Thermal annealing of an embrittled reactor vessel: Feasibility and methodology

Early light water reactor vessels with relatively high copper and/or nickel contents shows a significant radiation sensitivity in terms of the ductile-brittle transition temperature (DBTT) shift. In addition, a number of early light water plants were constructed from initial low Charpy upper-shelf materials having high copper contents. The United States Code of Federal Regulations (CFR) identifies thermal annealing of the reactor pressure vessel beltline region to recover the fracture toughness properties. As part of an Electric Power Research Institute program, thermal annealing procedures were developed and are discussed within this paper. It is concluded that dry in situ thermal annealing is feasible. (orig.)