Development of Analysis Procedure for Russian.NPP Piping Failure Probability on the Basis of R6 Crack Resistance Assessment Method

Current failure criteria (M-01-88, M-02-91, etc.) used in Russian nuclear institutions had been developed for deterministic analyses and therefore an attempt to use them for probabilistic ones has demonstrated some deficiencies inherent to them. They can include a polygonal failure surface in the space of random variables that makes this surface un-differentiable at some point. Moreover, the failure criteria are assumed by such mathematical expressions which sometimes loses their meaning in the area of lower tail values in random distributions. In this connection, this work has considered as a criterion basis the R6 criterion which sufficiently avoids the aforementioned deficiencies and has illustrated experimentally the conservatism of its assessment. A detailed analysis has been carried out to evaluate a failure probability of a perlite weld in the primary circuit piping of Russian NPPs. The experience gained in carrying out these calculations allows the assertion that the algorithm CL of FPI methods can be applied successfully to evaluate a structure failure probability using the R6 methods (This paper is a 3 page abstract)