The influence of microscopic defects in the crystal structure upon fission-gas transport out of grains and release from fuel pellets was described. The defects included point defects such as vacancies, interstitials and fission atoms, and extended defects such as bubbles, pores and dislocations. The mechanistic description of chemically active element behavior (fission-induced) was based upon a complex association of diffusion–vaporization mechanism involving multi-phase and multi-component thermo-chemical equilibrium at the grain boundary with accurate calculations of fuel oxidation.

Mechanistic Modelling of Urania Fuel Evolution and Fission Product Migration during Irradiation and Heating. M.S.Veshchunov, R.Dubourg, V.D.Ozrin, V.E.Shestak, V.I.Tarasov: Journal of Nuclear Materials, 2007, 362[2-3], 327-35