The microwave heating of a crystal-free and a partially trevorite-crystallized nuclear waste glass simulant was evaluated. Results show that a 500-mg monolith of partially crystallized waste glass can be heated from room temperature to above 1600 deg C within 2 minutes using a single-mode, highly focused 2.45-GHz microwave, operating at 300W. Using X-ray diffraction measurements, it is shown that trevorite is no longer detectable after irradiation and thermal quenching. When a crystal-free analog of the same waste glass simulant composition was exposed to the same microwave radiation, it could not be heated above 450 deg C, regardless of the heating time. The reduction in crystalline content achieved by selectively heating spinels in the presence of glass suggests that microwave-specific heating should be further explored as a technique for remediating crystal accumulation in a glass melt.
