Chlorinated cobalt dicarbollide based solvent extraction processes for the separation of CS, SR, and actinides from acidic waste

The universal solvent extraction (UNEX) process has been developed utilizing a synergistic extraction mixture containing chlorinated cobalt dicarbollide (CCD), polyethylene glycol (PEG), and diphenyl-N,N-dibutylcarbamoyl phosphine oxide (CMPO) in a suitable polar diluent for the simultaneous recovery of Cs, Sr, and the actinides from highly radioactive, acidic tank wastes. Alternatively, processes using CCD for the extraction of Cs and CCD/PEG mixtures for the extraction of Cs and Sr, both in a suitable polar diluent, have been developed for treatment of acidic tank wastes. Development of these processes has resulted from a successful collaboration between scientists from the Idaho National Engineering and Environmental Laboratory (INEEL) and the Khlopin Radium Institute (KRI) in St. Petersburg, Russia. Development efforts primarily focused on the treatment of radioactive waste currently stored at the INEEL. The development of these cobalt dicarbollide based solvent extraction processes has and continues to be an evolutionary process. Numerous countercurrent flowsheet demonstrations have been conducted to date using actual and surrogate tank waste. All countercurrent flowsheet tests have been performed in banks of centrifugal contactors. A summary of results from the countercurrent flowsheet testing is presented.