Abstract
In the Belgian Pressurized Water Reactors Doel 3-4 and Tihange 2-3, the Reactor Pressure Vessel (RPV) nozzle-to-safe-end Dissimilar Metal butt Welds (DMW) are made of nickel-base alloy 182. This material is known to be susceptible to Primary Water Stress Corrosion Cracking (PWSCC) if the stress level is high enough. As a part of the prevention strategy, weld residual stresses have been assessed from experiments and numerical simulations. Moreover, a Defect Tolerance Analysis (DTA) is conducted to assess the acceptability of flaws that could possibly be detected during In-Service Inspection campaigns and to define reasonable inspection intervals. This analysis accounts for the plant specific residual stress profiles and operating loads to calculate the time for a postulated flaw to grow up to an acceptable size limit. Most of the time, the flaw propagation rate induced by PWSCC relies on stress intensity factors calculated in simplified geometries such as plates or pipes without accounting for the actual weld geometry. Therefore, 3D XFEM crack growth calculations are conducted considering more realistic hypotheses in order to quantify the level of conservatism of the simplified approach. The present paper focuses on the benefit of using detailed simulations of crack growth.
