Stripping Radon From Air Samples -Reply

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

>>> Robert Augdahl wrote on Sat 9 May 98  17:48 >>>
I need help, I have been looking for a way to strip Radon (and
daughters) from air samples that I need to count in a relatively
quick time frame......
>>>>>>>>>>>>>>

Robert, 

You've got a couple of choices:

1.  Determine what your background radon levels are via the
beta-to-alpha ratio method.  Sample in what you would consider to
be a background area to determine what your outdoor radon
concentrations are.  Some folks come up with an average, or a
range, but most work of this type is done indoors where the levels
fluctuate less.  Working outdoors, your levels will be highly
dependent on the season and current weather patterns.  You may
want to establish this value with a weekly or even a beginning of
shift sample.  In doing so, I would recommend that you use a high
volume grab sampler (30 to 50 scfm) to allow you to sample for a
shorter period with better statistics.  Count the sample for one to ten
minutes to determine your current beta-to-alpha ratio.  Apply that
value against your working samples as a screening method. 
Samples with a b-to-a ratio below your current value should be
initially considered as above background.

2.  If you have an alpha CAM with spectral capabilities, you can
determine the amount of activity in the P0-218 peak (allow to decay
for 1 - 2 minutes, Po-214 will decay off rapidly) and subtract that
from your sample activity.

3.  Use a spectral alpha CAM that will give you direct readings in
the Pu-239 region of interest.  If you've got a lot of dust, you may
want to use a prefilter to remove the big chunks and only look at
the respirable stuff. 

'Hope this helps.
v/r
Michael
*************************
Michael S. Ford, CHP
Texas Radiation Advisory Board
Address:
Radiation Safety Department
Battelle Pantex
Amarillo, TX
806.477.5727 phone
806.477.4198 fax
mford@pantex.com
*************************