Development of the Am/Cm Batch Vitrification Process
A batch vitrification process, which utilizes an oxalate precipitate and frit (or cullet), is being developed at the Savannah River Technology Center (SRTC) to immobilize an Am-Cm solution. Prior to being accepted as the baseline flowsheet, numerous laboratory-scale tests were conducted to demonstrate its feasibility and to characterize the general melt behavior of the oxalate/frit system. The effects of frit particle size and oxalate precipitation temperature were the initial focus of these studies. Two technical issues were identified during these initial tests that warranted further study: a volume or bed expansion was observed at approximately 1140 degrees C and ''excessive'' bubble formation between 1220 - 1250 degrees C. Although high temperature bubble formation does not pose a serious process concern (i.e., longer residence times and/or higher process temperatures minimize bubble retention), the volume expansion is undesirable during processing. The volume expansion may limit the amount of glass that can be produced in a single batch. That is, the batch height may have to be controlled so that the material is contained within the Pt-Rh vessel at all times. Both the volume expansion and high temperature bubble formation have been linked to the thermal reduction of CeO{sub 2}. As part of the oxalate feed, Ce is reduced (3 plus state). Upon thermal decomposition of the oxalate under oxidizing conditions, Ce will oxidize (3 plus (r) 4 plus state) which provides the opportunity for thermal reduction at higher temperatures liberating O2. Tests using a ''Ce-free'' oxalate have been performed in which no indication of either the volume expansion or high temperature bubble formation were observed. Complementary studies focused on redox and off-gas related issues provided a fundamental understanding of the melting behavior of the oxalate/frit system and lead to the successful development of the batch vitrification process.
- Research Organization:
- Savannah River Site (US)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- AC09-96SR18500
- OSTI ID:
- 11322
- Report Number(s):
- WSRC-MS-99-00657
- Country of Publication:
- United States
- Language:
- English
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