Re: Thorium in old lens?

[LIPTONW@dteenergy.com]

See NCRP Report No. 95, "Radiation Exposure of the U.S. Population from 
Consumer Products and Miscellaneous Sources."  Section 3.2.8.3 (page 47), 
"Camera Lenses," states:  "The presence of elevated concentrations of 
radioactive material in camera lenses has been discussed in three recent 
reports ... All three reports identify Th-232 and its progeny as the source
of 
the radioactive material..."  The report mentions one camera lens reading 3 
mrad/h gamma and 10 mrad/h beta.   
 
The NCRP has a Web page (use a search engine) with information on report 
availability. 
 
The opinions expressed are strictly mine.   
It's not about dose, it's about trust. 
 
Bill Lipton 
liptonw@dteenergy 
 
 
You wrote: 
 
 
   > Hello. 
 
    >I have recently come across a lens system with the term "Rodenstock 
    >TV-Heligon" inscribed on it.  What is interesting about this lens is 
    >that it has a contact gamma field of about 2.5 mR/h. 
 
    >I would like to determine the source of this radioactivity.  Has 
    >anyone ever heard of such a radioactive lens?  Any ideas as to why a 
    >lens would be radioactive? 
 
    >Laura Boksman 

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