Electrochemical Treatment of Alkaline Nuclear Wastes. Innovative Technology Summary Report
Nitrate and nitrite are two of the major hazardous non-radioactive species present in Hanford and Savannah River (SR) high-level waste (HLW). Electrochemical treatment processes have been developed to remove these species by converting aqueous sodium nitrate/nitrite into sodium hydroxide and chemically reducing the nitrogen species to gaseous ammonia, nitrous oxide and nitrogen. Organic complexants and other organic compounds found in waste can be simultaneously oxidized to gaseous carbon dioxide and water, thereby reducing flammability and leaching risks as well as process interferences in subsequent radionuclide separation processes. Competing technologies include thermal, hydrothermal and chemical destruction. Unlike thermal and hydrothermal processes that typically operate at very high temperatures and pressures, electrochemical processes typically operate at low temperatures (<100 C) and atmospheric pressure. Electrochemical processes effect chemical transformations by the addition or removal of electrons and, thus, do not add additional chemicals, as is the case with chemical destruction processes. Hanford and SR have different plans for disposal of the low-activity waste (LAW) that results when radioactive Cs{sup 137} has been removed from the HLW. At SR, the decontaminated salt solution will be disposed in a cement waste form referred to as Saltstone, whereas at Hanford the waste will be vitrified as a borosilicate glass. Destruction of the nitrate and nitrite before disposing the decontaminated salt solution in Saltstone would eliminate possible groundwater contamination that could occur from the leaching of nitrate and nitrite from the cement waste form. Destruction of nitrate and nitrite before vitrification at Hanford would significantly reduce the size of the off-gas system by eliminating the formation of NO{sub x} gases in the melter. Throughout the 1990's, the electrochemical conversion process has been extensively studied at SR, the University of Sou th Carolina, and elsewhere. Testing at the bench-scale has been completed using both surrogate and actual waste streams. A pilot-scale test facility was constructed and operated briefly at SR. This document contains information on the above-mentioned technology, including description, applicability, cost, and performance data.
- Research Organization:
- Savannah River Site, Aiken, SC (US)
- Sponsoring Organization:
- USDOE Office of Science and Technology (OST) (EM-50) (US)
- OSTI ID:
- 779449
- Report Number(s):
- DOE/EM-0560; OST/TMS ID 39; OST/TMS ID 39; TRN: US0201027
- Resource Relation:
- Other Information: PBD: 1 Jan 2001; PBD: 1 Jan 2001
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
BOROSILICATE GLASS
CARBON DIOXIDE
NITROUS OXIDE
OFF-GAS SYSTEMS
OTHER ORGANIC COMPOUNDS
RADIOACTIVE WASTES
SEPARATION PROCESSES
SODIUM HYDROXIDES
WASTE FORMS
HIGH-LEVEL RADIOACTIVE WASTES
RADIOACTIVE WASTE PROCESSING
LOW-LEVEL RADIOACTIVE WASTES
HANFORD RESERVATION
SAVANNAH RIVER PLANT