Probabilistic and deterministic investigation on single crack growth in dissimilar metal welds of a piping system

Probabilistic and deterministic integrity analyses of piping are important issues with regard to the integrity and reliability of nuclear power plant (NPP) components. Since there is an ongoing controversial discussion concerning the positive and negative influence of weld residual stress (WRS) on the failure probabilities of piping with dissimilar metal welds (DMWs), we herewith present the analysis of a representative straight pipe with DMW in a boiling water reactor (BWR). In this case, we consider the WRS profile, internal pressure (IP), bending stress (BS), stress corrosion cracking (SCC) and relative depth (a/t) of circumferential cracks at the inner pipe wall for the calculation of crack growth and break probabilities by using the PROST software. Probabilistic analyses show that the dependence of various break probabilities of components is not only on WRS distribution profiles but also on the crack geometry. The analyses reveal that the break probability may increase nearly 100 times due to an increase of the WRS by a factor of 1.5. The sensitivity of the stress intensity factors on the WRS profile, IP, BS, SCC and on the relative crack depth (a/t) is compared.