A new reference electrode in fluoride melts and a new concept for a spent zircaloy wastes treatment using a mixture of fluoride and chloride melt are proposed. Electrochemical formation of Au 2 Na on Au wire in a LiF–KF–NaF shows the equilibrium potential of the reaction: 2Au+Na + +e − =Au 2 Na at 0.535V vs. K + /K in LiF–NaF–KF eutectic melt at 773K. The (Au 2 Na+Au) electrode demonstrates excellent characteristics as a reference electrode in terms of reproducibility, stability and reversibility. LiF–LiCl–KCl melt enhances dissolution and deposition rate of zirconium, which enable us to develop a new decontamination process for a spent zircaloy. Electrochemical decontamination using LiF–LiCl–KCl melt is experimentally achieved a clearance level.