Application of piping failure database to nuclear safety issues in Korea

This paper describes analyses and application of OPDE (OECD Piping Data Failure Exchange) database and NPFD (Nuclear Piping Failure Database) to some safety related issues for Korea nuclear power plants. Safety issues considered in this study include the piping rupture frequency assessment, the screening criteria of the leak before break application, and the augmented in-service inspection and the risk-informed ISI (RI-ISI). As a result of this study: (1) Piping rupture frequencies of the very small LOCA, feedwater line break events, and flood events were evaluated and used as initiating event frequencies for the PSA of Korean PWR plants; (2) Based on the review of OPDE DB and LBB screening criteria, LBB application to the pressurizer surge line, safety injection system, and shutdown cooling system were approved under the conditions that detailed thermal stress analyses should be performed to the systems. (3) For RI-ISI application, major degradation mechanisms in the reactor coolant system were analyzed based on the analysis of the OPDE and NPFD and augmented inspections were enforced to the pipe segments susceptible to degradation mechanism such as thermal stratification/fatigue.