Melt refining experiments in which irradiated uranium or synthetic EBR-II alloys were melted in oxide crucibles have shown that removal of zirconium as an oxide does not occur at temperatures up to 1400°C. Removal of zirconium by carbon scavenging of the melt was approximately 50% in 5-hr melts at 1400°C; the mechanism and products of reactions which lead to this separation are discussed. Zirconium contamination of uranium-cerium alloys melted in lime-stabilized zirconia crucibles was negligible.