Re: [fluka-discuss]: concrete activation, neutron point source

From: Stefan E. Mueller <stefan.mueller_at_hzdr.de>
Date: Sun, 7 Mar 2021 19:03:19 +0100 (CET)

Dear Angel,

if I understand you correctly, you want to compare two scenarios:

- using a pointlike neutron sourceterm, which isotropically irradiates the
concrete shell using the energy spectrum that you found in your previous
sudies

- using protons shooting on a water target as source, with the
secondary radiation produced by the protons in the target irradiating the
concrete shell.

From the inputs that you provided, it seems however that you can not
compare the two scenarios, because while the neutrons indeed emit
isotropically from the center, the proton beam starts at (0., 0., -1.cm)
outside the target, but then is also emitted isotropically - in this
scenario, most of the protons will not hit the target, but reach the
concrete and will activate it. Probably moving the proton source to the
center of the target or making it a beam in +z-direction would make the
two scenarios more comparable.

Cheers,

         Stefan

--
Stefan E. Mueller
Department of Information Services and Computing - Computational Science
and Institute of Radiation Physics
Helmholtz-Zentrum Dresden-Rossendorf
Tel: +49 (0351) 260 3847
Stefan.Mueller_at_hzdr.de
http://www.hzdr.de
Vorstand: Prof. Dr. Sebastian M. Schmidt, Dr. Diana Stiller
Vereinsregister: VR 1693 beim Amtsgericht Dresden
On Thu, 4 Mar 2021, angeld wrote:
> Dear FLUKA experts and users,
>
> In my last thread
> (http://www.fluka.org/web_archive/earchive/new-fluka-discuss/18366.html) I
> posted a question regarding the neutron fluence spectrum that we have
> obtained and its graphical presentation.
> My next step is to use it to study the activation of a spherical concrete
> shell with the obtained neutron spectrum. So I decided to test it vs direct
> simulation, i.e. with a simplified liquid target. The first issue is that
> the specific activity of the generated isotopes of interest, in the case of
> a neutron point source, is about 3-5 times higher than the direct
> simulation. Is this result to be expected?
> But what bothers me, even more, is that one of the isotopes 22Na is about
> 6000 times higher in the case of a direct simulation. Is it plausible to be
> generated via 24Mg(p, alpha)22Na reaction? There is 0.2% Mg in the
> concrete.
> I have attached the input files for the two simulations, the sorted
> results, the source.f subroutine that I used and the file with the obtained
> spectrum.
>
> Best regards,
> Angel
> -- 
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>

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Received on Sun Mar 07 2021 - 19:03:19 CET