A semi-empirical model for the air oxidation kinetics of UO2
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UO2 is readily oxidized to U3O8 at a high temperature, and this reaction has received considerable attention in the field of nuclear fuel cycles. A voloxidation process which makes use of the characteristics of a UO2 oxidation has been developed to treat the spent fuels produced by irradiation of UO2. In this work, semi-empirical kinetic models to describe the sigmoidal behavior of a UO2 oxidation were selected and compared in order to obtain a kinetic expression with different temperatures. Two basic approaches of a nucleation-and-growth model and an autocatalytic reaction model were adequate enough to describe the S-shaped oxidation behavior, and an equation to correlate the model parameters with the temperature was introduced. The calculation results of the two models satisfy the experimental data for UO2 spheres and the activation energy of a reaction rate constant was evaluated. The models were also adopted as a surface reaction time term for a UO2 pellet.
Key wordsUO2 Oxidation Kinetics Model Voloxidation
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