[ RadSafe ] Fwd: hand held meters

Fri Jan 24 12:48:51 CST 2014

To get a little into the nitty-gritty...some types of clay contain more K than others. Illite in particular can be up to 6% potassium by weight. I can't remember the activity concentration of K-40 that this gives you, but you can sure see it with any sodium iodide detector.

One of the things that makes clay challenging is that clay deposits are not always uniform - they can be variable thickness and buried to variable depths. This seemed especially bad in formerly glaciated areas and, as you noted, can make characterization of normal background difficult.


-----Original Message-----
From: radsafe-bounces at health.phys.iit.edu [mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of Chris Alston
Sent: Friday, January 24, 2014 12:10 PM
To: The International Radiation Protection (Health Physics) Mailing List
Subject: [ RadSafe ] Fwd: hand held meters

Andy and Dan

I guess that I'll throw my US$0.02 into the hat.  Watch out for
deposits of clay (K-40 again, I presume), e.g., the red kind found in
Missouri.  Some places, it is 2-3 feet under the dirt proper (or
whatever depth), other places, it is literally just below the surface,
or even visible at the surface.  We were having fits, when we started
work at a DOE site there, trying to establish a gamma background for
the site.  My take on it was that the clay was the culprit; I don't
know what the ultimate official take on it was.

---------- Forwarded message ----------
From: Dan McCarn <hotgreenchile at gmail.com>
Date: Thu, Jan 23, 2014 at 11:02 AM
Subject: Re: [ RadSafe ] hand held meters
To: "The International Radiation Protection (Health Physics) Mailing
List" <radsafe at health.phys.iit.edu>
Further to what Philip says, marine black shales such as the Kolm Shale in
Sweden, Chattanooga Shale in the Eastern USA and the Pierre & Mancos Shales
around the Rocky Mountains & Eastern Plains are endowed with about 0.01%
uranium. Other rocks such as the marine phosphorites in Florida, Louisiana,
Pre-Caspian & Morocco also have relatively high uranium endowments
naturally.  Most shales are also relatively high in potassium
Dan W McCarn, Geologist
On Thu, Jan 23, 2014 at 8:56 AM, KARAM, PHILIP <PHILIP.KARAM at nypd.org>wrote:
> One other thing to be aware of is that some rock and soils are
> potassium-rich, which can also mess with your interpretation of results.
> This happened to me once at a radium remediation in Illinois - until we
> realized what was happening we were "cleaning up" soil that was chock-full
> of high-potassium clay. When we were able to show this we changed our
> approach to doing gross measurements, followed by (for apparent hot spots)
> performing single-channel analysis at the K-40 peak. If we could show that
> the elevated counts were primarily due to K-40 then we didn't worry any
> further.
> The bottom line is that you should also consider that the rocks and soils
> might cause your readings to change in a way that has nothing to do with
> possible contamination. This might be the "second step" you mentioned.
> Andy
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