Improvement of CANDU Fuel Performance Analysis Code ELESIM - Fission Product Gas Release Model

Abstract

The release of fission product gas from UO₂ fuel has been modelled by the ELESIM CANDU fuel performance code, developing an analytical model for intergranular bubble formation and interlinkage, and ultimately gas escape to voidage. It incorporates the relevant physical parameters: critical bubble size dependent on thermal gradient, average bubble size for lenticular intergranular bubble and bubble size distribution from random coalescence, The model predicts the absolute magnitude and trend with power history in comparison with data.