Parabolic Oxidation Kinetics of a Plutonium Alloy at Room Temperature

Abstract Auger electron spectroscopy (AES) was used to characterize the oxide scale formed on an ∼0.5 wt. % Ga plutonium metal alloy. Analysis of changes to the characteristic Auger transitions for Pu and O during sputter depth profiles were used in combination with previously measured sputter yields to determine the thickness of the oxide scale and provide insight into its chemistry. From this data, the parabolic kinetics for the Pu-Ga alloy were determined as a function of relative humidity, RH = 14 – 92%, and oxygen partial pressure, p(O2) = 31 – 157 Torr, at 25 °C. For each relative humidity investigated, the parabolic rate constant was found to be independent of oxygen partial pressure. Power-law fits to the relative humidity effect on the rate constant was found to have a power of n = 1.265, indicating the diffusion species which rate-limits the reaction isn’t molecular water, which subsequent dissociates at the oxide-metal interface, or hydroxyl from dissociation at the gas-surface interface.