Re: Thorium in old lens?

["Frederic Dawson" <ydc90@dial.pipex.com>]

Many camera lenses have thorium; doses can be significant if the lens are in
the eye piece
e.g. periscopes

I understand that Thorium is used to improved the optical qualities of the
lens.

I have come across numerous examples of commercial lenses and military lens
(Photo reconnaissance) that are radioactive. I might have a couple of papers
at my office if your interested

-----Original Message-----
From: Laura_Boksman@cameco.com <Laura_Boksman@cameco.com>
To: Multiple recipients of list <radsafe@romulus.ehs.uiuc.edu>
Date: 15 February 1999 15:53
Subject: Thorium in old lens?


>
>
>
>    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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