Re: plutonium detection

[Chris Alston <alstonc@odrge.odr.georgetown.edu>]

One way is with an alpha scintillometer. The probe, which may look a lot
like a vacuum cleaner attachment, contains a sheet of ZnS(Ag), behind an
extremely thin, ~3mg cm^-2 aluminized Mylar, light and abrasion/moisture
shield. The photonic emissions, that result when the ZnS is tickled by the
alphas, are conducted by a light pipe to a PMT. The signal from that can go
to an ordinary ratemeter. An individual, or object, can be monitored exactly
as one does with a G-M probe, i.e., by holding the probe as closely as
possible to the surface and moving it slowly along. The active area of a
typical probe-face is 50-100 cm, and a 4 Pi efficiency of 15% would be
reasonable for Pu239. Geometrically similar probes are available, that
operate on the gas proportional principle.

chris alston
alstonc@odrge.odr.georgetown.edu
I do not here represent my employer.


At 11:35  03/12/98 -0600, you wrote:
>I'm often cautious about showing my ignorance, but I think I know 
>most of what I need to carry out my university RSO duties.  
>Nvertheless, I have a question.
>
> BobCherry wrote about:
>
>> LOS ALAMOS, N.M. (AP) - Small amounts of plutonium were found on the clothing
>of four Los Alamos National Laboratory workers after the radioactive element
>leaked from a container they were cleaning.
>The release was ``somewhere between pollen and a particle of cigarette
>smoke,'' Danneskiold said.>
>
>How is plutonium contamination routinely checked for?  My 
>understanding is that those big 'ol alphas have trouble getting 
>through air.  I know that when I do wipe tests for alpha emitters I 
>have to use a vacuum chamber.  How are these minute amounts of 
>material checked for?
>
>HANDBELL PEOPLE have all gone campan-
>
>David F. Gilmore
>Assistant Professor of Environmental Biology   
>P.O. Box 599, Dept. of Biological Sciences  
>Arkansas State University 
>State University, AR 72467
>dgilmore@navajo.astate.edu
>ph  501-972-3082    fax 501-972-2638
>