Evaluation of thermal recovery of neutron irradiated SA508-3 steel using magnetic property measurement

Abstract

The Vickers microhardness and magnetic properties have been used to investigate irradiation effects and thermal recovery characteristics of neutron-irradiated SA508-3 reactor pressure vessel steel specimens irradiated to a neutron fluence of 5.5 X 10(17) n cm(-2) (E > 1 MeV) at 70 degrees C. Two recovery stages were identified from the hardness results during isochronal annealing and the mechanism responsible for the two stages was explained using the results of Barkhausen noise on the basis of the interaction between radiation-induced defects and the magnetic domain wall. The neutron irradiation caused the coercivity to decrease, whereas the maximum magnetic induction increased. Barkhausen noise parameters associated with the domain-wall motion were decreased by neutron irradiation and recovered with subsequent heat treatments. From the sensitive changes in the Barkhausen noise upon annealing heat treatment, it is suggested that the Barkhausen noise measurements may be used as a useful tool for monitoring the early stage of the thermal recovery behaviour of neutron-irradiated reactor pressure vessel steels.