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Re: Radon Migration Through Concrete
Two questions that come to mind:
1. Are you measuring the radon or the radon daughters?
2. If you're measuring the radon daughters, are you using a filtering system which will only
measure the attached fraction?
If you are only measuring the attached fraction, this could account for a significant component
of the variation. There could be something which is changing the aerosol concentration, and,
hence, the attached fraction.
The opinions expressed are strictly mine.
It's not about dose, it's about trust.
Bill Lipton
liptonw@dteenergy.com
bill_goldsmith@urscorp.com wrote:
> Ron: With a couple of assumptions, maybe I can shed some light on the
> subject. First, I assume that the poured concrete is a floor slab.
> Second, I assume that the order of magnitude variations are from a few
> pCi/L to a few tens of pCi/L. If these assumptions are correct, then the
> variation you are seeing is normal.
> Consider two aspects of radon:
> The concentration of Rn in soil gas is on the order of a few thousands
> of pCi/L under normal circumstances. Rn will diffuse from the soil
> toward a lower concentration (such as room air of a few pCi/L). Also,
> soil gas will move through the path of least resistance. If surface
> soil is wet, Rn rich soil gas will move through cracks in concrete. Rn
> will diffuse through this path more quickly. Once it has come out of
> the soil, it isn't going to fight the concentration gradient to go back
> into the soil.
> The removal of Rn from the building is by one of two mechanisms: decay
> or ventilation. The rate for removal by decay is the decay constant,
> about 0.008 per hour. A "sealed" building will generally have
> ventilation rates on the order of 0.1 per hour. Hence, the dominant
> removal is by ventilation, which in turn may be influenced heavily by
> wind speed.
> Thus, wet soil would tend to pump Rn into the building and natural
> ventilation would tend to pump it out. You would reach a constant Rn
> concentration only when the two mechanisms were roughly equal in their
> effect. So, you could expect to see this kind of variation as one
> mechanism dominates the other. The concentration should be higher, but
> steadier in winter when ice covers the ground or the first several inches
> of ground are frozen. Hope this helps.
> Bill
> Bill Goldsmith
> Radian Remediation Services
> 865.220.8265
> bill_goldsmith@urscorp.com
>
>
>
> "Lavera, Ron" To: Multiple recipients of list
> <Ron.Lavera@nypa.g <radsafe@romulus.ehs.uiuc.edu>
> ov> cc:
> Sent by: Subject: Radon Migration Through Concrete
> radsafe@romulus.eh
> s.uiuc.edu
>
>
> 06/21/2000 12:47
> Please respond to
> radsafe
>
>
>
> We have a welded steel lined building that has a substantial amount of
> poured concrete inside the building. The building is about 25 years old.
>
> Can anyone provide information, explanations and/or examples that could
> indicate how the airborne radon concentration inside this sealed building
> could change by a factor of 10 over an 8 day period ? The change has been
> steady for over a month with little or no variation.
>
> Thank you for your time and consideration.
>
> Ron LaVera
> Lavera.r@nypa.gov
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