Development of the Fragility Curve of the Refuelling Water Storage Tank

The Institut de Radioprotection et de Surete Nucleaire (IRSN) carried out a Probabilistic Safety Assessment (PSA) of the standard French 900 MWe PWR. The general objective of this PSA is to supplement the deterministic analyses on which the reactor design is based in order to get better appraisal of nuclear risks. This PSA handles internal events and fire. To complete this PSA, IRSN carried out a study to examine the interest and the feasibility of a seismic PSA. This study showed that the equipment fragility evaluation constitutes one important step of the seismic PSA. So IRSN decided, in an exploratory way, to carry out the fragility study of an item of equipment. The item of equipment chosen was a Refuelling Water Storage Tank (RWST) of a typical PWR plant. The objective of this study was to define the methodology to implement in order to elaborate the fragility curve of static equipment. The purpose of the paper is to describe the methodology used to establish the fragility curve of the RWST, to present the results got as well the main insights underlined by this fragility study. (authors)