Hanford site workers have reached a key environmental cleanup milestone, emptying radioactive waste from a second tank farm.
“This is an important moment in our Hanford cleanup effort,” said Brian Vance, the Department of Energy manager for the 580-square-mile Hanford nuclear reservation.
The Department of Energy announced Tuesday that it had emptied waste from all tanks in the AX Tank Farm, a group of four underground tanks.
With the most recent of the tanks emptied, DOE now has 21 of 149 single-shell tank waste retrievals completed.
The single-shell tanks are prone to leaking radioactive and hazardous chemical waste into the ground of the Hanford nuclear reservation in Eastern Washington.
“We’re excited to see momentum continue building in cleaning up Hanford’s tank waste,” said Beth Rochette, Hanford cleanup section manager at the Washington state Department of Ecology, a Hanford regulator.
It’s been a long haul to get two tank farms emptied of radioactive waste, and 10 more tank farms still need to be emptied.
The first of the 149 single-shell tanks were emptied to regulatory standards 20 years ago, and the first of the site’s 12 single-shell tank farms was emptied in 2017.
“Mobilizing and transferring tank waste from older to newer tanks safely and efficiently continues to reduce risks to our workforce and our community,” Vance said.
The site’s 149 tanks with single-steel shells, some holding waste since World War II, are being emptied into 27 tanks with double-steel shells to contain waste if the inner shell leaks.
The Hanford site adjacent to Richland has 56 million gallons of waste stored in underground tanks until it can be treated for permanent disposal.
The waste is left from adding chemicals to uranium irradiated in Hanford nuclear reactors to separate out 74 tons of plutonium for the nation’s nuclear weapons program from World War II through the Cold War.
‘Challenging and complex’
The latest tank to be emptied is single-shell tank AX-101, built in the 1960s using carbon steel and reinforced concrete.
It is one of four in the grouping called the AX Tank Farm. Waste was added to the AX tanks, each with a capacity of 1 million gallons, from 1969 to 1980.
Washington state Department of Ecology standards required each tank to have waste removed until all that remained was about an inch of waste if it were spread evenly over the bottom of the tank.
Previously, as much of the liquid waste in the single-shell tanks as possible has been removed to limit leaking, leaving the more difficult solid waste to be removed through risers that extend from the enclosed tanks to the surface of the ground.
In addition to the four tanks in the AX Tank Farm, the 16 tanks in the C Tank Farm and one tank in the S Tank Farm have been emptied to regulatory standards.
Emptying tanks has been “some of the most challenging and complex” work of the DOE’s nationwide environmental management program, said Delmar Noyes, DOE assistant manager for Hanford tank waste operations.
Tank AX-101 had 350,000 gallons of waste when work began to empty its solid waste, mostly hard salt cake and a small amount of sludge with the consistency of peanut butter, in January 2023.
Three sluices, a pump and other equipment were lowered through risers, or narrow vertical pipes, into the tank.
Once in the tank, the sluices were extended to allow a nozzle to spray liquid as close as possible to the waste. The liquid was used to break up the waste and move it toward a pump for removal. A high-pressure water system also was used for areas where the normal sluicing stream could not break apart and for waste clinging to walls and equipment.
Workers were able to use liquid to help break up and move the waste because tank AX-101 is not one of the tanks suspected of leaking.
Leaking underground tanks
Two of Hanford’s single-shell tanks are known to be actively leaking, and in the past, as many as 67 single-shell tanks were suspected of leaking or spilling waste into the ground in central Hanford.
The waste moves through the soil toward the groundwater, which travels toward the Columbia River where it flows beside the plutonium production portion of the Hanford site.
While the tank farms operations workers have been emptying tank AX-101, construction workers have been preparing the next tank farm for retrieval, said Peggy Hamilton, retrievals manager for Washington River Protection Solutions.
Next to be tackled will be the A Tank Farm, where six underground tanks were built in the mid-50s. The AX and A Tank Farms are the two single-shell tank farms closest to the vitrification plant, which is being built and commissioned to turn much of the tank waste into a stable glass form for disposal.
Retrieval of tank A-101, which has mostly salt cake solids at about the same volume as AX-101, is planned to begin this month, thanks to the work already done by construction crews, including installing equipment and having electrical and water systems in place.
It is not an assumed or suspected leaker, but two of the A Farm tanks are. Both hold only small amounts of sludge.
Unlike the C Farm tanks, which were designed without airlift circulations, AX Tank Farms had 22 airlift circulators extending downward from the tank dome. Workers operating sluicing and other equipment from a remote control room had to carefully maneuver around them to retrieve waste.
Workers have been meticulous about managing hazards as the tank has been emptied, Noyes said.
They practiced operating a sluice around airlift circulators in a mock tank at the Hanford Cold Test Facility near Richland before starting to empty the tank.
The A Tanks have yet a different design, each with four airlift circulators attached to the floor, Hamilton said.
DOE’s next legal deadline for emptying tanks to regulatory standards is May 2028, when it must have five more tanks emptied.