Electrochemical reduction behavior of borosilicate glass in molten CaCl₂

Abstract

The electrochemical reduction behavior of borosilicate glass, which is the main component of vitrified radioactive waste, was investigated in molten CaCl₂ at 1123 K to establish a new nuclear waste disposal procedure. Cyclic voltammetry of borosilicate and silica glasses suggested that the reduction of B₂O₃ in borosilicate glass occurred at a more positive potential than that of SiO₂. X-ray photoelectron spectroscopy confirmed that the B₂O₃ component was reduced to B or a B-Si compound at 0.9 V vs. Ca²⁺/Ca. The reduction products prepared by the potentiostatic electrolysis of borosilicate glass at 0.9 V had granular morphology and consisted of crystalline Si. The Al₂O₃ component was not reduced at 0.9 V and the Na₂O component was suggested to be dissolved in molten CaCl₂ during electrolysis.