SEISMIC RESPONSE CORRELATION DATA BASED ON 3D FINITE ELEMENT ANALYSIS OF EPR BUILDINGS

摘要

The treatment of dependencies between seismic failures of structures and components in nuclear power plants (NPP) has a significant impact on the risk estimates derived from seismic probabilistic safety analysis (PSA). The frequently adopted, simplifying assumption of complete dependence between identical components of redundant safety system trains is known to be conservative. The present contribution follows up on a paper on the "Integration of correlation models for seismic failures into fault tree based seismic PSA" presented at SMiRT 21. One of the most important assumptions used in that paper consisted in adopting the response correlations proposed in the context of US seismic risk assessment studies in the 1990s (NUREG-1150). In quantitative terms, response correlation consists in the correlation coefficient between a representative seismic demand parameter (e.g. horizontal acceleration at the support) of two distinct components. Of particular interest is the correlation between the responses of identical components of redundant trains of critical safety systems, e.g. the medium-head safety injection pumps of the emergency core cooling system. In the present paper, correlation data based on a 3D finite element analysis of the four-loop PWR EPR are presented. These data are instrumental in order to substantiate assumptions regarding seismic-induced common-cause failures, especially in the context of refined seismic PSA modelling for those components which are found to be leading risk contributors in a standard seismic PSA.