Re: Radioactivity in soil

[clement@vaxxine.com (Clement)]

>that the national average (U.S.) of Ra226 in soil is just about 1 pCi/gm, at
>least that's my recollection of a paper of Fred Haywood's ca. 15-20 years
>ago. If the background were 1-2 pCi/gm, and Ra226 were the only radionuclide
>of concern, I'd think that 1pCi/gm above that would be detectable with, say,
>a 2x2"NaI probe. I hasten to CMA by stating that it's been many years since
>I've done environmental work, and my remembrance of likely countrates maybe
>off the mark.
>
>Chris Alston

Actually, you've got it about right.  The mean natural Ra-226 in soil in
Ontario (where I am) is around 0.025 Bq/g (or 0.7 pCi/g), and I expect the
US national average is slightly higher.

A semi-infinite source of Ra-226 in soil results in about 40 cps per pCi/g
in a 2x2" NaI scintillometer.  A typical background (of about 5 uR/h)
results in approximately 100 cps in the same instrument.  An increase of 1
pCi/g (ie. 100 to 140 cps) would easily be detected with even a one second
count.  Even using a 1x1" NaI probe you would see an increase from about 25
cps to about 35 cps, also easily detectable in a one second count.

Chris Clement
Low-Level Radioactive Waste Management Office
Atomic Energy of Canada Limited
clementc@crl.aecl.ca
clement@vaxxine.com