[ RadSafe ] Re: Fallout "preserved" in concrete

[Brennan, Mike (DOH)]

This is well outside of my area of expertise, but would it be possible
to break these samples all the way down and do mass spec on them?  If
you get something with an atomic weight of 3, then you know you have
tritium.  If you don't get any, then the false positive comes to the
fore.

Also, is the supposed tritium causing some problem with disposal?
Because it is really, really difficult to develop viable exposure
pathways.  In fact, at one time I proposed that some water contaminated
with tritium at the hundreds of thousands or pCi/l be disposed of by
making concrete with it, and using the concrete in highway barriers and
bridge abutments.  The scenario put forward as to why this was not
acceptable was, "What if a child chips pieces of concrete off and eats
them?"  I contended that if that was happening there were parenting
issues that posed greater risk than tritium, and perhaps they shouldn't
let their children play on the freeway and eat rocks.  

They don't send me to public meetings so much anymore. 

-----Original Message-----
From: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] On
Behalf Of welch at jlab.org
Sent: Tuesday, February 24, 2009 9:31 PM
To: radsafe at radlab.nl
Subject: [ RadSafe ] Re: Fallout "preserved" in concrete 

Thank you all for the ideas and information regarding radioactivity in
concrete.  Because I did not give a lot of detail in asking the
question, several of you have mentioned things that we have of course
thought about and assessed.  We have done gamma analysis on core samples
of the blocks, and we have a fair idea of the inventory of gamma
emitters.  What was a little puzzling to us was that we detected tritium
at considerably higher levels than the gamma emitters (it seemed high
even considering half-life differences), and the tritium was in every
block, even the ones that have no detectable gamma emitters.  There also
appears to be a lack of the expected depth profile (the expectation is
that the tritium concentration should simply be proportional to the
neutron flux at a given depth.  But, we have not done an exhaustive
study (number of samples is relatively small), and there's some question
as to the reliability of the analysis technique.  Also, we should
probably not expect an idealized distribution, given variations in
neutron fields and geometrical factors in the actual exposure
conditions.

There's also the possibility of an interfering agent (radiological or
not) in the material that is causing "false positive" tritium results.
That was the impetus for my original post - the idea that there is
interference from fallout (since the blocks were made in the early
sixties).  But, since we're not seeing any Cs137 in the blocks, the
possibility that other fallout nuclides are causing a problem seems
remote.  We're trying a few things to evaluate other interferences
(sampling concrete from the building in areas where there should not
have been any activation), and looking at sending our samples out for
alternative analysis techniques.  I will keep you posted as to what we
find out.  Again, thank you for your ideas, suggestions and reference
materials offered.  We will follow up on all of them.

Best regards,
Keith

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