U.S. High Fluence Power Reactor Surveillance Data—Past and Future

Abstract

Enhanced radiation embrittlement at high fluence, indicative of extended operating life beyond 60 years for current operating pressurized water reactor (PWR) vessels, has been identified as a potential limiting degradation mechanism. Currently, there are limited U.S. power reactor surveillance data available at fluences greater than 4 × 1019 n/cm2 (E > 1 MeV) for comparison with existing embrittlement prediction models. Additional data will be required to support extended operations to 80+ years, where some plants are projected to have peak vessel fluences approaching 1 × 1020 n/cm2. A number of programs are designed to contribute to the high fluence surveillance data to support extended operating life. The U.S programs include the Coordinated PWR Reactor Vessel Surveillance Program (CRVSP), the PWR Supplemental Surveillance Program (PSSP), and the Light Water Reactor Sustainability (LWRS) Program. The LWRS Program involves generation of high fluence test reactor data on many different reactor pressure vessel steels and model alloys, including some of the same PWR vessel materials irradiated to higher fluences in conventional power reactor surveillance programs. This paper surveys the existing high fluence data and the data projected to come from the above listed programs to show when such data will become available. The data will be used to validate or revise embrittlement trend correlations applicable for the high fluence regime. Mechanical property data are being developed, and fine-scale microstructure data are being produced using state-of-the-art methods.

The characterization of a nanoscale MnNi cluster in thermally aged reactor pressure vessel steels

“…Thereafter, many studies reported that high-fluence neutron irradiation could produce a high volume fraction of MNPs in both Western [8][9][10][11] and Russian [12][13][14][15] RPV steels, probably causing the second rise of the ductile-brittle transition temperature (DBTT) [16]. For both new NPPs with a design life of 60 or 80 years and existing NPPs that require an extension of the lifetime to 60 or 80 years [17], the full impact of MNPs on possible accelerated embrittlement of RPV steel is still a pending issue, which is still necessary to be adequately considered in the safety assessment of nuclear reactors.…”