EFAST Analysis Applied to a PA Model for a Generic HLW Repository in Clay

Abstract In this paper we investigate whether the EFAST method is suitable for use in long-term safety assessments of geological repositories for radioactive wastes. A generic test case for a HLW repository in a clay formation was selected. Despite the skewed and heavily tailed distribution of the model output, the EFAST results were surprisingly good compared to results previously obtained for a repository in rock salt. The important difference between the PA models in clay and salt is that the former produces a less skewed and less scattered distribution of the annual dose than the latter. As a result, the variance of the model output and the sensitivity indexes are more stable.