USNRC materials research for evaluation of pressurized thermal shock in RPV of PWRs

The recent definition of a postulated thermal shock accident followed promptly by system repressurization termed an overcooling or pressurized thermal shock accident has set a large analysis and research effort into motion. The essential elements are concerned with defining the accident transients, evaluating the instrumentation and controls that cause the postulated accidents and evaluating the metallurgical and structural mechanics aspects of the reactor vessel with respect to its failure potential. This paper discusses the research underway by NRC for the vessel material and fracture consideration of this postulated accident and also provides information on our plans for mitigation of this problem. (orig.)