Re: Re: Re: Deviations of flux caculation results by FLUKA and MCNP

From: <wdx456_at_mail.ustc.edu.cn>
Date: Thu, 31 Jan 2013 16:29:52 +0800 (CST)

Hi,Paola

You are correct. I'm testing all materials together in a complex geometry.

Self-shielding really made a big difference(about 50% and even more) at first.Then I choosed all materials as selfshielded in Flair and the difference was decreased to 10%. I'm not familiar with selfshielding effect in fact.
Is there anything I should notice when writing FLUKA input files(compared with MCNP input files) about selfshielding and databases?

Many thanks!

Walker


> -----Original E-mail-----
> From: "Paola Sala" <paola.sala_at_mi.infn.it>
> Sent Time: 2013-1-31 15:14:13
> To: wdx456_at_mail.ustc.edu.cn
> Cc: paola.sala_at_mi.infn.it, fluka-discuss <fluka-discuss_at_fluka.org>
> Subject: Re: Re: Deviations of flux caculation results by FLUKA and MCNP
>
> Hello
> with 14 MeV neutrons in most materials one would expect something better
> than 10%, however
> - self-shielding could make a big difference
> - different choices of databases could make some difference
> AND: if I understand correctly, you are testing ALL materials together in
> a complex geometry, therefore differences propagate themselves from one
> region to another, making it difficult to understand what and where really
> happens.
> Regards
> Paola
>
> > 2013 14:23:03 +0100 (CET)
> > X-Virus-Scanned: clamav-milter 0.97.6 at smtp2.mi.infn.it
> > X-Virus-Status: Clean
> > Sender: owner-fluka-discuss_at_smtp2.mi.infn.it
> >
> >
> > Hi Paola,
> >
> > The primary particle is neutron with energy 14MeV and the particle I'm
> > scoring is also neutron.
> > I didn't find any pattern in the diffferences(Really troublesome:£©).
> >
> > Maybe I should do more careful analysis to find out the true reason.
> >
> > Then,from your expert view,is it possible that 10% difference of FLUKA and
> > MCNP flux results are the right results?(considering material lib and
> > software differences)
> >
> > Thanks for your kindness!
> >
> > Best wishes,
> > Walker
> >
> >
> >> -----Original E-mail-----
> >> From: "Paola Sala" <paola.sala_at_mi.infn.it>
> >> Sent Time: 2013-1-30 15:39:26
> >> To: walker <wdx456_at_mail.ustc.edu.cn>
> >> Cc: fluka-discuss_at_fluka.org
> >> Subject: Re: Deviations of flux caculation results by FLUKA and MCNP
> >>
> >> Dear Walker,
> >> it is difficult to answer without more information:
> >> What is your primary particle? Its energy? Which particles are you
> >> scoring?
> >> Do you see some pattern in the differences? For instance, do they depend
> >> on the position , on the material, or other?
> >> Regards
> >> Paola
> >> > Dear all,
> >> >
> >> >
> >> >
> >> > Recently, I was trying to calculate flux distribution of a model via
> >> FLUKA
> >> > and MCNP respectively (in order to verify the correctness of my
> >> result).
> >> >
> >> >
> >> >
> >> > The model was made up of over 100 regions and the materials included :
> >> C,
> >> > V
> >> > , Cr, Mn, Fe, Ta, W, H, He, Li, Pb, Ni, etc.
> >> >
> >> > About 50 regions' fluxes were scored.
> >> >
> >> >
> >> >
> >> > I tried several ways to decrease the relative error. For example, the
> >> same
> >> > volume values were input into FLUKA and MCNP for flux calculation; the
> >> > primary particles were increased from 1.0e6 to 1.0e7 to 1.0e8; the
> >> > selfshielded material in FLUKA was also chosen.
> >> >
> >> >
> >> >
> >> > However, the FLUKA and MCNP results seemed not to match ideally: about
> >> 25
> >> > regions had deviation less than 1%; about 20 ones had deviation
> >> between 1%
> >> > and 2 %; most of the left ones had deviation beside 10% with the max
> >> > deviation 19%. Both the max statistical discrepancies of FLUKA and
> >> MCNP
> >> > are
> >> > no bigger than 1%.
> >> >
> >> >
> >> >
> >> > I' m wondering if my calculation result is correct. What's the
> >> reasonable
> >> > flux deviation of FLUKA and MCNP? How about 10%?
> >> >
> >> >
> >> >
> >> > Looking forward to any suggestion.
> >> >
> >> >
> >> >
> >> >
> >> >
> >> > Best wishes
> >> >
> >> > Walker
> >> >
> >> >
> >> >
> >> >
> >>
> >>
> >> Paola Sala
> >> INFN Milano
> >> tel. Milano +39-0250317374
> >> tel. CERN +41-227679148
> >>
> >
> >
> >
>
>
> Paola Sala
> INFN Milano
> tel. Milano +39-0250317374
> tel. CERN +41-227679148
>
Received on Thu Jan 31 2013 - 10:04:15 CET