Features of Uncertainty Analysis for Probabilistic Safety Analysis

Uncertainty analysis (UA) is one of the main problems in probabilistic safety analyses (PSAs) of level 2 [1, 2] solved with allowance for the characteristics of the uncertainty of the reliability parameters of the reactor plant components: failures of components and systems, severe accident (SA) events, etc. Many failures of the reactor plant systems depend on the SA scenario. The estimate of such probabilistic indicators of emergency conditions as the probability of dependent failures is impossible without additional calculation estimates. Therefore, PSAs of level 2 are usually accompanied by a series of deterministic supporting calculations with the corresponding UA [3]. In this study, a method for estimating the probability of dependent failures of reactor plant systems has been developed on the basis of recommendations for estimating the uncertainties of the results of calculated safety analyses [3] with allowance for the tasks of PSA of level 2.