A theoretical study of fission products release from oxide fuels taking into account both grain growth and precursors effect

Based on the thermodynamics of irreversible processes for heterogeneous systems applied to oxide fuels, a theoretical model for calculating fission products release simultaneously with grain growth has been proposed. A mathematical formalism for diffusion of radioactive products in systems with moving boundary when the moving law in time of the boundary is known, was also derived for the case of perfect sink boundary condition. The solution obtained is similar to the classical Bateman functions for buildup and decaying of radioactive products, and they are functions of the reactor system and the initial composition of fissile species. These equations can be u sed for every type of oxide fuel. Using a power type grain growth law, an analytical solution for diffusion of stable species has also been derived. ((orig.))