EVALUATION OF THERMAL RECOVERY OF NEUTRON-IRRADIATED SA508-3 STEEL USING MAGNETIC PROPERTY MEASUREMENTS

The Vickers microhardness and magnetic properties have been used to in vestigate irradiation effects and thermal recovery characteristics of neutron-irradiated SA508-3 reactor pressure vessel steel specimens irr adiated to a neutron fluence of 5.5 X 10(17) n cm(-2) (E > 1 MeV) at 7 0 degrees C. Two recovery stages were identified from the hardness res ults 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 ma gnetic domain wall. The neutron irradiation caused the coercivity to d ecrease, 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 hea t treatment, it is suggested that the Barkhausen noise measurements ma y be used as a useful tool for monitoring the early stage of the therm al recovery behaviour of neutron-irradiated reactor pressure vessel st eels.