The thermal decomposition kinetics of AUC [ammonium uranyl carbonate;
(NH4)4UO2(CO3)3] in an isothermal thermogravimetric (TG) reactor under
N2 atmosphere has been determined. The kinetic data can be represente
d by the two-dimensional nucleation and growth mode!. The reaction rat
e increases and activation energy decreases with increasing particle s
ize and precipitation time which appears in the particle size larger t
han 30 mum in the mechano-chemical phenomena.