In-Situ Remediation of Mixed Radioactive Tank Waste, Via Air Sparging and Poly-Acrylate Solidification

This paper describes remediation activities performed in accordance with the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) on an underground storage tank (UST) from the Idaho National Laboratory’s Test Area North (TAN) complex. The UST had been used to collect radioactive liquid wastes from and for the TAN evaporator. Recent analyses had found that the residual waste in Tank V-14 had contained quantities of tetrachloroethylene (PCE) in excess of F001 treatment standards. In addition, the residual waste in Tank V-14 was not completely solidified. As a result, further remediation and solidification of the waste was required before the tank could be properly disposed of at the Idaho CERCLA Disposal Facility (ICDF). Remediation of the PCE-contaminated waste in Tank V-14 was performed by first adding sufficient water to fluidize the residual waste in the tank. This was followed by high-volume, in-situ air sparging of the fluidized waste, using air lances that were inserted to the bottom of V-14. The high-volume air sparging removed residual PCE from the fluidized waste, collecting it on granular activated carbon filters within the off-gas system. The sparged waste was then solidified by educting large-diameter crystals of an acrylic acrylate resin manufactured by WaterWorks America into the fluidized waste, via the airsparging lances. To improve solidification, the air-sparging lances were rotated during the eduction step, while continuing to provide high-volume air flow into the waste. Eduction was continued until the waste had solidified sufficiently to not allow for further eduction of WaterWorks crystals into the waste. The tank was then disposed of at the ICDF, with the residual void volume in the tank filled with cement.