A Comparison of CANDU LZC Modelling Approaches for Generating Incremental Cross Sections

Abstract

A key step in the modelling of Canada Deuterium Uranium (CANDU) reactors is the generation of incremental cross sections which represent the local effect of reactivity devices such as liquid zone controllers (LZCs) on the core. These incremental cross sections are generated using a 3D lattice level simulation which was performed using Serpent 2 in this work. The modelling of the LZCs was performed using both an explicit model of the controller internals and a simplified smeared geometry for several fuel burnups. Comparisons of the thermal absorption incremental cross section observed variations of up to about 1.05% between geometry models and up to 5.1% between different fuel burnups. At the core level, differences in the incremental cross sections were found to result in up to about 0.25 mk differences in core reactivity and less than 0.7% variations in channel powers.