[ RadSafe ] Re: Fallout "preserved" in concrete

Mon Feb 23 04:06:20 CST 2009

Dear all,

Neutron-irradiated concrete at 10-20 years post shutdown may contain:

H-3, C-14, Cl-36, Ca-41, Fe-55, Co-60, Ni-63, Ba-133, Eu-152 and Eu-154 (and natural occuring radionuclides). H-3 and Eu-152 will be the dominating activities.

More information on an NPL intercomparison we organised on neutron-activated concrete powder samples can be found on  http://www.npl.co.uk/server.php?show=ConWebDoc.3031 (under "concrete results").

Kind regards,

Arvic Harms
National Physical Laboratory
UK

> -----Original Message-----
> From: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl]On
> Behalf Of Dale Boyce
> Sent: 23 February 2009 00:01
> To: radsafe at radlab.nl
> Subject: Re: [ RadSafe ] Re: Fallout "preserved" in concrete
> 
> 
> Keith,
> 
> A couple of things to think about. Concrete from accelerator 
> shielding tends 
> to have europium neutron activation to Eu152 and Eu154. I 
> don't have a chart 
> handy, but either 152 or 154 will dominate the activation 
> products in gamma 
> spectra at 10-20 years post shutdown.
> 
> If you are doing liquid scintillation spectroscopy of 
> concrete dust without 
> first fully chemically dissolving it, naturally occuring 
> alpha emitters can 
> mimic tritium. Alpha's in solution will show up as a peak 
> that is down 
> shifted in the spectrum by a factor of 6 or 7 from the alpha 
> energy. If they 
> are in a fine powder they can get further down shifted due to energy 
> straggling. Concrete frequently has a fair amount of Th232.
> 
> Dale
> ----- Original Message ----- 
> From: <welch at jlab.org>
> To: <radsafe at radlab.nl>
> Sent: Sunday, February 22, 2009 10:23 AM
> Subject: [ RadSafe ] Re: Fallout "preserved" in concrete
> 
> 
> > Thanks for the response, Mike.
> > We are indeed sampling and counting the concrete.  Our early results
> > indicated the presence of tritium, which I did not expect 
> to be uniformly
> > distributed in the material (this is a collection of large 
> shield blocks
> > from an old cyclotron).  We are scratching our heads a 
> little and trying
> > to come up with possible explanations.  One idea is that 
> the activity is
> > really from Sr-90.  But, we don't see any Cs137, so it's a 
> bit puzzling.
> > Other possible interference could be from naturally 
> occuring activity (as
> > you mentioned), but we haven't put all the pieces together 
> yet.  With
> > respect to the fallout, I'm mainly wondering if there have been any
> > attempts to benchmark such a thing, similar as has been 
> done with the
> > naturally occuring nuclides.  If would be nice to have a 
> reference to help
> > substantiate or refute the idea.
> > Thanks again.
> > Keith
> >
> >
> >> ------------------------------
> >>
> >> Message: 2
> >> Date: Fri, 20 Feb 2009 14:38:43 -0800
> >> From: "Brennan, Mike  (DOH)" <Mike.Brennan at DOH.WA.GOV>
> >> Subject: RE: [ RadSafe ] Fallout "preserved" in concrete
> >> To: <radsafe at radlab.nl>
> >> Message-ID:
> >> <37C41083D3480E4BBB478317773B845D0148EE62 at dohmxtum31.doh.wa.lcl>
> >> Content-Type: text/plain; charset="us-ascii"
> >>
> >> 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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