Correlation between the stability of irradiation defects and stress corrosion cracking in high temperature water of welded AISI 304 stainless steel

Stainless steels are used for the fabrication of some internal components of light water cooled reactors, thus being subjected to radiation, heat, and corrosive environment. Neutron irradiation induces different types of damage in stainless steels. As a consequence, these materials may become susceptible to stress corrosion cracking in the high temperature water environment of the reactor cooling circuit. The different types of defects induced by irradiation have been characterised using transmission electron microscopy and positron annihilation. The contribution of the different types of defects (vacancy type clusters, dislocation loops and grain boundary segregation) is assessed by post irradiation annealing treatments. After different time - temperature combinations, the defects are removed, as it is monitored by microscopy and positron annihilation spectroscopy. The removal of defects is correlated to the stress corrosion cracking behaviour of the irradiated material before and after post irradiation annealing.