BZA READINGS

["Alan R. Marchand" <radarm@accessnv.com>]

Hi RADSAFERS

I am working on a project trying to extract Pu-239 from soil. Personnel are
wearing BZAs. The BZA filters are held for 24 hours for Radon decay. The
detector counts the sample papers for 30 minutes. Readings are slightly
high at this time. A week later, they are counted again, 99% of the BZA
filters now read zero. Calculations show a Thoron element. 
We are using Excel worksheet to calculate dose equivalent for the workers
to determine respirator requirements according to our Radiological Work
Permit. if we go by the 24 hour results the mask usage goes up. If we rely
on the results from a week later some workers may actually receive an uptake.
This has the RCTs requiring respiratory protection for the workers and
management asking why the extra cost if the final results show negative data.

Is  there any way to properly calculate for the Thoron or is to error on
the side of safety the best plan?

Alan R. Marchand
Las Vegas, Nevada
<radarm@accessnv.com>