Hanford radioactive tank cleanout and sludge processing

The Hanford Site has successfully applied sluicing for the large-scale removal of radioactive sludges from underground storage tanks. The majority of the sludge recovery effort has been focused on retrieving relatively small quantities of sludge (2000 to 4000 gallons) for batchwise dissolution and shipment to uranium or fission product separation plants. Other efforts have involved transferring sludges between million-gallon tanks. The Hanford sluicing system uses a recirculating water inventory to carry sludge from underground storage tanks to the receiver. Equipment includes a medium pressure sluice pump (175 psi) in the slurry receiver tank, and a mechanical sluicing assembly and a slurry pump in the tank being sluiced. For batchwise sludge recovery, the water/slurry mixture is recirculated until the concentration reaches the 10 to 20 percent solids range. The solids are then settled, the supernatant decanted to the sluice tank, and the solids remaining in the sludge receiver shipped to a dissolution tank for further processing. Seventy-five foot diameter underground storage tanks have been cleaned out to 2000 to 4000-gallon sludge heels