ROCKY FLATS - 1957

Site of September 1957 fire
Photo: Wikipedia

Rocky Flats Fire Department in April 1987.
 Photo: U.S. Energy Department

Rocky Flats was a dangerous place to work and suffered a secret September 11 disaster in the late 1950s.

The federal government's now-shuttered industrial site near Denver fabricated components for nuclear weapons, such as bomb triggers.

Due to the danger, the facility fielded its own fire department.

On Sept. 11, 1957, the spontaneous combustion of plutonium inside a processing unit started a fire that poured contamination over the Denver region.

It was "the first major plutonium fire in a United States weapons laboratory," according to the Energy Department.

Firefighters tried and failed to douse the blaze with carbon dioxide and eventually knocked down the flames with water.

It was the Cold War-era and the government hid the incident from the public under the guise of top secrecy.

Another fire broke out under similar circumstance on May 11, 1969, though the level of contamination was less than 1957.

Officials were more forthright about that incident.

The Rocky Flats Fire Department - based at Building 331 - disbanded in 2005 after the government completed decontamination of the site.

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Excerpt of Energy Department historical summary:

At 10:10 p.m. on September 11, 1957, the smell of burning rubber led two Rocky Flats Plant guards in Building 71 to a glovebox emitting eighteen-inch flames in Room 180.

At the time of the fire, Building 71 (also called "C Plant" and, later, Building 771) was an essential component of the Rocky Flats Plant. 

Designed for work with delta-phase plutonium, Building 71 opened in 1953 to recover plutonium for hydrogen bomb triggers.

The September 1957 fire, apparently caused by the spontaneous ignition of a small amount of alpha-plutonium turnings or skulls (metallic casting residues), soon spread along the Plexiglas and set off a chain of events.

Additional building personnel and Rocky Flats Plant firefighters arrived at the scene of the fire two minutes after the guards alerted them, but the time they spent donning protective clothing and debating the best course of action delayed them from combating the flames for ten minutes.

A fire department lieutenant wanted to douse the flames with water, but both a building production shift supervisor and a plant health physicist initially rejected that plan out of fear of inducing criticality.

Workers tried, unsuccessfully, to put out the fire with available carbon dioxide extinguishers.

Firefighters eventually sprayed water on the Room 180 fire and extinguished it safely.

During that interval, however, unburned combustible gases apparently passed under pressure through ventilation ductwork and ignited the filters in the building's exhaust filter plenum.

Minutes after firefighters put out the Room 180 fire, the exhaust system exploded.

On order of the health physics supervisor, everyone evacuated the building to escape plutonium contamination, which spread throughout the building and out through the ventilation system.

Outside the building, observers saw a "very dark" smoke plume, 80 to 100 feet high, billow from the stack.

Arriving at the site after the evacuation, the section superintendent ordered the firefighters to concentrate on extinguishing the filter fire, although several minor rekindlings at the original site also occurred.

At 11:10 p.m., Building 71's electrical power failed, the darkness hampering all efforts. By late the next morning, most of the filter bank and the alpha-phase interim facility in Room 180 had been destroyed.

During the final hours of the fire, Rocky Flats personnel discovered burning cylinders of nickel carbonyl inside the exhaust plenum and cooled them with water.

The nickel carbonyl was used to provide a protective nickel coating to plutonium components so they could be handled in the open with less risk of personnel exposure to contamination or build up of static electricity.

A production section superintendent subsequently directed employees to place all the carbonyl cylinders in drums and temporarily bury the drums outside in a pit.

Thirteen hours after the guards first discovered flames, firefighters succeeded in totally extinguishing the fire at 11:28 a.m. on September 12.