Study of zirconium-uranium bearing silicates and oxides as phases of interest for corium

This proposal aims to investigate Zr1-xUxSiO4 and Zr1-xUxO2 solid solutions prepared by wet chemistry routes (hydroxide precipitation or hydrothermal conversion) then potentially purified by selective dissolution of secondary phases. Solid solutions of Zr1-xUxSiO4 with U contents higher than 70 mol.% have been selected to precise the maximum solubility of U in the zircon phase. HR-PXRD measurement would be necessary to determine the unit cell variation and the potential formation of secondary phases at the very low level.
The whole solid solutions of Zr1-xUxO2 will be examined to precise the relation between monoclinic and cubic forms for U low contents, to follow the incorporation of U4+ in ZrO2 through the establishment of a precise Vegard’s rule between ZrO2 and UO2 and to evidence potential fluctuations in the chemical composition at the micro-domain’s scale. By this way, it will be possible to validate the wet chemistry route developed for this king of solid solutions.