Defining and justifying assumptions for exposure groups in HLW repository performance assessment

It is usual for HLW repository performance assessments to include evaluation of individual radiation exposures for comparison with individual dose and risk related criteria for acceptable waste disposal. Typically the individuals are assumed to be members of a hypothetical critical group. However, there are difficulties in justifying and applying particular hypothetical assumptions for use in such long term assessments. This paper discusses developments and raises some questions concerning criteria relating to critical and other exposure group definitions and the guidance on interpretation of these criteria in terms relevant to carrying out a performance assessment. It is concluded that assessments involving other exposure groups, not just critical groups, are of growing interest