(2d) Yield Stress Reduction of Dwpf Melter Feed Slurries

The Defense Waste Processing Facility (DWPF) converts High Level Waste (HLW) currently stored in waste tanks at the Savannah River Site into borosilicate glass suitable for repository disposal. The vitrification process utilizes a slurry-fed joule-heated melter. The melter feed behaves in a manner consistent with a Bingham Plastic with the solids content of the melter feed is limited by the yield stress of the feed. A reduction of the yield stress could lead to higher solids loading in the melter feed and a faster feed rate.

During the pretreatment process at DWPF, glass formers are added to the waste as frit, sized +80/-200 mesh. The frit constitutes the majority of the solids in the final melter feed. Changing the shape of the glass former from the irregular frit to nearly spherical beads in the same particle size range was evaluated and found to reduce yield stress by up to 40%. The ?spherical frit? should also have other benefits during processing, such as reduced erosion of processing equipment.