A cooperative effort between the U.S. NuclearRegulatory Commission (NRC) and the Electric PowerResearch Institute (EPRI) has resulted in the developmentof the Extremely Low Probability of Rupture (xLPR) CodeVersion 2.0. xLPR is a probabilistic fracture mechanicscode which models nuclear power plant (NPP) piping,including the effects of primary water stress corrosioncracking (PWSCC) and mitigation, to calculate theprobability of leakage or rupture. One aspect of the xLPRproject was to develop recommended acceptance criteriafor use with the xLPR Version 2.0 Code in reviewingpotential leak-before-break (LBB) analyses for NPPscontaining piping welds susceptible to PWSCC. Therecommended acceptance criteria were considered to beoverly conservative by some industry representatives. Thispaper will examine the recommended acceptance criteriain the context of the associated regulatory history anddegradation modeling techniques and propose alternativeacceptance criteria for reviewing leak-before-breakanalyses. If found to be acceptable to the NRC, thealternative acceptance criteria would reduce unnecessaryregulatory burden, while maintaining the necessaryconservatism to address key assumptions and sources ofuncertainty, consistent with currently accepted practice.
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