EMBRITTLEMENT RECOVERY DUE TO ANNEALING OF REACTOR PRESSURE-VESSEL STEELS

The irradiation embrittlement of nuclear reactor pressure vessels (RPV ) can be reduced by thermal annealing at temperatures higher than the normal operating conditions. The objective of this work was to analyze the pertinent data and develop quantitative models for estimating the recovery in 41 J (30 ft-lb) Charpy transition temperature (TT) and Ch arpy upper shelf energy (USE) due to annealing. An analysis data base was developed, reviewed for completeness and accuracy, and documented as part of this work. Models were developed based on a combination of statistical techniques, including pattern recognition and transformati on analysis, and the current understanding of the mechanisms governing embrittlement and recovery. The quality of models fitted in this proj ect was evaluated by considering both the Charpy annealing data used f or fitting and a surrogate hardness data base. This work demonstrates that microhardness recovery is a good surrogate for shift recovery and that there is a high level of consistency between the observed anneal ing trends and fundamental models of embrittlement and recovery proces ses, (C) 1998 Published by Elsevier Science S.A.