Re: Radon daughter activity

[welch@CEBAF.GOV (welch)]

Correction:  The following was NOT according to Welch.  I responded to that
posting but my comments were not on this reply.  I don't know if my response
was garbled or something or whether Debby may have snipped it from her
reply. It does appear that what Debby is saying jives with my
assumptions/assertions;  That it takes a lot more than 4pCi/l, and
ventilation (as well as the construction of the enclosure) play a big role
in surface contamination buildup.


>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
>
>> 
>> 
>
>
KW