Survey of Postirradiation Heat Treatment as a Means to Mitigate Radiation Embrittlement of Reactor Vessel Steels.

Postirradiation heat treatment annealing is being investigated as a method for the alleviation of radiation embrittlement to reactor vessel steels. Objectives of this study were to identify those service and metallurgical variables which can affect annealing response, to report data comparisons available for qualification of suspected influences, and to survey experimental results from commercially produced reactor materials and duplicate materials from the laboratory. Twelve factors are identified as having potential for affecting the postirradiation heat treatment response of low-alloy pressure vessel steels. A tentative qualification of six factors as significant contributing variables is made on the basis of experimental comparisons. Of these, heat-treatment temperature was observed to exert the largest influence on the embrittlement relief by annealing. The evidence indicates that a 399C heat treatment, but not a 343C heat treatment, is a practical and effective method for reducing and controlling radiation embrittlement in reactor vessels.