Re: [fluka-discuss]: neutrons, reaction rates

From: Andrea Fontana <>
Date: Fri, 9 Nov 2018 13:06:44 +0100

Dear Angel,
    yes, your interpretation of the Fluka output is correct. But in this
case, without the DCYSCORE and DCYTIMES card, you do not need the IRRPROFI
card: your are simply calculating the production of residual nuclei per
primary. You can try to remove IRRPROFI and re-run: you will get the same

Regarding the new geometry, I have not enough details of your problem:
the behaviour seems to be reasonable. As a suggestion for a better
comparison with your reference data, do not forget to run multiple
histories and let Fluka calculate the statistical errors.

Hope this helps.
Kind regards,

Il 06/11/2018 16:05, Angel ha scritto:
> Dear Andrea,
> thank you for the support I really appreciate it!
> I did not define decay times or use the DCYSCORE card because I needed
> results presented in nuclei/primary (source neutron) rather then Bq. Do I
> understand correctly what I get? In the current case I suppose that I
> score the number of residual nuclei of a given isotope per source neutron
> in the whole volume of the detector. If I need to score
> nuclei/primary/cm^3 then I should divide by the volume of the detector by
> typing the correct volume in cm in the RESNUCLE card.
> I modified the geometry (please find .inp attached) by placing the
> activation foils on every 5 cm and changed the shape of one of th Nb
> detector from box to cylinder (it is how it is supposed to be initially),
> and this changed the situation. This resulted that the decline of 92mNb
> nuclei per/ source neutron is faster and the difference between mine
> results and the ones I am comparing with is now about 2.5-4 times. Could
> such behavior be expected?
> Kind regards,
> Angel
>> Hi Angel,
>>    in your case a normalization volume WHAT(6)=1 in the RESNUCLEI
>> card will not be necessary: it just just a number by which the final
>> score is divided.
>> Regarding the irradiation profile, if I understand correctly your
>> problem, I see that you have not defined ant DCYTIMES card nor a
>> DCYSCORE card: in this case, as stated in the manual under DCYSCORE,
>> no particles originated from radioactive decay can be scored and
>> any detector will only score the prompt particles. This might be
>> the source of the behaviour you observe. I think thst you need
>> to define DCYTIMES (a 0 value means EOB) and DCYSCORES associated
>> to your RESNUCLEI cards (details in the manual).
>> In addition, I suggest you to enable full ion transport with:
>> to have a more accurate energy deposit by fission fragments and
>> fragments from Fermi break-up.
>> The isomers patch is not active when simulating analog decays.
>> I send you a second revised input, where I score, for example,
>> residual nuclei after 1h from EOB and I see 92mNb. I save the
>> output in a separate file (UNIT=24). Please, give it a try...
>> Hope this helps,
>> Andrea
>> Il 31/10/2018 10:46, Angel ha scritto:
>>> Dear Andrea,
>>> thank you so much for the help and the advice! The results I'm comparing
>>> with are presented as [x10^-24/nuclide/source neutron] (I suppose the
>>> 10^-24 stands for barn). Thus I thought there is no need to normalize
>>> it.
>>> Anyway normalizing it made the results to differ even with additional
>>> one
>>> order of magnitude.
>>> I also tried to change the irradiation profile but it doesn't seem to
>>> have
>>> any effect - I get the same numbers. Is this expected for this model?
>>> Maybe I should try to change the beam profile?
>>> What should be scored in the Nb detector/foil is the isomer 92mNb. So I
>>> also tried switching on the patching for isomers but it is probably
>>> activated by default thus that didn't have effect.
>>> To have proper results for 198Au I need much better statistics. Thus my
>>> idea was to deal first with the 92mNb before running the model with more
>>> primaries.
>>> Best regards,
>>> Angel
>>>> Dear Angel,
>>>>    you are missing the correct volumes in the RESNUCLEI cards (that
>>>> in your case are 0.1 for NbDet and 0.00025 for AuDet regions). This
>>> volume is used to normalized the results and is needed if you want to
>>> compare with experimental results. If you add the correct values, you
>>> should get more reasonable results.
>>>> Other minor things I noticed in your input:
>>>> - when defining a material, if you need the natural isotopic
>>>>   composition, use WHAT(6)=0 and do not specify WHAT(2)
>>>>   (see also the manual);
>>>> - you can skip Z definition in a MATERIAL for a COMPOUND:
>>>>   it is ignored.
>>>> I attach a revised copy of the input file.
>>>> Hope this helps,
>>>> Andrea
>>>> Il 30/10/2018 13:21, Angel Demerdzhiev ha scritto:
>>>>> Dear FLUKA experts and users,
>>>>> I am a beginner trying to calculate the reaction rates at different
>>>>> depths
>>>>> in a concrete block in Nb and Au activation foil for a 14.1 MeV
>>>>> neutron
>>> source.
>>>>> For a reason not known to me I get results which differ in two orders
>>> of
>>>>> magnitude of what is expected. Can you take a squiz at my .inp file
>>>>> and
>>> tell me if I am doing anything wrong.
>>>>> Kind regards,
>>>>> Angel
>>>> --
>>>> ========================================================================
>>> Dr. Andrea Fontana tel: +39 0382 987991
>>>> Istituto Nazionale fax: +39 0382 423241
>>>> di Fisica Nucleare
>>>> Sezione di Pavia e-mail:
>>> Via Bassi 6 web :
>>> 27100 PAVIA, Italy
>>>> ========================================================================
>> --
>> ========================================================================
>> Dr. Andrea Fontana tel: +39 0382 987991
>> Istituto Nazionale fax: +39 0382 423241
>> di Fisica Nucleare
>> Sezione di Pavia e-mail:
>> Via Bassi 6 web :
>> 27100 PAVIA, Italy
>> ========================================================================

Dr. Andrea Fontana                    tel: +39 0382 987991
Istituto Nazionale                    fax: +39 0382 423241
di Fisica Nucleare
Sezione di Pavia                      e-mail:
Via Bassi 6                           web   :
27100 PAVIA, Italy
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Received on Fri Nov 09 2018 - 14:36:26 CET

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