium, neptunium and the long-lived fission products, iodine and technetium, are also separated from the other transuranic elements and fission products. Processes are being developed to separate, in subsequent stages, the remaining transuranic elements, americium and curium which, together with neptunium, are called minor actinides (MA) from the remaining fission products. The problem of this separation method is that certain essential chemicals in the separation processes are neutralised when they are exposed to strong ionising radiation. Therefore the radioactivity in the fuel must be allowed to decay during a relatively long period of time before separation can be conducted. All types of processing and separation processes entail increased risk of occupational exposure to radiation and radioactive releases to the environment.

The Swedish Inquiry into Radioactive Waste (“AKAutredningen”) proposed, in the early 1970s, that a Swedish reprocessing plant based on hydrochemical processes should be constructed on the Swedish west coast, north of Gothenburg. These plans were never realised. Instead, the nuclear industry decided to sign a contract with foreign reprocessing facilities (La Hague in France and Sellafield in Great Britain). These contracts have since ceased to apply, since they were no longer meaningful when the decision was made to phase out nuclear power in Sweden and to directly dispose of spent nuclear fuel as waste. An important point of reprocessing is that the plutonium formed in the reactor fuel should be recovered and used for the fabrication of fresh reactor fuel as a step in the efficient management of uranium as a natural resource and in order to prevent plutonium from going astray and being used for the manufacturing of nuclear weapons.

Technology for constructing a Swedish reprocessing plant based on hydrochemical technology is available abroad. However, experience from abroad shows that very large plants are necessary in order for the operation to be cost-efficient. The

Partitioning and Transmutation – An Alternative to Final Disposal … SOU 2004:67

reprocessing plants that currently exist abroad serve nuclear power customers in several different countries.

As was already mentioned, certain essential chemicals in the fluid separation process become inert when exposed to strong radiation. Therefore, research and development are underway in several countries to develop an alternative partitioning method. This method is based on pyrochemical processes which can also work in high radiation fields and, thereby, deal with irradiated fuel from P&T plants. With the pyrochemical method, which entails a more compact P&T plant, differences are exploited in the electrochemical properties of different elements in the highlevel part of the radioactive fuel which, during electrolysis, is dissolved in molten salts, comprising fluorides or chlorides at a high temperature. During electrolysis, the molten salts which contain the radioactive spent fuel, are placed in a container with two electrodes. Partitioning is achieved by letting the elements in the spent fuel precipitate on one electrode with different electrical voltages between the electrodes.

8.2.5. Technical Alternatives

What would a P&T plant look like? The different solutions which are currently being studied comprise the use of ion accelerators, critical and sub-critical reactors as well as thermal and fast reactors of different designs. A critical reactor is a reactor where the neutron production in the fuel exactly balances the neutron losses through reactions in fuel, coolant, construction material and from leakage, while a sub-critical reactor has neutron losses that exceed production. A thermal reactor has a thermal neutron flux in the core, which means that the neutron velocity is in equilibrium with the surrounding atoms in the reactor core, while a fast reactor has a fast neutron flux, namely, neutrons with an essentially higher velocity (energy) than the surrounding atoms. Practically all nuclear reactors that are in operation the world over, including Sweden’s

SOU 2004:67 Partitioning and Transmutation – An Alternative to Final Disposal …

light water reactors, are critical thermal reactors. A few fast critical reactors are in operation while other variations of fast reactors are still at the prototype or project stage.

The performance of a P&T plant is not only determined by the intensity and energy distribution of the neutrons in the core, as has been previously mentioned, but also by the neutron economy, namely how many neutrons are available for the transmutation of the waste. It can generally be said that fast critical reactors have a better neutron economy for P&T than thermal reactors. A type of P&T plant which consists of a combination of a powerful ion accelerator and a sub-critical reactor, known as an Accelerator-Driven System, has the best neutron economy.

Accelerator-Driven Systems (ADS) with Fast Sub-critical Reactors

Figure 8.3. Illustration of the spallation process. When protons (in red) from the accelerator collide at high speed with lead and bismuth nuclei in the centre of the sub-critical reactor, the nucleus splits into several fragments, releasing a large number of neutrons (in blue).

