NUCLEAR-REACTOR PRESSURE VESSEL-SPECIFIC FLAW DISTRIBUTION DEVELOPMENT

Vessel integrity predictions performed through fracture mechanics anal ysis of a pressurized thermal shock event have been shown to be signif icantly sensitive to the overall flaw distribution input. It has been shown that modern vessel in-ser-vice inspection (ISI) results can be u sed for development of vessel flaw distribution(s) that are more repre sentative of U.S. vessels. This paper describes the development and ap plication of a methodology to analyze ISI data for the purpose of flaw distribution determination. The resultant methodology considers detec tion reliability, flaw sizing accuracy and flaw detection threshold in its application. Application of the methodology was then demonstrated using four recently acquired U.S. PWR vessel inspection data sets. Th roughout the program, new insight was obtained into several key inspec tion performance and vessel integrity prediction practice issues that will impact future vessel integrity evaluation. For example, the poten tial application of a vessel-specific flaw distribution now provides a t least one method by which a vessel-specific reference flaw size appl icable to pressure-temperature limit curves determination can be estim ated. This paper will discuss also the development and application of the methodology and the impact to future vessel integrity analyses.