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

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.