title: Structural Investigation of (U0.7Pu0.3)O2-x Mixed Oxides.
abstract: Uranium-plutonium mixed oxide containing 30% of plutonium is a candidate fuel for several fast neutron and accelerator driven reactor systems. In this work, a detailed structural investigation on sol-gel synthesized stoichiometric U0.7Pu0.3O2.00 and substoichiometric U0.7Pu0.3O2-x, using X-ray diffraction (XRD), oxygen 17 magic angle spinning nuclear magnetic resonance ((17)O MAS NMR) and X-ray absorption spectroscopy is described. As observed by XRD, the stoichiometric U0.7Pu0.3O2.00 is monophasic with a lattice parameter in good agreement with Vegard's law, while the substoichiometric U0.7Pu0.3O2-x material is biphasic. Solid solution ideality in terms of a random distribution of metal atoms is proven for U0.7Pu0.3O2.00 with (17)O MAS NMR. X-ray absorption near-edge structure (XANES) spectroscopy shows the presence of plutonium(III) in U0.7Pu0.3O2-x. Extended X-ray absorption fine-structure (EXAFS) spectroscopy indicates a similar local structure around both cations, and comparison with XRD indicates a close similarity between uranium and plutonium local structures and the long-range ordering.
authors.affiliation: †European Commission, Joint Research Centre (JRC), Institute for Transuranium Elements (ITU), Postfach 2340, 76125 Karlsruhe, Germany.
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Vigier
authors.affiliation: ‡CEA, DEN, Cadarache DEC/SESC, F-13108 St-Paul-Lez-Durance Cedex, France.
authors.forename: Philippe M
authors.initials: PM
authors.lastname: Martin
authors.affiliation: †European Commission, Joint Research Centre (JRC), Institute for Transuranium Elements (ITU), Postfach 2340, 76125 Karlsruhe, Germany.
authors.forename: Laura
authors.initials: L
authors.lastname: Martel
authors.affiliation: †European Commission, Joint Research Centre (JRC), Institute for Transuranium Elements (ITU), Postfach 2340, 76125 Karlsruhe, Germany.
authors.forename: Damien
authors.initials: D
authors.lastname: Prieur
authors.affiliation: §Helmholtz-Zentrum Dresden-Rossendorf, Institute of Resource Ecology, D-01314 Dresden, Germany.
authors.forename: Andreas C
authors.initials: AC
authors.lastname: Scheinost
authors.affiliation: †European Commission, Joint Research Centre (JRC), Institute for Transuranium Elements (ITU), Postfach 2340, 76125 Karlsruhe, Germany.
authors.forename: Joseph
authors.initials: J
authors.lastname: Somers