A Study on the Mechanical Stress Improvement Process to Mitigate Residual Stresses in Reactor Pressure Vessel Head Penetration Nozzle Welds

摘要

A modified method was proposed herein to mitigate tensile welding residual stresses for preventing PWSCC in CRDM nozzle. Residual stress analyses using finite element method were performed to confirm benefit of the modified method. In case of applying the existing method, tensile axial residual stress decreases by 28% and tensile hoop residual stress decreases by 32%. On the other hand, in case of applying the proposed method, tensile axial residual stress decreases by 32% and tensile hoop stress decreases by about 43%. Therefore, we conclude the proposed method is more effective to prevent PWSCC than the existing methods.