[ RadSafe ] RE: Attn. Landauer Customers

Wed Aug 24 09:54:54 CDT 2005

The Smoky Mountains have always been thought of as a low-stress
environment. Perhaps it is due to our low radiation dose rate....

Seriously, though. Let me state up front that we use a calculated
background rate for personnel dosimetry at my facility. The background
dose rate was established from a year-long study that included several
dozen homes in our region. I like this method for our program, because
people take their dosimeters home with them. "Badge boards" don't work
well here because ORNL is a large site with many entrances and
facilities, literally miles apart. A calculated rate based on typical
"home" background is best for us. That's certainly not true for
everyone.

For your calculated rate, Jim, let me ask a couple of follow-up
questions. (Maybe others will find this helpful - please don't think
you're being audited!) What type of dosimeter do you use, and what
number of days did you use for the calculation? If you're using Luxel,
then I am going to guess that the dosimeters have been collecting
background from the day(s) they were manufactured until the day they
process them. You may or may not know those dates, but that could
greatly affect your calculated background rate (not to mention you might
have to consider the background rate in Oklahoma where the material is
manufactured, the background in Chicago where the dosimeters are put
together and later processed, in addition to the background in MA). The
same concept holds true for TLD dosimeters, just substitute the anneal
date (or previous read date if a pre-issue anneal is not done) for the
manufacturing date. If you have some dosimeters that were returned very
late and did not have background subtracted, see if your rate holds
true. It might take a controlled study to nail down the rate.

Kim McMAHAN    ORNL External Dosimetry    865.576.1566

-----Original Message-----
From: Jim Blute [mailto:jblute at NITON.com] 
Sent: Wednesday, August 24, 2005 9:57 AM
To: McMahan, Kimberly L.; radsafe at radlab.nl
Subject: RE: [ RadSafe ] RE: Attn. Landauer Customers

Kim and others,

I looked at my past dosimetry reports closely and concluded that 6
mrem/month was a bit low for me here in Massachusetts for whatever
reason.  I got results ranging from .34 mrem/day to .43 mrem/day (10
mrem/month to 13 mrem/month) when I randomly selected 3 groups of
results each having no background subtracted (and therefore reported
dose = gross dose = background)

So while caution is a good recommendation (as usual), I am guessing that
there are a lot of folks who could easily justify that the 6 mrem/month
value is a good conservatively low value to subtract in place of the
occasional absence of a truly representative background measurement.  

Would most everyone agree that any error left over after subtracting out
a reasonably thought out (i.e., investigated) conservative dose value is
within an acceptable margin for the overall purpose of monitoring
occupational worker doses in most radiation safety programs.

Jim Blute

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-----Original Message-----
From: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] On
Behalf Of McMahan, Kimberly L.
Sent: Wednesday, August 24, 2005 8:47 AM
To: radsafe at radlab.nl
Subject: [ RadSafe ] RE: Attn. Landauer Customers

I'd suggest caution using a 6 mrem/month "national average" option. Here
in East Tennessee the background gamma dose rate is about 0.11 mrem/day,
or a bit more than half of that. We practice ALARA, but not by
subtracting too much background.

In general, though, the comment is definitely worth discussing. I have
found problems with background subtraction methods on more than one
dosimetry program assessment. Working with your vendor to understand the
options, and finding what makes the best technical and operational sense
for your facility is time well spent.

Kim McMAHAN    ORNL External Dosimetry    865.576.1566

-----Original Message-----
Date: Tue, 23 Aug 2005 18:11:14 -0400
From: "Jim Blute" <jblute at NITON.com>
Subject: [ RadSafe ] Attn. Landauer Customers
To: <radsafe at radlab.nl>
Message-ID:
	<8EC7BA9EEA294F41B9EF5A1740B145D44C46D5 at chromium.NITON.com>
Content-Type: text/plain;	charset="us-ascii"

I want to share with everyone a solution I found to a problem that has
bugged me for some time.

I have experienced frustration with administering a dosimetry program
and frequently having control badges not subtracted from personnel badge
results.  I use Landauer and, admittedly, at times I was at fault by not
submitting the control badge for various reasons.  Other times I came to
suspect that Landauer made the mistake.  I have heard from other HPs who
use other companies for dosimetry services and they run into similar
problems so I am not writing this to criticize Landauer.  Regardless of
root cause, fixing the problem was a not always easy.  You can ask
Landauer to subtract any value you feel is appropriate after the fact,
but Landauer does not regularly report the control badge results so I am
left trying to choose an appropriate background without having knowledge
of what background to a badge might be for me.  Not to mention that I
would rather not have to deal with a correction each time the problem
occurs.  Often I would forget to do a correction or consciously decide
that I was too busy and the correction to minor for me to be bothered.
At these times I was left feeling guilty for not subtracting something
appropriate.

I spoke with Landauer today about it and for the first time I was made
aware of a reporting option that you have with them.  If you ask them
to, they will automatically subtract 6 mrem per month from any reported
result that did not have a control badge associated with it.  The 6 mrem
comes from a study they did of national average.  Granted it may not be
perfect, but it is likely close enough for most applications.  And it
keeps you from having to deal with the problem each time. 

I hope this info helps at least a few folks out there.  If it is common
knowledge, then I missed the boat somewhere along the line.

Of course, I always seem to be at the airport when my ship comes in :-)

Jim Blute, CHP

Thermo Electron Corporation

Corporate Radiation Safety Officer

Portable Elemental Analysis

900 Middlesex Turnpike, Bldg. #8

Billerica, MA 01821-3926 USA

1-800-875-1578

Fax: 978-670-7430

e-mail: jblute at niton.com

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