The Effect of Modal Interaction in the Xenon Instability Problem

Abstract

This paper deals with the space and time dependent reactor stability problem of neutron flux shape variations due to xenon-135. The effect of modal interaction on stability is investigated for a simple reactor model when the characteristic functions of the wave equation are used in a modal expansion. It is shown that modal interaction may contribute to or detract from stability depending on the circumstances, and that in the case of a very large reactor, stability can be seriously overestimated if modal interaction is neglected.