Real-time optical monitoring of non-isothermal bleaching of γ-irradiated International Simple Glass (ISG)

The thermal bleaching of γ-irradiated (0.83 and 1.99 MGy) nuclear waste glass simulant known as International Simple Glass (ISG, made by Mo-SCI Corporation, Rolla, MO) was studied in real time by non-isothermal in situ UV/Vis optical microspectroscopy. The method follows the Urbach energy temperature/time evolution for three constant heating rates. A novel opto-thermal technique for kinetic analysis, coined temperature scanning bleaching spectroscopy (TSBS) is proposed. The applicability of the Kissinger equation is extended by synergistic inflection point analysis of the Urbach energy time/temperature sigmoid. The sigmoidal behavior is discussed in the context of polaron time/temperature trends of the main factors of thermally generated polaron flux. The overall activation energy of the non-isothermal thermal bleaching is evaluated at 1.6 (±0.1) and 1.3 (±0.2) eV, for 0.83 and 1.99 MGy, respectively. The proposed TSBS methodology is applicable for real-time monitoring and robust quantitative comparison of non-isothermal thermal bleaching of any glassy material.