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Universal Solvent Extraction Technology (UNEX) The Universal Solvent Extraction (UNEX) Technology has been developed in Russia for removing cesium, strontium and transuranium elements from acid nuclear waste. The U.S. DOE/EM/Efficient Separations and Processing Crosscutting Program (ESP) has funded development of the UNEX process for potential application at the Idaho National Engineering and Environmental Laboratory (INEEL). This development is taking place at the Khlopin Radium Institute (KRI). The UNEX process is a modification of an earlier process developed for use at the Mayak Production Association facilities at Ozersk, Russia, which removed only cesium and strontium using cobalt dicarbollide and polyethylene glycol in a nitrobenzene diluent. Since nitrobenzene was considered to be hazardous in the U.S., scientists at the KRI have developed alternate diluents that are acceptable by U.S. standards, but are somewhat more costly. They also found conditions for adding a third extractant to the solvent so that transuranium elements can be removed simultaneously in the same process steps.
The UNEX process has been tested extensively in Russia, and in May 1999 at the Idaho National Engineering and Environmental Laboratory (INEEL) using actual acidic tank waste. The countercurrent flowsheet testing was performed using 24 stages of 2-cm diameter centrifugal contactors installed in a shielded hot cell facility. The UNEX process, which is based on a tertiary solvent containing chlorinated cobalt dicarbollide CMPO and polyethylene glycol successfully decontaminated the actual tank waste to below NRC Class A LLW criteria. Removal efficiencies obtained for Cs-137, Sr-90, and total alpha activity were 99.5%, 99.995% and >99.6%, respectively. Operational problems, such as precipitate formation or flooding, were not observed during testing. This demonstration is significant in that the acidic tank waste at INTEC could be treated in a single process to remove the major radionuclides as opposed to several separate processes for the removal of Cs, Sr, and the actinides. The demonstration was completed with the participation of five scientists from the Khlopin Radium Institute of St. Petersburg, Russia and from the Mayak Production Association in Ozersk, Russia. View Record of Meeting... (69K PDF)
A visit to the KRI in June 1999 gave the DOE sponsors and the potential users of the technology from INEEL an opportunity to discuss details of the process and its developments with the staff involved, to see how the Russian tests had been run, and to see the equipment and facilities in which these tests were run. The subsequent visit to the Mayak P.A. provided an opportunity to discuss the deployment of a closely related technology with those involved and to see the facility in which the process was deployed. The visit provided a chance to evaluate the UNEX Process, the personnel working to develop and test the process, and the status of the testing and deployment at Mayak PA. The impression of the delegation was favorable in all aspects. The technology was considered to be particularly promising. The removal of all of the components that must be removed from INEEL waste in a single solvent extraction step is likely to be much less expensive that the use of multiple steps that are required by the alternatives. View Record of Meeting... (25K PDF)
Two scientists from the Khlopin Radium Institute, St. Petersburg, Russia, visited their colleagues from INEEL in May 2000 to develop a plan for a comprehensive demonstration of UNEX technology at INEEL in the summer of 2000.
Two joint American -Russian patents were prepared and filed in 1999:
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