RICHLAND — Hanford workers are expected to begin pumping radioactive waste from a leak-prone underground tank at Hanford for the first time in nearly two years.
Work is scheduled to begin this weekend to empty several of the 10 single-shell tanks in the adjoining groups of tanks called the A and AX Tank Farms at the nuclear reservation north of Richland.
The Washington state Department of Ecology, the regulator on the project, called it “the beginning of another significant phase in the Hanford cleanup.”
The waste, which also includes hazardous, nonradioactive chemicals, will be transferred to newer double-shell tanks for storage until the waste can be treated for permanent disposal.
Work to empty an initial single-shell tank farm to regulatory standards — the C Tank Farm — was completed in November 2017 after 19 years of work on the 16 tanks.
But the Department of Energy (DOE) and its contractor, Washington River Protection Solutions, decided to pursue a new strategy on the next group of tanks.
Instead of installing infrastructure one tank at a time as was done in the C Tank Farm, workers spent several years installing all infrastructure to provide electrical power, ventilation, water and transfer lines before work starts to empty the tanks in both the A and AX Tank Farms.
Hanford officials have said the change will allow workers to quickly switch to another tank if they encounter an issue at one tank, such as the need to stop retrieval there to replace a pump.
First up will be Tank AX-102.
Unlike the C Tank Farms with tanks of 55,000 or 530,000 gallon capacity, AX-102 has a capacity of 1 million gallons.
Pumpable liquids were removed earlier in a campaign to help prevent all 149 single-shell tanks at the Hanford nuclear reservation from leaking.
The waste is left from the past chemical processing of irradiated uranium fuel to remove plutonium for the nation’s nuclear-weapons program from World War II through the Cold War.
Tank AX-102 has 30,000 gallons of waste to be removed, the majority of it salt-cake rather than the sludge with the consistency of peanut butter that was common in the C Tank Farms.
Workers will go after the waste with technology they already are experienced in using.
Pressurized water will be sprayed on the remaining waste in the tank to help dissolve the salt cake and then move the waste toward a central pump for removal and transfer to the double-shell tank AZ-102.
Two extended-reach sluicers have been lowered through risers extending from the ground into the tank to spray the water.
The project could be completed in three to four months, although there are uncertainties such as how much hardened material may be in the bottom of the tank, said Doug Greenwell, manager of single-shell tank retrieval, for Aecom-owned Washington River Protection Solutions in a message to employees.
The goal is to remove all but 360 cubic feet of waste, the equivalent of about an inch spread across the bottom of the tank.
“Well-trained personnel and proven controls for nuclear, industrial, radiological and industrial hygiene will be in place to support the project, Greenwell said.
Safety precautions will include starting the work on nights and weekends and then moving to round-the-clock operations when data on chemical vapors shows the working conditions are safe. Disturbing waste raises the possibility of the release of potentially harmful chemical vapors.
Reader boards will alert workers in the area when waste-disturbing work is in progress. Workers within the boundaries of the AX Tank Farm will wear supplied air respirators as protection against breathing in the vapors.
The work will help build up the inventory of waste available to send to the $17 billion vitrification plant under construction, DOE said in a statement.
It plans to start sending some low-activity radioactive tank waste to the plant to be turned into a stable glass-waste form by a federal-court ordered deadline of 2023.
DOE also has court-ordered deadlines for emptying all but one of the tanks in the A and AX Tank Farms by September 2026.
“We’re glad to see work beginning to retrieve the waste from another set of Hanford’s underground tanks,” said Nina Menard, cleanup section manager for the Department of Ecology’s Nuclear Waste Program.
“We’ve been working with Energy to approve plans for the retrievals and make sure that appropriate permits are in place for this work,” she said.
Tank AX-102 is not suspected of leaking in the past, but two of the A Farm tanks are suspected to be leaking, and care must be taken to limit the liquid added to the tanks during retrieval.
When Tank AX-102 is emptied to regulatory standards, it will bring the total emptied to 18 single-shell tanks and one double-shell tank that sprang a leak from its inner shell. In addition to the 16 C Farm tanks, single-shell Tank S-112 has been emptied.