Solid state reactions of UO 2, ThO 2 and (U,Th)O 2 with ammonium nitrate

Abstract

UO 2, ThO 2 and (U x Th 1− x )O 2 ( x = 0.1 and 0.5) were reacted with NH 4NO 3 in different molar ratios up to 400 °C in air, to study the dissolution behavior. Solid state reaction of UO 2 with different moles of NH 4NO 3 showed various intermediate products, depending on the amount of NH 4NO 3. The end products at 400 °C were identified as U 3O 8 and UO 3, respectively when 1 and 1.5 mol of NH 4NO 3 were used. When UO 2 and NH 4NO 3 were reacted in 1:4 molar ratio, the intermediate products identified were (NH 4) 2UO 2(NO 3) 4 and NH 4UO 2(NO 3) 3 at 180 and 220 °C, respectively. XRD data of both the compounds were indexed on orthorhombic system. ThO 2 did not show any reaction with NH 4NO 3 up to 400 °C. The reaction of (U,Th)O 2 with 4 mol of NH 4NO 3 was studied to see the dissolution and separation of U from the mixed oxide. X-ray diffraction, thermal analysis and chemical analysis techniques were used for the characterization of the products.