Modeling of oxidation of UO2 pellets

•A mathematical model has been developed for the oxidation of pellets of uranium dioxide in the air.•This model has two stages for the oxidation process of this pellet, before and after the breaking-down of the pallet.•These stages have different physical properties of the pellet and also different mechanisms of the reaction. In this study, a mathematical model has been developed for oxidation of pellets of uranium dioxide in the air at the bulk temperature range between 605 and 727 K. Oxidation of this pellet causes an increment in the size of the UO2 particles, decrement of the pellet porosity and breaking-down of this pellet, subsequently. Therefore, the presented model has two stages for this oxidation process, before and after the breaking-down of the pallet. These stages have different physical properties of the pellet and different mechanisms of the oxidation reaction. The predictions of the presented model is validated using the existed experimental data. It is resulted that increasing the bulk temperature increases the rate of the oxidation reaction and decreases the required times for the breaking-down and complete conversion of the pellet. In addition, increasing the size of the pellet increases the required time for breaking-down and decreases the required time complete conversion of the pellet.