The Researches of UO2 Powder Oxidation in air by TG/DSC

The oxidation of wastes should be conducted at recovery process for reuse economically. In order to manage the wastes in fuel manufacturing process well, it is important to know the phenomena and the thermodynamic properties of UO2 oxidation. The aim of this research is to confirm the phases and to obtain the activation energies of oxidation of natural UO₂ powder in dry air. Two kinds of experiments were performed in the dry air at the constant heating rate and the isothermal conditions using TG/DSC. The constant heating rate experiment from 25 to 500 .deg. C and the isothermal experiment at 300, 350, 400 and 450 .deg. C were conducted. And in order to know the phases of UO₂ powder oxidation, XRD measurement was taken with the samples obtained by the time step oxidation at 350 .deg. C . The oxidation of un-irradiated UO₂ powder in the dry air was studied according to the three kinds of experiments. The constant heating rate and the isothermal experiments were conducted using TG/DSC. And in order to analyze the phase of UO₂ products, the experiment was performed at 350 .deg. C with the samples by using muffle furnace and XRD. In the constant heating rate experiment, two types of oxidation; mild and rapid oxidation were observed in TG curve and two peaks in DSC curve were also presented following the two oxidations. In the isothermal experiments were conducted at 300, 350, 400 and 450 .deg. C. Two types of oxidations in TG curves and two regions of oxidations in DSC curves appeared at 300 and 350 .deg. C.