Analysis of Weld Overlay Residual Stress for Dissimilar Metal Welds in Qinshan Nuclear Power Plant

Alloy 82/182 were used extensively in PWR primary coolant system as the DMW weld structure for the pipe nozzle and pipelines. The dissimilar metal welds（DMW） easily appears cracking due to the stress corrosion and fatigue after long operation. Based on the service data from foreign nuclear powers, the primary water stress corrosion（PWSCC） is the major factor for cracking, which is sensitive to the stress of pipe inside surface. The structural weld overlay repair is an appropriate way to repair the operating nuclear reactor piping according to the international experiences. Based on the nozzle of Qingshan nuclear power phase I, the axis symmetric FE model was set up to simulate the welding procedures and obtain the thermal field and residual stress field at the area of DMW weld by ANSYS finite element analysis software. The residual stress analysis indicated that PWSCC will be prevented by the resulted inside surface stresses after weld overlay.