Carbothermic synthesis of uranium-plutonium mixed carbide

Mechanically blended powder of UO2, PuO2 and graphite and its compact were heated in a vacuum to have some informations on the formation of mixed carbide (U, Pu) C. It was experimentally confirmed that PuO2 was reduced to sesquicarbide without forming a solid solution with UO2 in the reduction process. Larger quantity of sesquicarbide was formed in the compacted sample than in the powder one in the intermediate products. Compacts of UO2, PuO2 and graphite were also heated at 1,665--1,920 K in He, in order to investigate the effects of reduction temperature, He flow rate and blending time on the rate constant of reduction. The reaction proceeded from the surface toward the center of the compact. It was inferred that the rate-determining step was the reaction at the interfacial boundary between the reacted layer and the unreacted zone. The activation energy for the reduction was determined to be 375+-20 kJ/mol. The Pu loss due to vaporization could be sufficiently suppressed, when compacted samples were reduced in He. (author)