[ RadSafe ] Question on Subtracting TLD Background

[Neill Stanford]

Hi Kevin,
Background subtraction can be a significant source of headaches for large
sites with multiple storage locations.

Ideally the control badges live with the worker badges at all times from
anneal to processing except when being worn. If you go to a site-wide value,
then you should (actually, it's a shall with DOE) have some blanks (extra
controls) at the storage racks that get processed and trended. This will
show you how good your site background value is, and help with investigating
questioned doses.

There is another interesting issue here: if the storage locations have a
different background rate (typically higher, because they are more
conveniently located, closer to the work areas), should you really be
subtracting all of it? It's easiest to see with an exaggerated example. Say
the laboratory controls (stored where you process) show 30 mrem in a
quarter, and the badge rack controls show 100 mrem. I seems reasonable to
say that some, if not all, of that 70 mrem diff is due to 'occupational'
dose and some portion of it should in fact be assigned. Some programs
subtract a % of the control badges, equal to the % of time the worker badge
is actually stored with the control badge. 

Sincerely,

Neill Stanford, CHP
Stanford Dosimetry
-------------------------------------------
stanford at stanforddosimetry.com
360 733-7367 (v)
360 933-1794 (f)
360 770-7778 (cell)
www.stanforddosimetry.com
--------------------------------------------

-----Original Message-----
From: Konzen, Kevin K [mailto:Kevin.Konzen at icp.doe.gov] 
Sent: Thursday, May 28, 2009 7:31 AM
To: radsafe at radlab.nl
Subject: [ RadSafe ] Question on Subtracting TLD Background

Hello,

 

I have a question regarding the practice of subtracting beta-gamma
background dose from TLDs in general.  Our facility has multiple storage
board locations where TLDs are kept when not being worn.  When the TLDs
are gathered at a prescribed interval (e.g., monthly or quarterly) for
processing, the background TLDs located on each storage board, are also
processed and used for the TLD background which is subtracted from the
individual TLDs.  We are investigating the feasibility of using a
centralized TLD background location in order to reduce the labor and
costs associated with using multiple background locations.  I haven't
been able to find any clear guidance prescribing the specifics of
measuring the background, other than to subtract it from the TLDs during
processing.  As part of this analysis, I would like to include other
facility practices.  If you have any information on current specific
guidance or practices, please respond to me directly at
Kevin.Konzen at icp.doe.gov. 

 

Thank You,

Kevin Konzen, CHP

ICP Technical Advisor 

Kevin.Konzen at icp.doe.gov

(208) 745-7108

 

 

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