The Accelerator-Driven System has attracted the greatest interest in the research sphere. A powerful ion accelerator

Partitioning and Transmutation – An Alternative to Final Disposal … SOU 2004:67

delivers its ion beam (protons i.e. hydrogen atom nuclei) to a sub-critical reactor. The protons bombard a body made of heavy material (for example, a mixture of lead and bismuth in molten form), which is at the centre of the reactor core. When very high-energy (velocity) protons hit atoms of a heavy material such as lead or bismuth, they split into several fragments, releasing a large number of neutrons. The process is called spallation. During each spallation, a few dozen neutrons are released. An intensive radiation field of neutrons is created through the interaction with the fuel which comprises the longlived transuranic elements from the spent fuel. As a result of its sub-criticality, the reactor will be automatically switched off as soon as the accelerator beam is shut off. This means that the inherent safety for preventing criticality accidents is very high.

As mentioned above, in order to efficiently burn transuranic elements, and especially heavy transuranic elements (MAs), a reactor with fast neutrons is required. To avoid fast neutrons from being slowed down (thermalised), a medium with heavy atoms is required. The use of liquid lead/bismuth as a coolant, experience of which has been gained from Russian submarine reactors, has attracted the greatest interest. A sub-critical reactor has safety-related advantages compared with a critical reactor. The reason is that the addition of a large quantity of MAs (minor actinides) at the expense of uranium-238 in the fuel results in a lower level of safety to prevent criticality accidents since the nuclear physics properties of uranium-238 contribute to preventing criticality accidents in a critical reactor.

As has been indicated above, thermal neutrons are required to efficiently transmute long-lived fission products. For this reason, the aim has been to achieve a zone of thermal neutrons on the periphery of the fast sub-critical reactor core, where the transmutation of the fission products can occur. Alternatively, the possibility has been studied of using the resonances in the neutron capture process (transmutation process for fission products) which occurs in a narrow energy field above the thermal zone and which the neutrons pass through as they are

SOU 2004:67 Partitioning and Transmutation – An Alternative to Final Disposal …

gradually slowed down through recurring collisions with heavy atomic nuclei in the coolant (lead/bismuth).

Figure 8.4. Illustration of an Accelerator-Driven Transmutation System (ADS).

1. An intense proton beam is generated and accelerated to high energy by a proton accelerator.

2. The high energy protons from the accelerator hit a target of molten lead and bismuth in the centre of a sub-critical reactor. A high neutron flux is generated by spallation reactions.

3. The radioactive waste is put in fuel pins of a molten lead/bismuth cooled reactor. The radioactive species of the waste are transmuted to new species with shorter half-lives by neutron-induced reactions.

4. The heat generated in the reactor can be converted to electrical power in the same way as in ordinary nuclear power reactors.

Partitioning and Transmutation – An Alternative to Final Disposal … SOU 2004:67

Accelerator-Driven System (ADS) with a Thermal Subcritical Reactor

Accelerator-driven systems with thermal sub-critical reactors have also been studied. Systems with molten salts (beryllium and lithium fluorides or sodium and zirconium fluorides) as a coolant, in which the radioactive waste to be transmuted is dissolved, have attracted the greatest interest. Operating experience has been gained from a molten salt critical reactor for energy generation. The reactor was constructed and operated for a few years in the 1960’s at Oak Ridge National Laboratory in the USA. Calculations have been performed on the reduction of the radioactive substances in the high-level part of the spent fuel during irradiation in an accelerator-driven system with a subcritical molten salt reactor. The calculations show that a relatively large reduction in the active substances in the fuel has been obtained after one irradiation cycle without separation. If the newly formed short-lived fission products from the fuel in the molten salts are partitioned, a greater reduction of the radioactive elements can be achieved than if no partitioning of these products is conducted. Studies have been conducted on the possibility of carrying out this “cleaning process” in a directlyconnected partitioning facility through which the molten salts from the reactor are continuously circulated. However, this method entails several problems which have not yet been resolved.

