Interim glycol flowsheet reduction/oxidation (redox) model for the Defense Waste Processing Facility (DWPF)

Jantzen, C. M.¹  Williams, M. S.¹  Zamecnik, J. R.¹  Missimer, D. M.¹ 

[1] Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

关键词: RADIOACTIVE WASTE PROCESSING;    FORMIC ACID;    GLYCOLIC ACID;    TECHNETIUM 99;    NITRIC ACID;    GLYCOLS;    CHROMIUM IONS;    HIGH-;   

DOI  :  10.2172/1244066
RP-ID  :  SRNL-STI--2015-00702
PID  :  OSTI ID: 1244066
Others  :  TRN: US1601033

美国|英语

来源: SciTech Connect

【 摘 要 】

Control of the REDuction/OXidation (REDOX) state of glasses containing high concentrations of transition metals, such as High Level Waste (HLW) glasses, is critical in order to eliminate processing difficulties caused by overly reduced or overly oxidized melts. Operation of a HLW melter at Fe⁺²/??Fe ratios of between 0.09 and 0.33, a range which is not overly oxidizing or overly reducing, helps retain radionuclides in the melt, i.e. long-lived radioactive ⁹⁹Tc species in the less volatile reduced Tc⁴⁺ state, ¹⁰⁴Ru in the melt as reduced Ru⁺⁴ state as insoluble RuO₂, and hazardous volatile Cr⁶⁺ in the less soluble and less volatile Cr⁺³ state in the glass. The melter REDOX control balances the oxidants and reductants from the feed and from processing additives such as antifoam. Currently, the Defense Waste Processing Facility (DWPF) is running a formic acid-nitric acid (FN) flowsheet where formic acid is the main reductant and nitric acid is the main oxidant. During decomposition formate and formic acid releases H₂ gas which requires close control of the melter vapor space flammability. A switch to a nitric acid-glycolic acid (GN) flowsheet is desired as the glycolic acid flowsheet releases considerably less H₂ gas upon decomposition. This would greatly simplify DWPF processing. Development of an EE term for glycolic acid in the GN flowsheet is documented in this study.