Effects of washing conditions on the thermal decomposition behaviour of gelled UO3 microspheres

DTA, TG and DTG curves obtained in various atmospheres using different heating rates were used together with X-ray examinations to study the thermal decomposition mechanisms of two types of gelled UO₃ microspheres: ammonia-washed (UN) and hot water-washed (UH) microspheres. The kinetics of the thermal decompositions were studied. The specific reaction rate constantk _r for the decomposition of UO₃ to U₃O₈ could be expressed in terms of the activation energy and the pre-exponential factor by the expressions: $$begin{gathered} K_r (s^{ - 1} ) = 1.277 times 10^{18} exp frac{{ - 295.4}}{{RT}}for the UN spheres, hfill K_r (s^{ - 1} ) = 8.406 times 10^{19} exp frac{{ - 263.2}}{{RT}}for the UH spheres. hfill end{gathered} $$