RE: Swab Conversions

["William G. Nabor" <wgnabor@uci.edu>]

In Message Wed, 19 Feb 97 12:22:41 -0600,
  David Biela <bielad@wv.doe.gov> writes:

>1.  Has anyone performed any test converting dpm on a swab (small wad of
>cotton on a stick) used for example inside a pipe to dpm/100cm-sq?

How important is it to stick to the /100cm-sq part of the rules here?  The
most rational approach would be to just assume that you have swiped 100
cm-sq and forget the conversion.  If you find something above BKG, clean it
up, if not, forget it.  If strict compliance is a requirement, then you have
to measure the width of the swab in cm, wipe a number of complete inside
diameters of the pipe then multiply the diameter of the pipe in cm times the
number of complete turns of the swab times the width of the swab in cm.  Be
sure to rotate the swab so as to evenly expose all the clean areas of the
cotton as you are wiping.  Counting the swab has to be taken into
consideration, too.  Be sure you know the efficiency of the counter for
cotton swabs.  Counting in LSC, for example, may depend on how long you let
the swab soak in the cocktail before counting.  If you are really concerned
about the 100 cm-sq, then you need to be really concerned about the
efficiency calibration of your counter, which should be calibrated by
putting a known amount of radioactivity on a clean swab and counting that.
**********************************************************************
William G. Nabor
University of California, Irvine
EH&S Office
Irvine, CA,  92697-2725
WGNABOR@UCI.EDU
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