The US Department of Energy (DOE) has completed two shipments of 2,000 gallons of treated, low-activity tank waste from the Hanford site in Washington state to be solidified in grout and permanently disposed of at Waste Control Specialists in Andrews County, Texas, and at EnergySolutions in Clive, Utah.
Hanford is home to 177 underground waste storage tanks – a legacy of nuclear weapons development and nuclear energy research during World War II and Cold War. These include 149 single-shell tanks and 28 double-shell tanks, ranging from 55,000 to 1.265m gallons in capacity. The tanks, some of which are reportedly leaking, hold 56m gallons of waste.
The work was the second phase of a demonstration project to show that at least some Hanford tank waste could be successfully grouted and disposed of offsite. Routinely grouting rather than glassifying some of the least radioactive tank waste has the potential to save billions of dollars and speed up work to retrieve the waste.
“The Test Bed Initiative (TBI) is a demonstration to evaluate a safe, effective and efficient option for accelerating environmental cleanup of the Hanford site”, said acting Hanford Deputy Manager Brian Harkins. “This successfully executed demonstration will provide valuable information options moving forward.”
The approximately 2,000 gallons of TBI waste from Tank SY-101 was treated using an in-tank filtration system to remove 99.99% of the radioactive caesium and other radionuclides. The treated waste in liquid form was then shipped in Department of Transportation compliant robust double-walled steel containers.
As well as showing that shipping low activity radioactive waste could be done from Hanford safely across multiple states, DOE demonstrated that a new system inserted inside individual tanks could separate out some of the least radioactive waste that is potentially suitable for grouting, rather than more costly treatment by vitrification. Routinely grouting rather than vitrifying some of the least radioactive tank waste has the potential to save billions of dollars and accelerate clean-up work.
“Implementation of this technology on an industrial scale has the potential to safely treat low-activity waste from Hanford tanks, solidify the waste in grout, and dispose of it offsite in a manner that would reduce risks to workers, the public and the environment consistent with industry standards”, added Harkins.
In 2017, in the initial phase of the project a TBI demonstration executed in partnership with Permafix validated the approach by treating and solidifying three gallons of low activity tank waste for disposal. The three gallons were separated out of waste at the Hanford 222-S Laboratory for grouting. However, a more efficient system was needed to separate 2,000 gallons.
In October, former Hanford tank waste contractor Washington River Protection Solutions used a pretreatment system lowered through a narrow opening into an enclosed underground tank to separate the most radioactive constituents from a portion of the waste. It used a filtration system to remove the large, undissolved solids that are highly radioactive from the waste and an ion exchange column to remove radioactive caesium 137 and some strontium.
This produced 2,000 gallons of waste that was even less radioactive that anticipated, said Katie Wong, DOE programme manager. It removed almost all of the radioactivity from the waste, she said. The pretreated waste was then loaded into containers, with half going to Texas and half going to Utah. Shipping was done by the new tank farm contractor, Hanford Tank Waste Operations and Closure.
The containers are made of double-walled stainless steel and can withstand a drop from 30 feet. They measure 4-feet high, wide and deep and can each hold 330 gallons of liquid waste. At the out-of-state facilities, the waste will be turned into a concrete-like grout for permitted and regulated disposal there.
At Hanford, DOE has already constructed a lined landfill, the Integrated Disposal Facility, for disposal of vitrified low activity waste. Because of the groundwater that flows toward the Columbia River, the Department of Ecology, a Hanford site regulator, allows only the most robust waste forms (vitrified but not grouted) for disposal at Hanford. However, Ecology supported the grouting demonstration project by issuing a permit for the waste management activities at Hanford before it was shipped out of state.
Both the EnergySolutions disposal facility in Utah and the Waste Control Specialists disposal facility in Texas are in areas where the geography is conducive to disposal that is more protective of the environment than at Hanford.
