Accurate Evaluation of Multigroup Transfer Cross Sections and Their Legendre Coefficients

Abstract

For transport problems with fine energy group structure, the group-to-group transfer cross sections are usually quite anisotropic in the scattering angle. It is shown for neutron inelastic scattering that explicit use of the characteristic shape of these transfer cross sections permits more efficient and accurate numerical evaluation of their Legendre expansion coefficients than is afforded by existing techniques. In addition, transfer cross sections can often be well approximated by piecewise, low-order polynomials with which very accurate and simple expressions can be derived for the Legendre coefficients. This analytical approach both minimizes the access of nuclear data files and accurately determines even the higher order coefficients.