Filtration, Washing, and Caustic Leaching of Hanford Tank AZ-101 Sludge
The world’s largest vitrification facility is being designed and constructed at the U.S. Department of Energy’s Hanford Site, near Richland, Washington to convert radioactive waste stored in underground tanks into glass. Flow sheets call for washing and caustic leaching to pretreat the Hanford Envelope D sludge before it undergoes high-level waste (HLW) vitrification. These pretreatment steps reduce the quantity of HLW generated, by removing components that are soluble in water or caustic solutions, and often limit the waste loading in the glass. Crossflow filtration is specified to separate the wash and leach solutions from the solids. In crossflow filtration, the majority of the filter cake is swept away by the fluid flowing across it. Approximately 4313 g of slurry from Hanford Tank AZ-101 were evaluated by the pretreatment processes of crossflow filtration, washing, caustic leaching, and rinsing. The filterability was measured with a 0.1-mm sintered metal filter using a single-element, crossflow filtration system. Permeate flux of the as-received and washed slurries decayed linearly with the log of the undissolved solids concentration. The permeate flux of these slurries was also shown to be inversely proportional to the permeate viscosity. Statistical analysis indicated that the permeate flux of an 8-wt% insoluble solids slurry was also dependent on transmembrane pressure. As the slurry was concentrated to 18-wt%, the flux was dependent on axial velocity, with little dependency on transmembrane pressure. Samples of permeate from each wash were analyzed for chemical and radiochemical constituents. Primary component removal during the washing and leaching steps are discussed. This work provides important confirmation that the pretreatment of Hanford Envelope D wastes will have acceptable filterability and component removal during the pretreatment steps specified.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 15020525
- Report Number(s):
- PNWD-SA-6207; TRN: US0504673
- Journal Information:
- Separation Science and Technology, 40(1-3):1-15, Vol. 40, Issue 1-3
- Country of Publication:
- United States
- Language:
- English
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