This invention was made in the course of, or under a contract with the Energy Research and Development Administration. In its broadest form it relates to the removal of carbon contamination from uranium and uranium alloys by reaction with yttrium.
High purity uranium is required for many applications in the nuclear industry. During the course of refining and melting operations, uranium normally picks up carbon from contact with graphite ware and from CO.sub.2 and CO evolved from carbonaceous materials at high temperatures. Carbon contamination is present in molten uranium chiefly as dissolved carbon and in solid uranium as both dissolved carbon and uranium carbide inclusions. This carbon contamination causes considerable reduction in tensile strength, ductility, and corrosion resistance of uranium. For purposes of this invention, the term "carbon contamination" refers to total carbon content, regardless of form. Carbon contamination is particularly bothersome in the production of uranium alloys with alloying metals such as niobium, tantalum, vanadium, and titanium. Such alloys are produced by melting the desired amount of alloying metal with the required amount of uranium or uranium alloy. When the metals are melted together, carbon present in the uranium or uranium alloy feed reacts with the alloying metals forming carbides which float to the top of the melt. This carbide formation makes precise control of the alloy composition very difficult; therefore, the lower the level of carbon contamination in the feed materials, the greater is the composition control capability.