The effect of irradiation-induced gas-atom re-solution on grain-boundary bubble growth

Abstract

The rim region of high-burnup fuels is characterized by an exponential growth of intergranular porosity. In particular, the understanding of the dynamics of irradiation-induced recrystallization and subsequent gas-bubble swelling requires a quantitative assessment of the nucleation and growth of grain-boundary bubbles. Calculations of bubble growth on the grain boundaries of irradiated nuclear fuels at relatively low temperatures have, in general, been performed under the assumption that these bubbles are not appreciably affected by irradiation-induced gas-atom re-solution. In contrast, matrix bubbles are strongly affected by this bubble shrinkage mechanism and as a consequence are generally two to three orders or more of magnitude smaller than the grain-boundary bubbles. A variational method is used to calculate diffusion from a spherical fuel grain. The junction position of two trial functions is set equal to the bubble gas-atom knock out distance. The effect of grain size, gas-atom re-solution rate and diffusivity, gas-atom knock out distance, and grain-boundary bubble density on the growth of intergranular bubbles is studied, and the conditions under which intergranular bubble growth occurs are elucidated.