Oxidative ammonolysis of uranium(IV) fluorides to uranium(VI) nitride

Actinide nitrides, in particular UN, are being considered as fuel types for advanced reactor systems. Here, we demonstrate a low-temperature synthesis route on uranium that could be developed into a commercial fabrication process for UN and mixed actinide nitride fuels. UN was successfully synthesized from UO2 by first reacting with NH4HF2 in a ball mill at 20 °C to form tetravalent ammonium uranium fluorides. Then, reaction with an ammonia atmosphere at 800 °C oxidized tetravalent uranium fluorides to hexavalent UN2. The final product, UN, was obtained by decomposing UN2 at 1100 °C under argon to produce UN through an intermediate phase of U2N3.