Characterization of radioactive waste melter feed vitrified by microwave energy

Liquid high-level nuclear waste will be immobilized at the Savannah River Site (SRS) by vitrification in borosilicate glass. The glass will be processed in the Defense Waste Processing Facility (DWPF) and poured into stainless steel canisters for eventual disposal in a geologic repository. Vitrification of melter feeds is necessary for DWPF process and product control. Microwave fusion at ∼ 1,200C for 10 minutes has been shown to yield glasses comparable to those melted in a conventional furnace for 4 hours. Microwave fusion for longer times and/or lower temperatures causes spinel formation while higher temperatures and shorter times causes significant volatilization and recrystallization. Redox measurements indicate that microwave vitrification may also yield a more accurate measure of glass redox