PWR Supplemental Surveillance Program

Abstract

A pressurized water reactor (PWR) supplemental surveillance program (PSSP) is being designed to provide high-fluence reactor vessel material embrittlement data for the operating U.S. PWRs. Peak reactor pressure vessel (RPV) fluence levels as high as 7 × 1019n/cm2 (E > 1.0 MeV) will be attained as PWRs operate to 60 years and potentially beyond. Therefore, a need exists to obtain high-fluence PWR surveillance data to validate or revise embrittlement trend correlations (ETC) applicable for the high-fluence regime. Without the availability of high-fluence PWR surveillance data, it may be necessary to use an overly conservative ETC, or an ETC with a high margin at high fluence, which could constrain plant pressure–temperature operating curves, increasing startup and shutdown times and costs or increasing the potential of exceeding the pressurized thermal shock screening limit. The PSSP is designed to supplement data produced by the existing 10 CFR 50 Appendix H surveillance programs. The two proposed PSSP capsules will contain Charpy specimens reconstituted from tested PWR surveillance capsule materials, carefully selected for material type, chemistry, and fluence to optimize future ETC development. These capsules will be inserted into one or two U.S.-based Westinghouse-designed operating nuclear power plants for continued irradiation. The selected host plant(s) have relatively high capsule irradiation flux locations, enabling production of high-fluence data prior to the U.S. plants reaching 60 years of operation. The PSSP capsule irradiation will increase the fluence levels up to 1 × 1020n/cm2 on select groups of reactor vessel materials. This paper describes the basis for the PSSP, plant selection for irradiation, and material selection.