The effects of irradiation, annealing and reirradiation on RPV steels

An atom probe tomography microstructural characterization has been performed on an A533B pressure vessel steel (JRQ) after irradiation to a fluence of 5 × 1023 n m−2 (E > 1 MeV) and a subsequent annealing treatment of 168 h at 460 °C and also through two cycles of neutron irradiation (0.85 × 1023 n m−2 (E > 1 MeV)) and annealing (168 h at 460 °C). The alloy that was neutron irradiated to a fluence of 5 × 1023 n m−2 exhibited a high number density of Cu-enriched precipitates and a shift in the ductile-to-brittle transformation temperature of ΔT41J = 96 °C. Annealing for 168 h at 460 °C coarsened these Cu-enriched precipitates and recovered the embrittlement. The material that was re-irradiated to a total fluence 1.7 × 1023 n m−2 also exhibited a high number density of Cu-enriched precipitates and a ΔT41J shift of 56 °C. Annealing the re-irradiated material for 168 h at 460 °C coarsened these precipitates and recovered the embrittlement.