An essential difference between transmutation in a thermal neutron flux compared with transmutation in a fast neutron flux is that a small portion of very heavy elements are formed by the thermal flux. These relatively long-lived elements remain in the residual products after transmutation and must be disposed of.

SOU 2004:67 Partitioning and Transmutation – An Alternative to Final Disposal …

Thermal Critical Reactors

The most proven method of disposing of plutonium is to mix it with depleted or natural uranium to form MOX fuel and to use this fuel in, for example, thermal reacors of the type that we now have in Sweden. A corresponding quantity of enriched uranium does not have to be purchased and the uranium that has been extracted to manufacture the original uranium fuel is managed in a better way. However, this process cannot be repeated more than a few times, since the quantity of heavy plutonium isotopes successively increases, and these isotopes cannot be partitioned from the “recoverable” plutonium (plutonium-239) by chemical means, since they are all the same element. In order to continue to burn the residual plutonium, a critical or sub-critical fast reactor is needed.

Besides plutonium, which has been mentioned above, most of the fission products can be transmuted in reactors with a thermal neutron flux. However, the transmutation of fission products consumes neutrons, unlike the burning of plutonium which produces new neutrons. As mentioned above, neutron economy (the number of neutrons available for transmutation processes) is low for thermal critical reactors, namely nuclear reactors of a conventional type. In order not to obtain unreasonably long transmutation times, the better neutron economy is required that is provided by an accelerator-driven system or other critical reactors specially adapted to transmutation.

Fast Critical Reactors

For residual plutonium from MOX burning of plutonium, and for efficient burning of most of the other transuranic elements in spent fuel (the minor actinides, neptunium, americium and curium), fast reactors are required. The neutrons in fast reactors have higher velocities than the thermal kinetic energy of the atoms in the core. The properties for the transmutation of

Partitioning and Transmutation – An Alternative to Final Disposal … SOU 2004:67

several different types of fast critical reactors have been studied. Even if the neutron economy for transmutation is better for these reactors than for the thermal critical reactors, a substantial park of fast neutron reactors are required in order to achieve a reasonable transmutation capacity. The reason for this is that only a small addition of minor actinides (neptunium, americium and curium) can be achieved in the uranium fuel in order to avoid jeopardising the reactor safety margins.

Prototype fast critical reactors for power generation have previously been constructed abroad. Usually, these reactors are fuelled with plutonium and cooled by liquid sodium. Furthermore, a feature of these reactors is that plutonium can form in a blanket zone of natural or depleted uranium surrounding the core, and the amount can exceed the amount of plutonium burnt up in the reactor core. Such reactors are therefore often called fast breeder reactors. About forty years ago, it was believed that breeder reactors would successively replace today’s reactors, particularly because they make efficient use of the Earth’s uranium resources. However, in reality, this has not turned out to be the case, at least not so far. The technology is more problematic than for present-day reactors, especially since the reactor is cooled by liquid sodium which is explosive on contact with oxygen.

Since there is a plentiful supply of uranium on the global market as well as a good enrichment capacity, the demand for plutonium for reactor fuel is very low. Instead, plutonium has become something that we would like to get rid of. This is also related to the fact that fuel costs in a nuclear power plant represent a very small portion of the production cost for electricity. It is the high fixed asset costs that affect the price. It could be said that a nuclear power plant is expensive to construct but inexpensive to operate. Therefore, the plant should be operated at full capacity as much as possible. The opposite can be said of an oil-fired plant, for example, which is relatively inexpensive to construct but expensive to operate since oil is expensive as is flue gas cleaning etc.

SOU 2004:67 Partitioning and Transmutation – An Alternative to Final Disposal …

Furthermore – in the present climate of disarmament – a large quantity of plutonium is becoming available as nuclear weapons are dismantled. This is contributing to making plutonium a surplus good that we would like to render harmless in order to ensure that disarmament is sustainable and so that the plutonium can not be used again for nuclear explosives.

