R: R: [fluka-discuss]: Lead prompt gamma spectrum

From: Giuseppe Mazzola <giuseppe1.mazzola_at_mail.polimi.it>
Date: Thu, 8 Apr 2021 10:44:58 +0000

Dear fluka discuss,

I have checked and the cross section used by MCNP for natural lead is the ENDF-V.0, so an older version.
I have recently tried to make the same simulation changing the cross section in the MNCP input and I have found that ENDF-VII.1 doesn't show the peak too, as you described, while ENDF-VI.1 seems to work.

Thank you for the responses and for the help!


Da: Paola Sala <paola.sala_at_mi.infn.it>
Inviato: gioved́ 8 aprile 2021 11:54
A: Giuseppe Mazzola <giuseppe1.mazzola_at_mail.polimi.it>; fluka-discuss_at_fluka.org
Oggetto: Re: R: [fluka-discuss]: Lead prompt gamma spectrum

Dear Giuseppe,

thank you for pointing this out.

FLUKA is using ENDF-VIII for data on Pb.

Unfortunately, the gamma production in ENDF does not include the 7367KeV peak.

Probably because the latest versions of ENDF tend to rely more on models than on data...

The same happens in ENDF 7.1 and TENDL.

Do you know which database is used by MCNP in your case?


On 4/6/21 12:07 PM, Giuseppe Mazzola wrote:
Dear Fluka discuss,

thank you for the response.
I am aware of the groupwise algorithm used by Fluka for the transport of low energy neutron and for the generation of gamma radiations from such particles (with some exceptions) and as a manner of study, I was analysing the difference between Fluka results and MCNP results, which instead uses a pointwise transport and generation algorithm.
I have made the analysis for different materials and confronted with the IAEA Database for prompt gamma radiations.
The spectrum obtained, with the differences in the discrete gamma lines from MCNP and the Fluka peak distributed along the energies of the gamma group, are correct for any materials that I studied with the exceptions of natural lead.
Confronting the two spectrum, Fluka hasn't any evidence of the 7367KeV peak, which should be the predominant peak and it is present in the MCNP spectrum and also tabled by the IAEA Database.
For this reasons, I was wondering if this is related to a problem with my input or something connected to the cross section used by Fluka.
I am sending with this email also the input text and the result comparison between Fluka and MCNP, for a better explanation of my problem.

Kindest regards,

Da: Paola Sala <paola.sala_at_mi.infn.it><mailto:paola.sala_at_mi.infn.it>
Inviato: marted́ 6 aprile 2021 11:36
A: Giuseppe Mazzola <giuseppe1.mazzola_at_mail.polimi.it><mailto:giuseppe1.mazzola_at_mail.polimi.it>; fluka-discuss_at_fluka.org<mailto:fluka-discuss_at_fluka.org>
Oggetto: Re: [fluka-discuss]: Lead prompt gamma spectrum

Dear Pierfrancesco

Fluka transports

neutrons below 20 MeV with a groupwise algorithm (see the manual for

details). With this method, photons from neutron captures and

interactions are also produced in energy "groups", not as discrete gamma


A better treatment is available for a few isotopes (see the manual again).

 Extension to more isotopes is in the to-do list



On 4/2/21 7:13 PM, Giuseppe Mazzola wrote:

Dear fluka discuss,

Evaluating the prompt gamma emitted by natural lead, using thermal neutron as source, there is no evidence of the 7367 KeV gamma from Pb207, which should be the predominant peak as tabulated in IAEA database.

I'm using for the low mat card, the cross section associated to the natural lead at 296K.

Could you give me some advices?

Kindest regard,

Giuseppe Mazzola

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Received on Thu Apr 08 2021 - 14:14:42 CEST

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