Sensitivity Analyses of Finite Element Method for Estimating Residual Stress of Dissimilar Metal Multi-Pass Weldment in Nuclear Power Plant

In nuclear power plants, ferritic low alloy steel components were connected with austenitic stainless steel piping system through alloy 82/182 butt weld. There have been incidents recently where cracking has been observed in the dissimilar metal weld. Alloy 82/182 is susceptible to primary water stress corrosion cracking. Weld-induced residual stress is main factor for crack growth. Therefore exact estimation of residual stress is important for reliable operating. This paper presents residual stress computation performed by 6” safety & relief nozzle. Based on 2 dimensional and 3 dimensional finite element analyses, effect of welding variables on residual stress variation is estimated for sensitivity analysis. 1. 서 론 최근 V.C Summer 원전 등에서 이종금속용접부 (Dissimilar Metal Weld) 균열이 관찰되었다. (1~3) 균열은 Inconel 계열 용접 금속에서 발생하였으며 일차수응력부식균열(PWSCC)이 균열의 주요 발생 원인이었다. 일차수응력부식균열은 재료의 민감도, 용접부 인장 잔류 응력 및 사용 중 하중(In-service load), 부식 환경과 같은 3가지 인자의 상호작용에 의해 발생한다. (2,4,5)