RE: Smears (AKA Swipes) -Reply

["Jim F. Herrold" <Herrold@UWyo.Edu>]

In 1993, Packard Instruments put out a 6-page summary of various studies
on swipe assays where collection efficiency was measured using different
materials, methods and cocktails. It's just called "alpha beta
application note, Swipe Assays, ABA-006". It doesn't have a lot of data,
but shows bar charts and gives references (including Klein et al). I've
used this hand-out for the same purpose of demonstrating statistics, as
well as a quick reference when I get questions on swipe methodology and
materials. Their phone number is 800-323-1891. It's been a while, so I
don't know if it is still available, or if they have updated it.


Jim F. Herrold
Radiation Safety Officer
University of Wyoming
Environmental Health & Safety
312 Merica Hall
Laramie, WY 82071

herrold@uwyo.edu
(307) 766-3277


>----------
>From: 	ABELQUIE@ORAU.GOV[SMTP:ABELQUIE@ORAU.GOV]
>Sent: 	Thursday, February 12, 1998 9:46 AM
>To: 	Multiple recipients of list
>Subject: 	Smears (AKA Swipes) -Reply
>
> Tony wrote:
>
> Does anyone know of any studies on taking smears/swipes?  I am
>trying to
>put together a Statistics class for technicians who are hostile to training. 
>You know the types: "This won't help me do a better survey . . ."  The
>thought
>came to me that no one has studied the manner of smear taking.  Many
>plants use
>1 3/4 inch smears, but some still use 1" smears.  The wider smear allows
>the
>surveyor to place an extra finger on the backside surface and thus
>swipe more
>area if they use the same 16 to 18 inch "S" shape.  I would sure
>appreciate any
>input here.
>
>
>Tony-
>
>A few studies have been reported in the HP Journal describing the
>tremendous variability (in collection efficiency) inherent in smear
>sampling.  References include:
>1) Campbell et al. "Wipe Testing for Surface Contamination by Tritiated
>Compounds" Health Phys. 64(5):540:544, 1993
>2) Klein et al. "Detecting removable surface contamination" Health Phys.
>62(2):186-189; 1992
>
>Recognizing this variability, the guidance in ISO-7503 ("Evaluation of
>Surface contamination - Part 1:Beta emitters (maximum beta energy
>greater than 0.15 MeV) and alpha emitters, 1988) states that "the smear
>material should be chosen to suit the surface to be checked (for example
>filter paper for smooth surfaces, cotton textile for rough surfaces)" and
>adds that if the collection efficiency is not determined experimentally, a
>value of 10% should be used. Of course, collection efficiency is also
>affected by  "human factors" such as finger pressure on smear, size of
>"S", etc.  
>
>In practice, the collection efficiency is frequently ignored and is
>implicitly
>taken to be unity (i.e., the smear is counted and only the detector 
>efficiency, not collection efficiency, is used to evaluate the amount of
>removable surface activity).   
>
>The MARSSIM recognizes the limitation in using smears to quantify
>removable activity.  Section 8.5.3 (note: there are two sections identified
>as 8.5.3, removable activity is discussed in 2nd section) states  "...
>measurements of smears are very difficult to interpret quantitatively. 
>Therefore, the results of smear samples should not be used for
>determining compliance.  Rather, they should be used as a diagnostic tool
>to determine if further investigation is necessary."  
>
>However, I realize that smears are certainly necessary for evaluating
>compliance with surface activity limits on packages, etc. for
>transportation. 
>
>Hope this helps.
>
>Regards,
>Eric Abelquist
>abelquie@orau.gov
>
>
> 
>