Status of Regulatory Issues and Research in Light Water Reactor Surveillance Dosimetry in the U.S.

Abstract

Operating experience with light water reactors has generated regulatory needs for more precise information on neutron radiation embrittlement of vessel beltline material. Accurate prediction of fluence exposure continues to be required for setting pressure-temperature limits for start-up and cool down operations of reactors and for improved surveillance programs. But, the emergence of the pressurized thermal shock issue has established a new impetus for more precise and accurate flux and fluence determinations and predictions at specific locations of the vessel wall. Such issues have led NRC to establish a cooperative research program to validate and improve methodologies used to predict radiation damage in pressure vessel steels. The program includes the validation of experimental and analytical methods of fluence determination in surveillance programs, data bases, and estimates of uncertainties in predictive methods using well-defined, reproducible benchmark facilities traceable to standard fields. Finally, the program culminates in a set of ASTM standards for analysis of LWR vessel irradiation surveillance.