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Cocooning begins at N Reactor

04.15.2009

Washington Closure Hanford has begun placing part of N Reactor in interim safe storage, where it will remain for up to 75 years. N Reactor is the last of nine plutonium reactors to be shut down at the U.S. Department of Energy’s Hanford Site.

N Reactor began operation in 1963 and was shut down in 1987. It was the only reactor at Hanford – and the nation – to serve a dual purpose; it produced plutonium for nuclear warheads and steam for electricity.

Because it was the newest of Hanford’s reactors and had a dual purpose, it presents unique challenges. One major difference is that it contained the 109-N Heat Exchange Building, which housed the turbines and steam generators necessary to produce electricity. The 109-N Heat Exchange Building will be placed in interim safe storage, otherwise known as cocooning, along with the reactor core for N Reactor.

Cocooning involves demolishing each facility down to the four-foot-thick shield walls that surround the radioactive steam generators in the 109-N Building and the reactor core for N Reactor. Conduit penetrations and other openings are sealed with concrete or steel plates. A new roof, called a safe storage enclosure, is installed over the remaining structure. Finally heat and moisture sensors are installed to monitor remotely for fire and water.

Periodically, workers will enter the facilities to check on their condition and make any needed repairs.

Under subcontract to Washington Closure, the Wm. Dickson Co. of Tacoma, Washington, began removing equipment and other structures surrounding 109-N in December 2008. That task is scheduled to be completed in August 2009.

Installation of the roof and walls of N Reactor will begin later this year and will be completed by 2012. The N Reactor and 109-N represent the sixth of Hanford’s nine reactors to be cocooned. C Reactor was cocooned in 1998, DR in 2002, F in 2003, D in 2004 and H in 2005.

Construction of N Reactor began in 1959. The reactor began operation in 1963. It was later decided to use the reactor cooling water to produce electricity and President John F. Kennedy presided at the groundbreaking for the Hanford Generating Plant, which used N Reactor steam to generate electricity.

At its peak, N Reactor generated enough electricity to power the city of Seattle.

After the Chornobyl accident in 1986, N Reactor was shut down for upgrades because of its similarities to the Soviet reactor. Although the upgrades were completed, the reactor never operated again. It finally was decommissioned when the Cold War ended in 1989, marking the beginning of the clean-up era at Hanford.

Washington Closure manages the $2.2 billion, eight-year River Corridor Closure Project at the U.S. Department of Energy’s Hanford Site in southcentral Washington state. It is responsible for cleaning up 370 waste sites, demolishing 486 buildings and operating the 11-million-ton- capacity Environmental Restoration Disposal Facility.

Background Information

• N Reactor Fact Sheet
• N Reactor Photos