abs

RADIOLOGICAL CONDITIONS OF THE WESTERN KARA SEA

1,48

127

stron

2485

International Atomic Energy Agency

2001

rok

CONTENTS

EXECUTIVE SUMMARY 1

1. Background . 1

2. Radiological protection considerations . 1

3. Current radiological situation . 2

4. Future radiological situation 3

5. Remediation 5

6. Conclusions . 6

7. Recommendations 7

1. INTRODUCTION . 9

1.1. Radioactive waste disposal at sea and the international system for its control . 9

1.1.1. London Convention 1972 . 9

1.1.2. Dumping operations . 10

1.1.3. Dumping in the Arctic in relation to the London Convention 1972 12

1.2. Rationale for establishing IASAP 13

2. RADIOLOGICAL PROTECTION AND DECISION MAKING 15

2.1. Basic concepts in radiological protection relevant to IASAP 15

2.1.1. Practices 15

2.1.1.1. Exclusion, exemption and clearance . 15

2.1.2. Intervention . 15

2.2. Basic requirements of radiological protection as established in the basic safety standards 16

2.2.1. Practices 16

2.2.2. Intervention . 16

2.3. Previous sea dumping in the Arctic - A practice or an intervention situation? 16

2.4. Making decisions regarding remedial actions 17

2.4.1. Decision aiding techniques 17

3. THE ARCTIC ENVIRONMENT 21

3.1. Description of the region . 21

3.1.1. Oceanography 21

3.1.1.1. Arctic Ocean 21

3.1.1.2. Barents Sea . 23

3.1.1.3. Kara Sea . 25

3.1.1.4. Kara Sea dumpsites . 27

3.1.2. Ecology 30

3.1.2.1. Biological production in the Arctic . 30

3.1.2.2. Marine food webs in the Arctic 32

3.1.2.3. Fish and fisheries in the Barents and Kara Seas 34

3.2. Radioactivity of the Arctic Seas 35

3.2.1. Marine radioactivity database 35

3.2.2. Pre-1992 radionuclide concentrations 35

3.2.2.1. Water 35

3.2.2.2. Sediment . 39

3.2.3. Present radionuclide concentrations in the Kara Sea . 39

3.2.3.1. Dumpsites 39

3.2.3.2. The open Kara Sea . 42

3.2.3.3. Ob and Yenisey estuaries . 43

3.2.3.4. Biota 43

3.2.3.5. Conclusions on radionuclide concentrations in the Kara Sea 43

3.2.4. Intercomparison exercises . 43

3.3. Distribution coefficients and concentration factors 45

4. THE RADIOACTIVE SOURCE TERM 47

4.1. Source term development 47

4.1.1. Characteristics of the steam generating installations . 47

4.1.2. Reactor operating histories 47

4.1.3. Radionuclide inventories 47

4.1.4. Disposal operations . 50

4.1.4.1. Submarine pressurized water reactors . 50

4.1.4.2. Submarine liquid metal reactors 50

4.1.4.3. Icebreaker pressurized water reactors and the fuel container 50

4.2. Modelling strategy 51

4.2.1. Methods and assumptions . 51

4.2.2. Model construction 51

4.2.2.1. Submarine pressurized water reactors . 52

4.2.2.2. Submarine liquid metal reactors 52

4.2.2.3. Icebreaker pressurized water reactors and the fuel container 52

4.2.3. Corrosion rates . 52

4.2.3.1. Containment barriers 53

4.2.3.2. Release rates of spent nuclear fuel 54

4.2.3.3. Release rates of activation products . 54

4.2.4. Release scenarios . 54

4.2.4.1. Submarine pressurized water reactors . 54

4.2.4.2. Submarine liquid metal reactors 56

4.2.4.3. Icebreaker pressurized water reactors and the fuel container 58

4.2.4.4. Total release rates for the Kara Sea . 62

4.2.5. Potential criticality of reactors . 62

4.3. Results and analyses 64

4.3.1. Reliability . 64

4.3.1.1. Information on the steam generating installation structures and materials . 64

4.3.1.2. Radionuclide inventory 64

4.3.1.3. Values of best estimate corrosion rates . 65

4.3.1.4. Degree of pessimism used in the models . 65

4.3.2. Sensitivity . 65

4.4. Issues relating to possible remedial measures . 66

4.4.1. Reinforcement of existing barriers 66

4.4.2. Recovery of spent nuclear fuel for land storage . 67

4.4.3. Structural integrity of spent nuclear fuel containers 67

4.5. Conclusions . 67

5. ENVIRONMENTAL MODELLING FOR RADIOLOGICAL IMPACT ASSESSMENT 71

5.1. Introduction 71

5.1.1. Aims and objectives of modelling . 71

5.1.2. Brief oceanographic basis of the modelling work . 71

5.1.2.1. Significant features of the Kara Sea . 72

5.1.2.2. Features of the Barents Sea . 72

5.1.2.3. The Arctic Ocean . 72

5.1.2.4. The fjords of Novaya Zemlya . 72

5.1.3. Productivity of the Barents and Kara Seas 73

5.2. Models used in the IASAP study . 73

5.2.1. Introduction . 73

5.2.1.1. Compartmental models 73

5.2.1.2. Hydrodynamic models . 73

5.2.1.3. Advantages and disadvantages of the different modelling approaches . 73

5.2.2. Description of the models used in IASAP . 74

5.2.2.1. Compartmental models 75

5.2.2.2. Hydrodynamic models . 75

5.2.2.3. Hybrid model . 75

5.2.3. Model validation 76

5.3. Source scenarios for radiological assessment 76

5.4. Dose estimation and evaluation of results 76

5.4.1. Maximum individual dose rate . 76

5.4.1.1. Definition of population (critical) groups . 76

5.4.1.2. Kd values, concentration factors and dose conversion factors 77

5.4.1.3. Pathway exposure estimation 77

5.4.1.4. Results of Scenario A . 77

5.4.1.5. Results of Scenario B . 82

5.4.1.6. Results of Scenario C . 82

5.4.1.7. Comments 83

5.4.2. Collective dose calculations . 83

5.4.2.1. Fishery statistics . 83

5.4.2.2. Truncation times . 83

5.4.2.3. Results . 86

5.4.2.4. Comments 86

5.4.3. Submarine No. 601 86

5.4.3.1. Scenario A 86

5.4.3.2. Scenario C 86

5.4.3.3. Special nuclides 86

5.4.4. Model intercomparison . 86

5.4.4.1. General comments 86

5.4.4.2. Design of the intercomparison . 88

5.4.4.3. Results and conclusions of the intercomparison 88

5.5. Other transport mechanisms 89

5.5.1. The effect of sea ice . 89

5.5.1.1. Sediment transport in ice . 89

5.5.1.2. Estimating the transport from the Kara Sea . 89

5.5.1.3. A simple scoping calculation 89

5.6. Impact of dumping on populations of wild organisms . 90

5.7. Final conclusions and discussion . 92

6. POSSIBLE REMEDIAL ACTIONS 93

6.1. Initial considerations for remedial measures 93

6.1.1. Radioactive wastes dumped in the Kara Sea . 93

6.1.2. Implications of environmental conditions for remedial measures 93

6.1.3. Possible remedial measures . 95

6.2. Case study of remedial measures for the container of spent fuel from the icebreaker 96

6.2.1. Preparatory survey 96

6.2.2. Engineering evaluation of remedial actions 98

6.2.2.1. Recovery . 98

6.2.2.2. In situ capping . 99