RE: Stripping Radon From Air Samples

["Joe Alvarez" <jalvarez@auxier.com>]

There may be a simple solution if you know the concentration of the Pu and 
Am in soil.  The Threshold Limit Value (TLV) for nuisance dusts is 10 
mg/m3.  If the soil concentration in pCi/g times 0.010 g is less than 1/10 
DAC then you are very unlikely to exceed your limit.  10 mg/m3 is a lot of 
dust.  There are very inexpensive, alarming dust monitors that alarm below 
the TLV.

Joe Alvarez
Auxier & Associates
jalvarez@auxier.com

-----Original Message-----
From:	Robert Augdahl [SMTP:augie@macconnect.com]
Sent:	Saturday, May 09, 1998 7:48 PM
To:	Multiple recipients of list
Subject:	Stripping Radon From Air Samples

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.

Here's my situation; we are doing soil clean-up activities, the soil
contains primarily Pu-239 and Am-241, we're running air samplers in the
area to check for airborne concentrations. We would like to only have the
personnel in the immediate area wear respirators. In the past we have
always done air sampling but waited 24hrs to allow for decay before
counting the sample. This could be a serious delay time if we found we
had exceeded a 10th of a DAC the previous day.

I have found in Cember 'Intro to Heath Physics' a calculation to strip
the Rn and Th counts out, but it requires a 20hr delay in counting. Not
much help. I have been told by some of the old hands that they used to
have a calculation for doing this but no one remembers it. I don't mind
if it is a quick and dirty method, I can always count the filter again at
a later date and get a final number for the records, I just need
something to show with some certainty that the work area was below a 10th
of a DAC. Also all the workers will be wearing BZA samplers for dose
estimations, which are counted after a 24hr decay.

My plan is to run a sampler pulling approx. 5 CFM, start it at the
beginning of the shift. Change the filter at lunch (about 4hrs) and stop
(change) at end of shift. The filter changed at lunch I would like to
count after 2hrs decay, and again after 2 hrs. Using those two counts,
can I strip the Rn and Th counts out with any degree of certainty?  Would
some other time frame (that would fit in a single day) work better? The
filter I change at end of shift could be counted at the start of the next
day before work began. That should give me enough of a decay time to show
a count below 10% DAC.

I'm open to any ideas, and would like to hear how its done other places.

On a related note, I have a copy of a program by K. Skrable and C. French
for a HP-42S calculator that allows the user to count the sample a couple
of times, enter the info and leave you with only the long lived nuclides.
The problem I have is I can't for the life of me find how to enter one of
the program instructions.

The instruction is    J+   it will increment the column pointer in an
indexed matrix. I can't find anywhere in the owner's manual how to enter
that command. Anyone familiar with it?

Bob Augdahl
RRPT
augie@macconnect.com
Las Vegas, NV