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Re: Removable Contamination Surveys



Title: Removable Contamination Surveys
Just, a quick note:  I have some literature at work concerning loose contamination studies, including something about the 100 cm^2 area.  I will send some further information later.  But for now, wiping a smear over greater than 100 cm^2 generally does not improve the collection efficiency of the action, but compacts the material on the smear giving a false value for the removable component.  At one time the swipe area was a lot larger (back when Charlie Willis was a youngster).   When wiping over a larger area the surveyor would press harder than he would by using a quick motion over a smaller area.   100 cm^2 area (approximately an area of 4"X4") is easily swipe with one motion with out over lapping the area being surveyed.  By the way, how many of you still start numbering your swipe envelopes at 2?  Guess no one saves the first one for the background measurement.
 
"In science there is only physics; everything else is stamp collecting."
                                      --Ernest Rutherford
 
Dean Chaney, CHP, IBA (aka High Plains Drifter)
Fairfield, CA
magna1@jps.net
----- Original Message -----
Sent: Friday, February 01, 2002 1:29 PM
Subject: RE: Removable Contamination Surveys

One source document (for reference) is ANSI/HPS-13.49-2001 Performance and Documentation of Radiological Surveys (it is available in the "members only" section of the HPS website www.hps.org ).  Also numerous NRC Reg. Guides (1.86, 8.21, 8.23, 8.24, etc.).  These all recommend smearing a 100 cm^2 area.  It will also depend on what was written in your radioactive materials (RAM) license.  Your facility may have committed to a certain protocol or to following a certin Reg Guide.  If so you would have to amend your RAM license to use a different area.  Hope this helps.
 
Tom Huston, PhD, CHP
-----Original Message-----
From: Jenkins, Peter [mailto:PJenkins@ahs.llumc.edu]
Sent: Friday, February 01, 2002 1:51 PM
To: 'radsafe@list.vanderbilt.edu'
Subject: Removable Contamination Surveys

Can anyone give me some insight (and possible source documents) into the reasons for the 100cm^2 standard (or suggestion?) used for removable contamination surveys?  Why is it 100cm^2 and not 1,000cm^2, or something smaller or larger?  Is there anything wrong with increasing the swiped area to increasing the likelihood of detection? 

Specifically, assume a removable contamination limit is set at 200 dpm/100cm^2 for a laboratory and a researcher wishes to use a survey meter to count the swipes.  According to the manufacturer's formula and values (for efficiency of the radionuclide, etc), the meter has an MDA of 400 dpm.  Is there anything wrong with performing the survey over 200 cm^2 so that the detection limit would meet the removable contamination limit?

Thanks,

Pete Jenkins






















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