Kinetics and mechanism of UO2 + C reaction for [formula omitted] preparation

Abstract

The kinetics of the carbothermic conversion of ( UO 2 + C) microspheres to UC UC 2 in the temperature range of 1473 to 1973 K has been studied under nonisothermal heating conditions in vacuum and flowing argon. Reduction of UO 2 microspheres, dispersed in a carbon matrix was also studied under vacuum. The carbon monoxide gas concentration in the effluent stream during reduction was used to determine the rate of carbide formation. A model representing stepwise conversion of the reactant to the product has been proposed and the probable rate controlling steps, under different reaction conditions, have been identified. The reaction of oxide with carbon under vacuum appears to be controlled by diffusion of carbon. However, under flowing gas conditions, the diffusion of carbon monoxide gas through the carbide layer was the rate-controlling process. The activation energies for the reaction carried out under different conditions varied between 332 to 373 kJ/mol.