Nuclear fuel cladding oxidation model based on diffusion theory in a multiphase ZrO₂, α-ZrO and β-ZrO medium

In this work, a mathematical model is developed to simulate the oxidation process in the cladding of nuclear fuel rods due to contact with steam at high temperatures. The diffusion process of O₂ in the zircaloy is taken into account, the generation dynamics by oxidation of the ZrO₂, α-ZrO and β-ZrO phases and their feedback with the transfer of heat in the fuel rods by the energy released during the oxidation reaction. The oxidation phenomenon is simulated in the temperature range from 1273 K to1800 K. The model contemplates the formulation of an equivalent bar for the analysis of the heat transfer in the fuel rod in the radial and axial directions, the transport of one-dimensional heat in the vapor generated by evaporation, cladding oxidation by O₂ diffusion and the feedback of the heat released by the oxidation reaction. With this model developed, is possible to determine the thickness of the ZrO₂ layer in the cladding and the amount of the H₂ generated by reaction. (author)