Evaluation of nuclear transmutation effects due to beta decay on borosilicate glasses

In the study of deep geological disposal of high-level radioactive waste (HLW), beta decay has been widely studied, whereas the nuclear transmutation effects due to beta decay on vitrification are generally neglected. In this work, a series of sodium borosilicate glasses doped with cesium was fabricated. The nuclear transmutation due to beta decay evolving with the deposited time was simulated by substituting for cesium with barium. The macroscopic properties of the glasses, including density, hardness, and Young's modulus, were measured using the Archimedes (buoyancy) method and nanoindentation, respectively. The microscopic structures of the glasses were characterized by grazing incident X-ray diffraction, infrared spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, and Raman spectroscopy. The nuclear transmutation effects were significant. With the substitution of barium for cesium, the density, hardness, and modulus of the glasses increased and eventually tended to saturation. A decrease of [BO₃] units and an increase of [BO₄] units were observed in the infrared spectra and NMR spectra. In addition, the results were systematically compared to previous strontium-doping work in order to evaluate nuclear transmutation effects due to beta decay on vitrification in HLW comprehensively. The comparison demonstrated that the nuclear transmutation effect of cesium is completely opposite to that of strontium. The research is expected to contribute to a deeper understanding on the nuclear transmutation effects due to beta decay in HLW on vitrification.