Effectiveness of Flux Reduction Measures Instituted at the Maine Yankee Atomic Power Station

Abstract

Concern over the effect of radiation embrittlement of the reactor pressure vessel on heatup and cooldown pressure-temperature limits and pressurized thermal shock (PTS) resulted in a decision to implement low-leakage fuel management at Maine Yankee during the early 1980s. This paper provides background information leading up to this decision and describes the transition from standard OUT-IN to low-leakage fuel management. Various methods to determine the effectiveness of flux reduction measures are described and results compared. Results of cavity measurements and use of measurement results to (a) confirm effectiveness of flux reduction measures and (b) benchmark neutron transport calculations are also discussed. The results of neutron transport calculations are used to project fast neutron fluence and RTNDTs at expiration-of-license.