PARTITIONING RATIO OF DEPLETED URANIUM DURING A MELT DECONTAMINATION BY ARC MELTING

Abstract

In a study of the optimum operational condition for a melting decontamination, the effects of the basicity, slag type and slag composition on the distribution of depleted uranium were investigated for radioactively contaminated metallic wastes of iron-based metals such as stainless steel (SUS 304L) in a direct current graphite arc furnace. Most of the depleted uranium was easily moved into the slag from the radioactive metal waste. The partitioning ratio of the depleted uranium was influenced by the amount of added slag former and the slag basicity. The composition of the slag former used to capture contaminants such as depleted uranium during the melt decontamination process generally consists of silica (<TEX>$SiO_2$</TEX>), calcium oxide (CaO) and aluminum oxide (<TEX>$Al_2O_3$</TEX>). Furthermore, calcium fluoride (<TEX>$CaF_2$</TEX>), magnesium oxide (MgO), and ferric oxide (<TEX>$Fe_2O_3$</TEX>) were added to increase the slag fluidity and oxidative potential. The partitioning ratio of the depleted uranium was increased as the amount of slag former was increased. Up to 97% of the depleted uranium was captured between the ingot phase and the slag phase. The partitioning ratio of the uranium was considerably dependent on the basicity and composition of the slag. The optimum condition for the removal of the depleted uranium was a basicity level of about 1.5. The partitioning ratio of uranium was high, exceeding <TEX>$5.5{\times}10^3$</TEX>. The slag formers containing calcium fluoride (<TEX>$CaF_2$</TEX>) and a high amount of silica proved to be more effective for a melt decontamination of stainless steel wastes contaminated with depleted uranium.