Electron irradiation-induced elements depletion and macroscopic changes in ternary borosilicate glasses: Mechanism and composition dependence

Abstract

Glass, utilized for immobilizing high-level radioactive waste, experiences a decrease in mechanical properties and an increased risk of radioactive release after being exposed to β-radiation. A series of ternary borosilicate glasses were irradiated with 10 MeV electrons to doses ranging from 1 × 104 to 1 × 107 Gy. Nano-indentation, X-ray photoelectron spectroscopy, Time-of-Flight secondary ion mass spectrometry and Fourier-Transform infrared spectroscopy were used to characterize the glasses. After irradiation, the hardness of the glass decreased dramatically; the depletion of sodium, boron, oxygen and the enrichment of hydrogen, carbon in the glass surface were observed. The diffusion coefficients and depletion depths at different doses were fitted, both related to the composition of glass. With the absorbed dose increasing, Q0 ∼ Q2 transformed to Q3 and Q4, BO3 and BO4 decreased, molecular water and hydroxyl appeared. The formation of the depletion zone caused the reduction in hardness induced by irradiation. The glass showed phase separation characteristics. The mechanism and detailed process of element depletion were discussed. The composition dependence of depletion was explained based on the energy barrier model. The diffusion coefficient of elements depends on the activation energy of alkali.