Intermediate Neutron Resonance Absorption with Interference Scattering in Heterogeneous Systems

Abstract

A new method for intermediate treatment of resonance absorption developed for homogeneous systems has been applied to heterogeneous systems. In the present method, the interference between potential and resonance scattering is taken into account. Also taken into account is the temperature dependence of the parameters used in the intermediate treatment. By making use of the Wigner type of simple rational approximation for the collision probability, heterogeneous systems are treated by means of the intermediate-resonance absorption, and an analytic expression is given for calculating the resonance integral. Discussions are given on the assumption of the spatially flat flux, from the intermediate resonance approach. Calculations of the resonance integral have been performed for typical resonances of 236U in square lattices of UO2 fuel rods and moderator. The results for the resonance integral obtained with the IR approximation are compared with the exact results. Comparisons are also made for the Doppler coefficient of the resonance integral. The results obtained with the present method will be shown to be infairly good agreement with those obtained from exact numerical approach.