Fracture toughness characterization of irradiated, low upper shelf welds

Previous studies have shown that after irradiation steels used in the beltline region of commercial, light water reactor pressure vessels can show both a significant increase in the temperature of the brittle-to-ductile transition and a reduction in Charpy-V (C/sub v/) upper shelf energy level. Certain A 533-B and A 508 submerged arc weld deposits containing a high copper impurity level can exhibit C/sub v/ upper shelf energy levels below 68 J. For vessels which attain such low toughness, Federal Regulations (10 CFR Part 50) require, as an option, the performance of a fracture mechanics analysis that conservatively demonstrates the existence of adequate margins of safety for continued operation. In the upper shelf region, the vessel material is assumed to exhibit elastic-plastic behavior so that a linear elastic fracture mechanics approach is inappropriate. Work performed by Materials Engineering Associates on the J-R curve characterization of seven welds irradiated in the HSST Program is discussed