Construction and quantification of a fire probabilistic safety assessment model using support system initiating event fault trees

Abstract This study investigated the effect of the fire-induced initiating event fault trees (IE FTs) related to the support systems of a reference plant, Hanul 3,4, on the risk quantification results by comparing the results of two (2) different kinds of fire probabilistic safety assessment (PSA) models: one based on the FT approach (with IE FTs) and the other based on the conventional approach (without IE FTs). The results show that the FT modeling of fire-induced IEs decreases fire-induced core damage frequencies (CDFs) if the IE FTs involve relatively many AND logic gates, because the fire-induced component failure events, the probabilities of which are less than '1′(TRUE), constitute the fire-induced IE FTs. The results also show that the CDFs increase if the fire-induced IE FTs involve relatively many OR logic gates. This is because a rare event approximation leads to overestimation of the real fire-induced risks.