Flux effect analysis in WWER-440 reactor pressure vessel steels

The results of long term research programme concerning the determination of irradiation embrittlement dependence on fast neutron flux for WWER-440 reactor pressure vessel steels before and after annealing are presented in this paper. The study of flux effect was carried out on commercial WWER-440 steels which differ significantly in phosphorous (0.013–0.036wt%) and copper (0.08–0.20wt%) contents. All specimens were irradiated in surveillance channel positions under similar conditions at high ∼4×1012сm−2s−1 and low ∼6×1011сm−2s−1 fluxes (E>0.5MeV) at a temperature of 270°С. The radiation embrittlement was evaluated by transition temperature shift on the basis of Charpy specimens test results. In case of low flux, the measured Tk shifts could be 25–50°C bigger than the Tk shifts obtained from high flux data. A significant flux effect is observed in WWER-440 reactor pressure vessel steels with higher copper content (>0.13wt%).