RE: Re: Can FLUKA (or flair ) be used to caculate region volumes?

From: Jean-Emmanuel Groetz <jegroetz_at_univ-fcomte.fr>
Date: Fri, 13 Apr 2012 17:16:34 +0200

Alberto,

Here is the part (as attachment) of the MCNP4C2 documentation related to
the calculation of volumes. You will find at the end the ray-tracing
method for stochastic volume.

On the MCNPX forum, I just find a similar trick (from Sergio
Korochinsky), which follows below :

--------------------------------------------------------------------------
Consider a spherical cell.
F4 tallies the total track length in the cell.
Before printing out, MCNP normalizes it with the VOLume of the cell
and
the NPS in order to approximate the average flux in the cell.
Now consider this:
1- If the material is VOID, there is no interaction of the particle
within the cell and the track lengths are actually cords of the cell.
2- If the flux at your spherical surface is ISOTROPIC, the track
lengths
go from any point on the sphere to any other point on the sphere, and
therefore every possible cord is sampled.
3- Dividing the total track length (sumation of all the cords
uniformly
sampled) by NPS gives you the average cord of the sphere, which is
equal
to 4*vol/sur = 4*r/3. To get this in the print out you must avoid
dividing the tally by the volume of the cell (which in any case you
don't
know!).
4- If you artificially renormalize the tally multiplying it by pi*r^2,
the tally gives you the volume of the sphere!
5- I leave it for you, as an exercise, to demonstrate that if this is
valid for the sphere then it's also valid for any body included in the
sphere.

So, to implement the method you have to:
1- Use the card VOID and set all the importances to 1 (any internal
region with imp=0 would create an artificial "absorption" and
therefore
cut the cord).
2- Create an inward cosine current at the spherical surface source.
3- Set the volume of the tally to 1, either with the cards VOL or SD.
4- Renormalize the tally by pi*r^2 either with the cards FM or wgt in
SDEF.

-- 
_______________________________________________
Jean-Emmanuel Groetz
Laboratoire Chrono-Environnement UMR CNRS 6249
Chimie-Physique & Rayonnements
Université de Franche-Comté
16 route de Gray
25030 Besançon Cedex
France
mailto : jegroetz_at_univ-fcomte.fr
tel : +33 (0) 3 81 66 65 07
fax : +33 (0) 3 81 66 65 22
_______________________________________________
Le vendredi 13 avril 2012   16:38 +0200, Alberto Fasso' a écrit :
> Hi Jean-Emmanuel,
>
> I don't know how does MCNP calculate the volumes. Do you have any information
> about it?
>
> Alberto
>
>
> On Fri, 13 Apr 2012, Jean-Emmanuel Groetz wrote:
>
> > Dear all,
> >
> > In addition to previous messages from Mina and Chris, volume calculation
> > could still remain a problem:
> > - for FLUKA/FLAIR users with Linux OS, SimpleGeo works very well with
> > Windows under the VirtualBox software, without any difficulty. The
> > geometry file could be imported between both OS through shared folders
> > - once before with a complex geometry (concentric spheres and tori),
> > MCNP was unable to assess the region volume for an energy deposition
> > tally. So I had to calculate every region volume...
> >
> > The method described by Anna (from Alberto) seems to be neat.
> >
> > Jean-Emmanuel
> >
> >
> >> Dear Walker,
> >> SimpleGeo offers two kinds of volume calcultions. The one is called
> >> "geometric" and uses the visualized and as such
> >> discretized geometry. As a consequence it is very fast but might
> >> fail in case of
> >> rendering artefacts. There is another one which is called "Quasi
> >> Monte Carlo" which calculates the volume integral by using stratified
> >> numerical sequences which act on the analytic description of the geometry.
> >> Therefore, this method also works in the presence of rendering artefacts.
> >> If you are looking for the functionality to calculate volumes of arbitrary
> >> regions directly in your input, like it is provided for example in MCNP(X),
> >> then I'm afraid that FLUKA itself does not provide such a feature
> >> - at least not to my present knowledge. Eventually you can do it but you
> >> will need to do a bit of programming or set up a specific geometry, input
> >> and post-processing to achieve this.
> >> Hope that helps
> >> Chris
> >> --------------------------------------------------------------------------=
> > --------------
> >> Chris Theis
> >> CERN/DGS-RP - European Organization for Nuclear Research
> >> 1211 Geneva 23, Switzerland
> >> Phone: +41 22 767 8069                    Office: 892-2A-015
> >> e-mail: Christian.Theis_at_cern.ch<mailto:Christian.Theis_at_cern.ch>
> >> www: http://www.cern.ch/theis
> >> --------------------------------------------------------------------------=
> > ---------------
>

Received on Sun Apr 15 2012 - 12:39:27 CEST

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