Neutron-irradiated reactor pressure vessel steels investigated by positron annihilation

The recovery of the defects produced m neutron-irradiated low alloy ferritic steels has been investigated by positron annihilation techniques during is ochronal annealing programs. A good correlation was found between the annealing stages observed with positrons and the changes of the mechanical properties. A dramatic change in the positron parameters was observed around 400 ° C in the A533B samples irradiated at 290° C with high dose. An interpretative model is proposed which presents good consistency with the results obtained for the non-irradiated and the irradiated steels.