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criticality incident in 1972 or 73? [FW]
> http://www.thehawkeye.com/daily/stories/ln10068.html
> Local News: 6/10/2001
>
> Reports of 'blue flash' studied
>
> By Dennis J. Carroll
> The Hawk Eye
>
> * Scientists offer varying theories about what may have caused event.
>
> Federal and state regulators are investigating the possibility that a
> runaway nuclear chain reaction at the Middletown munitions plant in the
> early 1970s released a large burst of radiation that may have killed two
> workers and sent large amounts of radiation into the environment.
>
> One regulator, Dan McGhee of the Radiological Bureau of the Iowa
> Department of Public Health, said there appears to be "a 50-50 chance"
> that a nuclear "criticality" occurred in which people were killed.
>
> According to Department of Energy reports, a criticality accident occurs
> when the minimal amount of fissionable material necessary to sustain a
> nuclear reaction inadvertently comes together, setting off the chain
> reaction.
>
> There is a sudden release of energy and deadly radiation, but not
> necessarily an explosion.
>
> Such an event is accompanied by a blue flash of light or a glow that can
> linger for some time.
>
> It is thought that if such an event did occur at the Iowa Army Ammunition
> Plant, it may have occurred in one of the areas used to assemble and
> disassemble nuclear bombs.
>
> In the entire Atomic Age, there have been only 60 documented criticality
> events reported worldwide, according to scientists at the Los Alamos
> National Laboratory in New Mexico, and only 21 fatalities reported since
> 1945.
>
> Such an occurrence at the Middletown plant is not listed among those
> events, as published in a 2000 update of "A Review of Criticality
> Accidents" by the Los Alamos lab and Russian nuclear experts.
>
> Investigators, who include the Iowa Department of Public Health, the
> Environmental Protection Agency and the U.S. Army Corps of Engineers, have
> centered their probe around information contained in recently declassified
> documents and the accounts of former IAAP workers who said they witnessed
> or were familiar with the event.
>
> Pinning down a date has been difficult, but the reported flash is believed
> to have occurred in the summer of 1972 or 1973, according to researchers
> at the University of Iowa College Public Health who have talked with
> former nuclear weapons workers who said they saw or knew of the flash.
>
> A report from the university survey team includes the account of a worker
> who said he witnessed a blue flash in a nuclear assembly room, then helped
> two injured workers who later died.
>
> However, former workers remain reluctant to say much more -- assuming they
> know more -- and the reported victims have not been identified.
>
> One is said to have died the day after the flash, the other a year later.
>
> Nuclear weapons were assembled and, in later years, disassembled at
> Middletown in circular reinforced-concrete rooms, about 30 feet wide. The
> rooms were surrounded by earth and topped with tons of gravel to contain
> radiation from possible nuclear explosions or other radiation releases.
>
> Daniel Bullen, former director of the nuclear reactor program at Iowa
> State University, said it is unlikely that a criticality would have
> occurred during the assembly or disassembly of a nuclear weapon.
>
> "I would be extremely skeptical," he said.
>
> Bullen is not involved in the IAAP investigation.
>
> Other nuclear scientists have said such a glow could have been caused by a
> chemical fluorescence or phosphorescence or a glow from tritium -- a
> radioactive material sometimes handled by IAAP nuclear workers.
>
> Scott Marquess, project manager for the EPA Superfund cleanup at the Iowa
> Army Ammunition Plant, said his agency is trying to determine whether
> there are residual signs of such a criticality that would remain nearly 30
> years later.
>
> For example, it is considered possible that fission materials from a
> criticality still might be embedded in nearby glass, and there still could
> be lingering radiation.
>
> Bill Field, radiation expert with the university's team surveying the
> health of former IAAP nuclear workers, said the blue flash or glow seen by
> workers could have been what is known as Cerenkov radiation, in which
> charged radioactive particles traveling faster than the speed of light
> from a fission reaction release a blue glow.
>
> That often is observed at nuclear power plants when spent nuclear rods are
> submerged in water, but that is a controlled environment.
>
> In an April letter to Army officials urging a aerial radiological survey
> of the plant, Gov. Tom Vilsack cited recently declassified documents that
> he said refer to plutonium, "ground zero" and "an incident that may have
> led to contamination" in the early 1970s.
>
> It has not be determined whether that "incident" was the blue flash seen
> by workers.
>
> The Atomic Energy Commission assembled, test-fired and in later years,
> disassembled nuclear weapons and their components at IAAP from the late
> 1940s to the mid 1970s.
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