Dear FLUKA experts,
Greetings from China!
I am a graduate student, Xianpeng Yin working on the FLUKA for about one year. Currently, I am calculating the radionuclide inventory and time-dependent activation evolution of the naturally abundant pure iron under a typical fusion reactor neutron spectrum. I have a few concerns:
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About the source beam definition: If I need to input a text-format neutron spectrum file to define the incident neutron energy distribution, is it appropriate to use only an empty SOURCE card after successfully compiling the executable file in Compile? I am not quite sure whether the format of the energy spectrum file (.txt) I input meets the specifications or rules of FLUKA. (A .txt file has been provided below, where the first column is the lower limit of energy range in MeV, the second column is the upper limit of energy range, and the third column is the neutron flux fluence.)
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About the low energy neutron reactions: Since the energy range of the aforementioned neutron spectrum file is between 1E-11 MeV to 20 MeV, does FLUKA have an energy threshold X for neutron-nucleus reactions, or it only depends on the range of nuclear dataset? I used the LOW-PWAS card to activate the point-wise mode. When the energy is lower than X, there is almost no production of radioactive nuclides, and thus there is no subsequent radioactive decay. Is this correct? During the process of radioactive nuclide production, does FLUKA include all possible reactions such as elastic scattering, inelastic scattering, radiative capture, emission of charged particles, and heavy nucleus fission in its calculation scope? Or does it select important neutron reactions for calculation?
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About the target geometry setting: Now, I would like to reproduce a benchmark study, as the attached the reference paper. During the “play” with FLUKA and flair, I found that the volume setting of the target material and the grid density setting of usrbin greatly affect the activity (ATOMASS scoring, Bq/g) calculation results. This may be due to FLUKA calculating the average values within the “BIN.” However, when I set the thickness of the target as 0.00438cm, there is only one radionuclide produced. Therefore, my question is, how should I set the target geometry in FLUKA simulation, so that I could make a reasonable comparison with such 0-deminension, inventory calculation code, such as FISPACT?
Lastly, could you help me to check the below input file? Dose it fully or correctly represents the below irradiation information. Do I need to activate other cards to calculate all possible reaction types between iron nuclei and neutrons?
Here are the key input parameters and files:
Material: Naturally abundant pure iron
Target: Thin slice with a side length of 1 cm and thickness of 0.0438 cm
Beam: Neutron spectrum of a typical fusion reactor, coinciding with the target in terms of cross-section
Irradiation time: Continuous 2 years, with a flux: 5.0422E14/cm2s
Shutdown time: Starting from the shutdown initiation.
Thank you very much for your kind guidance! Happy new year in advance!
Attachment:
acti_exer_12.28.flair (3.1 KB)
acti_exer_12.28.inp (2.5 KB)
DEMO.txt (16.8 KB)
source_newgen_neutron_DEMO.f (18.9 KB)