The Department of Energy announced that it has determined that an underground single-shell waste tank at its Hanford Site near Richland, Wash., is likely leaking into the soil beneath the tank. The DOE said that the leaking tank poses no increased health or safety risk to the Hanford workforce or the public.
The determination was made after monthly monitoring detected a small drop in the level of liquid in the tank, equivalent to approximately 3.5 gallons per day. A formal leak assessment began in July 2020 and concluded on April 29, when the DOE made the announcement.
The DOE said that the Washington State Department of Ecology and the U.S. Environmental Protection Agency have been notified of the leak at Tank B-109, which was previously emptied of pumpable liquids, leaving a very small amount of liquid waste in the tank.
Hanford’s tanks: A total of 149 single-shell tanks were built at Hanford between 1943 and 1964 to hold chemical and radioactive liquid waste generated from the production of plutonium for the U.S. nuclear arsenal. Heat generated by the waste and the composition of the waste caused an estimated 67 of these tanks to leak some of their contents into the ground. Most of the waste from the single-shell tanks has been pumped to 28 sturdier double-shell tanks that were built between 1968 and 1986.
One double-shell tank, AY-102, was emptied and taken out of service after it was discovered in 2012 that waste was leaking into the annulus between the primary and secondary tanks.
Mitigation efforts: Because of the previous leaking single-shell tanks, mitigation actions have been in place at Hanford for decades. Active groundwater treatment systems operating in the B Complex area, where Tank B-109 is located, were installed several years ago to capture and treat contamination resulting from the discharge of approximately 52 million gallons of contaminated liquids to the soil surrounding the tank farm during historical operations, the DOE said.
The water table in the area ranges from 210 to240 feet below Tank B-109. The DOE estimates that it could take more than 25 years for any contamination from the tank to reach the water table, and it would then be captured and removed by the pump and treat systems.
The DOE said it is continuing to assess and explore other capabilities to reduce the release of contaminants to the environment, such as surface barriers that to prevent water from precipitation from intruding into the tank.