To regenerate the spent UNEX-extractant, a technique for the distillation of the diluent (phenyltrifluoromethylsulfone — FS-13) water steam in the presence of sodium carbonate was elaborated. In this way it is possible to distill more than 90% of practically pure diluent (with purification coeffi­cients from the radionuclides — above 1000). During this process, over 40% CCD transfers into the sodium carbonate aqueous solution, from where it can be precipitated in the form of cesium salt suitable for re-use.

Specific experiments have shown that the properties of UNEX-extractant prepared from regenerated FS-13 and CCD do not differ from those of a fresh extractant. By using this regeneration technique, the radionuclides contained in the spent extractant remain almost completely in the still residue along with CMPO, PEG and a portion of CCD. This residue is a viscous liquid which can be removed and then treated with other high-level waste.