Solid state reactions of UO2,ThO2 and their mixed oxides with sulphates of potassium

Solid state reactions of UO2,ThO2 and their mixed oxides (Ux,Th1−x)O2, where x=0.05, 0.25 and 0.50, were carried out with KHSO4,K2S2O8 and K2S2O7 at 400°C, 600°C and 900°C with an aim to study the formation of various products and to investigate their dissolution behaviour. The products obtained at 400°C by heating UO2,ThO2 and their mixed oxides with potassium salts were identified as K4U(SO4)4,K4Th(SO4)4 and K4(Ux,Th1−x)(SO4)4, respectively. The products formed at different temperatures were found to be soluble in 2M HNO3 or H2SO4. From the solution of the dissolved products of the mixed oxides, thorium was separated quantitatively by precipitating it as thorium oxalate. X-ray, thermal and chemical methods were used to characterise the products formed at various temperatures.