Neutron resonance treatment with details in space and energy for pin cells and rod clusters

Abstract

Two new codes for calculating with space and energy details in the resonance region are presented here: RMET21 and RMET22. The first one is for homogeneous mixtures and pin cells and the second for cluster type fuel elements. The methods used in these codes are based on the solution of the integral form of the Boltzmann transport equation, with first-flight collision probabilities. Resonance profile tabulations are used, constructed from basic evaluated nuclear data files. In the RMET21 program, there is an option to calculate resonance cross-sections with the Breit—Wigner formula, using any set of resonance parameters. This option is useful, e.g. in comparisons with analytical methods and to make sensitivity studies. In the RMET22 code, a new procedure is presented in the resonance region, using collison probabilities, without the approximation of annularization, commonly used to deal with this geometry. In the RMET22 code, the different pins and other regions within a cluster of rods are treated allowing for the details of space and energy. A new method is used to obtain collision probability tables for interpolations and other approximations to speed up the calculations. Comparisons of results obtained by different treatments and experiments are included, showing the accuracy of the methods presented here and their applicability.