SOLID-STATE REACTIONS OF URANIUM-OXIDES WITH AMMONIUM-SULFATE

Solid state reactions of uranium oxides of O/U ratio from 2.0 to 3.0 with ammonium sulphate were studied in an attempt to understand the nature of the oxidation state of uranium in them. The two end members, UO2 and UO3, react at 250 degrees C to form (NH4)(4)U(SO4)(4) and (NH4)(2)UO2(SO4)(2) and at 350 degrees C to form (NH4)(2)U(SO4)(3) and (NH4)(2)(UO2)(2)(SO4)(3), thereby retaining the oxidation state of uranium in the parent oxide. The intermediate oxides UO217, U4O9, U3O7 and U3O8 react at the above two temperatures to form a mixture of ammonium uranium double sulphates containing both U(IV) and U(VI) in the ratios satisfying overall O/U values in the oxides. Chemical, X-ray, thermal and spectral methods were used to identify and characterise the products.