RE: A "dirty bomb" question

["Jaro" <jaro-10kbq@sympatico.ca>]

The smoke detectors I've looked into (literally) have the Am-241 source

placed inside a little metal box, as Dimiter says.



I would just add that the source itself was, in that case a metal disc,

about 1.5 inches in diameter.

Moreover, although it wasn't labeled, my GM counter detected the Am-241 on

one side of the disc only -- the other side gave no reading (I suspect I was

getting the alphas).



 Jaro

^^^^^^^^^^^^^^^^^^^^^



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

From: owner-radsafe@list.vanderbilt.edu

[mailto:owner-radsafe@list.vanderbilt.edu]On Behalf Of Dimiter Popoff

Sent: Tuesday, October 28, 2003 3:00 PM

To: radsafe@list.vanderbilt.edu

Subject: Re: A "dirty bomb" question





 The 241Am 59.5 keV gamma peak is well pronounced (apr. 36% yield), there

are

also some with much lower yield at lower energies (apr. 2.3% @ 26 keV

etc.).

 However, the 241Am smoke detector sources I have seen are mounted in a

thick brass housing which would probably make them undetectable

with a GM tube. A source which was doing 40 kCpS on a Ge detector,

when turned with the brass side to the detector was de facto invisible

(well, I did not have the patience to collect an hours spectrum on that,

I was using and not evaluating the source). Anyway, the GM counter

is unlikely to be very useful around a closed smoke detector.



Dimiter



--------------------------------------------------------------------

Dimiter Popoff

Transgalactic Instruments, Gourko Str. 25 b, 1000 Sofia, Bulgaria

http://transgalactic.freeyellow.com





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