Work under way to cocoon N Reactor

By Annette Cary, Herald staff writerApril 27, 2011 

Work is under way to cocoon Hanford's N Reactor, the nuclear reservation's most modern plutonium production reactor and one that repeatedly made national news.

It was the nation's only reactor to produce both plutonium and power, drawing President John F. Kennedy for a visit shortly before his assassination.

N Reactor was back in the news 25 years ago this week, when the Chernobyl nuclear reactor unit 4 exploded and the Department of Energy was pressured to shut down the last Hanford reactor because of perceived similarities to the Russian plant.

Today, N Reactor is fast becoming just a part of history.

The heat exchanger building attached to the reactor has been cocooned and work has begun to cocoon the reactor, DOE contractor Washington Closure Hanford announced Tuesday.

"We're ahead of schedule," said Gary Snow, deputy director of deactivation and demolition for Washington Closure. He expects cocooning to be finished by the end of the year, well ahead of a legal deadline of September 2012.

Cocooning is the process DOE is using to put all of Hanford's plutonium production reactors, except the historic B Reactor, into long-term storage. The reactors are torn down to little more than their radioactive cores, the remaining structures are reroofed and openings are sealed up.

Then they are left for up to 75 years to allow radioactivity to decay to more manageable levels.

"This is the sixth reactor we'll have cocooned at Hanford and certainly the largest by far," said Cameron Hardy, DOE spokesman.

The five Hanford reactors cocooned so far -- D, DR, F, C and H -- largely are cookie-cutter copies of each other.

But the N Reactor complex, when cocooned, will be about three times larger than the other cocooned reactors.

Construction began in 1959 to build N Reactor to produce plutonium for nuclear weapons. The ninth production reactor at Hanford, it was designed to take advantage of new technologies and address concerns about radioactive materials that were released into the Columbia River by older reactors.

But with a push from the late U.S. Sen. Henry "Scoop" Jackson, D-Wash., the project was expanded to include power production.

Water used to cool the reactor, which became radioactively contaminated, got hot enough to heat clean water in the adjoining building that is been cocooned, the heat exchanger building.

Steam then was sent through pipes on a trestle to the nearby Hanford Generating Plant.

Kennedy visited Hanford on Sept. 26, 1963, two months before his assassination, to speak at the ground-breaking for the power production plant.

"A nation dedicated to living in peace is forging, not a sword but a plowshare, the Hanford Generating Plant," he said.

Steam from the plant produced enough electricity for about 650,000 homes.

N Reactor ultimately was decommissioned in 1989, not because of pressure from the Chernobyl disaster but because the nation had enough plutonium, said Mike Lawrence, DOE's manager of Hanford at the time.

As word spread of the Chernobyl disaster April 26, 1986, national reporters gathered at the Richland Federal Building with questions about the similarities between the Chernobyl reactor and N Reactor, the only Hanford production reactor that had not been permanently shut down.

Despite similarities that only were superficial, "(N Reactor) drew tremendous attention and tremendous pressure" to shut down, Lawrence said.

Both reactors used graphite to moderate the nuclear reactions, and unlike commercial nuclear power reactors in the United States, neither had a large containment dome.

But unlike the Chernobyl reactor, N Reactor had a confinement system that allowed venting through filters to relieve pressure and had heavy concrete construction, Lawrence said.

He recalls how he took the reporters out to the reactor and showed them the 4-foot thick concrete construction, including the heavy concrete doors.

Upgrades were done after the Chernobyl disaster and the plant did operate at least briefly before the nation decided its stockpiles of plutonium were sufficient to end production, Lawrence said.

Now, as part of cocooning, the 80-foot tall reactor has been torn down to little more than its radioactive core and its face, where fuel assemblies were held, is exposed. The holes have been plugged and sealed.

Work also is under way to clean up about 140 waste sites and buried piping around the reactor.

"This is the last reactor built so we had pretty good historical drawings," said Mark Buckmaster, Washington closure project manager for field remediation of the reactor area.

Work is just starting to dig up six miles of piping, the largest of which were 9-foot diameter pipes used for water intake. Most of the piping is wrapped in asbestos and some of it is radiologically and chemically contaminated from carrying discharge.

However, unlike earlier Hanford reactors, there are no major burial grounds at N Reactor holding radioactive debris.

DOE has a December 2012 legal deadline to finish cleanup of the waste sites associated with N Reactor.

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