A mathematical model that predicts the extent of fission-product release and fuel evaporation during a loss-of-coolant accident has been developed for a specific set of conditions. Theories of boundary-layer diffusion have been applied. The composition and pressure of the cover gas; the time molten; the chemical forms of the fission products and fuel; and the temperature, surface area, and amount of molten fuel are related to the amount of fission product and fuel released.