The Impact of Fracture Toughness and Weld Residual Stress of Inconel 82/182 Bimetal Welds on Leak-Before Break Behavior

Cracks have been discovered in Inconel 82/182 bimetal welds at the hot leg to reactor pressure vessel (RPV) nozzle welds at the V. C. Summer nuclear power plant in the United States and at the Ringhals plant in Sweden. One question raised by these incidents is what impact will cracks such as these have on the possible acceptability of leak-before-break for these large-diameter piping systems. In order to address this question, fracture toughness tests in both the L-C and L-R orientation with the crack centered in both the Inconel 82/182 weld as well as in the buttered region of the bimetal weld were conducted on specimens machined from a bimetal weld obtained from a cold leg from a cancelled CE plant. In addition, weld residual stress analyses have been conducted to assess the propensity for primary-water stress-corrosion cracking (PWSCC). As part of this paper, the results from both the fracture toughness tests and weld residual stress analyses will be discussed, along with their potential impact on LBB.