Abstract
Uranium-Plutonium mixed oxides U$_{1-y}$Pu$_y$O$_{2-x}$ are considered as the reference fuels for Sodium-cooled Fast neutron Reactors (SFRs). Nevertheless, there is a lack of experimental data on their thermal properties for a Pu content above 0.45. The first step to fill this gap is to manufacture samples with high plutonium contents, which is the purpose of this work. Here, the manufacturing of U$_{1-y}$Pu$_y$O$_2$ samples with y = 0.60, 0.65 and 0.70 by a co-milling powder metallurgy process is detailed. Relying on an optimization of each manufacturing step (blending, co-milling, sieving, pelletizing and sintering), in order to obtain dense, monophasic, stoichiometric and homogenous materials. A multi-scale characterization strategy was used to determine sample microstructural properties including density measurements, Thermal-Ionization Mass Spectrometer (TIMS), ceramography, Electron Probe Micro Analyses, µ-Raman Spectroscopy and X-Ray Diffraction. The results obtained show that dense (> 95% TD), homogenous (chemical distribution of cations and oxygen), monophasic and stoichiometric (O/M = 2.00) samples have been achieved. These properties correspond to those needed to optimize the thermo-physical properties measurements. This also shows that the coupling of multi-scale characterizations is mandatory to evaluate the structural and microstructural properties of this kind of material.