The Use of Viscous Liquid Grouts for Temporary Repair at Underground High-Level Waste Storage Tanks at Hanford during Sludge Removal

70623 Leakage of contaminants during the removal of sludge from underground storage tanks at DOE¿s Hanford facility poses a serious risk to the environment. Contaminated sludge is planned for removal by sluicing the tanks with liquid (water) to dislodge the sludge and then pumping from the tank. Unfortunately, as a result of tank deterioration, the potential exists for the release of a large volume of radioactive contaminants into the subsurface that can migrate to the groundwater. This project will develop technology for injecting viscous liquid grout in the subsurface area around the tank(s) to prevent the release of contaminants mobilized by the sluicing of the tanks for sludge removal. In Phase I, a series of injection and column tests are proposed on two types of viscous grouts, colloidal silica and polysiloxane, to determine injectability and compatibility with the subsurface soils at Hanford. Test measurements will include gel time, gel strength, and cure time and properties. Hydraulic conductivity testing will be performed after curing of the grout to determine soil hydraulic conductivity. Commercial Applications and Other Benefits as described by the awardee: The subsurface sealing material would allow for the emplacement of a containment barrier around suspected leaking tanks to control and prevent the release of subsurface contamination during sludge and tank removal. Compared to excavation and disposal of highly contaminated soils, this technology would provide a cost-effective method for source control and interim isolation of waste, reduce worker exposure at hazardous/radioactive sites, and allow emplacement without damaging underground infrastructure.