Impact of Antifoam Agent Addition on Hydrogen Formation in the Hanford Waste Treatment and Immobilization Plant

Ventilation and mixing systems in the Hanford Waste Treatment and Immobilization Plant (WTP) are being designed to account for the flammable gas hydrogen that will form in process streams, just as it also does in the radioactive liquid wastes awaiting immobilization at the Hanford Tank Farms. Tank wastes forming hydrogen at the highest rates do so by reactions involving dissolved organic complexant compounds, even though hydrogen is also formed by the better known radiolysis pathway. Hydrogen generation rates (HGRs) are predicted with a correlation relating waste properties to reaction pathways involving radiolysis of water and the degradation of organic compounds. This correlation accounts only for aqueous phase reactions. An antifoam agent (AFA) will be added to waste processed in the WTP. This organic liquid mixture is immiscible in aqueous systems and will therefore form a nonaqueous phase liquid layer on the processed waste, unless some of its compounds are unstable in the hostile physical/chemical environment and break down into soluble degradation products. Dissolved organic species increase the organic source term in the WTP HGR correlation, but the correlation requires adaptation to address hydrogen formed from immiscible organic liquids. Here, we report our initial evaluation of the hydrogen formed by ⁶⁰Co gamma irradiation of a waste simulant containing Dow Corning Q2-3183A AFA with an adapted WTP HGR correlation.