Review of Operating Experience on Engineered Safety Features Actuating Systems

Operating experience with the Engineered Safety Features Actuating System (ESFAS), as reported in the Nuclear Power Experiences data base, and selected plant records, is presented. The purpose of this study is to evaluate the potential significance of aging, including cycling, trips, and testing as contributors to degradation of the ESFAS. Tables are presented that show the percentage of failure events classified by component, subcomponent, and cause for boiling water reactors and pressurized water reactors. A representative engineered safeguards actuating channel was selected for detailed study. Functional indicators of degradation and testing requirements are evaluated.