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Safety and explosives factors in N Reactor cleanup

06.23.2008

The U.S. Department of Energy (DOE) today announced two large stacks of the N Reactor and heavy steam-generating equipment in an adjacent powerhouse were demolished. Using explosives, workers safely achieved this demolition milestone at N Reactor over the weekend.

N Reactor is one of nine reactors that once produced plutonium at the Hanford Site in southeast Washington State, and this weekend’s work brings the N Reactor one step closer to its final chapter.

“The demolition work at N Reactor is key to dismantling and removing structures around the reactor itself so we can safely prepare the reactor for cocooning “said Kurt Kehler, Washington Closure Hanford D4 Project Manager. “It takes months of planning and preparation to get ready for a demolition project. In this case, using explosives was the safest option for our workers.”

The use of explosives reduced the time workers and machinery will spend removing the two stacks and the powerhouse building. The demolished 116-N stack once stood 200 feet tall and ventilated filtered exhaust from N Reactor during its operation from 1964 to 1987. The other stack once stood 55 feet above the 184-N Powerhouse, a facility that produced steam for generating electricity. Explosives were also used to drop heavy steam-generating equipment from the upper floors of the powerhouse to the lower levels, thereby making it more accessible to conventional demolition machinery. Prior to and during demolition, workers surveyed the facilities to verify that contamination was below regulatory levels of concern.

“N Reactor is the last of the reactors at Hanford to operate during the Cold War,” said Joe Franco, Assistant Manager for River Corridor, Department of Energy Richland Operations Office. “This demolition activity is an important and visible step in cleaning up Hanford and shrinking our environmental footprint, as well as the skyline along the Columbia River.”

Controlled Demolition Inc. (working under Clauss Construction) performed the demolition work for Washington Closure Hanford and has conducted demolition using explosives at other Hanford reactor sites, as well as at several other nuclear facilities, including Rocky Flats, Idaho, Fernald, and the Maine Yankee Nuclear Power Station. Washington Closure Hanford manages the River Corridor Closure Project for the U.S. Department of Energy’s Richland Operations Office and is responsible for demolishing 486 buildings, cleaning up 370 buried waste sites, placing four reactors in interim safe storage, and operating the Hanford Site’s Environmental Restoration Disposal Facility.

More About N Reactor

N Reactor began operations in 1964. At the time, it was the largest reactor in the world and the United States’ only dual-purpose reactor, meaning it produced plutonium for weapons and steam for electricity. It continued operating until the Chernobyl accident in 1986 and was permanently shut down in 1989.

About 50 outbuildings and other facilities that supported N Reactor operations have been demolished in accordance with regulatory agreements in order to allow final 100-N area remediation, as well as to prepare for cocooning N reactor. Interim safe storage – or cocooning – is the process isolating radioactive contents from the environment by demolishing all but the essential shield walls, sealing all openings and replacing the roof of the reactor.

Reactors C, D, DR, F, and H have already been cocooned and will remain in that state for up to 75 years, giving the DOE, regulatory agencies, and the public time to decide on their ultimate disposition. Washington Closure is expected to cocoon N Reactor by 2012.

At N Area, more than just the reactor building, which contains the radioactive core, will be cocooned. Since the facility was a dual-purpose reactor, it had a six steam generators not present in the other reactors. In addition to the 105-N Reactor building itself, Washington Closure will also cocoon the 109-N Building, which contains steam generators that were contaminated during reactor operations. The portion of the 105-N building that supported maintenance and contained office space will be demolished prior to cocooning.

Background - Explosive Demolition at N Reactor