Mathematical Modeling of Fluorination Reaction of Uranium Dioxide and Evaluation of Existing Gas-Solid Reaction Models.

In this study a mathematical model is developed in order to simulate fluorination reaction of uranium dioxide which leads to the production of uranium hexafluoride. The model considers homogeneous reaction for intermediate solid and a heterogeneous one for unreacted shrinking core. Also, this study tries to clearly show the shortcoming of some of the well-known models that take heterogeneous reactions for both solids. In fact, one may not trust the accuracy of those models due to the importance of diffusion phenomena into the interm ediate solid and the reaction taking place within it. On the other hand, neglecting the undeniable effects of some operating conditions such as temperature and particle sizes on gas concentration distribution and reaction rates may introduce large deviations. In this study, the governing equations are developed on the basis of the mass conservation law and solved numerically . Besides, far the first time, some dimensionless equations and groups are introduced to predict reaction rates and amounts of the main and intermediate products for use in numerical procedures.Comparing the model results with corresponding experimental ones represents the desirable preciseness of the model. After validation of the model, the effect of some operating variables such as temperature and initialsize of the particle are investigated on the reaction rates and conversions.