CFD model for predicting spent nuclear fuel drying conditions

Abstract

Background A significant quantity of aluminum-clad spent nuclear fuel (ASNF) is currently managed by the United States (U.S.) Department of Energy (DOE) at several sites in the U.S. Much of this fuel develops a corrosion layer with adsorbed water either through pre-corrosion, in-reactor, or in wet storage depending on the source. Gamma radiation from the fuel after removal from the reactor can cause evolution of hydrogen from this corrosion layer. For long-term safety it is desirable to remove the adsorbed water from the fuel surface to limit the production of hydrogen gases when the fuel is placed in road-ready sealed canisters for eventual final disposition. Methods This study presents a series of experiments showing the effectiveness of both forced helium drying and vacuum drying methods for the removal of water from surrogate fuel assemblies. A computational fluid dynamics (CFD) model is constructed to replicate the drying processes and simulate the experiments. Results The model suggests that increasing the inlet temperature is a more efficient way of improving the efficacy of a drying process. An increase in inlet temperature leads to a reduction in drying time 28–55% greater than the same relative increase in flow rate. One of the assemblies inside the canister consistently experiences the least amount of turbulent flow and require the longest time to dry. Therefore, the assembly with the highest decay heat should be placed in this slot in the basket in order to facilitate the drying of this assembly. Conclusions The validated CFD model can be used in the future as a design and analysis tool for a full-scale drying setup with actual fuel assemblies.