A large-scale expansion of fast critical reactors, where plutonium and minor actinides could be burnt is therefore not probable at present. Instead, accelerator-driven sub-critical systems are used for this purpose, possibly combined with initial plutonium burning, in the form of MOX fuel, in thermal reactors.

Combinations of ADS and Critical Reactors

In order to achieve the best possible incineration of the radioactive portion of spent fuel and also a reasonable economy, combinations of the above-mentioned transmutation methods are also being studied in the national and international programmes. Two main lines can be distinguished depending on whether the irradiation of the radioactive waste is achieved in one step (a single strata), with or without the return of the waste fuel after separation of the fission products, or in two steps (double strata), where plutonium, for example, is burnt in a thermal reactor followed by transmutation of the remaining waste in an accelerator-driven system or in a critical reactor built for this purpose.

The national research programmes focus on transmutation methods that are adapted to each country’s nuclear energy programmes so that the two-step principle (double strata) is prioritised in countries where plutonium burning in reactors is already underway (MOX fuel) while research in countries without plutonium burning focuses on the single-step principle. The number of ADS facilities that are required for the incineration of nuclear waste from a group of light water

Partitioning and Transmutation – An Alternative to Final Disposal … SOU 2004:67

reactors varies depending on the transmutation method. If all transuranic elements are to be burnt in ADS facilities, the need for such facilities is estimated at about 20 % of all of the total number of nuclear reactors, (namely, one ADS facility for each five nuclear reactors). In the two-step alternative, with only burning of MAs in ADS facilities, the need is about 15 % (namely, one ADS facility for each seven nuclear reactors). A description of the research situation in a few prominent countries is provided in Section 8.4.

Stratum/Tier 0

Stratum/Tier 1

Stratum/Tier 2

High Level

Waste Repository

Once-Through

Fuel Cycle

Single-Tier

Transmutation System

Double-Tier/Strata Transmutation System

ADS or Fast

Reactors

ADS or Fast

Reactors

MA

Pu

Pu+MA

Pu+MA

Pu+MA

Pu+MA

Stratum/Tier 0

Stratum/Tier 1

Stratum/Tier 2

High Level

Waste Repository

Once-Through

Fuel Cycle

Single-Tier

Transmutation System

Double-Tier/Strata Transmutation System

ADS or Fast

Reactors

ADS or Fast

Reactors

MA

Pu

Pu+MA

Pu+MA

Pu+MA

Pu+MA

Conventional reactors

Thermal and/or fast reactors

Figure 8.5. Direct or once-through disposal, one-step and two-step transmutation systems (Pu plutonium. MA minor actinides: Neptunium, americium and curium).

SOU 2004:67 Partitioning and Transmutation – An Alternative to Final Disposal …

8.3. State-of-the-Art

What is our current level of knowledge to apply P&T with the aim of reducing the radiotoxicity and lifetime of spent nuclear fuel?

P&T is based on known principles and scientific facts. The processes (nuclear reactions) in the spent nuclear fuel which lead to the desired results are sufficiently well known so that we can judge the applicability of the method. On the other hand, more detailed knowledge is required to optimise the systems included in a transmutation facility, with respect to operating characteristics, economy etc.

However, the practical application is complex. The level of technical knowledge has developed differently for each of the many parts that make up a P&T plant. This primarily applies to accelerator-driven systems with sub-critical reactors which are intended to be used in practically all concepts for the transmutation of all or parts of the spent nuclear fuel.

The international development of accelerators for high-energy physics in recent decades has represented a technological breakthrough. In itself, this development provided the incentive to start more conscious research in transmutation: This idea existed already during the 1950’s and 1960’s but was then considered to be technologically difficult to implement. However, the general perception today is that accelerators which meet the requirements for accelerator-driven P&T can be built but with certain reservations with respect to the requirement on sustainable, uninterrupted operation (without short or long outages) for long periods of time.

