A model of fuel pellet swelling and its relation with grain growth

In this paper, an efficient model (from a computational point of view) is implemented to evaluate the gaseous and solid swelling in nuclear fuels under irradiation conditions. The model contemplates the precipitation of fission gases as intragranular and intergranular bubbles in the form of two coupled systems. For the intragranular gas, the diffusion equation is solved taking into account the processes of gas production, as well as the nucleation, growth and destruction of bubbles. In the case of the intergranular gas, bubbles are considered to have a lenticular shape and grow due to diffusion-controlled vacancy absorption. The results obtained and their comparison with experimental data indicate that the model is capable of performing realistic simulations of the pellet swelling processes, both under constant power conditions and fast power transient conditions. After that, the model was coupled with a solid swelling model and a grain growth model in order to analyze its performance as a whole.