Thermal Decomposition of Gelled UO3

The thermal decomposition behavior of gelled UO3 microspheres have beenstudied. The thermal analysis included DTA and TG with XRD analysisexamination. The gelled were prepared by reacting uranyl nitrate with urea +HMTA, then dropped into a column containing paraffin oil at temperature of 95oC. The obtained gel were washed using NH40H and then dried. There wereanalyzed their thermal behavior using STA (Simultaneous Thermal Analyzer) upto 700 oC and were prepared for XRD analysis by heating at 200 oC, 400 oC,500 oC and 600 oC. The results showed that thermal decomposition of gelledUO3 microsphere consisted of five steps. The first and second steps wereendothermic reaction of the removal of the physics absorbed water started at100 oC, and the removal of chemically bounded water. The third and fourthsteps were exothermic reactions of the ammonia removal and the last steps wasexothermic reaction of change of compound UO3.xNH3 to U3O8. The XRDpatterns showed that compound of gelled UO3, which had been heated at 600oC give an indication the form of U3O8 compound, so that the minimumtemperature of calcination was 600 oC. (author)