The German PSA Guideline and its technical documents on PSA methods and data require probabilistic safety analyses (PSA) to be carried out in the frame of safety reviews for nuclear power plants. Since 2005 this also includes a seismic PSA (SPSA) for sites with design earthquake intensities exceeding the value VII (MSK-64/EMS-98). It is shown how the plant model of PSA Level 1 for internal events can be extended on the level of fault tree basic events to get a quantifiable seismic plant model. A two-step screening procedure can be applied to derive the seismic equipment list (SEL) and a list of all possibly seismic-induced dependent equipment failures. The screening procedure is supported by a database. The database keeps at hand all the data and information to extend the plant model of PSA Level 1 in a proper manner.

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As part of a larger nuclear regulatory investigation project, a contribution to the development of methodologies for the fire hazard assessment has been provided. Within the framework of probabilistic fire risk analyses, a methodology for the selection of critical plant areas as starting point for the detailed analysis has been developed. This method is mainly based on the systematic compilation of comprehensive fire related information for each individual compartment. The primary information gathered is used for ranking of compartments in terms of fire load, conditional fire occurrence frequency, and possibilities of fire propagation. For the implementation and application of the methodology within the framework of probabilistic safety assessment studies, an ACCESS database has been developed, both for compilation of the raw data as well as for further data analysis.

In the following, an advanced German approach for state-of-the-art probabilistic fire risk assessment (Fire PSA) to be performed within comprehensive safety reviews of nuclear power plants is presented on the background of the current German PSA Guide. This approach has been successfully applied in the frame of a Fire PSA recently performed for a nuclear power plant with boiling water reactor (BWR-69 type). The set of all compartments in a nuclear power plant is the starting point for determining the annual frequency of fire induced plant hazard and core damage states. Fire PSA has to be carried out in several steps. First step of the analysis is a selection process (‘screening’) providing critical fire zones, 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. Detailed analyses providing compartment specific fire induced hazard state frequencies are performed only for those compartments, where in case of fire a relevant contribution to the overall hazard state frequency can be expected. Both analytical steps, selection of relevant compartments as well as detailed analyses, are based on a comprehensive compartment related compilation of fire specific data and information.

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