Insights From Plant Specific Common Cause Failure Analysis

Insights from three plant specific common cause failure (CCF) analyses, which used CCF Data Base and Analysis System software by US NRC, were presented in this paper. It was found that detailed guidelines/criteria were needed for performing a plant specific CCF analysis, especially for more systematic and consistent determination of the impacts of historical CCF events on a specific target system. Information collection task, impact of using unscreened independent events, and insights from specific components CCF analyses were also discussed. Finally, the following recommendations were made: (1) Develop procedures and criteria, like those developed for the plant specific CCF analyses, for more systematic and consistent plant specific CCF analysis. In developing criteria, it should be considered to credit existing plants for the enhanced defenses against CCFs based on their accumulated operating experiences. (2) Use of generic CCF data is strongly discouraged. Instead, perform plant specific CCF analysis, at least initial screening of the original events as a minimum, in order to avoid potential over-conservatism. (3) Enhance the current internet based information data bases and develop a communication network among CCF analysts in order to facilitate the information collection task.