MICROSTRUCTURAL EVOLUTION IN LOW-DOSE NEUTRON-IRRADIATED FE-16NI-15CR ALLOY

Reactor irradiation of the base alloy of modified austenitic stainless steel, a candidate alloy for fusion reactor application, was performed with improved temperature control. All three types of defects - vacancy clusters in the form of stacking-fault tetrahedra, interstitial-type dislocation loops and voids - are more pronounced in samples irradiated with conventional temperature control than those with improved control. They are attributed to the nucleation of those defects during the start-up of the reactor. From the irradiation of thin foils, the role of freely migrating interstitials was extracted. For bulk irradiation, the variations of the three types of defects mentioned above with irradiation temperature are thoroughly investigated. Reaction of the less freely migrating point defects in SUS than in pure metals is pointed out.