Fabrication of Uranium-Plutonium Mixed Carbide Pellets

Abstract

Uranium-plutonium mixed monocarbide pellets, which had densities over 90% T.D. and near-stoichiometric compositions, were fabricated in the gloveboxes of the atmosphere of purified Ar. The carbide powder was first synthesized by reducing mechanically blended oxides with graphite at 1, 510°C in a vacuum of 0.2 Pa. This condition was selected so as to minimize the loss of Pu during the reduction in vacuum. The synthesized carbide was milled and compacted, followed by sintering in flowing Ar at 1, 540 to 1, 750°C. The experimental conditions covered wide ranges of milling time, compacting pressure, sintering temperature and sintering time. The most suitable condition has been established for fabricating uranium-plutonium mixed carbide pellets by the mechanical-blend carbothermic reduction and sintering method. For the case of Ni addition as a sintering aid, the efficacy of the addition for fabricating dense pellets was confirmed, but it was noticed that the composition tended to hyperstoichiometry and the sesquicarbide phase precipitated especially at the pellet surface.