ORAL

SESSION: MoltenMonAM-R3	Gaune-Escard International Symposium on Sustainable Molten Salt and Ionic Liquid Processing (5th Intl. Symp. on Sustainable Molten Salt and Ionic Liquid Processing)
Mon Oct, 23 2017	Room: Peninsula 1
Session Chairs: Tamas Oncsik; Session Monitor: TBA

15:00: [MoltenMonAM06]
Electrochemical Behaviors of Uranium and Lanthanide Cations in LiCl-KCl Melt Investigated by Electrochemical and Spectroscopic Methods
Sang-eun Bae¹ ; Suhee Choi¹ ; Tae-hong Park¹ ; Jong-yun Kim¹ ; Young Hwan Cho¹ ; Jei-won Yeon¹ ; ¹Korea Atomic Energy Research Institute, Daejeon, Korea (Republic of [South] Korea);
Paper Id: 164 [Abstract]

Pyrochemical process has been considered as one of the options for a recycling technique of spent nuclear fuels. In the pyrochemical process, there exist a number of chemical elements, especially nuclear materials such as uranium, plutonium, and various fission products. In order to successfully accomplish the research for the pyrochemical process, accurate information on the chemical and electrochemical reactions of the elements in the molten salt should be acquired. A number of works have been performed to investigate the chemical and electrochemical properties of actinide and lanthanide ions in LiCl-KCl melt. It is well-known that spectroscopic tools such as UV-VIS absorption and laser induced luminescence spectroscopies as well as electrochemical tools such as cyclic voltammetry (CV) and rotating disk electrode (RDE) methods can give useful information for the chemical and electrochemical behaviors of the actinide and lanthanide ions in the solution. In this work, the spectroscopic and electrochemical methods were employed to investigate the behaviors of the elements in the LiCl-KCl melt. The oxidation state shift of the elements during electrochemical reactions of the uranium and lanthanide cations in LiCl-KCl melt was monitored by using the spectroscopic methods. Many useful electrochemical properties for the elements were collected in LiCl-KCl melt by using electrochemical methods such as CV and RDE. In particular, the RDE measurement could produce very useful parameters such as diffusion coefficients, Tafel slope, exchange current density, electron transfer coefficient, etc. In this presentation, we will show the research progress for the spectroscopic and electrochemical measurements of the actinide and lanthanide cations in the LiCl-KCl molten salt.

SESSION: MoltenTueAM-R3	Gaune-Escard International Symposium on Sustainable Molten Salt and Ionic Liquid Processing (5th Intl. Symp. on Sustainable Molten Salt and Ionic Liquid Processing)
Tue Oct, 24 2017	Room: Peninsula 1
Session Chairs: Rasmus Fehrmann; Georges Kipouros; Session Monitor: TBA

12:30: [MoltenTueAM04]
Real-Time Monitoring of Metal Ion Concentration in LiCl-KCl Containing Multi Component
Suhee Choi¹ ; Sang-eun Bae¹ ; Tae-hong Park¹ ; ¹Korea Atomic Energy Research Institute, Daejeon, Korea (Republic of [South] Korea);
Paper Id: 163 [Abstract]

Spent nuclear fuel (SNF) includes a significant amount of unreacted uranium with high-level radioactive fission products. Pyroprocess has attracted much attention for recovering the unreacted uranium and useful actinides and for reducing the volume of the high-level radioactive wastes. The main steps in the pyroprocess are electrorefining and electrowinning, where the U and actinide elements are recovered from the SNF. It is very important to monitor the concentrations of actinide and lanthanide ions during the operation of the process because the SNF includes nuclear materials. We previously reported that an electric charge obtained from a repeating chronoamperometry (RCA) technique was linearly proportional to the concentration of the neodymium up to 9 wt%. In this work, we applied the RCA technique for the measurement of the concentration of the uranium ion in LiCl-KCl melts containing multi-ions, which likely resembled a real reaction medium in the pyroprocess. We chose uranium, magnesium, and lanthanum as representatives for actinides and lanthanides. In particular, magnesium was selected as a surrogate of plutonium because standard redox potentials of magnesium and plutonium are similar. We measured apparent reduction potential of three elements using cyclic voltammetry (CV) before applying RCA. According to CV results, we carried out the RCA measurements of two-component and three-component systems with the electrodeposition at potentials of -1.7V, -2.05V, and -2.3V for U, Mg, and La, respectively, and the dissolution at a potential of -1V. Sequential electrodeposition and dissolution were repeatedly performed and the passed charges of the U dissolution increased linearly with the concentrations up to 9 wt% in the both two-component and three-component systems. The electric charge of Mg and La dissolution increased linearly with concentration up to 5wt%. Therefore, the RCA technique enabled the determination of the metal ion concentration in multi-component LiCl-KCl melts, demonstrating a potential for on-line monitoring of metal ion in the pyroprocess.