Implementation of a Dominant Modes Solver in Dragon

Abstract

Solution of the k-eigenvalue transport problem has been limited in lattice codes to the fundamental mode corresponding to the largest eigenvalue. Despite the fact that the higher order modes have no physical meaning, they can have significant uses in different applications. While the fundamental mode represents the asymptotic behaviour of the neutron flux, higher modes describe the small perturbations about it; hence, they can be employed in perturbation studies. Another important application of the higher modes is flux synthesis or mapping. Starting with a reference solution of the neutron flux at a coarse level and a number of modes at a finer level, detailed flux distribution can be reconstructed from a coarse solution. In this work, an implementation of a neutron flux modes solver in DRAGON is described. The solver is based on the QZ decomposition algorithm. The approach is described and results are presented.