Determining seismic fragility of structures and components in nuclear power plants using multiple ground motion parameters - Part II: Application

This study presents an application of the innovative fragility method proposed in companion paper (Part I) to a horizontal heat exchanger in Darlington nuclear generating station. To illustrate the advantages of the proposed method, seismic fragility curves and High Confidence of Low Probability of Failure seismic capacity of the heat exchanger are calculated by the conventional and proposed fragility methods. The results show that, by using two ground motion parameters, the median seismic capacity of the heat exchanger has remarkable 53.9% increase, and the High Confidence of Low Probability of Failure seismic capacity is increased by 25.0%. These increases come from the reduction of conservatism of the median seismic demand by incorporating the correlation between two ground motion parameters. Although applications of components mounted on supporting structures are not presented, seismic capacities of components are expected to increase as long as the effect of structural dominant modes on seismic responses are captured by employing the proposed method. For critical structures, systems, and components that limit the plant seismic capacity, the proposed fragility method should be implemented to evaluate their seismic capacities.