Weld Residual Stress Inputs for a Probabilistic Fracture Mechanics Code

Weld residual stress (WRS) is known to be an important driver for stress corrosion cracking. Therefore, in probabilistic Leak-Before-Break calculations for safety-related nuclear piping systems, it is necessary to offer best-estimate WRS inputs along with an informed characterization of the associated uncertainty. This paper discusses the finite element (FE) analysis work performed to develop the WRS inputs for probabilistic models used for dissimilar metal (DM) welds at pressurized water reactors (PWRs). Three different weld geometry cases were considered representing typical nuclear piping system DM welds. In accounting for modeling uncertainty, the FE results from three independent analysts for the various weld geometry cases were compared and evaluated. This paper describes the modeling strategies used to develop the best-estimate inputs and the uncertainty distributions, including approaches to eliminate unnecessary sources of uncertainty, such as inconsistent post processing.