The universal solvent extraction (UNEX) process. II. Flowsheet developmentand demonstration of the UNEX process for the separation of cesium, strontium, and actinides from actual acidic radioactive waste

A novel solvent extraction process, the Universal Extraction (UNEX) process , has been developed for the simultaneous separation of cesium, strontium, and the actinides from acidic waste solutions. The UNEX process solvent con sists: of chlorinated cobalt dicarbollide for the extraction of Cs-137, pol yethylene glycol for the extraction of Sr-90, and diphenyl-N,N-dibutylcarba moyl phosphine oxide for the extraction of the actinides and lanthanides. A nonnitroaromatic polar diluent consisting of phenyltrifluoromethyl sulfone has been developed for this process. A UNEX flowsheet consisting of a sing le solvent extraction cycle has been developed as a part of a collaborative effort between the Khlopin Radium Institute (KRI) and the Idaho National E ngineering and Environmental Laboratory (INEEL). This flowsheet has been de monstrated with actual acidic radioactive tank waste at the INEEL using 24 stages of 2-cm diameter centrifugal contactors installed in a shielded cell facility. The activities of Cs-137, Sr-90, and the actinides were reduced to levels at which a grout waste form would meet NRC Class A LLW requiremen ts. The extraction of Tc-99 and several nonradioactive metals by the UNEX s olvent has also been evaluated.