COMMON CAUSE FAILURES - AN ANALYSIS METHODOLOGY AND EXAMPLES

This paper presents the framework developed for the treatment of common cause failures in risk and reliability analyses in a project jointly sponsored by the Electric Power Research Institute (EPRI) and the US Nuclear Regulatory Commission (NRC). The framework is developed as a systematic guide for identification, modeling, and quantification of common cause failures. It provides step-by-step procedures for performing each task of the analysis and allows the flexibility of choice among alternative acceptable models and analytical techniques. The major aspects of the analysis addressed in the framework include logic model development, screening of common cause events, logical and probabilistic representation of common cause failure events, data analysis, system quantification, and interpretation of results. In addition to describing the framework, this paper presents certain key methodological developments that came about in the process of formulating the systematic procedure. The framework and several of the most important elements of the procedure are applied to an example involving common cause failure of nuclear power plant station batteries.