Octanol as Diluent in a Grouped ActiNide EXtraction Process Mu Lin Department of Chemistry and Chemical Engineering CHALMERS UNIVERSITY OF TECHNOLOGY Gothenburg, Sweden 2016 I Octanol as Diluent in a Grouped ActiNide EXtraction Process Mu Lin © Mu Lin, 2016 Examiner: Christian Ekberg Supervisor: Jenny Halleröd Department of Chemistry and Chemical Engineering Chalmers University of Technology SE-412 96 Gothenburg Sweden Telephone: +46 (0)31-7721000 Chalmers Reproservice Gothenburg, Sweden 2016 II Octanol as Diluent in a Grouped ActiNide EXtraction Process MU LIN Nuclear Chemistry & Industrial Materials Recycling Department of Chemistry and Chemical Engineering Chalmers University of Technology Abstract Since the beginning of the development of nuclear power plants nuclear energy has played a significant role in the worldwide electricity supply. More than 20% of the total electricity in the world comes from nuclear power plants. Nuclear energy has both advantages and disadvantages. On one hand, it contributes to clean energy in terms of low greenhouse gas emissions, and on the other hand, it causes problems with radioactive waste. By the end of May 2016, 444 nuclear reactors were in operation for the worldwide electricity generation. 63 new reactors are under construction, meaning that a large amount of nuclear waste has to be handled every year. Used nuclear fuel is highly radiotoxic when it is discharged from the reactor and has to be stored for at least 100,000 years for the radiotoxicity to reach the same level as the natural uranium needed to produce one tonne of enriched fuel. The storage time could, however, be reduced to around 1,000 years if the long-lived actinides are separated from the rest of the used nuclear fuel and transmuted into the short-lived or even stable isotopes. One of the separation methods are liquid-liquid extraction, where several different processes have been developed during the years. One of them is the GANEX (Grouped ActiNide EXtraction) process, which is still under development with the purpose of extracting all the actinides together as a group from the lanthanides and the other fission products. In order to reach a promising separation, different diluents and extraction agents are under investigation. In this work, the Chalmers GANEX process has been investigated using 6,6´-bis(5,5,8,8-tetramethyl- 5,6,7,8-tetrahydro-benzo[1,2,4]triazin-3-yl)[2,2´]bipyridine (CyMe4-BTBP) and tri-butyl phosphate (TBP) as extraction agents and 1-octanol as diluent. This system has also been compared with another system using FS13 (Phenyl Trifluoromethyl Sulfone) as diluent. Extraction of both active and inactive metal ions has been investigated. The experiments shows that both systems have a high actinide extraction and low extraction of the majority of both the lanthanides and the other fission products. In comparison with the FS13 based GANEX system the 1-octanol based GANEX system has a slightly higher extraction of both americium and curium but a lower extraction of both uranium and plutonium. The time to reach extraction equilibrium is slower for all actinides in the 1-octanol based GANEX system compared to the FS13 based GANEX system. Investigations with different volumes of TBP in the 1- octanol based GANEX system shows that the extraction of plutonium and europium increases with an increasing TBP concentration while the there is no big difference in the europium extraction. Keywords: Solvent Extraction, GANEX, 1-octanol, CyMe4-BTBP and TBP. III Contents 1. Introduction and Background ............................................................................................................ 1 1.1 Nuclear Waste ............................................................................................................................... 1 1.2 Once through ................................................................................................................................. 2 1.3 Reprocessing.................................................................................................................................. 2 1.4 Recycling ........................................................................................................................................ 3 1.5 Chalmers GANEX ........................................................................................................................... 3 1.5.1 Extractants .............................................................................................................................. 3 1.5.2 Diluents ................................................................................................................................... 4 2. Theory ................................................................................................................................................. 6 2.1 Liquid-Liquid Extraction ................................................................................................................. 6 2.1.1 Distribution Ratio and Separation Factor ............................................................................... 6 2.1.2 Kinetics and Equilibrium ......................................................................................................... 6 2.1.3 Stripping ................................................................................................................................. 7 2.2 Lanthanides, Actinides and Fission Products ................................................................................ 7 3. Experimental ....................................................................................................................................... 9 3.1 Solvent Extraction Experiments .................................................................................................... 9 3.2 Analysis .......................................................................................................................................... 9 3.2.1 Gamma Spectrometry ............................................................................................................ 9 3.2.2 Liquid Scintillation Counting ................................................................................................. 10 3.2.3 Inductively Coupled Plasma Mass Spectrometry ................................................................. 10 4. Results and Discussions .................................................................................................................... 11 4.1 Equilibrium Kinetics ..................................................................................................................... 11 4.1.1 Extraction of actinides and europium .................................................................................. 11 4.1.2 Extraction of fission products ............................................................................................... 13 4.2 Separate Ligand Extraction .......................................................................................................... 19 4.3 Varying TBP volume in the octanol based GANEX system .......................................................... 21 4.4 Stripping ...................................................................................................................................... 22 5. Summary and Conclusions ............................................................................................................... 25 6. Future work ....................................................................................................................................... 26 7. Acknowledgements .......................................................................................................................... 27 Bibliography .......................................................................................................................................... 28 Appendix 1 ............................................................................................................................................ 31 IV LIST OF ABBREVIATIONS ADS Accelerator Driven System BTBP Bis-triazine bi-pyridine CHON Carbon, Hydrogen, Oxygen and Nitrogen CyMe4-BTBP 6,6´-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-benzo[1,2,4]triazin-3- yl)[2,2´]bipyridine D Distribution ratio DEHBA N,N-di-2(ethylhexyl)-butyramide DIAMEX DIAMide Extraction DMDOHEMA N,N’-(dimethyl)-N,N’-dioctyl-hexylethoxy-malonamide FP Fission Products FS13 Phenyl trifluoromethyl sulfone GANEX Grouped ActiNide Extraction HDEHP di(2-ethylhexyl)phosphoric acid HPGe High Purity Germanium HSAB Hard Soft Acid Base IAEA International Atomic Energy Agency ICP-MS Inductively Coupled Plasma Mass Spectrometry ICRP International Commission on Radiological Protection LSC Liquid Scintillation Counting MOX-fuel Mixed Oxide Fuel NEA Nuclear Energy Agency NEI Nuclear Energy Institute OECD Organization for Economic Co-operation and Development PUREX Plutonium Uranium Reduction EXtraction P&T Partitioning and Transmutation SANEX Selective ActiNide Extraction SF Separation Factor TBP Tri-Butyl Phosphate tHM Tonne of Heavy Metals TODGA N,N,N’,N’-tetraoctyl diglycolamide V 1. Introduction and Background The worldwide electrical energy demand is high and is increasing every day due to an increasing population [1]. Electrical energy has played an important role for both developed and developing countries [2]. Developing countries need a big amount of energy to keep developing and developed countries needs energy to maintain the