The universal solvent extraction (UNEX) process. I. Development of the UNEX process solvent for the separation of cesium, strontium, and the actinides from acidic radioactive waste

A synergistic extraction mixture containing chlorinated cobalt dicarbollide (CCD), carbamoylmethyl phosphine oxide (CMPO), and polyethylene glycol (PE G) has been investigated for the simultaneous recovery of cesium, strontium , lanthanides, and actinides from highly acidic media. The extraction prope rties of this mixture depend on the concentration ratio of the components. For recovery of all major radionuclides, the optimal ratio of [CCD]:[PEG]: [CMPO]=5:1:1 should be used. The use of diphenyl-N,N-dibutylcarbamoylmethyl phosphine oxide and PEG-400 provides the most efficient recovery of cesium , strontium, lanthanides, and actinides. The possibility of using polyfluor inated ethers, esters, ketones, and sulfones as diluents was examined. Phen yltrifluoromethyl sulfone was the most suitable diluent tested. The use of this diluent allows good extraction properties, chemical and radiation stab ility, excellent explosion/fire-safety properties, and favorable hydrodynam ic characteristics. The extraction of radionuclides from HNO3 media by mixt ures of CCD:PEG:CMPO in phenyltrifluoromethyl sulfone and the subsequent st ripping behavior were evaluated.