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. (C) 2016 The Electrochemical Society. All rights reserved.