As described in Section 8.2, the strong ion beam from the accelerator drives an intensive neutron source placed in the centre of a sub-critical reactor. Neutrons which are produced when the ion beam is stopped by a target made of heavy material (usually a mixture of lead and bismuth in molten form) can, with a relatively high accuracy, be calculated for different properties in the ion beam and the target material and design. The technical

Partitioning and Transmutation – An Alternative to Final Disposal … SOU 2004:67

difficulties are mainly related to the robustness of the window that separates the accelerator from the target. This window is exposed to high radiation doses which result in radiation damage in the material. However, the window is also subjected to thermal forces when the accelerator starts and stops. Another technical problem is the corrosion in the wall material of the container which contains the molten lead/bismuth. The solution to this problem has been taken from the design of Russian submarine reactors which also used molten lead/bismuth as a coolant. A further problem which must be handled is the production of a radioactive polonium isotope which is formed during the irradiation of bismuth and which has a half-life of 138 days. Several projects are underway to solve these problems were the properties of molten lead/bismuth, radiation-resistant material and complete targets with and without windows are being studied.

Programs for calculating operating characteristics, safety aspects, burnup etc. in an accelerator-driven sub-critical reactor are being tested in a number of ongoing experiments. At the same time, methods for continually measuring the criticality (sub-criticality) of the reactor, are being developed. This is important from the standpoint of safety.

Several different coolants are being studied for the sub-critical reactor (molten lead/bismuth, molten sodium or helium gas). Molten lead/bismuth has been judged to be the best coolant in physical and safety terms. The same technological problems with corrosion and polonium production which have been described above for the neutron source placed centrally in the reactor also exist in connection with the reactor design. In addition, there is a problem with the manufacturing of reactor fuel which is to contain plutonium and the minor actinides, neptunium, americium and curium, from the spent nuclear fuel. Several different types of fuel are being studied (nitride, oxide and metallic fuels) where the aim is to achieve a good thermal conductivity, a high melting point and a high radiation acceptance. The latter is required due to extremely high radiation levels in the fuel which

SOU 2004:67 Partitioning and Transmutation – An Alternative to Final Disposal …

can lead to material damage. The mixture of ceramic material in the fuel is being studied in order to reduce radiation damage in the fuel elements.

As described in Section 8.2, an alternative concept is also being studied for the sub-critical reactor, where the spent fuel is dissolved in molten salt, namely fluorides comprising beryllium and lithium or sodium and zirconium fluorides. Knowledge of this type of reactor is based on experience from the operation of a critical molten salt reactor at Oak Ridge National Laboratory, USA, in the 1960’s. Even if this type of sub-critical reactor is of interest in principle due to the simpler fuel handling, the technical difficulties are considered to be greater than with the previously described lead/bismuth-cooled reactor. In spite of this, several research projects are underway which are focusing on improving the knowledge of molten salts and their use in reactors.

As was previously mentioned, in order for transmutation to be efficient, a more or less extensive separation of the elements in the spent nuclear fuel is required. In principle, two different methods are being studied. One is based on hydro chemistry and the other on pyrochemistry (see Section 8.2). The first method has been tried and tested and is applied in France (La Hague) and Great Britain (Sellafield) on a commercial basis for the manufacturing of MOX fuel. Research is underway to also be able to partition the other transuranic elements (minor actinides) and certain fission products by similar methods. As was mentioned in Section 8.2, chemicals in the partitioning process are destroyed by high radiation doses. Consequently, the method is not suitable for fresh spent nuclear fuel, especially not recycled transmutation fuel. The radioactivity must decay for several years before partitioning can be conducted using this method which leads to a long treatment time for the spent nuclear fuel, comprising decay, partitioning, fuel manufacturing and transmutation in several cycles. With the second method, which is based on pyrochemistry, high-level material can be treated, but the method is not as developed as the method based

Partitioning and Transmutation – An Alternative to Final Disposal … SOU 2004:67

on hydrochemical processes. The pyrochemical method has so far been applied with success on a laboratory scale and extensive development work is underway to raise the separation capacity to a commercially interesting level. It is important for the separation process which, as a result of the very high radiation intensity, must take place in radiation-shielded “hot cells”, to also be designed so that radioactive releases are as small as possible.

