Surface Oxidation Study of Uranium Dioxide under Wet and Dry Conditions

The surface oxidation of pressed uranium dioxide (UO2) powder under controlled environmental conditions and the oxidation and reduction of pressed uranium trioxide (UO3) powder are presented. This is a continuing research project in the investigation of the oxidation of UO2 powder using Photoluminescence (PL) Spectroscopy. UO2 particles exposed to the ambient atmosphere will oxidize into a number of chemical complexes (specifically hydrates, hydroxides, and carbonates). During certain of these oxidation processes, the uranium ion can lose two of its electrons and change from uranous (UIV+) to uranyl (UVI+). This research is an attempt to monitor and control the oxidation of UO2 as well as the development of the uranyl ion from the uranous ion and model their behavior under both wet and dry atmospheric conditions. Two UO2 samples were created by pressing UO2 powder into a tungsten screen and were then subjected to a pure, dry oxygen environment and a wet oxygen environment at temperatures below 200°C. The UO2 oxidation was periodically monitored with in-situ PL spectroscopy. Using this analysis method, I was not able to successfully distinguish between the different uranium oxide compounds as they were formed under the different weathering conditions enforced at this temperature