The development of conceptual approaches for the assessment of the long-term safety of underground radioactive waste repositories

To date, the approach most commonly used for the assessment of the long-term impact of underground radioactive waste repositories involves the estimation of radiation dose or risks to hypothetical individuals living in the far future. Recognising that the uncertainty is large in such assessments and that it increases with time into the future, alternative proposals have been made with the aim of producing a more realistic approach, an approach which lessens the uncertainty of the assessment and which may be credible to a wider spectrum of people. Briefly it involves: a recognition that doses and risks can only be regarded as quantitative measures of safety for a few hundred years into the future; beyond this time they are only qualitative safety indicators. the establishment of alternative and supplementary indicators of safety which have less uncertainty associated with them, for example, environmental fluxes and concentrations. the adoption of standardized approaches for modeling components which have a high degree of uncertainty associated with their prediction in the far future, for example, the biosphere and critical groups. the establishment of a standardized approach for assessing and evaluating human intrusion into a geological repository. The IAEA is exploring and developing these ideas through its WASSAC Subgroup on Principles and Criteria for Radioactive Waste Disposal. (author)