Conversion of simulated high-level liquid waste to chloride for the pretreatment of pyrometallurgical partitioning process

A pyrometallurgical partitioning process is being developed for recovering minor actinides from high-level liquid waste resulting from PUREX reprocess ing. Since the high-level liquid waste consists of concentrated raffinate, concentrated alkaline waste and insoluble residues, the various elements in the waste must be converted to chlorides before they can be sent on to the pyrometallurgical partitioning process. The conversion to chlorides is don e by a combination of denitration and chlorination. The mass balance of the se processes was measured in the present study using simulated high-level l iquid waste. The results indicate that almost all of the alkali elements an d Re, substituting for Tc, and significant amounts of Se, Cr, and Mo were s eparated by denitration, and that Cr, Fe, Zr, Mo, and Te were separated by chlorination. The remaining noble metals, Ni, U, and alkaline-earth and rar e-earth elements were efficiently converted to chlorides, which were then s upplied to the reductive extraction test using a molten salt/liquid-Cd syst em to demonstrate that the obtained chlorides are appropriate for processin g by pyrometallurgical partitioning. In further reduction, noble metals and Ni were reductively extracted into the liquid-Cd phase, and the rare-earth elements and U into the liquid-Cd phase by adding Li reductant. These elem ents were completely separated from the alkaline-earth elements remaining i n the chloride phase.