[ RadSafe ] Advection / Diffusion of Radon through Media

Fri Aug 29 12:02:12 CDT 2008

Sorry Dan,

This was an appendix to a larger report and it looks like the references 
didn't get in there. (I was no longer with that company when the final 
report was published.)

Anyway, I think Tanner 1964 is

Tanner, A.B. 1964. Radon migration in the ground: A review, in Adams, J.A.S. 
and Lowder, W.M., eds., The Natural Radiation Environment: Chicago, III., 
University of Chicago Press, pp. 161-190.

and Bigu 1994 is

J Bigu. Theoretical considerations regarding the migration of 222Rn and 
220Rn from uranium- and thorium-bearing underground environments. Health 
physics. 1994 Jul;67(1):60-9

The (non radioactive) diffusion equation and Bessel functions etc come out 
of the CRC Handbook of Chemistry and Physics (AKA 'Rubber Bible') or similar 
generic reference.

Regards,
Kai

Kai Kaletsch
Environmental Instruments Canada Inc.

----- Original Message ----- 
From: "Dan W McCarn" <hotgreenchile at gmail.com>
To: "'Kai Kaletsch'" <eic at shaw.ca>; "'Radsafe'" <radsafe at radlab.nl>
Sent: Friday, August 29, 2008 9:54 AM
Subject: RE: [ RadSafe ] Advection / Diffusion of Radon through Media

Dear Kai:

Thank you for your paper.  Was there a list of references? There were 14 
pages total, but no references cited.

Advection: Assume a gas pressure difference between two sides of a slab of 
granite; a common method for removing radon from under a floor is to drop 
the pressure and cause soil gas to flow away from the foundation.

Dan ii

Dan W. McCarn, Geologist; 3118 Pebble Lake Drive; Sugar Land, TX 77479; USA
Home: +1-281-903-7667; Austria-cell:  +43-676-725-6622
HotGreenChile at gmail.com   mccarn at unileoben.ac.at   UConcentrate at gmail.com

-----Original Message-----
From: Kai Kaletsch [mailto:eic at shaw.ca]
Sent: Friday, August 29, 2008 9:58 AM
To: Dan W McCarn; 'Radsafe'
Subject: Re: [ RadSafe ] Advection / Diffusion of Radon through Media

Hi Dan,

Please take a look at
http://members.shaw.ca/eic/RadonExhalationFromSurfaces.pdf (Be patient, it's
a scanned pdf. So, it's kinda big: 5 Meg).

This is something that I wrote up at my first real job. It gives you the
equations. The point of this paper is that you do not need to have a uniform
source distribution in order to calculate the radon flux through a surface.

My experience with granite is fairly limited. I took measurements in a
refuge station in granite and the measured Rn values corresponded well with
the assumptions of 10% emanation and 60 cm diffusion length (which are my
default values for low grade ore), when I used uranium concentrations
derived from gamma measurements (30 - 50 ppm U).

Of course, other combinations of emanation and diffusion length would also
work, like 20% emanation and 30 cm diffusion length. The point is, however,
that you need a substantial diffusion length (tens of cm) to make the
numbers work out. I'm pretty sure diffusion was the main transport
mechanism, since the refuge station was in permafrost and therefore no water
inflows. That means that a 10 cm slab would release almost 10 times the
amount of radon as a 1 cm slab.

I'm not sure if I completely understand your question about advection. Radon
definitely gets carried with flowing water. Water inflows in underground U
mines usually carry radon. When you de-water an open pit mine, you will see
radon reporting to the de-watering wells hundreds of meters away from the
orebody. I am trying to convince exploration people to use this property
when they are looking for orebodies. The trick is that you have to get the
water flowing. It doesn't work if it is just sitting there. (Still water is
actually a good radon barrier with a diffusion length ~ 2 cm.)

Regards,
Kai

Kai Kaletsch
Environmental Instruments Canada Inc.

----- Original Message ----- 
From: "Dan W McCarn" <hotgreenchile at gmail.com>
To: "'Radsafe'" <radsafe at radlab.nl>
Sent: Thursday, August 21, 2008 1:32 PM
Subject: RE: [ RadSafe ] Advection / Diffusion of Radon through Media

Hello Group:

What I'm really fishing for transport equations for diffusion / advection
including
time and decay or some papers / pubs that describe the mechanisms.

Dan ii

Dan W. McCarn, Geologist; 3118 Pebble Lake Drive; Sugar Land, TX 77479; USA
Home: +1-281-903-7667; Austria-cell:  +43-676-725-6622
HotGreenChile at gmail.com   mccarn at unileoben.ac.at   UConcentrate at gmail.com

From: "Dan W McCarn" <hotgreenchile at gmail.com>
To: "'Radsafe'" <radsafe at radlab.nl>
Sent: Wednesday, August 20, 2008 7:18 PM
Subject: [ RadSafe ] Advection / Diffusion of Radon through Media

> Hello:
>
> Perhaps this has been done somewhere before:  How does one go about
> estimating that component of radon that emanates from a granite or other
> material? There are several factors that I can think of:
>
> 1 - Nature of uranium mineralization: a) contained within minerals e.g.
> zircon, monazite; biotite and b) epigenetic mineralization via solutions
> precipitating U minerals in pore spaces and fractures.  Most granites show
> secular equilibrium in the uranium series.  Is this a macroscopic or
> microscopic property?  Does the 5 MeV or so recoil dislodge the radon that
> far away from the origin in a mineral grain? Since granites are massive
> rock
> bodies, emanation of radon and subsequent decay would / could occur within
> the same granite, except near the margins.
>
> Does the accumulation of alpha decays e.g. U-238, Th-234, U-234, Th-230,
> Ra-226 ⇒ Rn-222 make it more accessible to mobilization? Because U-234 is
> more easily leachable than U-238 (Wyoming Basins, Kazakhstan), this
> suggests
> to me that the Ra-226 has been fairly well dislocated prior to decay to
> Rn-222.
>
> 2 - Dual porosity matrix - the nature of the permeability associated with
> fractures or porous fractions of a material vs. that portion that is
> contained within a mineral grain.  I can imagine that if the rock was
> porous
> / permeable enough to be an aquifer, that the radon would advect at the
> same
> rate as the water.  This is borne-out by borehole measurements in and near
> sandstone U deposits.
>
> 3 - Distance to a surface (e.g. fracture or actual surface of material)
>
> Empirically, does a 1 or 2 cm slab of uniform composition granite emanate
> at
> the same rate per unit surface area as a 10 cm slab?
>
> Dan ii
>
> Dan W. McCarn, Geologist; 3118 Pebble Lake Drive; Sugar Land, TX 77479;
> USA
> HotGreenChile at gmail.com   UConcentrate at gmail.com
>
>
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