Scientific and Technical Basis for the Near Surface Disposal of

0,31

MB

Low and Intermediate Level Waste

74

stron

4676

ID

International Atomic Energy Agency

2002

rok

CONTENTS

1. INTRODUCTION . 1

1.1. Background 1

1.2. Objective 3

1.3. Scope . 3

1.4. Structure 3

2. NEAR SURFACE DISPOSAL CONCEPTS . 4

2.1. Multiple barrier concept 4

2.2. Disposal systems 5

2.2.1. Basic disposal system concepts . 5

2.2.2. Repository design components 7

2.3. Types of radioactive waste 9

2.4. Developing a repository 10

2.4.1. Pre-operational phase . 11

2.4.2. Operational phase 12

2.4.3. Post-closure phase . 13

2.5. Developing a safety case . 14

2.6. Monitoring and surveillance . 17

3. NEAR FIELD . 20

3.1. Near field environment . 20

3.1.1. Host geological environment . 20

3.1.2. Hydrogeological conditions 21

3.1.3. Chemical conditions 22

3.2. Waste packages . 24

3.2.1. Waste form performance 24

3.2.2. Container performance 26

3.3. Engineered barriers 27

3.3.1. Functions and materials . 27

3.3.2. Degradation processes 29

3.4. Gas generation . 31

3.5. Transport of radionuclides 32

4. FAR FIELD 33

4.1. Geology . 33

4.2. Hydrogeology 35

4.2.1. Saturated zone 35

4.2.2. Vadose zone 36

4.3. Geochemistry 37

4.4. Migration of radionuclides 39

4.5. Potential impacts of climate change on the far field 41

5. BIOSPHERE . 42

5.1. Reference biosphere concept 43

5.2. Migration and accumulation of radionuclides . 45

6. CONFIDENCE IN REPOSITORY PERFORMANCE AND SAFETY 46

6.1. Confidence in waste isolation 46

6.1.1. Suitability of the site . 47

6.1.2. Robustness of the design 48

6.1.3. Robustness of the assessment . 48

6.2. Building confidence in the safety case . 48

6.2.1. Structuring the safety assessment 49

6.2.2. Uncertainty management 50

6.2.3. Testing models 51

6.2.4. Natural and archaeological analogues 51

6.2.5. Documentation and maintenance of records . 52

7. SUMMARY AND CONCLUSIONS . 53

REFERENCES 57

CONTRIBUTORS TO DRAFTING AND REVIEW . 67