Analyses of the concrete attack and ex-vessel aerosol release using various assumptions for the molten corium/concrete interaction have been performed. The study involved variations in several parameters, such as initial debris temperature, amount of unoxidized zirconium, amount of melt, concrete ablation temperature, and concrete type. At high initial corium temperatures the periodic contact (nucleate-boiling-like) model leads to more rapid concrete attack, higher decomposition gas release, and higher fission product release than the gas film model. At low initial corium temperatures, when a corium crust is initially formed, the various heat transfer models do not lead to significant differences in the fission product releases. Besides the initial debris temperature, the most significant parameter in prediction of the fission product release is the amount of unoxidized zirconium. Among the various fission products, the nonvolatiles, such as lanthanum, are more sensitive to changes in the parameters.