A major radioactive contamination threat to the Columbia River should be removed at the Hanford nuclear site before the end of summer.
Hanford workers have started to pump contaminated water from the final basin of the nuclear reservation's nine reactors along the Columbia River.
"This effort will eliminate the risk of a leak of contaminated water to the groundwater about a quarter-mile from the Columbia River," said Andy Wiborg, the Department of Energy acting deputy assistant manager for river and plateau cleanup.
"Getting the contaminated water out of this basin is a key step in our risk-reduction mission," he said.
The Hanford nuclear reservation adjacent to Richland in Eastern Washington was used to produce about two-thirds of the plutonium for the nation's nuclear weapons program from World War II through the Cold War.
After uranium fuel was irradiated, the fuel was pushed out of the back of the reactors into indoor basins for cooling, and some of it was stored unprocessed in basins after the end of the Cold War. Sixteen-feet-deep water in the basin shielded workers as they stood on grating above the pool to move the fuel into storage bins.
Seven of the reactors have had their cooling basins demolished, and the basin at B Reactor, the nation's first full-scale nuclear reactor, is preserved as part of the Manhattan Project National Historical Park.
But the 1.2-million-gallon basin at the K West Reactor, built in the 1950s, still holds contaminated water that provides shielding for the radioactive debris in the basin.
"The 100-K West basin work, approved by the EPA, started in the 2000's with the removal of spent nuclear fuel," said Roberto Armijo, remedial project manager for the Environmental Protection Agency, the Hanford regulator for the work.
Reactor basin held radioactive sludge
The K West and K East Reactor basins were the last to be used, after storing irradiated fuel from N Reactor that was not processed following the end of the Cold War. Before the fuel was removed in 2004, it corroded underwater, contributing to a highly radioactive sludge.
In 2019 the last of the sludge was removed, leaving draining the water the next major task to reduce risk from the basins.
The nearby K East Reactor basin was emptied first.
Then in June, the first tanker truck with basin water pulled away from the K West Reactor.
About 400,000 gallons have been pumped out of the basin so far, which is the equivalent of six residential swimming pools, said Heather Dale, DOE Hanford assistant manager for the river and plateau. About 60 tanker trucks have been filled with basin water.
Workers for DOE contractor Central Plateau Cleanup Co. spent about two years preparing to drain and filter the K West Basin water.
They moved and sorted radioactive debris left in the basin since as early as the 1950s into underwater bins. The debris included canisters once used to hold fuel, canister racks, pumps, hoses, hand tools, construction materials and components of a water treatment system.
Workers stood on the grating above the water and used long-handled tools and underwater cameras for the work, which included placing some of the most radioactive debris into vertical steel tubes in the basin.
They also installed a system to pump out and then filter the contaminated water before it it loaded into tanker trucks.
The filtering system removes particles and also uses an ion exchange system to remove radioactive cesium and strontium from the water. The initial resin used in the ion exchange system did not work well, the Defense Nuclear Facilities Safety Board said in January.
But improvements were made by this summer to allow the water to meet standards to be trucked to central Hanford for final treatment to remove a small amount of remaining contaminants at the Effluent Treatment Facility.
Reactor basin to be grouted
"The work by multiple teams to characterize, sort and stage debris in the basin has made it possible for us to begin to remove the water and prepare for grouting the basin," said Mike Kruzic, who manages closure projects at the reactor area for DOE's contractor.
Once the water is removed the basin and the vertical pipe casings will be filled with concrete-like grout, which could be left to cure for a year or two. After the roof of the basin is removed, a drill rig can be brought in with an auger to blend the waste in the casings with grout.
It's a technique that was developed and successfully used previously on one of Hanford's worst underground radioactive waste sites, the 618-10 Burial Ground.
Some of the contents of the vertical pipe units in the K West Reactor basin may be required to be sent to the nation's repository for transuranic radioactive waste in New Mexico for disposal.
The rest of the grout, including the grout that fills the basin, plus the walls and floor of the basin, will be broken up with excavators and taken to a lined landfill at Hanford for disposal.
"Once the dewatering and grouting is completed, the future steps for the project will include soil remediation and cocooning of the 105-K West Reactor building," Armijo said.
The K East Reactor basin had leaked contaminated water from one of its joints into the ground, but no indication has been found of any significant leaks from the K West Reactor basin.
The final step in the coming years will be encasing the K East Reactor in a temporary steel cocoon to allow radiation in its core to decay to lower levels over 75 years before a permanent solution is attempted.
The K West Reactor will be the final Hanford reactor to be cocooned and the Tri-Party Agreement has a deadline of September 2032 for the work to be completed.
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