Retrospective quantitative analysis of common cause failures and human interactions in Swedish PSA studies

This paper reports that following recommendations from qualitative analyses comprehensive sensitivity studies of the treatment of common cause failures (CCFs) and human interactions in available Swedish Probabilistic Safety Assessment (PSA) studies for BWR-plants have been carried out. Among the issues which have been investigated in the context of CCF-contributions are: impact of lower failure multiplicities, plant-specific CCf-parameters for motor-operated valves (MOVs) and comparison between two quantification methods. Several studies concerning data variation, systematic misconfiguration of redundant components, test arrangements and treatment of multiple failures in systems with non-standard level of redundance, are in progress. Studies of human interactions have focused on errors of omission and on recovery actions. Sensitivity analyses provide guidance for future efforts and have lead to specific recommendations with respect to treatment of CCFs and human interactions within the plant-specific reference plant models to be generated in the near future