RE: Pb-210 on air filters

[Marty.Bourquin@grace.com]

We have had a similar problem. We are also a thorium site (but we have 
some uranium as well- although the ratio to Th is small).  Our 
"solution" was to take a composite of the filter papers and analyze 
them for isotopic U, isotopic Th and Pb-210 (along with a few other 
such as Ra-226 &228) as well as gross alpha beta.  After several 
samples we were able to establish a ratio of Pb-210 to the other 
isotopes of concern and to the total gross alpha beta.  

Interestingly the Pb-210 was the single greatest contributor to the 
total gross alpha beta.  We then used this ratio as an indicator of 
potential problems with our sample results.  Feel free to contact me 
directly if you want any further info on our process.

Marty Bourquin
W.R. Grace & Co.
Marty.Bourquin@grace.com
-----Original Message-----
From: brian.keele@swec.com [mailto:brian.keele@swec.com]
Sent: Friday, December 08, 2000 8:48 AM
To: radsafe@romulus.ehs.uiuc.edu
Cc: brian.keele@swec.com
Subject: Pb-210 on air filters




Does anybody have any information relating to the amount of Pb-210, or 
other
natural ambient isotopes, that could realistically accumulate on an air 
filter
in
an outdoor environment and present an interference in a gross alpha 
measurement?
The filters are held for 14 days before a gross alpha counting to allow 
short
half-life radon/thoron daughters to decay.  We have a thorium site.  I 
suspect a
large proportion of the observed counts from our perimeter stations may 
be from
Pb-210.

Thank-you,
Brian Keele


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