Chemical Oxygen Demand (COD) For Monitoring Reduction-Oxidation (Redox) Equilibrium During High Level Waste (HLW) Vitrification

Technical Report · Fri Apr 30 04:00:00 EDT 2004

DOI:https://doi.org/10.2172/829692· OSTI ID:829692

JANTZEN, CAROLM

High-level nuclear waste is being immobilized at the Savannah River Site by vitrification into borosilicate glass at the Defense Waste Processing Facility. Control of the REDuction/OXidation (REDOX) equilibrium in the DWPF melter is critical for processing high level liquid wastes. Based upon previous research, an acceptable iron REDOX ratio was defined for the DWPF melts as 0.09 Fe2/SFe 0.33. Controlling the DWPF melter at a REDuction/OXidation (REDOX) equilibrium ofFe2/SFe 0.33 prevents the potential for metallic and metallic sulfide species to form and accumulate on the floor of the melter. Control of foaming due to deoxygenation of manganic species is achieved by converting 66-100 of the MnO2 or Mn2O3 species in a waste feed to MnO before the waste is fed to the DWPF melter. At the lower redox limit of Fe 2/SFe 0.09 about 99 of the Mn 4/Mn 3 is converted to Mn 2. Therefore, the lower REDOX limit eliminates melter foaming from deoxygenation. Organic and nitrate concentrations in the DWPF melter feed are the major parameters influencing melt REDOX. Organics such as formates act as reductants while nitrates, nitrites, and manganic (Mn 4 and Mn 3) species act as oxidants. During melting, the REDOX of the melt pool cannot be measured. Therefore, the Fe 2/SFe ratio in the glass poured from the melter must be related to melter feed organic and oxidant concentrations to ensure production of a high quality glass without impacting production rate (e.g., from foaming) or melter life (e.g., from metal formation and accumulation).

• Research Organization: Savannah River Site (US)
• Sponsoring Organization: US Department of Energy (US)
• DOE Contract Number: AC09-96SR18500
• OSTI ID: 829692
• Report Number(s): WSRC-TR-2003-00322
• Country of Publication: United States
• Language: English

Related Subjects

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
54 ENVIRONMENTAL SCIENCES
BOROSILICATE GLASS
CHEMICAL OXYGEN DEMAND
COAL
DWPF
FORMATE
FORMATES
GLASS
IRON
LIQUID WASTES
MELTING
MONITORING
NITRATE
NITRATES
NITRITES
OXALATE
OXIDATION
OXIDIZERS
RADIOACTIVE WASTES
REDUCTION.
SLUDGE BATCH 3
SULFIDES
VITRIFICATION
WASTE PROCESSING