Use of the existing shielded cells melter for CST vitrification

Oak Ridge National Laboratory (ORNL) and SRTC are participating in a joint project in which supernate waste from the Melton Valley Storage Tanks at Oak Ridge (OR) will be treated by passage through a crystalline silicotitanate (CST) ion exchange medium1. The CST was designed to sorb cesium, the primary radionuclide (Cs-137) in the supernate of the Melton Valley tanks. A smaller amount of strontium will also be sorbed. The loaded sorbent will then be shipped to SRTC where it will be mixed with glass formers and fed as an aqueous slurry to a joule-heated melter within the SRTC Shielded Cells. The molten glass (approximately 1150 degrees C) will be poured into 500 mL stainless steel beakers which in turn will be placed in 30 gallon drums for shipment to and disposal at the Nevada Test Site (NTS). This paper focuses on the requirements necessary for disposal of the vitrified CST at NTS. This work is funded by the Tank Focus Area with additional funding from EM-30 at OR. A reduction in scope is currently under consideration for the vitrification demonstration. This change in scope would reduce the number of drums sent to SRTC from seven to one. The amount of CST that would be vitrified in this case is approximately 38 Kg. If this scope change is realized, then the vitrified CST in the 500 mL beakers will be disposed of at Savannah River Site (SRS). The results presented in this report will also be useful if the vitrified waste remains at SRS. The Shielded Cells Melter currently contains glass produced during a 1995 DWPF demonstration campaign. That campaign incorporated radioactive Tank 51 sludge into a DWPF borosilicate glass. The Tank 51 campaign in the Shielded Cells Melter was preceded with a flushing of the melter using non-radioactive glass. This flushing was preceded by a different Tank 51 campaign again using borosilicate glass. The 1995 Tank 51 campaign and the melter flushing each used less than one melter volume of material. (Abstract Truncated)