Representative evaluation of Cernavoda NPP seismic hazard and vrancea seismic prognosis activity

For representative safety evaluation of a NPP located on a seismic site, the seismic acceleration level to which the NPP should sustain must be as representative as possible for that site, with a conservative degree of safety but not too exaggerated. The consideration of the seismic events as independent events affecting the site and the use of statistic methods to define some safety levels with very low annual occurrence probabilities (10 -4 ) may lead to some exaggeration evaluations if it is not considered the maximum capacity of a focus release energy and the ultimate capacity of soil to transfer dynamic loads. On the other hand the use of some very high values for the seismic accelerations imposed by the seismic safety levels required by the hazard analysis, may lead to very costly technical solutions that can make the plant operation more difficult and increase the maintenance costs.