The thermodynamics and kinetics of nitrogen-nitride reactions in liquid uranium-tin alloys have been investigated experimentally. In the presence of dissolved metal impurities in the alloys, the nitrogen has been found to react with the uranium to form UN which can, under proper conditions, be precipitated as a pure phase from the melt, leaving impurities behind. Thus, the concept of nitride precipitation offers a possible metallurgical separation method applicable to the reprocessing of spent fast reactor fuels. Based on laboratory studies for uranium and the extrapolated behavior for plutonium, it appears possible to attain 99% uranium recovery and 98% plutonium recovery, with decontamination factors of 106.