In Situ XANES monitoring of reductive hydrothermal conversion of uranyl to UO₂₊ₓ using organic molecules

The development of next-generation nuclear reactors demands innovative methods for nuclear fuel production. Recent research has focused on the hydrothermal conversion of An(IV) oxalates (An = Th, U, Np, Pu), enabling the direct and quantitative precipitation of hydrated oxides from solution. Our group has also demonstrated the hydrothermal reduction of uranium(VI) to uranium(IV) dioxide in oxalic solutions. Additionally, other carboxylic acids, such as formic acid, can reduce U(VI), offering alternative synthesis routes with faster kinetics and lower carbon content in the reaction medium.
Building on recent work by Benarib et al., in situ HERFD-XANES experiments will directly monitor uranium’s oxidation state during hydrothermal conversion under varying temperature, pH, and organic molecule conditions. Understanding these mechanisms and kinetics will help identify optimal conditions for the direct fabrication of UO₂ powders from U(VI)-bearing solutions.