Abstract
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 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. In that frame, it is of utmost importance to precisely assess the residual welding stress field. For that purpose, residual stress measurements on a DMW from the cancelled Spanish NPP of Lemoniz are performed with the hole-drilling strain gage method according to ASTM E837. The nozzle-to-safe-end specimen is successively sectioned (machined) from the outside to deduce the residual stress profile through the weld thickness. On the other hand, welding residual stresses in these nozzle-to-safe-end welds are calculated using Finite Element Method. These simulations include the application of buttering, the machining, and the influence of the safe-end-to-piping stainless steel weld. Moreover, the impact of the different steps followed to machine the measured specimen are simulated. The welding heat source as well as some simulation parameters are then calibrated to optimize the match with the experimental data obtained by the described measurement procedure. Based on these results, the plant-specific weld residual stresses are calculated by FE, including partial repairs as well as post-weld heat treatments. These plant specific profiles will be useful to assess the acceptability of flaws that could possibly be detected during In-Service Inspection campaigns and to define reasonable inspection intervals.
Published Version
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