Application of risk-informed decision making to the steam generator overfill design basis for the Catawba Nuclear Station (PSAM 5)

Preventing steam generator overfill following a steam generator tube rupture (SGTR) is part of the design basis for the Catawba Nuclear Station. A small number of single failures have been identified that are more limiting, with respect to steam generator overfill, than the single failure assumed in the design basis SGTR evaluation. The purpose of this work is to assess the risk significance of these failures and evaluate the appropriateness of excluding these failures from the design basis. The risk significance of these single failures is judged by the contributions to core damage frequency (CDF) and large early release frequency (LERF) associated with their occurrence in conjunction with an SGTR event. The resulting CDF and LERF constituents are estimated to be less than lE09/RY for each single failure. It is concluded that the single failures considered in this analysis are appropriate for exclusion from the design basis for the Catawba Nuclear Station. (author)