Irradiation effects on magnetic properties in neutron and proton irradiated reactor pressure vessel steel

The effects of neutron and proton dose on the magnetic properties of a reactor pressure vessel (RPV) steel were investigated. The coercivity and maximum induction increased in two stages with respect to neutron dose, being nearly constant up to a dose of 1.5/spl times/10/sup -7/ dpa, followed by a rapid increase up to a dose of 1.5/spl times/10/sup -5/ dpa. The coercivity and maximum induction in the proton irradiated specimens also showed a two stage variation with respect to proton dose, namely a rapid increase up to a dose of 0.2/spl times/10/sup -2/ dpa, then a decrease up to 1.2/spl times/10/sup -2/ dpa. The Barkhausen noise (BN) amplitude in neutron irradiated specimens also varied in two stages in a reverse manner, the transition at the same dose of 1.5/spl times/10/sup -7/ dpa. The BN amplitude in proton irradiated specimens decreased by 60% up to 0.2/spl times/10/sup -2/ dpa followed by an increase up to 1.2/spl times/10/sup -2/ dpa. The results were in good accord with the one dimensional domain wall model considering the density of defects and wall energy.