Temperature Dependence of Uranium Carbide Fission-Gas Swelling: An Analytical Evaluation

A simple model for the gas-diffusion-controlled growth of stationary gas bubbles in an isothermal solid, under constant rate of gas generation, is used to evaluate the temperature dependence of fission-gas swelling in uranium monocarbide. Using experimental data for the temperature-dependent volume diffusivity of xenon in uranium carbide, it is found that the predicted temperature at which the onset of fission-gas swelling occurs, evaluated at a given fission density, correlates relatively well with swelling data and is of the order of one-half the absolute melting point. Variations of bubble concentration and gas-generation rate are found to affect this predicted swelling-onset temperature only to a relatively slight extent.