Phenyl Trifluoromethyl Sulfone as Diluent in a Grouped ActiNide EXtraction Process

Licentiate thesis, 2015

The demand for electricity and electrical energy is very high both in Sweden and in the other industrialised countries in the world. An upgrade of the nuclear power plants, including recycling of the used nuclear fuel, would make nuclear power a sustainable energy option. Over the years different types of nuclear reactors have been developed. Current research focuses on the concept of generation IV systems. The generation IV concept is based on a closed nuclear fuel cycle including both a reactor and a used nuclear fuel recycling process. Recycling of the used nuclear fuel would increase the energy utilization of the uranium and make the final repositories significantly more sustainable, with regard both to capacity and storage time. Different types of recycling processes are under development. One of these is the Grouped ActiNide EXtraction (GANEX) process. The Chalmers GANEX process is a solvent extraction process extracting all the present actinides together as a group by combining two extracting agents and a diluent into one single solvent. In this work, a GANEX solvent based on the diluent phenyl trifluoromethyl sulfone (FS-13) containing the extraction agents CyMe4-BTBP and tri-butyl phosphate (TBP) has been investigated. Initial studies have shown that a FS-13-based solvent is promising, with good actinide extraction, relatively fast kinetics and a high stability against both hydrolysis and radiolysis. The two extraction agents seem to behave synergistically in the FS-13 GANEX system. This has to be further investigated for process development, and possible process optimisations can be made. The thermodynamic data shows an exothermic reaction with a slight decrease of the americium and europium extraction with an increasing temperature. The last step of the GANEX process is actinide stripping. Stripping seems feasible from the FS-13-based GANEX solvent, but this has to be further investigated, together with possible acid-scrubbing steps.