How to construct a seismic risk model?

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. (orig.)