[ RadSafe ] Fallout "preserved" in concrete

[Brennan, Mike (DOH)]

I would expect it to differ from location to location, due to different
amounts of fallout.  Any fallout that was cast in concrete in the 60s
has decayed to a little bit of Cs-137, a little Sr-90, and so few
plutonium atoms that you could name each one.  I would expect that in
almost all cases it would be insignificant in comparison to the
naturally occurring radioactivity, which would also vary depending on
where the materials came from.  Without knowing the particulars of the
gravel, sand, etc., I would guess that most of the activity comes from
K-40 and isotopes in the U-238 and Th-232 decay chains (probably in
secular equilibrium).  For newer concrete, I suspect that the
controlling factor would be how much fly ash was used in it, as I
understand that radium and thorium is concentrated in the ash when the
coal is burned (I have no direct experience with this, however).  

In the end, I suspect that if you want to know the activity from a given
piece of concrete, you will just have to sample and count it. 

-----Original Message-----
From: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] On
Behalf Of Keith Welch
Sent: Friday, February 20, 2009 1:34 PM
To: radsafe at radlab.nl
Subject: [ RadSafe ] Fallout "preserved" in concrete

Hello Radsafers,

I'm looking for data regarding levels of radioactivity in concrete as a
result of weapons fallout.  I'm evaluating some concrete that was cast
in the early to mid 1960s, and trying to determine if there might be
elevated levels of Sr-90 or other nuclides in the concrete due to the
prevailing levels in the environment at the time.  I've searched the
on-line literature pretty thoroughly, and have not come up with
anything.  Existing documentation that I can find only speaks to natural
radioactivity in concrete (NCRP etc.).
Thanks for anything you can suggest.
Keith Welch
Jefferson Lab
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