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The process by which reactor pressure vessel steels respond to neutron radiation exposure is very complex. Not only are the nuclear vessel materials varied in chemistry and processing history, but the embrittlement accumulation process is a function of many different variables, some of which we can only guess at their contributions. The nuclear industry has sponsored many theoretical studies, mechanical properties test programs, and microstructural examinations to understand better the embrittlement process. Mechanistic models have been developed by several people leading to a fairly sophisticated understanding of radiation embrittlement, but a comprehensive tool for direct prediction of transition temperature shift and upper shelf toughness reduction is still lacking. This paper reviews previous work in mechanistic modeling and identifies areas where more research activities are needed. A plan to improve the predictive capabilities of mechanistic models is discussed, which centers on real vessel materials. The goal of such models is to understand the interactions of microstructure, processing history, chemical composition (for example, copper, nickel, phosphorus), radiation temperature, time at temperature, possible thermal annealing response, neutron flux, flux spectrum, and flux attenuation through the vessel wall.
reactor vessel steel, radiation embrittlement, mechanistic modeling, Charpy shift, trend curve, drop in upper shelf, microstructure
Principal consultant, Grove Engineering, Knoxville, TN
Project manager, Electric Power Research Institute, Palo Alto, CA
Vice president, ATI Consulting, San Ramon, CA