Comparison of resonance absorption theory used in the codes GYMEA and PEAS and evaluation of residual background reaction rates

Abstract

Details of the resonance theory used in the code GYMEA are described and compared with exact solutions for resonance's in Th232, U235, and Pu240. The relative merits of two methods for including background cross sections are evaluated, by an exhaustive study of the reaction rates across the resonance's. It was found that the analytical procedure for calculating resonance reaction rates leads to tolerable errors in reactor physics calculations. The resonance adjusted calculations emerged as the most accurate method for computing the fine structure of the reaction rates across a resonance.