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Advancing Environmental Cleanup Along the Columbia River

KE ISS cocoon complete

Metamorphosis: ‘Cocooning’ Complete for Seventh Hanford Reactor Building

RICHLAND, Wash. – Just over a year after breaking ground, crews recently completed construction of a protective enclosure, or “cocoon,” around another former plutonium production reactor at the Hanford Site, leaving just one more to go.

This EM 2022 priority, completed ahead of schedule and under budget, marks a significant accomplishment in the EM risk-reduction cleanup mission along the Columbia River.


One of EM’s key construction priorities for 2022, the huge steel structure is more than 120 feet tall and 150 feet wide. The interim safe storage structure will protect the K East Reactor building while the radioactivity in the deactivated reactor core decays over the next several decades, making it safer to complete disposition of the reactor in the future.

“Our team continues to deliver taxpayer value by safely completing projects that reduce risks to our region. This achievement is monumental and continues the exceptional progress we are making in cleaning up the Hanford site.”

Workers with the Amentum led EM contractor Central Plateau Cleanup Company (CPCCo) broke ground on the project last fall after awarding a subcontract to a local business for the work in August 2021.

Placing Panel on RoofEarlier this year, crews finished backfilling and compacting the area around the former reactor with approximately 34,000 cubic yards of sand and gravel to level the site before pouring a 6-foot-thick concrete foundation to support construction of the cocoon. The first steel columns for the enclosure were placed in mid-May with construction of the frame and installation of metal sheeting on the walls and roof continuing through the summer.

The cocoon’s design allows for routine inspections of the reactor every five years. During this “checkup,” radiation technicians will confirm that no contamination is leaving the sealed reactor core, and that nothing is entering the building from the outside. Additional safety features include new lighting between the structure and the reactor building, as well as upgraded lighting inside the building.

“I’m very proud of our team’s performance on this complex project. So many different skillsets were needed to successfully complete this work. From laborers to trades and crafts to the support of the Department and our regulators, it was a true collaborative effort, and we did it all with a spotless safety record.”

The K East Reactor operated from 1955 to 1971 and is the seventh of Hanford’s nine former reactors to be cocooned. The nearby K West Reactor will be the eighth. The ninth, the B Reactor, has been preserved as the world’s first full-scale plutonium production reactor and is part of the Manhattan Project National Historical Park. Hanford’s other six reactors were cocooned between 1998 and 2012.

John Eschenberg




John Eschenberg

President, CPCCo

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