Nuclear Techniques ›› 2018, Vol. 41 ›› Issue (6): 60301-060301.doi: 10.11889/j.0253-3219.2018.hjs.41.060301


Electrochemical behaviors of Ln3+ in LnF3-LiCl-KCl molten salt

WANG Xianbin1,2, LONG Dewu1, ZHU Tiejian1, ZHENG Haiyang1, JIANG Feng1, SHE Changfeng1, HUANG Wei1, LI Qingnuan1   

  1. 1 Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Jiading Campus, Shanghai 201800, China;
    2 University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2017-06-16 Revised:2017-10-20 Online:2018-06-10 Published:2018-06-06
  • Supported by:
    Supported by the Strategic Priority Research Program of Chinese Academy of Sciences (No.XDA02030200), National Natural Science Foundation of China (No.21601200), Youth Innovation Promotion Association of Chinese Academy of Sciences (No.2017307)

Abstract: [Background] The separation and cyclic utilization of thorium is an important part of thorium-uranium fuel cycle for molten salt reactor. Therefore, separation of thorium from fission products, especially lanthanides, is the key step to electrochemical separation of thorium in molten salt because of their similar chemical properties.[Purpose] The aim of this work is to explore the influence of fluorine ion (F-) on electrochemical properties of 5 lanthanides in LnF3-LiCl-KCl molten salt and to confirm the feasibility of electrochemical separation of thorium from lanthanides in chloride molten salt.[Methods] Transient electrochemical techniques such as cyclic voltammetry and square wave voltammetry were employed to investigate the reduction mechanism and diffusion coefficient of Ln ions on a tungsten inert electrode.[Results] In LnF3-LiCl-KCl molten salt, Ce3+ and Gd3+ were reduced into metal Ce and Gd according to a one-step process by exchanging 3 electrons; Nd3+ was reduced into metal Nd through two steps; Sm3+ and Eu3+ couldn't be reduced into metal in tungsten electrode, and both of them were transformed into divalent state. The existence of F-would not change the electrode reaction process of Ln cations. The differences of deposition potential between Th and the 5 Lns on inert electrode were larger than 0.19 V, which demonstrated theoretically that it was feasible to separate Th from Lns in LiCl-KCl molten salt. Compared with pure chloride molten salt, the existence of F-decreased the activity of Ln3+, resulting in the decrease of diffusion efficiency of all Ln ions.[Conclusion] The study provided experimental foundation for feasibility investigation of the separation of thorium fluoride from lanthanides fluoride in LiCl-KCl molten salt.

Key words: LnF3-LiCl-KCl, Cyclic voltammetry, Square wave voltammetry, Electrode process, Diffusion efficient

CLC Number: 

  • TL426