In parallel with research into the above-mentioned problems in P&T, design studies are underway, partly as a project in the EU’s framework programme, on demonstration facilities for transmutation. Tenders have also been submitted in a few cases for full-scale accelerator-driven transmutation facilities where Prof. C. Rubbia (Nobel prize winner and former head of CERN) is behind a concept involving liquid lead/bismuth as a coolant and Dr C. Bowman (former head of P&T research at Los Alamos National Laboratory, USA, now with his own company in the P&T area (ADNA)) is behind another concept involving molten salts as a coolant. None of the concepts is considered feasible with the current level of knowledge. Initially they will require extensive technical development work.

In summary, it can be said with respect to the state-of-the-art concerning P&T that several technical problems must be solved before a definitive evaluation of the applicability of P&T can be made in technical, safety, economic terms etc. This problem particularly concerns the manufacturing of fuel elements and partitioning of the high-level transmutation fuel. Work is in progress to solve these problems, as has already been mentioned and will be described in greater detail in Section 8.4. So far, the ongoing research has not led to any results that contradict the idea that it might be possible to apply P&T with the aim of reducing the toxicity and lifetime of spent nuclear fuel.

SOU 2004:67 Partitioning and Transmutation – An Alternative to Final Disposal …

8.4. Ongoing and Planned Research

The extensive research programme that has started in many countries in P&T is of a long-term nature. Basic research is mainly being conducted which provides a basis to judge which P&T concept is optimum with respect to efficiency, capacity, safety and economy under given technological and political conditions. The competence and infrastructure in the nuclear energy area that is required to develop a P&T capacity for spent nuclear fuel can be found primarily in the countries that have an active nuclear programme. For this reason, a short description of the nuclear power programmes in each country conducting research on P&T is provided as an introduction.

A common goal of research on P&T of spent nuclear fuel is to construct a demonstration facility in 10-20 years’ time. The development of partitioning for spent nuclear fuel and particularly, of the method that is based on pyrochemistry is underway in parallel with this research.

8.4.1. European Research

In Europe, P&T research is being conducted, partly with economic support from the EU and within national programmes as well as within multinational programmes with or without the participation of the EU.

Multinational Projects

In the EU states, France, Italy and Spain are playing a leading role with respect to research on P&T. Jointly, these countries (the ministers of research in each country) took the initiative to propose a plan for research in the EU, with the aim to construct a demonstration facility for accelerator-driven P&T by 2012,

Partitioning and Transmutation – An Alternative to Final Disposal … SOU 2004:67

followed by a prototype facility around 2030 which will lay the foundation for industrial facilities around 2040.

At a later stage, Belgium, Finland, Portugal, Sweden, Germany, Austria and EURATOM joined this multinational initiative. The work resulted in a report in 2001, which describes how a facility with an accelerator-driven system for transmutation could be constructed by 2010 (Eur 01). The work in the group was led by Prof. Rubbia. The report describes the ongoing projects in Europe which, together, comprise a broad research and development programme on the basic principles of accelerator-driven systems.

Another multinational project (Megawatt Pilot Experiment, MEGAPIE), which was initiated by laboratories in Switzerland, France, Italy and Germany with the participation of laboratories in the USA, Japan and South Korea, concerns the design and operation of one of the main components of an acceleratordriven system, namely, the equipment – the target – that delivers neutrons to the sub-critical reactor with the help of the accelerator. The equipment will be assembled and tested with a powerful accelerator which exists at a national laboratory (Paul Scherrer Institute, PSI), in Switzerland.

EU-funded Projects

The EU’s support for P&T research has increased from about EUR 5 million in the third framework programme (1990-1994) to EUR 37 million in the ongoing sixth framework programme (2002-2006).

The EU has not officially adopted a position to the proposed plan from the group led by Prof. Rubbia, but is nevertheless following the proposed research plan from the group as a whole (Eur 01). A central project in this plan is a preliminary study of an accelerator-driven demonstration facility which was started during the fifth framework programme, 1998-2002.