Residual Stress Evaluation of Dissimilar Weld Joint Using Reactor Vessel Outlet Nozzle Mock-Up Model: Report 2

In recent years, the occurrence of primary water stress corrosion cracking (PWSCC) in Alloy 600 weld regions of PWR plants has increased. In order to evaluate the crack propagation of PWSCC, it is required to estimate stress distribution including residual stress and operational stress through the wall thickness of the Alloy 600 weld region. In a national project in Japan for the purpose of establishing residual stress evaluation method, a test model was produced using the same fabrication process in Japanese PWR plants in order to measure stress distribution change of the Alloy 132 weld region during fabrication process such as a hydrostatic test, welding a main coolant pipe to the stainless steel safe end and operation condition test. For the mock up test model, the stress distribution of selected fabrication processes was measured using the Deep Hole Drilling (DHD) method. From the measurement results, it was found that the stress distribution in thickness direction at the center of the Alloy 132 weld line was hardly varied with the hydrostatic test at site and operating condition test history. FE analysis was performed to calculate the stress distributions for each fabrication process. Comparing with measurement results, the validity of the FE analysis was confirmed. From the validation procedure, a standard residual stress evaluation method was established.