Recent Developments on Seismic PRA

Abstract

Recent developments of the Probabilistic Risk Assessment (PRA) applications have tendency to use one integrated model for Level 1 both internal and external events. In this approach external events logic models are mapped on internal model. Some relevant aspects related to selection of seismic initiating events, seismic sequences, seismic basic events, fragility analysis, development of seismic logic model and seismic quantification are discussed in the paper. Development of seismic model mapped on internal PRA model may require to define seismic basic events (and associated switches) that may replace a group of internal basic events (at the level of system function or top event). Seismic fragility task is very resource intensive especially for high quality SPRA. When more than one seismic scenario is used significant effort can be saved by scaling fragility parameters developed for one earthquake scenario to correspond to the other earthquake scenario. The paper presents some tools developed by the authors capable to perform damage state fragility calculations and fragility scaling.