Re: Radon daughter activity

["Deborah P. Steva" <dps3c@kelvin.seas.virginia.edu>]

According to welch:
> 
> >Does anyone out there have information or experience on surface
> >contamination levels that can be expected due to radon decay products. A
> >colleague of mine here at LANL reports hundreds to thousands of dpm
> >detectable on surfaces in areas with radon levels around 4 pCi/L. Since it
> >has an apparent half-life of 25 minutes it certainly looks like radon decay
> >products. Does anyone have a general rule of thumb or has this relationship
> >been published? Thanks.
> 
> 
We recently had an experience with significant surface
contamination from radon daughters.  We have a below ground
indoor 10 x 10 foot (roughly) pit about 9 feet deep.  Pit is
not covered routinel, however, at one point it was covered
temporarily with boxes.  During this time an individual had to
go down into the pit.  After coming out, it was discovered he
was contaminated.  Making a long story short, the contamination
was frm radon daughters and was easily detected by a pancake
GM, on the order of 1000's of cpm/100cm2.  The radon levels
measured in the pit subsequent to that were in the neighborhood
of 700 pCi/L.  We have another pit in which we store
radioactive sources that require leak testing.  We have to wait
for decay before counting the leak test wipes because of high
daughter levels, again radon levels in neighborhood of 700
pCi/L.  These are closed environments, little to no
ventillation.  Don't have any rules of thumb although I seem
to remember an article in the HP Journal some years ago where
someone correlated radon daughter activity from a wipe of a
television picture tubes with radon levels in air?  

Debby Steva
University of Virginia

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