Re: Xenon-133 monitoring

["Robert Gunter" <rjgunter@icnpharm.com>]

Everyone else here at ICN has gotten into this, so I guess it must be my
turn....

About a month ago we had an unusual reading on a film badge where the response
of film under the lead filter was higher than all the other filters with no
other obvious pattern (No Cu, Al, or Open Window, or Plastic filter elevated
response).  Hmmmm....At first you think bremsstrahlung.  We spoke with the
client who said the badge was left in an area where they were using Kr-85.  The
badge definitely received a dose (as seen by the Pb pattern and difference from
the control), but the filter pattern was puzzling as there was no filter pattern
with the exception of the higher reading under the lead.

Talking with one of our Panasonic Dosimeter Experts we came across a possible
explanation.  If you irradiate a Panasonic dosimeter at 90 degrees from the
face, you can get an elevated reading on the CaS0 dosimeter under the lead.
Apparently the photons scattered off the lead and back onto the CaSO material
gave a higher signal.

Film, undergoing an immersion dose would be very sensitive to lower E photons,
expecially those scattered back into the film from the hanger and would register
much signal than otherwise.

So, my guess is that the film would be sensitive, but the dose as which you
would be able to use it is unknown because you don't have a calibration for that
type of source and geometry.  One of the things I like to say about film is that
it is very sensitive and can give you a lot of information about very low doses
and low energies that you may not see with other dosimeters.

Rob




"Engelbretson, David A." <DEngelbret@tmh.tmc.edu> on 05/17/99 12:31:46 PM

Please respond to radsafe@romulus.ehs.uiuc.edu

To:   Multiple recipients of list <radsafe@romulus.ehs.uiuc.edu>
cc:    (bcc: Robert Gunter/HQ/ICN)
Subject:  Xenon-133 monitoring




Is film used in occupational dosimetry practices very effective for
monitoring exposure to Xenon-133 gas?


David Engelbretson, MS
Assistant Radiation Safety Officer
Environmental & Radiation Safety Department
The Methodist Hospital
713-790-2761 phone
713-793-1341 fax

dengelbret@tmh.tmc.edu


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