Recovery of EU²⁺ and Sr²⁺ Using Liquid Metallic Cathodes in Molten NaCl-KCl and KCl System

Abstract

In the pyrochemical reprocessing of spent metallic nuclear fuels using molten salt bath, recovery of Eu and Sr as fission products having electrochemically negative potentials is important. In order to develop the electrowinning method, cathodic deposition of Eu²⁺ in the NaCl-KCl melt and Sr²⁺ in the KCl melt at some metallic cathodes (Al, Bi, Pb, Sn and Zn) was examined by cyclic voltammetry and chronopotentiometry. Transfer coefficient, standard rate constant and diffusion coefficient for Eu₂₊ and Sr²⁺ were determined by cyclic voltammetry with conventional, semi-integral and semi-differential methods and by chronopotentiometry. It was revealed that a quasi-reversible cathodic reaction Eu²⁺ +2e⁻ +3Pb → EuPb₃ on liquid Pb electrode takes place in the NaCl-KCl melt at 1,073K. As for Sr²⁺, a quasi-reversible cathodic reaction Sr²⁺ +2e⁻ +3Pb→SrPb₃ takes place at liquid Pb electrode in the KCl melt at 1,073K. These propose possibility to recover Eu into Pb cathode and Sr into Pb cathode as well as into Al cathode.

KEYWORDS:

• chronopotentiometry
• cyclic voltammetry
• europium
• liquid metallic cathodes
• metallic fuels
• molten salts
• recovery
• pyrochemical reprocessing
• strontium
• fission products