It was recalled that, when subjected to ultra-high vacuum conditions, a thin surface dioxide covering on a Pu substrate underwent spontaneous thermodynamically driven reduction to the trivalent sesquioxide, Pu2O3. Kinetic information about this surface transformation, from to Pu2O3, was gained by following the changing depths of these 2 oxide layers, using X-ray photoelectron spectroscopy as a probe. A mathematical model was proposed to follow this auto-reduction reaction, based upon a simple 3-dimensional layered structure. The rate of this plutonium oxide interconversion was controlled by the diffusion of O across the steadily expanding Pu2O3 layer. By investigating the kinetics of this auto-reduction reaction, a value of 1.4 x 10−16cm2/s was obtained for the diffusion coefficient of O through α-Pu2O3.

Plutonium Oxide Transformation Kinetics and Diffusion Coefficient Measurement. P.Morrall, S.Tull, J.Glascott, P.Roussel: Journal of Alloys and Compounds, 2007, 444-445, 352-5