Effects of Irradiation and Thermal Annealing on Fracture Toughness of the Midland Reactor Weld WF-70

摘要

The influence of irradiation damage and recovery of properties by thermal annealing for low upper-shelf WF-70 weld metal has been evaluated. The test material was obtained from the beltline and nozzle course girth welds of the Midland Unit 1 reactor pressure vessel. The two welds, ostensibly made with the same heat of weld wire and the same lot of submerged-arc flux, were determined to be separable for evaluations by virtue of differing copper contents. Conventional transition temperature methods of drop-weigh nil-ductility transition and Charpy V-notch (CVN) transition curves could not distinguish a difference in transition temperature. However, a recently developed master curve method of data evaluation revealed the difference by virtue of achieving better sensitivity using only fracture mechanics-based test data.