(477b) Improved Foam Control during High Level Radioactive Waste Processing

Antifoam is needed during processing of 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 SRS² 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 (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 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. SRNL identified three flammable antifoam degradation⁹ products using mass spec and FTIR offgas analyzers during experiments¹⁰. Equipment has not been used in identifying decomposition products from antifoam agents used elsewhere.

A new Antifoam or a new method to control foam is needed to minimize DWPF processing time. The progress in developing the new foam control method will be discussed.

1. Bindal, S. K.; Nikolov, A. D.; Wasan, D. T.; Lambert, D. P.; Koopman, D. C., Foaming in Simulated Radioactive Waste. Environ. Sci. Technol. 2001, 35 (19), 3941-3947.
2. Wasan, D. T.; Lambert, D. P. Foaming and Antifoaming in Radioactive Waste Pretreatment and Immobilization; Illinois Institute of Technology: Chicago, IL, 2001.
3. Calloway, J. T. B.; Martino, C. J.; Jantzen, C. M.; Wilmarth, W. R.; Stone, M. E.; Pierce, R. A.; Josephs, J. E.; Barnes, C. D.; Daniel, W. E.; Eibling, R. E.; Choi, A. S.; White, T. L.; Crowley, D. A.; Baich, M. A.; Johnson, J. D.; Vijayaraghavan, K.; Nikolov, A. P.; Wasan, D. T., Radioactive Waste Evaporation: Current Methodologies Employed for the Development, Design and Operation of Waste Evaporators at the Savannah River Site and Hanford Waste Treatment Plant. 2003, (37327), 157-170.
4. Choi, A. S.; Smith III, F. G.; McCabe, D. J. Preliminary Analysis of Species Partitioning in the DWPF Melter. Sludge batch 7A; SRNL-STI--2016-00540; Savannah River National Laboratory: Aiken, SC, 2017.
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.
7. Koopman, D. C. Comparison of Dow Corning 544 Antifoam to IIT747 Antifoam in the 1/240 SRAT; WSRC-TR-99-00377; Savannah River Technology Center: Aiken, SC, 2000.
8. Lambert, D. P.; Koopman, D. C.; Newell, J. D.; Wasan, D. T.; Nikolov, A. P.; Weinheimer, E. K., Improved Antifoam Agent Study End of Year Report, EM Project 3.2.3. 2011.
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.