RE: Unidentified device

["Kolb, William (WKOLB)" <WKOLB@arinc.com>]

While it appears thorium is not the culprit in this particular instance,

photographic lenses remain a widespread potential source. "Living With

Radiation: The First Hundred Years" lists more than 100 lenses from 35

manufacturers with surface activities ranging from about 0.1 to 15 mR/h. In

addition, the percent of thorium oxide by weight is given for specific

glasses manufactured by Kodak and Schott. Kodak ceased production of thorium

glass in the 1980s, incurring a cost in millions for decontamination of

their facilities.



Bill

WM Kolb

ARINC Inc.



-----Original Message-----

From: William V Lipton [mailto:liptonw@DTEENERGY.COM] 

Sent: Friday, September 26, 2003 7:14 AM

To: Flood, John

Cc: 'NIXON, Grant (Kanata)'; 'Todd Brautigam'; radsafe@list.vanderbilt.edu

Subject: 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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