The Rocky Flats Plant, a former United States nuclear weapons production facility located about 15 miles (24 km) northwest of Denver, Colorado, caused radioactive contamination (primarily from plutonium, americium, and uranium) within and outside its boundaries. The contamination primarily resulted from two major plutonium fires in 1957 and 1969 (plutonium is pyrophoric, and shavings can spontaneously combust) and from wind-blown plutonium that leaked from barrels of radioactive waste. Much lower concentrations of radioactive isotopes were released throughout the operational life of the plant from 1952 to 1992, from smaller accidents and from normal operational releases of plutonium particles too small to be filtered. Prevailing winds from the plant carried airborne contamination south and east, into populated areas northwest of Denver. The contamination of the Denver area by plutonium from the fires and other sources was not publicly reported until the 1970s. According to a 1972 study coauthored by Edward Martell, "In the more densely populated areas of Denver, the Pu contamination level in surface soils is several times fallout", and the plutonium contamination "just east of the Rocky Flats plant ranges up to hundreds of times that from nuclear tests." As noted by Carl Johnson in Ambio, "Exposures of a large population in the Denver area to plutonium and other radionuclides in the exhaust plumes from the plant date back to 1953." Weapons production at the plant was halted after a combined FBI and EPA raid in 1989 and years of protests. The plant has since been shut down, with its buildings demolished and completely removed from the site. The Rocky Flats Plant was declared a Superfund site in 1989 and began its transformation to a cleanup site in February 1992. Removal of the plant and surface contamination was largely completed in the late 1990s and early 2000s. Nearly all underground contamination was left in place, and measurable radioactive environmental contamination in and around Rocky Flats will probably persist for thousands of years. The land formerly occupied by the plant is now the Rocky Flats National Wildlife Refuge. Plans to make this refuge accessible for recreation have been repeatedly delayed due to lack of funding and protested by citizen organizations. The Department of Energy continues to fund monitoring of the site, but private groups and researchers remain concerned about the extent and long-term public health consequences of the contamination. Estimates of the public health risk caused by the contamination vary significantly, with accusations that the United States government is being too secretive and that citizen activists are being alarmist.
Background
The Rocky Flats Plant was south of Boulder, Colorado, and northwest of Denver. Originally under the Dow Chemical Company's management, it was transferred to Rockwell in 1975. It initially had an area of 4 sq mi (10 km2); a 4,600 acres (19 km2) buffer zone was added in 1972. Construction of the first buildings began on July 10, 1951. Production of parts for nuclear weapons began in 1953. At the time, the precise nature of the work at Rocky Flats was a closely guarded secret. The plant produced fission cores for nuclear weapons, used to "ignite" fusion and fissionable fuel. Fission cores resemble miniaturized versions of the Fat Man nuclear bomb detonated above Nagasaki. They are often called "triggers" in official and news documents to obfuscate their function. For much of its operational lifetime, Rocky Flats was the sole mass-producer of plutonium components for the United States' nuclear stockpile. Management of the site passed to EG&G in 1990, which did not reapply for the contract in 1994. Management of the site passed to the Kaiser-Hill Company on July 1, 1995. The Department of Energy now manages the central portion of the site, where the production buildings once were, while the Fish and Wildlife Service has taken over management of the Peripheral Outer Unit.
Sources of contamination Most of the radioactive contamination from Rocky Flats came from three sources: a catastrophic fire in 1957, leaking barrels in an outdoor storage area in 1964–1968, and another, less severe fire in 1969. Plutonium, used to construct the weapons' fissile components, can spontaneously combust at room temperature in air. Additional sources of actinide contamination include inadequate pondcrete vitrification attempts and routine releases during the plant's operation.
1957 fire
On the evening of September 11, 1957, plutonium shavings in a glove box in building 771, the Plutonium Recovery and Fabrication Facility, spontaneously ignited (plutonium is pyrophoric). The fire spread to the flammable glove box materials, including plexiglas windows and rubber gloves. It rapidly spread through the interconnected glove boxes and ignited a large bank of high-efficiency particulate air (HEPA) filters in a plenum downstream. Within minutes the first filters had burned out, allowing plutonium particles to escape from the building exhaust stacks. The building exhaust fans stopped operating due to fire damage at 10:40 PM, which ended most of the plutonium release. Firefighters initially used carbon dioxide fire extinguishers because water can act as a moderator and cause plutonium to go critical. They resorted to water hoses when the dry fire extinguishers proved ineffective. The 1957 fire released 11–36 Ci (160–510 grams or 0.35–1.12 pounds) of plutonium, much of which contaminated off-site areas as microscopic particles entrained in smoke from the fire. Isopleth diagrams from studies show parts of Denver in the area where surface sampling detected plutonium. That the fire had resulted in significant plutonium contamination of surrounding populated areas remained secret. News reports at the time reported, per the Atomic Energy Commission's briefing, that there was slight risk of light contamination and that no firefighters had been contaminated. No abnormal radioactivity was reported by the Colorado Public Health Service.
Pad 903 leakage
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