Investigation of gamma radiation effects on spectroscopic, thermal, and corrosion properties of the International Simple Glass (ISG)

This paper reports on the effects of gamma ray irradiation on various properties of the nuclear waste glass simulant known as International Simple Glass (ISG). The study was performed on the original ISG produced by Mo-SCI Corporation (Rolla, MO, USA) following accumulated gamma ray doses of 0.83 and 2 MGy. It encompassed Fourier-transform infrared (FT-IR) spectroscopy, Raman scattering, glass dissolution analysis (product consistency test, PCT), dilatometry, differential scanning calorimetry (DSC), electron paramagnetic resonance (EPR), optical absorption, and photoluminescence (PL) spectroscopy evaluations done in comparison with the pristine glass. The data indicated that the structural (FT-IR, Raman) and thermal (dilatometry, DSC) properties, as well as the chemical durability (static-leach PCT) of the ISG were not significantly altered after the gamma ray exposures. EPR showed distinct radiogenic signatures from spin defects after irradiation which were absent in the pristine ISG. The optical properties were also markedly different for the gamma-irradiated glasses. The irradiated ISG exhibited defects-related absorption features after 0.83 MGy which appeared slightly more intense after 2 MGy. The PL assessment which included time-resolved measurements however did not show any new emission features following gamma irradiation. The intrinsic PL of the ISG was rather quenched in accord with the absorption increase, while the qualitative luminescence features were preserved. Finally, optical absorption and PL properties were evaluated for the 2 MGy-irradiated ISG after a subsequent thermal treatment at 570 °C. The data showed substantial restoration of the optical properties in connection with electron-hole recombination while unveiling a photo-reduction of Fe³⁺ impurities.