Seismic design of nuclear facilities in Germany

Seismic design forms an integral part of the overall safety concept of German nuclear power plants, despite the generally low seismic activity in Germany. Even the more active zones in Germany represent regions with low seismic hazards. The development of specific nuclear standards in Germany regarding the seismic design of nuclear power plants is outlined. The first specific nuclear standard was issued in 1975, prescribing two design earthquake levels. It was revised in 1990. Today a single design basis earthquake is considered for which the plant safety has to be demonstrated by dynamic analyses on the basis of a site-specific seismic assessment. The seismic safety of older plants that had not already been constructed according to a specific nuclear standard regarding the seismic design, have been re-evaluated recently. This resulted in backfitting measures such as the installation of bunkered emergency systems at many older plants. Furthermore, the seismic safety of all nuclear power plants is now assessed within the framework of periodic safety reviews. For future reactors like the European pressurized water reactor (EPR), the design provisions will have to ensure that external hazards will not constitute a significant part of the residual risk of the plant. A ground level acceleration value of 0.25 g is adopted for the design, which should provide ample safety margins for all relevant sites in France and Germany.