Design of a Molybdenum Based Oxygen Sensor to Assist in the Characterization of Defective CANDU Nuclear Fuels as a Function of Burnup

Abstract

In a CANDU® reactor, ceramic uranium dioxide (UO₂) fuel pellets are contained in Zircaloy cladding. On the rare occurrence of a fuel defect, heavy water (D₂O) steam can come into direct contact with the fuel resulting in oxidation of the fuel and fission products. The objective of this project is to understand the fundamental relationship between the partial pressure of oxygen (pO₂) and UO_2±x (where x is the stoichiometric deviation of oxygen in UO₂) with mixtures of fission products. A special emphasis will be placed on molybdenum (Mo) fission products because of the relationship between Mo oxidation states and pO₂. An understanding of this relationship could lead to a method of estimating the local pO₂ exposure based on the oxide to metal ratio in the Mo/U/O system. In future, this method could be employed as a forensic tool to evaluate the propagation of oxygen through defective fuel with increased spatial resolution.