Decomposition and reduction of AUC in hydrogen

AUC (Ammonium Uranyl Carbonate) conversion processes have been adopted extensively in nuclear fuel cycle. The kinetics investigation of these processes, however, has not yet been reported in detail at the published literatures. In the present work, the decomposition kinetics of AUC in hydrogen has been determined by non-isothermal method. DSC curves are solved with computer by Ge Qingren method. The results show that the kinetics obeys Avrami-Erofeev equation within 90% conversion. The apparent activation energy and preexponent are found to be 113.0 kJ/mol and 7.11 x 1011 s-1 respectively. The reduction kinetics of AUC decomposition product in hydrogen at the range of 450 - 600 deg C has been determined by isothermal thermogravimetric method. The results show that good linear relationship can be obtained from the plot of conversion vs time, and that the apparent activation energy is found to be 113.9 kJ/mol. The effects of particle size and partial pressure of hydrogen are examined in reduction of AUC decomposition product. The reduction mechanism and the structure of particle are discussed according to the kinetics behaviour and SEM (scanning electron microscope) photograph