Scint Counting

["FS BUSBY BRUCE A" <BUSBBRUC@fs.isu.edu>]

Hi all;

    I have a question and perphaps a problem some one out there might 
be able to help me with. Question - Anyone use liquid scint counting 
for alpha, primarily for source swipe-leak checks.  Problem -  We 
were going to try, so we made up some Am-241 standards, 50 and 100 
pCi.  The problem was that our efficiency came out to 200%.  A quick 
call to our friendly beckman rep confirmed our fears, he said that it 
should be about 100%.  The lab swears that their standards were the 
correct activity (Hmmmm....). We have counted the standards on two 
machines, with the same result.  Cal checks on our machine also 
shows it is operating correctly. I made up a standard using Uranium 
Acetate, which came out to 184%, but the build up of shortlived 
daughters probably account for this. The decay daughter of Am-241 
(our standard isotope) is long lived so should not be a factor in our 
counts.
Any ideas, answers, comments or just a friendly "don't know" would be 
much appreciated, thanks to all... :>


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Bruce Busby
Idaho State University
Radiation Safety Office

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