[ RadSafe ] FW: OSL/TLD Comparison Experience

Fri Apr 23 16:10:01 CDT 2010

Hi, Neill.

The fade isn't that great, and really only becomes obvious when you look
at multiple years, and multiple stations, and are actually looking for
it.  As these are environmental TLDs, the seasonal differences can be
large.  Summer highs can be 110+ F (43+ C), and in the winter it can
remain below freezing for weeks.  I don't consider it to be a big
problem; just something to be aware of.

-----Original Message-----
From: Neill Stanford [mailto:stanford at stanforddosimetry.com] 
Sent: Friday, April 23, 2010 1:31 PM
To: Brennan, Mike (DOH); radsafe at health.phys.iit.edu
Subject: RE: [ RadSafe ] FW: OSL/TLD Comparison Experience

Mike,
What you note in your point #3 is not good. There are seasonal
variations,
but if you are seeing variations that you can be sure are due to fading
of
the dosimeters in the heat, you should contact your vendor, or your
system
if it is in-house. The effect of TL fade is minimized with a properly
controlled heat/collection process and further corrected in the
analysis.
With a properly maintained system, any bias introduced by fade should
not be
more than 5% (unless the badge had an acute exposure and the fade
correction
assumptions were inappropriate.) While old and a bit out of date, ANSI
N545
discusses this for environmental monitoring.
LiF is slightly more complicated due to pre-and post-irradiation fade,
but
there are well established corrections for this developed by the
manufacturer. OSL, by the way, shows insignificant (thermal induced)
fade
and requires no fade correction, even up to 12 months.

Sincerely,

Neill Stanford, CHP
Stanford Dosimetry, LLC
stanford at stanforddosimetry.com 
www.stanforddosimetry.com 
(360) 733-7367 (V)
(360) 933 1794 (F)

-----Original Message-----
From: Brennan, Mike (DOH) [mailto:Mike.Brennan at DOH.WA.GOV] 
Sent: Friday, April 23, 2010 8:56 AM
To: radsafe at health.phys.iit.edu
Subject: Re: [ RadSafe ] FW: OSL/TLD Comparison Experience

Hi, Dan.

This isn't my area of expertise, but I love a tech puzzle.  First, a
couple of the obvious questions:

1)  Is something new?  Have you just started using OSL badges, or have
you changed vender and/or crystal for your TLDs?

2)  Have you compared the energy spectra of the isotopes in the
different departments with the energy sensitivity of the OSL and TLD
systems?  

3)  With the environmental TLD programs I am familiar with, you can see
a seasonal variation due to more electrons escaping the traps in the
heat of the summer than in the cold of the winter.  Is the work and/or
badge storage environment noticeably hotter (thermally, not
radiologically) in the departments where the TLDs read low? 

-----Original Message-----
From: radsafe-bounces at health.phys.iit.edu
[mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of Hoffman,
Daniel E
Sent: Friday, April 23, 2010 6:21 AM
To: radsafe at health.phys.iit.edu
Subject: [ RadSafe ] FW: OSL/TLD Comparison Experience

Hi All.  I just realized that I misstated the facts in my original post.
What I meant to say was that the OSL results have been higher (not
lower) than the TLD results in some departments.  Sorry about the
miscommunication.

Dan

-----Original Message-----
From: radsafe-bounces at health.phys.iit.edu
[mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of Hoffman,
Daniel E
Sent: Thursday, April 22, 2010 12:39 PM
To: radsafe at health.phys.iit.edu
Subject: [ RadSafe ] OSL/TLD Comparison Experience

Hello RadSafers.  Our plant (nuclear medicine production involving both
reactor- and accelerator-produced isotopes) is seeing significantly
lower results using OSL badges vs. TLD badges, but only in some
departments.  For other departments the results are virtually the same.
Has anyone else had similar experiences at their facilities?

I know the 'dosimetry bunch' will enjoy kicking this one around.

Please feel free to contact me offline if you prefer.

Thanks. 

Dan Hoffman

Daniel E. Hoffman, CHP, CSP
Radiation Safety Officer
Covidien
2703 Wagner Place
Maryland Heights, MO 63043
314-654-7906 (office)
314-625-1881 (cell)

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