[ RadSafe ] Re: Fallout "preserved" in concrete

Arvic Harms Arvic.Harms at npl.co.uk
Wed Feb 25 03:31:02 CST 2009

Dear Keith,

The excellent paper below gives more information on tritium in concrete. Some of the tritium is mobile which will affect the depth profile.

Tritium Speciation in Nuclear Reactor Bioshield Concrete and its Impact on Accurate Analysis

Dae Ji Kim, Phillip E. Warwick and Ian W. Croudace (GAU-Radioanalytical, Southampton UK)

Analytical Chemistry, 2008, 80 (14), pp 5476-5480

Kind regards,

Arvic Harms
National Physical Laboratory
Teddington, UK

> -----Original Message-----
> From: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl]On
> Behalf Of welch at jlab.org
> Sent: 25 February 2009 05:31
> 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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