For the first time in a decade, the reactor at the Hanford site has become a cocoon.
The addition of a new steel enclosure to the 1950s reactor was a “symbolic change in the landscape” of the Columbia River Nuclear Reserve, helping to protect the river, said contractors from the Department of Energy. said John Eschenberg, president of Central Plateau Cleanup.
Eight of the nine plutonium-producing reactors along the Columbia River in eastern Washington state have been placed on temporary hold for up to 75 years to attenuate core radiation to lower levels before permanent solutions are attempted. stored properly.
With straight sides and a sloping roof, the newest cocoon is very different from other cocoon reactors that retain much of the reactor’s original shape, creating a new look for Hanford’s skyline. .
Once the K-East reactor cocoon is complete, there will be only one more cocoon to be made at Hanford.
The K-East reactor is Unit 7, and its twin, the K-West reactor, was not expected to cocoon until around 2030.
A ninth reactor, Reactor B, will be unsealed and open to tour as part of the Manhattan Project Historical National Park.
From World War II to the Cold War, Hanford produced about two-thirds of the plutonium for the country’s nuclear weapons program.
Production stopped with the end of the Cold War, and the country now spends more than $2.5 billion a year on environmental cleanup efforts on Richland’s 580-square-mile nuclear reserve.
At the K-East reactor, Hanford officials say a new form of temporary storage will be implemented in the coming decades, which they hope will save money and better protect the reactor while it awaits final disposal. used.
No decision has yet been made on final plans to dispose of Hanford’s defunct reactors, but attenuating the radiation will provide a safer environment for workers.
In Hanford’s traditional cocoon, the reactor is demolished for a little less than the radioactive core, all openings are sealed, and the roof is put back on.
New Reactor Cocoon
But at the K-East Reactor, a new free-standing structure, 123 feet high and about 154 feet wide, was built on top of the reactor for the first time.
Eschenberg says the cocoon’s new method should better protect the nearly 80-year-old reactor concrete from wind, sand, and the freeze-thaw cycles that damage Hanford’s structures.
It should also reduce the need for roof maintenance.
The new steel enclosure was designed to last 75 years, but final disposal of the reactor won’t be too late, Eschenberg said. No decision has been made as to what the final disposition will be.
Every five years, Hanford workers enter the reactor to check its condition.
Installed inside the reactor and between the iron cocoons and the original reactor wall, new lighting allows workers to check the condition of the concrete, look for rodents and other animals, and make sure there is no water intrusion. Useful for easy verification.
Not only was the cocoon construction job done safely, but the project was completed months ahead of schedule and well under budget, said Brian, DOE Office of River Protection and Richland Operations Office Manager. says Vance.
A budget of $13.5 million was set for cocooning the reactor, but it was completed for $9.5 million, Eschenberg said.
The project fell short of budget last year despite problems with the country’s supply chain and rising steel costs.
The project used 620 tons of structural steel.
Good planning, efficient work, and the performance of employees and businesses in eastern Washington are keeping costs flat, he said.
The Central Plateau Cleanup Co. hired Richland’s DGR Grant as a cocooning contractor. Earthwork was done by Watts Construction of Kennewick, electrical work was done by American Electric Company of Richland, and steel supply and erection was done by American Ironworks and Erectors of Spokane.
Eschenberg also praised the work of the craftsmen of the Central Washington Council of Construction and Building Trades.
Decades of cleanup before cocooning
The first work on the K-East reactor, which operated from 1955 to 1971, began decades ago to enable cocooning of the reactor.
The K West and K East reactor reservoirs were used to store irradiated uranium fuel in the N reactors, but were not treated to remove the plutonium at the end of the Cold War.
Fuel was removed from two basins, each holding 1.2 million gallons of water, in a 10-year project completed in 2004.
But the fuel decayed after decades in water, leaving a highly radioactive sludge that wasn’t transported to dry storage at Hanford’s T plant until 2019 after it was first integrated at the K-West reactor. rice field.
Water was then discharged from the K-East reactor basin, which has not yet been done in the K-West reactor. The dry K-East reactor basin was filled with grout and the grout was cut into pieces and removed, requiring the site to be backfilled.
A village of support structures, including a nuclear power plant and a fuel oil depot, had to be demolished. In addition, the settling basins used for reactor cooling water had to be cleaned.
Tens of thousands of tons of contaminated soil and debris were removed and most of it was taken to a huge landfill in central Hanford for disposal.
Most of the soil contamination was due to chromium used as a corrosion inhibitor in reactor water. Chromium-contaminated groundwater is pumped, cleaned, and returned to the ground before entering the Columbia River, approximately 300 yards from the K reactor.
The reactor structure was ready for cocooning by removing the asbestos and isolating the electrical system.
The cocoon took about a year
DGR Grant was awarded the cocoon contract in August 2021, and the work took just over a year.
Earlier this year, crews completed backfilling and compaction around the K East reactor, using approximately 34,000 cubic yards of sand and gravel to level the site.
A six-foot base was then poured to support the construction of the cocoon.
“The new approach does not rely on any of the existing (reactor) structures to support the new cocoon structure,” said Eschenberg.
Cocoon’s first steel columns were installed in mid-May, and construction of the frame and installation of metal sheets to the walls and roof continued through the summer.
Many of Hanford’s other environmental cleanup workers, such as emptying underground waste tanks and cleaning up contaminated groundwater, are less visible.
“The skyline change is impressive for everyone,” said Vance.
This story was originally published October 26, 2022 at 4:35 PM.
