KENNEWICK —Emptying of another leak-prone underground tank holding radioactive and other hazardous waste at the Hanford nuclear reservation has begun for the first time since August 2021.
The Hanford site has 149 single-shell tanks built as early as World War II storing waste until it is transferred to a limited number of tanks that better guard against leaks and then treated for disposal. At least some of it will be treated at the Hanford vitrification plant under construction.
To date, 20 of those single-shell, underground tanks have been emptied to regulatory requirements, with waste transferred to 27 newer double-shell tanks.
“Seeing retrieval begin on another single-shell tank is always good news,” said Ryan Miller, spokesman for the Washington state Department of Ecology, a Hanford regulator.
“One of our agency’s biggest priorities is getting waste out of single-shell tanks, moved to safer double-shell tanks, and eventually treated and disposed of permanently in a way that’s protective of human health and the environment,” he said.
The waste is left from the past production of plutonium at Hanford, adjacent to Richland, Wash., for the nation’s nuclear weapons program through the Cold War.
Chemicals were used to separate plutonium from uranium fuel irradiated at Hanford reactors, leaving a stew of chemical and radioactive waste to be stored in the tanks.
Work has started to remove waste from Tank AX-101, one of four tanks with a 1 million-gallon capacity each in the group called the AX Tank Farm in the center of the 586-square-mile Hanford site.
Retrieval of waste from the three other tanks in the AX Tank Farm has been completed, putting it on track to be the second tank farm with retrieval finished.
The 16 tanks of the C Tank Farm already have been emptied to regulatory standards, plus one tank in the S Tank Farm.
“Operations to retrieve and finish the second farm at the Hanford site reflect our ongoing commitment to the community, the environment and the Columbia River,” said Delmar Noyes, the Hanford Department of Energy assistant manager for tank farm work.
“This is a significant step in our mission to reduce risk on the site,” he said.
Leaking waste tanks
In the past, as many as 67 single shell tanks were suspected of leaking or spilling waste into the ground at the nuclear reservation in Eastern Washington adjacent to Richland. Two tanks are known to be leaking waste now.
The waste moves through the soil toward the ground water, which travels toward the Columbia River flowing along the border of the plutonium production portion of the Hanford site.
Tank AX-101, which is not suspected of having leaked, was built in the mid-1960s using carbon steel and reinforced concrete. Waste was added to the four AX tanks from 1969 to 1980.
The AX tank being emptied now holds 426,000 gallons of waste, including solid saltcake and sludge with the consistency of peanut butter.
Most of its liquid was removed earlier in a Hanford campaign to remove as much liquid as possible from the site’s 149 single-shell tanks, to reduce the amount of waste that could leak into the ground.
Sluicing — a procedure using high-pressure water spray — will break up the waste so it can be pumped out of the tank and transferred to a double-shell tank.
Tank farm workers operate the equipment remotely from a nearby control trailer.
Before work could start to empty the tank, DOE contractor Washington River Protection Solutions removed contaminated and outdated equipment and then began installing the equipment needed to retrieve waste.
“It has been a long preparation and installation process for this tank,” said said Wes Bryan, president of the tank farm contractor.
Tank waste level uneven
Before installing the last of three sluicers in the tank, workers lowered video cameras through a tank riser — a pipe that extends from above ground to the inside of the enclosed tank — and shot footage of the tank interior and waste surface.
The images showed the waste level was uneven, ranging from about 11 feet to nearly 14 feet deep.
A tool called a “wolverine” used water pumped through high-velocity nozzles to create a hole in the saltcake of Tank AX-101 to allow the last sluicer to be installed.
To avoid submerging the sluicer in about two feet of saltcake waste on the deeper, uneven side of the tank and potentially plugging its nozzles, workers modified a high-pressure washing system normally used to clean tank risers. Nicknamed the “wolverine,” it made a hole in the saltcake waste for the sluicer nozzles to fit.
In addition to the three sluicers, a pump and other equipment were lowered into the tank through risers to allow the start of waste removal.
Emptying the tank to regulatory standards is expected to take about a year and a half.
Next up will be the A Tank Farm, which has six tanks.
While AX-Farm retrieval activities progress, tank farm workers continue to install the infrastructure to support future waste retrieval operations there.