A multiphysics numerical model of oxidation and decomposition in a uranium hydride bed

The reaction of uranium hydride and oxygen gas in a hydrogen storage bed has been studied with multiphysics finite element modeling. The model considers rates of chemical reaction, heat transport, and mass transport within a hydride bed. Three scenarios of oxygen gas injection have been considered and the model predictions are in good agreement with experimental measurements. We find that, under the conditions studied, uranium hydride and oxygen react quickly, forming U3O8 and hydrogen gas. We also find that oxidation of uranium hydride to U3O8 produces significant material swelling which, in the reactor studied, reduces the bed porosity from 0.60 to 0.39, and decreases the permeability by a factor of almost 20. A simple, yet reasonably general, description of the process is proposed which accounts for the major changes in global bed flow properties. This model may be used to better anticipate the effects of air-ingress accidents on uranium hydride storage beds and possibly also to explore design options for uranium hydride based hydrogen generation systems.

► A multiphysics finite element model was developed for the reaction of oxygen gas and uranium hydride within a hydrogen storage bed.
► Uranium hydride and oxygen react quickly, forming U3O8 and hydrogen gas.
► The UD3+O2 reaction is faster than the U+O2 reaction.
► The reactions produces material swelling which reduces the bed porosity and permeability.