Effects of compression molding on meltability of uranium dendrites for ingot consolidation in a pyroprocess

Abstract

Compression molding was carried out to enhance the meltability of uranium dendrites. Uranium dendrites were successfully compressed, increasing their bulk density more than 9 times from 1.1 to 10 g/cm3. The average bulk density was about 8.7 g/cm3 which was almost half of the material density. The compressed dendrites were favorably melted at a temperature of 1,400 °C in an induction furnace. 3 kg of the compressed dendrites were consolidated into an ingot form, showing 96.7 % yield. About 3 % of dross was formed during the melting test in the form of fine powder which was characterized as a uranium oxide. This compression molding method was compared to the supplemental charge method in which uranium dendrites were poured into a molten metal pool produced from a uranium ingot. The capacity of dendrite melting was higher in the compression molding method than in the supplemental charge method. We consider that the higher capacity can be attributed to enhanced thermal conductivity as the bulk density was increased by the compression. These results suggest the high feasibility of the compression molding method for uranium melting in a pyroprocess at an engineering scale.