| AVS 62nd International Symposium & Exhibition | |
| Actinides and Rare Earths Focus Topic | Wednesday Sessions |
| Session AC+AS+MI-WeA |
| Session: | Chemistry and Physics of the Actinides and Rare Earths |
| Presenter: | Paul Roussel, AWE, United Kingdom of Great Britain and Northern Ireland |
| Correspondent: | Click to Email |
In this study fcc γ-cerium has been used as a non radioactive surrogate material for fcc δ-plutonium. The common cerium oxides are the trivalent sesquioxide and the tetravalent dioxide both of which are iso-structural with the oxides formed on plutonium metal. Similarly, cerium (1) like plutonium (2) dsiplays parabolic oxidation kinetics at low temperatures and linear kinetics elevated temperatures. This makes cerium an ideal surrogate material to study the kinetics and mechansim of plutonium oxidation. The initial oxidation of cerium at 274 K was studied using X-ray Photoelectron Spectroscopy. On exposure to Langmuir quantities of oxygen cerium rapidly oxidizes to to the trivalent oxide followed by the slower growth of the tetravalent oxide. The growth modes of both oxides have been determined. It was found the surface formed tetravalent oxide was unstable in ultra high vacuum and reduced to the trivalent oxide by an apparent solid state diffusion reaction with cerium metal. This reduction reaction can be explained by the thermodynamic unstability of the tetravalent dioxide with respect to cerium metal. The complexity of this reduction reaction appears to be enhanced by the formation of surface hydroxyl species as a function of time. Time of Flight Secondary Ion Mass Spectrometry was used to support characterization of the surface hydroxyl species.
(1) D. Cubicciotti, J. Am. Chem. Soc., 74 (1952) 1200.
(2) J. L. Stakebake, J. Less Common Met., 123 (1986) 185.
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