Abstract
The rate for the carbothermic synthesis of UC2 from UO2+ C powders and compacts was determined from the amount of CO gas released into flowing He. The reduction rate was found to be greatly influenced by the characteristics of oxide powders. For the UO2 powder having a small particle size, the reaction at the UO2-UC2 interface in every particle may control the reduction. For the powder of a large particle size, about 100 μm, the reduction was found to be controlled by the diffusion of oxygen through the carbide layer to the surface of the particle. The shape of compacted samples also influences the reduction behavior of UO2+ C mixtures to UC2. The reduction was controlled by the reaction at the interface between the produced UC2+C layer and the unreacted core in the sample compacted using the fine UO2 powder at 80100 MPa. In the case of the sample compacted at 470 MPa, the reduction was controlled by the diffusion of CO gas from the interface of the compact through the UC2+C layer. The activation energy was estimated to be 350 to 405 kJ/mol for both of powder and compacted samples.
