Low temperature decomposition of U(IV) and Th(IV) oxalates to nanograined oxide powders

Oxalate precipitation is a powerful technique for actinide oxide preparation at either laboratory or industrial scales. In this study we focused on the low temperature decomposition of Th(C2O4)2•2H2O and (N2H5)2U2(C2O4)5•nH2O into nanograined ThO2 and UO2 powders, which will be used later as precursors for the generation of materials emulating the nuclear fuel high burnup structure (HBS). The evolution with temperature of the nanoparticles properties has been investigated using several solid state analytical techniques (transmission and scanning electron microscopy, room and high temperature powder X-ray diffraction, Raman spectroscopy, thermogravimetry). Oxide powders with a high degree of crystallinity and grain size from ~10 nm were prepared. Their purity was examined with special focus on the presence of carbonates. It was found that carbonate content in the final powder did not exceed 3.4 wt.%, for the powder treated at 600°C for 1 hour.JRC.E.4-Nuclear Fuel Safet