Sodium Recycle Economics for Waste Treatment Plant Operations
Sodium recycle at the Hanford Waste Treatment Plant (WTP) would reduce the number of glass canisters produced, and has the potential to significantly reduce the cost to the U.S. Department of Energy (DOE) of treating the tank wastes by hundreds of millions of dollars. The sodium, added in the form of sodium hydroxide, was originally added to minimize corrosion of carbon-steel storage tanks from acidic reprocessing wastes. In the baseline Hanford treatment process, sodium hydroxide is required to leach gibbsite and boehmite from the high level waste (HLW) sludge. In turn, this reduces the amount of HLW glass produced. Currently, a significant amount of additional sodium hydroxide will be added to the process to maintain aluminate solubility at ambient temperatures during ion exchange of cesium. The vitrification of radioactive waste is limited by sodium content, and this additional sodium mass will increase low-activity waste-glass mass. An electrochemical salt-splitting process, based on sodium-ion selective ceramic membranes, is being developed to recover and recycle sodium hydroxide from high-salt radioactive tank wastes in DOE’s complex. The ceramic membranes are from a family of materials known as sodium (Na)—super-ionic conductors (NaSICON)—and the diffusion of sodium ions (Na+) is allowed, while blocking other positively charged ions. A cost/benefit evaluation was based on a strategy that involves a separate caustic-recycle facility based on the NaSICON technology, which would be located adjacent to the WTP facility. A Monte Carlo approach was taken, and several thousand scenarios were analyzed to determine likely economic results. The cost/benefit evaluation indicates that 10,000–50,000 metric tons (MT) of sodium could be recycled, and would allow for the reduction of glass production by 60,000–300,000 MT. The cost of the facility construction and operation was scaled to the low-activity waste (LAW) vitrification facility, showing cost would be roughly $150 million to $400 million for construction and $10 million to $40 million per year for operations. Depending on the level of aluminate supersaturation allowed in the storage tanks in the LAW Pretreatment Facility, these values indicate a return on investment of up to 25% to 60%.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 963235
- Report Number(s):
- PNNL-SA-59228; 830403000
- Resource Relation:
- Conference: Waste Management Symposium 2008: Phoenix Rising - Moving Forward in Waste Management , February 24-28, 2008, Phoenix Arizona., Paper No. 8431
- Country of Publication:
- United States
- Language:
- English
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