Computed Phase Equilibria for Burnable Neutron Absorbing Materials for the Advanced CANDU Reactor Design

Abstract

Burnable neutron absorbing materials are expected to be an integral part of the new fuel design for the Advanced CANDU Reactor which is intended to use low enriched uranium. The neutron absorbing material is composed of gadolinia, dysprosia and yttria dissolved in an inert zirconia matrix. A thermodynamic model based on Gibbs energy minimization has been created to determine phase equilibria as a function of composition and temperature. The aqueous solubility and consequent potential release of neutron absorbing elements into the reactor coolant is calculated to be low in the case of a cladding breach. The calculations are consistent with a limited number of ambient solubility product measurements.