Background: Primary water stress corrosion cracking (PWSCC) is commonly produced in the dissimilar metal welded joints for connecting the pipe-nozzles of nuclear reactor pressure vessels to the safe ends. The technology to repair and mitigate PWSCC is usually to make the weld overlay of higher corrosion resistant Alloy52M on the pipe joints. Purpose: We need to assess the integrity of the welded overlay structures

and to make Leak-before-break (LBB) analyses. The effect of the weld overlay thickness on the LBB behavior needs to be studied. Methods: Based on the three-dimensional finite element fracture mechanics analyses

the ABAQUS software was applied to construct the LBB curves and ligament instability lines of the dissimilar metal welded overlay structures. The effects of the weld overlay thickness on the LBB curves and ligament instability lines were analyzed. Results: The results show that the LBB curves and ligament instability lines with the weld overlay are located above those without the weld overlay. With increasing weld overlay thickness

the LBB curves and ligament instability lines both shift upward. Conclusion: The weld overlay can increase the LBB safe margin of the dissimilar metal welded joints. With increasing weld overlay thickness

the LBB safe margin of the joint structure can be further increased.Cited