The Department of Energy plans to announce Thursday that Hanford's unique N Reactor has been cocooned.
David Huizenga, the DOE senior advisor for environmental management, will visit the reactor and make the announcement. Huizenga is visiting the Tri-Cities with Energy Secretary Steven Chu, who will be here Thursday and Friday.
N Reactor has been cocooned, or put in temporary storage, in a process that includes tearing down as much as possible of the reactor and its support structures and then sealing up what remains, including the attached heat exchanger building.
It is planned to remain cocooned for up to 75 years to allow radioactivity to decay to more manageable levels.
N Reactor was Hanford's longest-running and most modern plutonium production reactor. It operated from 1963 to 1987.
It is the only reactor to produce weapons plutonium and power for utility customers, prompting President John F. Kennedy to visit shortly before his assassination.
The cocooned N Reactor complex is about three times larger than previously cocooned reactors at Hanford because of the attached heat exchanger building needed for power production.
DOE has cocooned six reactors, including N Reactor, and has started work to cocoon the K East Reactor.
That will leave only the K West Reactor to be cocooned after radioactive sludge is removed from water in its attached basin.
Hanford's ninth plutonium-production reactor, B Reactor, is being preserved as a museum.