Comprehensive evaluation of new probabilistic safety analyses (PSA) for nuclear power stations outside Germany and status report on safety engineering

This report was prepared on behalf of the Minister of Environment, Nature Conservation and Nuclear Safety. It summarizes the results of an analysis of the state of the art of foreign Probabilistic Safety Assessments (PSA) for nuclear power plants. Main features of selected PSA documents, characterizing methods and their application within the framework of operational safety assessment, are presented as well as insights gained from discussions with utilities and an authority. German examples of PSA were compared to the foreign analyses using experiences of the TUeV Nord e.V. from reviewing PSA. This comparison covers PSA of level 1. It was found that German PSA methods are generally comparable to the foreign approaches. Nevertheless differences were found with respect to the scope of operational states covered by the analyses, the details down to which human error analyses were performed as well as some special issues. The foreign examples demonstrate an extended application of PSA within the operational safety management. Experiences that were gained within this process over years form an appropriate basis for the establishment of probabilistic safety criteria as well as procedures for incorporating PSA into the operational safety evaluation process. A procedure is proposed for further performing and evaluating PSA and their results in Germany. (orig.)