Postirradiation heat treatment (annealing) at 399°C has demonstrated a capability for the relief of radiation embrittlement to reactor vessel steels. Building on an earlier investigation, this report describes a study of Charpy-V (C_V) notch ductility and tensile properties behavior of two representative reactor vessel welds under cyclic 399°C postirradiation annealing and 288°C reirradiation. The welds were by the submerged-arc process and were chosen for their high radiation sensitivity (high copper content) and for their difference in as-fabricated C_V upper-shelf energy levels derived from different welding fluxes. Weld properties were determined at each phase of the anneal-reirradiation-reanneal-reirradiation sequence.

The study clearly demonstrates the capability of the annealing method for maintaining property changes for reactor steels, including C_V upper-shelf reduction and transition temperature elevation, below prefixed limits. In addition, the study confirms a significantly greater rate of embrittlement by heat-treated material compared with nonheat-treated material. Pronounced dissimilarities between C_V upper-shelf energy and transition temperature behavior were observed, but parallels were shown with tensile ductility and strength changes, respectively, during annealing and reirradiation.