|
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
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
Confidentiality Note: The preceding e-mail
message (including any attachments) contains information that may be
confidential, protected by applicable legal privileges, or constitute
non-public information. It is intended to be conveyed only to the
designated recipient(s). If you are not an intended recipient of this
message, please notify the sender by replying to this message and then
delete it from your system. Use, dissemination, distribution or
reproduction of this message by unintended recipients is not authorized and
may be unlawful.
|