Influence of Zirconia Addition on the Leaching Stability of Borosilicate Glass

Immobilization of high-level radioactive wastes (HLW) in borosilicate glass for deep geological disposal has been widely used in the treatment of HLW around the world. The chemical durability of borosilicate glass, especially ability of resisting aqueous corrosion, is a crucial property, since the vitrification is carried out to prevent the dissipation of radioactive elements towards the biosphere. The addition of zirconia (ZrO2) to nuclear waste glasses could affect chemical properties such as chemical durability. In this work, borosilicate glasses with different composition were fabricated and leaching properties and the corresponding microstructures of borosilicate glasses in deionized water were investigated using the MCC-1 static leaching method at 90 ℃. The leaching rate was characterized by Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) and the microstructure of the glass was analyzed by Fourier transform infrared spectroscopy (FTIR) and grazing incident X-ray diffraction (GIXRD). The results of FTIR and GIXRD spectra showed that the strength of the glass network improved with the addition of zirconia, which might lead to an increase in the hydrolytic resistance of the glass. The addition of zirconia decreased the dissolution rate of the borosilicate glasses. The normalized mass losses of the borosilicate glasses with the addition of zirconia were much less than that of the ternary sodium borosilicate glasses. The changes in structure and leaching rate of quaternary glass also suggest that the addition of ZrO2 could obviously affect the leaching stability of the borosilicate glasses as well. Zirconia will strengthen the borosilicate glass network and improve the hydrolytic durability of glass. Finally, the changes in microstructure and leaching rates of borosilicate glasses undoped and doped with ZrO2 were obtained, which is of great significance for revealing the zirconia addition effect on the leaching process of borosilicate glass.