Safety indicators in different time frames for the safety assessment of underground radioactive waste repositories. First report of the INWAC subgroup on principles and criteria for radioactive waste disposal

Principles and criteria for the disposal of long lived radioactive waste involve issues which go beyond those normally considered in the basic system of radiation protection. Safety criteria based on radiation risk an dose limitation are commonly accepted as the principal basis for judging the acceptability of radioactive waste repositories. However, the long time-scales of interest mean that risks or doses to future individuals cannot be predicted with any certainty as they depend, amongst other things, on assumptions made about the integrity of the waste matrix, the man-made barriers, the geology, the dispersion of groundwater, etc. and future biospheric conditions and human lifestyles. This document discusses various safety indicators and their applicability in the context of the future time-scales which have to be considered in safety assessments of deep geologic repositories. Quantitative assessment are based on numerical estimates of consequences (e.g. risk or dose) and the assessment is made against numerical criteria. Qualitative assessments are based on estimates of hazard potential which are not exact or absolute and the assessment is made against criteria which may not be numerically defined. Examples of such criteria are the convenient reference values provided by levels of radionuclides in the natural environment. Refs, figs and tabs