Implementation of the results of the uncertainty analysis of the COSYMA package for zoning purposes

The EC and US probabilistic accident consequence codes, COSYMA and MACCS, respectively, estimate the risks and other endpoints associated with hypothetical accidents at nuclear installations. A joint project for an uncertainty analysis of these two codes used a rigorous expert judgement procedure with multiple experts. For all assessments, eight panels of six to ten experts were used. The uncertainty analysis of COSYMA evaluated the uncertainty on 191 endpoints for three different situations that are of relevance to regulatory processes in different European countries. The uncertainties were evaluated for three source terms. In this way the study encompassed a wide range of source terms and other situations that have been considered in safety assessments of nuclear power plants. This paper will mainly deal with two aspects: (1) relating predictions using default parameter values and providing a basis for determining where the 95th envelope in the uncertainty analysis lies and (2) how to estimate uncertain...