RE: Q:film badges and filter patterns

["M. Woo" <melissa@zelda.ehs.uiuc.edu>]

On Fri, 25 Sep 1998 14:59:34 -0500 (CDT), William Lorenzen wrote:

>Interesting...  That has happened to some of our badges too.  I got the same 
>response and always assumed someone did not load the film in the holder 
>correctly.  

In most cases that's very possible, as we have certainly had users load
film incorrectly.  Some of the creative methods used were pretty
amusing; it's really hard to load the holders wrong.  This is why our
techs load a pretty good number of the holders themselves now.

As far as the problem I posted goes, I received a possible answer via
private e-mail, so I am not sure that the individual wants to be
identified (he can do so himself if he wishes) or that he wants me to
give too much data away as it appears to be preliminary, but in general
terms...

What I didn't mention in my posts was that most of the badges were
pointing in the direction of some drums of Co-60 waste at various
distances from the drums.  This was intentional; I'd wanted to compare
film results with the ion chamber readings I'd already collected.

The individual's response mentioned that the pattern from Cs-137 under
a lead filter is "very slight" at a 90 degree incidence, single
exposure.  Extrapolating from that a bit, it is possible (though I
don't know how likely) that the higher energy gammas from cobalt,
combined with environmental factors or processing anomalies, might make
the pattern difficult to detect.

Granted, I did know who to contact at Landauer with technical
questions, so I might've been able to resolve this a few months ago. 
However, after my first phone call about the May badge report, this
became more of a test of customer service than anything else.

The first rep kept insisting that the film had to have been irradiated
outside the holder, even after:

- I told her I know how to put film in a holder :)
- I told her that I had a pretty good idea of the chain of custody of
the film during its time on campus
- I asked her to check another badge of the same wear date to see if
had a filter pattern (it did; so, if the film had been irradiated
during shipping, it had to have only affected an extremely localized
portion of the box, since AFAIK the films are pretty bunched up
together when shipped here and when we ship them back)

I was not offered a chance to speak to someone with more technical
experience, though I should note that I did not ask.

Similar responses about the June and August badge reports just made me
more miffed. When asked directly, the last rep I spoke to did mention
that they have had this phenomenon occur before with the higher energy
photons, but did not know above what energy this had occurred.  So, I
posted the question to RADSAFE.

(I don't want to turn this into another "I hate my dosimetry vendor"
thread.  I do wish to point out that we've had pretty good service from
Landauer over the years.)

>Is "Luxel" our answer?

We have not yet been switched to the Luxel dosimeter, but you don't
want to know my experiences asking questions about it.  <big,
mischievous grin>

Vendors must *really* hate people like me. :)

--
Melissa Woo, Health Physicist                    |mailto:m-woo@uiuc.edu
University of Illinois at Urbana-Champaign       |ofc 1.217.244.7233
DEHS, MC225, 101 S. Gregory St., Urbana, IL 61801|fax 1.217.244.6594
http://www.uiuc.edu/ph/www/m-woo                 |


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