A B S T R A C T This paper presents finite element simulation results of residual stresses in dissimilar metal welds of a PWR pressurizer safety/relief nozzle. The present results are believed to be significant in two aspects. The first one is to consider the effect of the presence of similar metal welds on resulting residual stresses. The second one is the mitigation effect of the overlay welding thickness on residual stresses. After dissimilar metal welding, tensile residual stresses are present both at the inner surface and at the outer surface of dissimilar metal welds. Adjacent similar metal welding, however, decreases residual stresses to compressive ones at the inner surface of dissimilar metal welds, possibly due to the bending mechanism caused radial contraction of the weld. At the outer surface of dissimilar metal welds, similar metal welding increases residual stresses. Overlay welding further decreases residual stresses at the inner surface of dissimilar and similar metal welds, but increases slightly residual stresses at the outer surface.Keywords finite element simulation; PWR pressurizer safety/relief nozzle; weld overlay; welding residual stress. I N T R O D U C T I O NRecently stress corrosion cracks were found in dissimilar metal welds of some pressurized water reactor (PWR) nuclear plants. [1][2][3][4][5] As a result, several mitigation methods have been discussed, 5-7 one of which is the weld overlay. 5,8-10 As the weld overlay method has been applied to piping systems in boiling water reactor components over some decades, 11,12 its effectiveness in mitigation is well appreciated. In addition, the weld overlay can also provide other benefits, for instance, improved inspectability and structural reinforcement effects due to an increasing thickness. 5,10,12 Although some guidelines on the weld overlay for dissimilar metal welds in pressurized water reactor nuclear plants are available, 13-15 numerical simulations are desirable to assess the weld overlay effect on residual stresses, as the weld overlay process is expensive. Furthermore such numerical simulations can be used to help optimise the weld overlay process.Welding residual stress simulation of stainless pipes using the finite element (FE) analysis is relatively well established, and accordingly many papers have been published Correspondence: Yun-Jae Kim.in the literature. [16][17][18][19][20] Some relevant works are briefly described here. Brickstad and Josefson 16 performed a parametric study for multipass circumferential butt-welding of stainless steel pipes to quantify residual stresses and their sensitivity to variation in weld parameters. Yaghi et al. 17 presented another parametric study on effects of the thickness and radius-to-thickness ratio on residual stresses in butt-welded stainless pipes. Related to repair welds and overlay welding for dissimilar metal welds in PWR plants, many works have been published in American Society of Mechanical Engineers, Pressure Vessel and Piping Division (ASME PVP) conferences. [4][5][6]8,9 One ...