Fabrication of Stabilized Uranium Monocarbide Compacts

Abstract

UC and (U, Pu)C are considered promising source materials for high gain fast breeder reactor fuel. Stoichiometric UC possesses good compatibility with sodium and stainless steel, combined with low swelling-rate and fission gas release, but these qualities of UC fade when the composition deviates from the stoichiometric to either hypo or hyper ranges. UC fuels produced by conventional sintering process contain UC₂ which reacts with adsorbed oxygen and releases CO gas at high temperatures. These considerations urged the authors to a study of methods of compacting UC by high pressure impaction and the stabilization of UC by the addition of certain metallic elements. The main results obtained were that:

1.	UC compacts of up to about 97% T.D. could be obtained by impaction forming with 25–30 kbar at],200°C, but no significant further improvement could be gained by heating treatment at 1.200°–1,550°C.
2.	All the specimens with the metallic elements added were found with UC2 content completely decarburized, and with their additive metals forming carbides upon impaction and vacuum heating, thus proving that these additives are effective in accelerating the decarburization of UC2.
3.	In consideration of the expected conditions to which UC would be subjected in actual use as fast breeder reactor fuel, three of the ten additive elements tried, namely, V, Cr and Ti were judged most suitable for possible use as stabilizing agents, and the addition of W or Mo would be also available for the high temperature application.