Geological Disposal of Radioactive Wastes and Natural Analogues, Volume 2

1 The issue of radioactive waste disposal. 1.1 The nature of radioactive wastes. 1.2 The concept of geological disposal. 1.3 Evaluating repository safety. 1.3.1 Key uncertainties in safety calculations. 1.3.2 Requirements for supporting natural data. 1.4 Natural analogue studies. 1.5 Other field-based studies of natural systems. 1.5.1 Site characterisation. 1.5.2 Palaeohydrogeology. 1.5.3 Natural safety indicators. 1.5.4 Biosphere studies. 1.6 Toxic waste disposal.

2 Radioactive waste types and repository designs 2.1 The nuclear fuel cycle and radioactive wastes. 2.1.1 Used fuel and reprocessing wastes. 2.1.2 Operational wastes. 2.1.3 Decommissioning wastes. 2.1.4 Other wastes. 2.2 Classification of radioactive wastes. 2.3 Repository designs. 2.3.1 Deep repository designs for HLW. 2.3.2 Deep repository designs for ILW. 2.3.3 Near-surface repository designs for LLW. 2.4 Geological disposal environments.

3 Varieties of analogue studies 3.1 Chemical analogues. 3.2 Natural geological and geochemical systems. 3.2.1 Uranium orebodies. 3.2.2 Geochemical discontinuities in clays. 3.2.3 Hyperalkaline environments. 3.2.4 Hydrothermal systems. 3.2.5 Natural occurrences of repository materials. 3.3 Archaeological analogues. 3.4 Sites of anthropogenic contamination.

4 Analogues of repository materials. 4.1 Silicate glass. 4.2 Spent fuel. 4.3 Mineral and ceramic wasteforms. 4.4 Metals. 4.5 Bentonite. 4.6 Concretes and cement. 4.7 Bitumen. 4.8 Organic materials.

5 Analogues of transport and retardation. 5.1 Elemental solubility and speciation. 5.2 Elemental retardation processes. 5.3 Matrix diffusion. 5.4 Radiolysis. 5.5 Redox fronts. 5.6 Colloids. 5.7 Microbiological activity. 5.8 Gas generation and migration.

6 The application of analogue information. 6.1 Natural analogues in the support of performance assessment. 6.1.1 The reality of analogue application to performance assessment. 6.2 Natural analogues in non-technical demonstrations of safety. 6.3 Natural analogues applied to other environmental issues.

7 Summary, conclusions and recommendations. 7.1 Summary of analogue results. 7.1.1 Analogues of repository materials. 7.1.2 Analogues of transport and retardation. 7.2 Conclusions. 7.2.1 Suggested areas for future analogue investigation. References Case histories: The proposed Swedish and Finnish spent fuel repositories. The proposed Swiss repository for vitrified HLW. The Swedish L/ILW repository at Forsmark. The Oklo natural fission reactors. The Cigar Lake uranium mine. The Peña Blanca uranium mine. The Inchtuthil Roman nails. The Kronan cannon. The Dunarobba forest. Hadrian's Wall. The Maqarin hyperalkaline system. The Broubster uranium mineralisation. The Needle's Eye uranium mineralisation. Poços de Caldas. The Alligator Rivers uranium orebody. The Palmottu uranium orebody. El Berrocal. The Tono uranium orebody.

Many countries are currently exploring the option to dispose of highly radioactive solid wastes deep underground in purpose built, engineered repositories. A number of surface and shallow repositories for less radioactive wastes are already in operation. One of the challenges facing the nuclear industry is to demonstrate confidently that a repository will contain wastes for so long that any releases that might take place in the future will pose no significant health or environmental risk.

One method for building confidence in the long-term future safety of a repository is to look at the physical and chemical processes which operate in natural and archaeological systems, and to draw appropriate parallels with the repository. For example, to understand why some uranium orebodies have remained isolated underground for billions of years. Such studies are called 'natural analogues'.

This book investigates the concept of geological disposal and examines the wide range of natural analogues which have been studied. Lessons learnt from studies of archaeological and natural systems can be used to improve our capabilities for assessing the future safety of a radioactive waste repository.