Crack and Reliability in Different Working Situations of Nuclear Island Nozzle Welded Dissimilar Metal Joints with and Without Buttering

For the primary nozzle safe end welding (A508/Alloy52Mw) of the nuclear island, a new high-efficiency low-cost direct welding process than the traditional joint with a buttering (JWB), joint with no buttering (JNB), has a research gap on its reliability. This study used simulation methods to compare the fracture process of assumed pre-cracked JWB/JNBs, revealed their similar load-carrying capacity and crack-extension resistance. Reliability studies under different working situations of JNB and JWB based on the English R6 Option 3 method showed the the ¼, ½ wall thickness (a/t = 0.25, 0.5) depth crack assumed in the ASME code anti-fracture design were safe under different working situations (design, emergent, accident, etc.) and conditions (a safety factor being used or unused) with large safety margins. Specially, in the JNBs, while a/t = 0.5, the safety margin of A508/Alloy52Mw interface was relatively small due primarily to its low fracture toughness, which needing additional focus.