Fouquet-Métivier Pauline, Medyk Laetitia, Lebreton Florent, Guéneau Christine, Hunault Myrtille O J Y, Solari Pier-Lorenzo, Dardenne Kathy, Rothe Jörg, Martin Philippe M
CEA, DES, ISEC, DMRC, Université Montpellier, Marcoule, BP1717, 30207 Bagnols-sur-Cèze, France.
Université Paris-Saclay, CEA, Service de recherche en Corrosion et Comportement des Matériaux, 91191 Gif-sur-Yvette, France.
Inorg Chem. 2024 Oct 28;63(43):20482-20491. doi: 10.1021/acs.inorgchem.4c03084. Epub 2024 Oct 16.
Uranium-plutonium mixed oxides, containing few mol % of Am, are currently studied as fuel for Sodium Fast Reactors. The study of the O/M ratio of these fuels is of main interest, as its variation can induce issues for reactor safety. For this purpose, four UPuAmO samples (0.235 ≤ ≤ 0.39 and 0.005 ≤ ≤ 0.02) were studied using electron probe microanalysis (EPMA), X-ray powder diffraction (XRD), and X-ray absorption spectroscopy (XAS) experiments. EPMA analyses revealed a homogeneous matrix phase with few U- and Pu-rich agglomerates. A matrix phase of fluorite structure (face-centered cubic), as well as a small contribution of a UO phase of the same structure, was evidenced for all of the samples by XRD. The O/M ratios of the (U,Pu)O matrix were calculated based on the obtained lattice parameters. XANES experiments highlighted the simultaneous presence of U and Pu/Am for all of the samples, indicating a charge compensation mechanism even for stoichiometric samples. Based on the EPMA and XRD results, it was evidenced that this coexistence of U, U, Pu, Pu, and Am was not originating from the U- and Pu-rich agglomerates. It was found to be rather a peculiarity of the UPuAmO matrix phase, discussed with the help of thermodynamic calculations performed on the U-Pu-Am-O system.
