Positron annihilation study of proton-irradiated reactor pressure vessel steels

The microstructures, irradiation-induced defects and changes of mechanical property of Chinese domestic A508-3 steels after proton irradiation were investigated by TEM, positron lifetime, slow positron beam Doppler broadening spectroscopy and hardness measurements. The defects were induced by 240 keV proton irradiation with fluences of 1.25×1017 ions cm−2 (0.26 dpa), 2.5×1017 ions cm−2 (0.5 dpa), and 5.0×1017 ions cm−2 (1.0 dpa). The TEM observation revealed that the as-received steel had typical bainitic–ferritic microstructures. It was also observed that Doppler broadening S-parameter and average lifetime increased with dose level owing to the formation of defects and voids induced by proton irradiation. The correlation between positron parameters and hardness was found.

► Chinese domestic A508-3 steels are damaged by proton radiation.
► Microstructure evolution is evaluated by TEM and positron annihilation spectroscopy.
► Microhardness of irradiated steels increases with dose.
► Biggest hardening rate appears at low radiation dose level.