A hybrid approach for fault tree analysis combining probabilistic method with fuzzy numbers

Conventional fault tree analysis in safety analysis of complex engineering systems calculates the occurrence probability of the top undesired event using probabilistic failure rates. However, it is often very difficult to obtain those failure rates well in advance due to insufficient data, environment changing or new components. Fuzzy numbers can be applied to estimate failure rates by handling linguistic terms. This study proposes a hybrid approach of Fuzzy Numbers and Fault Tree Analysis to solve the conventional problem and describes its procedures using a case study of emergency core cooling system of a typical nuclear power plant