A preliminary study of pilot-scale electrolytic reduction of UO2 using a graphite anode

  • Kim, Sung-Wook (Pyroprocessing Division, Korea Atomic Energy Research Institute) ;
  • Heo, Dong Hyun (Pyroprocessing Division, Korea Atomic Energy Research Institute) ;
  • Lee, Sang Kwon (Pyroprocessing Division, Korea Atomic Energy Research Institute) ;
  • Jeon, Min Ku (Pyroprocessing Division, Korea Atomic Energy Research Institute) ;
  • Park, Wooshin (Pyroprocessing Division, Korea Atomic Energy Research Institute) ;
  • Hur, Jin-Mok (Pyroprocessing Division, Korea Atomic Energy Research Institute) ;
  • Hong, Sun-Seok (Pyroprocessing Division, Korea Atomic Energy Research Institute) ;
  • Oh, Seung-Chul (Pyroprocessing Division, Korea Atomic Energy Research Institute) ;
  • Choi, Eun-Young (Pyroprocessing Division, Korea Atomic Energy Research Institute)
  • Received : 2017.03.06
  • Accepted : 2017.05.23
  • Published : 2017.10.25


Finding technical issues associated with equipment scale-up is an important subject for the investigation of pyroprocessing. In this respect, electrolytic reduction of 1 kg $UO_2$, a unit process of pyroprocessing, was conducted using graphite as an anode material to figure out the scale-up issues of the C anode-based system at pilot scale. The graphite anode can transfer a current that is 6-7 times higher than that of a conventional Pt anode with the same reactor, showing the superiority of the graphite anode. $UO_2$ pellets were turned into metallic U during the reaction. However, several problems were discovered after the experiments, such as reaction instability by reduced effective anode area (induced by the existence of $Cl_2$ around anode and anode consumption), relatively low metal conversion rate, and corrosion of the reactor. These issues should be overcome for the scale-up of the electrolytic reducer using the C anode.


Supported by : National Research Foundation of Korea (NRF)


  1. H.-S. Lee, G.-I. Park, K.-H. Kang, J.-M. Hur, J.-G. Kim, D.-H. Ahn, Y.-Z. Cho, E.-H. Kim, Pyroprocessing technology development at KAERI, Nucl. Eng. Technol. 43 bm (2011) 317-328.
  2. H. Ohta, T. Inoue, Y. Sakamura, K. Kinoshita, Pyroprocessing of light water reactor spent fuels based on an electrochemical reduction technology, Nucl. Technol. 150 (2005) 153-161.
  3. T. Inoue, L. Koch, Development of pyroprocessing and its future direction, Nucl. Eng. Technol. 40 (2008) 183-190.
  4. J.-M. Hur, S.M. Jeong, H.S. Lee, Underpotential deposition of Li in a molten $LiCl-Li_2O$ electrolyte for the electrochemical reduction of U from uranium oxides, Electrochem. Commun. 12 (2010) 706-709.
  5. S.M. Jeong, H.-S. Shin, S.-H. Cho, J.-M. Hur, H.S. Lee, Electrochemical behavior of a platinum anode for reduction of uranium oxide in a LiCl molten salt, Electrochim. Acta 54 (2009) 6335-6340.
  6. Y. Sakamura, T. Omori, T. Inoue, Application of electrochemical reduction to produce metal fuel material from actinide oxides, Nucl. Technol. 162 (2008) 169-178.
  7. Y. Sakamura, T. Omori, Electrolytic reduction and electrorefining of uranium to develop pyrochemical reprocessing of oxide fuels, Nucl. Technol. 171 (2010) 266-275.
  8. S.-W. Kim, E.-Y. Choi, W. Park, H.S. Im, J.-M. Hur, TiN anode for electrolytic reduction of $UO_2$ in pyroprocessing, J. Nucl. Fuel Cycle Waste Technol. 13 (2015) 229-233.
  9. Y. Sakaumra, M. Iizuka, Applicability of nickel ferrite anode to electrolytic reduction of metal oxides in $LiCl-Li_2O$ melt at 923 K, Electrochim. Acta 189 (2016) 74-82.
  10. S.-W. Kim, E.-Y. Choi, W. Park, H.S. Im, J.-M. Hur, A conductive oxide as an $O_2$ evolution anode for the electrolytic reduction of metal oxides, Electrochem. Commun. 55 (2015) 14-17.
  11. A. Merwin, D. Chidambaram, Alternative anodes for the electrolytic reduction of $UO_2$, Metall. Mater. Trans. A 46 (2015) 536-544.
  12. S.-W. Kim, W. Park, H.S. Im, J.-M. Hur, S.-S. Hong, S.-C. Oh, E.-Y. Choi, Electrochemical behavior of liquid Sb anode system for electrolytic reduction of $UO_2$, J. Radioanal. Nucl. Chem. 303 (2015) 1041-1046.
  13. S.-W. Kim, S.-K. Lee, H.W. Kang, E.-Y. Choi, W. Park, S.-S. Hong, S.-C. Oh, J.-M. Hur, Electrochemical properties of noble metal anodes for electrolytic reduction of uranium oxides, J. Radioanal. Nucl. Chem. 311 (2017) 809-814.
  14. J.-M. Hur, J.-S. Cha, E.-Y. Choi, Can carbon be an anode for electrochemical reduction in a $LiCl-Li_2O$ molten salt? ECS Electrochem. Lett. 3 (2014) E5-E7.
  15. S.-W. Kim, M.K. Jeon, H.W. Kang, S.-K. Lee, E.-Y. Choi, W. Park, S.-S. Hong, S.-C. Oh, J.-M. Hur, Carbon anode with repeatable use of LiCl molten salt for electrolytic reduction in pyroprocessing, J Radional. Nucl. Chem. 310 (2016) 463-467.
  16. T. Biju Joseph, N. Sanil, K.S. Mohandas, K. Nagarajan, A study of graphite as anode in the electro-deoxidation of solid $UO_2$ in $LiCl-Li_2O$ melts, J. Electrochem. Soc. 162 (2015) E51-E58.
  17. H.Y. Ryu, S.M. Jeong, Y.C. Kang, J.-G. Kim, Electrochemical carbon formation from a graphite anode in $LiCl-Li_2O$ molten salt, Asian J. Chem. 25 (2013) 7019-7022.
  18. E.-Y. Choi, J. Lee, M.K. Jeon, S.-K. Lee, S.-W. Kim, S.-C. Jeon, J.H. Lee, J.-M. Hur, Electrolytic reduction of $1kg-UO_2$ in $Li_2O-LiCl$ molten salt using porous anode shroud, J. Korean Electrochem. Soc. 18 (2015) 121-129 (in Korean).
  19. F. Lantelme, H. Alexopoulos, D. Devilliers, M. Chemla, A gas electrode: behavior of the chlorine injection electrode in fuse alkali chlorides, J. Electrochem. Soc. 138 (1991) 1665-1671.
  20. Y. Sakamura, M. Kurata, T. Inoue, Electrochemical reduction of $UO_2$ in molten $CaCl_2$ or LiCl, J. Electochem. Soc. 153 (2006) D31-D39.