Mixed energy reactor simulations using the discrete generalized multigroup method

Abstract

An innovative approach to mixed energy simulations was proposed. This approach is based on the generalized multigroup theory using discrete orthogonal polynomials. The discrete expansion provides a link between a coarse group structure and a fine group structure, thus allowing for coarse group calculations to provide an approximation of the within group spectral information. A mixed energy scheme can be adapted from this work by which certain regions are based on the coarse group energy structure which is a subset of a finer group structure that can be used in certain regions. The higher moment equations of the coarse group calculations are used to provide fine group spectral information at the boundaries of the regions. Simple 1-D diffusion results indicate that fine group flux can be reproduced accurately in a mixed energy solution and that significant improvement of the eigenvalue estimate can be obtained when comparing with common coarse and fine multigroup solutions.