Solid state reactions of UO2, ThO2 and (U,Th)O2 with ammonium nitrate

UO2, ThO2 and (UxTh1−x)O2 (x = 0.1 and 0.5) were reacted with NH4NO3 in different molar ratios up to 400 °C in air, to study the dissolution behavior. Solid state reaction of UO2 with different moles of NH4NO3 showed various intermediate products, depending on the amount of NH4NO3. The end products at 400 °C were identified as U3O8 and UO3, respectively when 1 and 1.5 mol of NH4NO3 were used. When UO2 and NH4NO3 were reacted in 1:4 molar ratio, the intermediate products identified were (NH4)2UO2(NO3)4 and NH4UO2(NO3)3 at 180 and 220 °C, respectively. XRD data of both the compounds were indexed on orthorhombic system. ThO2 did not show any reaction with NH4NO3 up to 400 °C. The reaction of (U,Th)O2 with 4 mol of NH4NO3 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.