A MODEL FOR FISSION-PRODUCT RELEASE FROM LIQUID-METAL POOLS - DEVELOPMENT AND SENSITIVITY INVESTIGATION

A computational model is described for fission product release from mo lten pools of uranium-aluminum (U-Al) metal. Liquid-metal pools may fo rm during severe accidents in U-Al-fueled reactors if multiple core as semblies melt and relocate to the bottom of the reactor vessel. At pre sent, data for the release of fission products from intact U-Al fuel a re sparse, and no data are available for the release of fission produc ts from U-Al in the form of molten pools. This investigation postulate s three phenomena that govern fission product release from such a syst em: (a) Rayleigh cell convection in the molten pool; (b) nucleation of volatile radionuclide species with concomitant bubble dynamics; and ( c) diffusion from the pool surface. Selected sensitivity analyses have been performed to study th e dependence of model predictions on uncer tain input parameters and thus to characterize critical needs for expe rimental data. The results of the sensitivity analysis indicate that p arameters that characterize the nucleation rate of volatile species in the pool have the greatest effect on the calculated rate of fission p roduct release.