Common cause failure probability and model parameters, A method for estimating.

In this study, an alternative for the analysis of common cause failures (CCFs) is investigated. The method studied consists of using the Licensee Event Report (LER) data to get single component failure probability and using stress and strength parameters to evaluate multiple component failure probabilities. Since an inversion of stress-strength interference (SSI) theory is involved, the approach is called the inverse stress-strength interference (ISSI) technique.The ISSI approach is applied to standby systems in commercial nuclear power plants. At a component level, major pumps and valves are studied. Comparisons with other CCF analysis methods indicate that the medians based on the ISSI method are slightly higher because of the inclusion of potential failure causes. Applications to multiple-train systems show that the ISSI method agrees well with the beta factor method. In all cases studied, it appears that uncertainty intervals associated with the ISSI are smaller than other methods.This study suggests that the ISSI method is a promising. alternative to estimate CCF probabilities. The method will be particularly valuable when: (1) Component-specific and system specific values are needed. (2) Failure data are scarce. (3) Level of redundancy is high. (4) Uncertainty needs to be quantified.Sponsored by Northeast Utilities Service Company and Pickard, Lowe and Garrick Incorporated under the MIT Energy Laboratory Electric Utility Program