EFFECT OF MATERIAL PROPERTIES ON CRACK LENGTH IN DMWJS OF SAFE-END IN PRESSURIZED WATER REACTORS

Abstract

Dissimilar metal welded joints (DMWJs) are widely used in the primary systems of pressurized water reactors (PWRs), particularly in the connection between the reactor pressure vessel (RPV) nozzle and the safe-end. Due to the differences in mechanical properties between the joined materials and the presence of welding residual stresses, these regions are susceptible to complex crack initiation and propagation behaviour. The present study investigates crack propagation in a DMWJ of an RPV safe-end using the Extended Finite Element Method (XFEM) implemented in ABAQUS. A one-inch compact tension (1T-CT) specimen was developed to represent the dissimilar material region consisting of A508 low-alloy steel, Alloy 182 weld metal, and SS316L stainless steel. Four initial crack configurations were considered near the interfaces between the dissimilar materials. The study mainly examines the effects of residual stress and Young's modulus on the crack propagation path. The numerical results show that residual stress has a significant influence on the direction of crack growth. In the absence of residual stress, the crack generally tends to propagate toward the region with lower yield strength. However, with increasing residual stress, the crack propagation direction changes and shows a tendency to deflect toward the material having higher yield strength. The influence of Young's modulus on crack deflection was found to be comparatively small when compared with the effect of residual stress. The results also indicate that the initial crack location and its distance from the material interface influence the resulting crack propagation behaviour. The findings provide useful insight into the fracture behaviour of DMWJs and may contribute to improved structural integrity assessment of safe-end components in nuclear power plants.