Modeling high burnup structure in oxide fuels for application to fuel performance codes. Part II: Porosity evolution

Abstract

We propose a model describing the high burnup structure inter-granular porosity evolution under irradiation. The evolution of the porosity collecting the gas diffusing from the grains is modeled by exploiting a second-order Fokker-Planck expansion of the cluster-dynamics master equations governing the problem, considering nucleation of pores, gas absorption due to the diffusional flow from the grains, size-dependent re-solution of gas from pores due to interaction with fission fragments, vacancy absorption, and pore coalescence. Model predictions on xenon local retention, matrix fuel swelling, and porosity evolution are compared to experimental data and to models available in fuel performance codes.