121 Fire PSA for a German BWR (BWR-69 Type) — Methodology Applied and Results — (PSAM-0052)
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Published:2006
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Comprehensive safety reviews of nuclear power plants (NPP) at a time interval of ten years are mandatory in Germany since April 2002. Fire PSA is part of such a comprehensive safety review and has to be performed in several steps. First step is a selection process (“screening”) providing critical fire areas, where a fully developed fire has the potential to both cause an initiating event and impair the function of at least one nuclear safety related component or system. In the recently revised guidance document on PSA methods a new screening approach is described. This method was successfully applied to a German boiling water reactor for full power operation states. After direct exclusion of several buildings the screening approach has been applied to the reactor building (without the containment being protected against fires during full power operation by means of inert gas atmosphere), the switchgear building, the turbine hall, the diesel generator building and the bunkered independent emergency systems building. Detailed analyses have been carried out with fire specific event trees for those plant areas having remained after the screening. The final states of the event tree have been classified and the probabilistic results have been included in the plant PSA model with its event and fault trees. The results of the screening process as well as the estimated fire induced system and core damage frequencies are presented.