(415b) Antifoam Development for Processing of High Level Waste in the Defense Waste Processing Facility

Antifoam is needed during processing of High Level Waste (HLW) due to the high gas generation from steam and chemical reaction offgas products to prevent foam from contaminating the condensate. Antifoam is used to minimize foam¹ during chemical processing and HLW evaporation at the Savannah River Site (SRS)² and Hanford³. The antifoam used in the Defense Waste Processing Facility (DWPF) impacts flammability during chemical processing (generates three flammable degradation products) and while feeding the melter^4-5 since the antifoam can decompose to CO/hydrogen. It also is the likely source of methyl for the methyl mercury present in the tank farm and excessive mercury in Saltstone⁶. The planned startup of The Salt Waste Processing Facility (SWPF), with much higher throughput, will challenge the Defense Waste Processing Facility (DWPF) to process more efficiently.

DWPF employs Antifoam 747⁷, a superspreader produced by Momentive Performance Materials, as an antifoaming agent during waste processing. Despite its ability to control foam, processing issues have risen from use, which has led to two “Potential Inadequacy in the Safety Analyses” (PISAs) and has limited DWPF facility throughput.

During DWPF chemical processing, antifoam must be effective up to 103ËšC between pH of 3-13. Antifoam 747 is most effective at pH 6-8⁸ and degrades as pH deviates. Researchers at the Savannah River National Laboratory (SRNL) identified three flammable antifoam degradation⁹ products using mass spec and Fourier Transformed InfraRed (FTIR) offgas analyzers during experiments¹⁰.

A new Antifoam has been recommended for use in DWPF. The new antifoam was the best of the 30 antifoam candidates (identified by six antifoam manufacturers) that were evaluated in SRNL testing. The new antifoam is hydrolysis resistant which results that much less antifoam is needed for foam control. No degradation products were identified in the offgas or condensate. The testing leading to the new antifoam recommendation will be discussed.

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2. Wasan, D. T.; Lambert, D. P. Foaming and Antifoaming in Radioactive Waste Pretreatment and Immobilization; Illinois Institute of Technology: Chicago, IL, 2001.
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5. Evaluation of the Safety of the Situation (ESS): Melter Feed Rate Temperature Correlation Basis (PISA PI-2014-0009); Savannah River Remediation LLC: Aiken, SC, 2016.
6. Meraw, H. J. Volatilization and Flammability Characteristics of Elemental and Organic Mercury; X-ESR-G-00048, Revision 2; Savannah River Remediation LLC: Aiken, SC, June 2015, 2015.
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9. McCord, J. B. Evaluation of the Safety of the Situation (ESS): Melter Feed Rate Temperature Correlation Basis (PISA PI-2014-0009); Savannah River Remediation LLC: Aiken, SC, 2016.
10. Lambert, D. P.; Zamecnik, J. R.; Newell, J. D.; Martino, C. J. Impact of Scaling on the Glycolic-Nitric Acid Flowsheet; Savannah River National Laboratory: Aiken, SC, 2016.