Structural Investigation of (U 0.7 Pu 0.3 )O 2-x Mixed Oxides

J.F. Vigier , P.M. Martin (1) , D. Prieur , Ac. Scheinost , J. Somers

1 CEA-DES (ex-DEN) - CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire)

Uranium-plutonium mixed oxide containing 30 per cent 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.

Mots clés: XRD

Domaines: Physique Nucléaire Théorique [nucl-th]; Physique Nucléaire Expérimentale [nucl-ex]

J.F. Vigier, P.M. Martin, D. Prieur, Ac. Scheinost, J. Somers. Structural Investigation of (U 0.7 Pu 0.3 )O 2-x Mixed Oxides. Inorganic Chemistry, 2015, 54 (11), pp.5358-5365. ⟨10.1021/acs.inorgchem.5b00392⟩. ⟨cea-02386006⟩