Intra-granular fission gas bubbles growth in crystalline U ₃ Si ₂ : Rate theory modeling

Abstract A model of intra-grain fission gas bubble growth in U 3 Si 2 coupled with defect microstructure is generalized to take into account the influence of point defect sinks and defect clustering. The dynamics of bubble growth and defect structure properties are studied under different irradiation conditions. The influence of temperature and flux on bubble growth, defect ensemble evolution, and changes in material properties (elastic moduli and thermal degradation factor) are examined in detail. The universality of the bubble size distribution and the crossover of dynamical regimes of bubble growth are studied under various irradiation conditions. It is shown that a change in the dominant (fission gas atom- or vacancy-mediated) mechanism of bubble growth results in a crossover from a parabolic to a sub-parabolic bubble size growth law. The proposed modification of the rate theory model provides more accurate predictions and more detailed insight into fuel performance, especially fission gas behavior in crystalline U 3 Si 2 .