Re: Radon daughter activity

[welch@CEBAF.GOV (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.


Steve, from my own observations, I would not expect thousands of dpm at 4pCi/l.
I have seen a few thousand in areas where the atmosphere is "trapped" in an
enclosed space, particularly in concrete enclosures with little or no
ventilation - but my guess is that the Rn levels were well above 4pCi/l in
these spaces.  The big limiting factors in my view would be, 1) The space
must have very "calm" conditions,  2) The space must be able to maintain an
elevated equilibrium activity (constant supply, limited exhaust) in the air
long enough for daughter product fallout to achieve an elevated equilibrium
- i.e. a 'spike' of 5 or 10 pCi/l for an hour or so in a typical room where
people and ventilation are at work would not be enough to see much surface
activity.

Anybody seen anything to support or refute this?

Keith Welch
welch@cebaf.gov
KW