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Re: Unidentified device
See NCRP Report No. 95, "Radiation Exposure of the U.S. Population From
Consumer Products and Miscellaneous Sources," page 47. This summarizes recent
reports on elevated Th-232 and daughters in the camera lenses. Dose rates of
up to 9.3 mR/hr were found on contact with the lens surface. The NCRP
concludes that, "If these samples are representative of Th-232 concentrations
in popular 35 mm camera lenses, this source might constitute a significant
exposure of the population...."
On a more practical level, at Fermi 2, we require anyone bringing a camera into
the restricted area to have it surveyed before entering. Otherwise, it may not
be possible to free release it. As the Eagles sing in, "Hotel California,"
"You can check out any time you like, but you can never leave..."
The opinions expressed are strictly mine.
It's not about dose, it's about trust.
Curies forever.
Bill Lipton
liptonw@dteenergy.com
"Flood, John" wrote:
> >I have heard of old camera lenses being marginally
> >radioactive (Th-232+decay products).
>
> True. At one time, thorium oxide was widely used in manufacturing glass to
> change the index of refraction for microscope and camera lenses. However,
> it hasn't been used for this in decades.
>
> Bob Flood
> Nevada Test Site
>
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