RE: BZA READINGS

[MICHAEL S FORD <MFORD@pantex.com>]

Alan,

First of all, if you haven't already done so, check out
NUREG-1400, "Air Sampling in the Workplace" (Sep '93) by
Eva Hickey, Dan Strom, et al.  These folks have put
together an excellent document that is a great resource for
anyone working in this area.

Secondly, think "flow rate."  If you're not using your BZA's
to determine dose (i.e., using lapel samplers), but only for
determination of RP requirements, think about using some
portable air samplers that will give you a relatively high flow
rate (3-5 cfm vs. 10 LPM).  This generally gives you much
better statistics for the same sampling period and/or
reduces you counting period significantly because you
have a much larger sample volume.  

If you have a reasonably constant source term, which
sounds like your case here, you can do some in-depth
source characterization up front to determine what a "fresh"
thoron sample's alpha/beta ratios look like.  With that in
hand, you should be able to use those ratios as part of a
field screening technique with a simple alpha/beta type
scaler.  Again, this technique works much better with larger
sample volumes by significantly reducing you count times.

Finally, if you have access to some of the newer
alpha-spec CAMs, you can set one up to be able to view a
spectrum from an air sample filter to do a qualitative sort
for Pu vs. Thoron spectra.

'Hope this helps!
v/r
Michael
*************************
Michael S. Ford, CHP
Radiation Safety Department
Battelle Pantex
Amarillo, TX
806.477.5727 phone
806.477.4198 fax
mford@pantex.com
The above comments are those of the author and in no
way should be attributed to Battelle Memorial Institute,
Mason & Hanger Corp, or the Department of Energy.
*************************