Activation of alloy materials with specific energy spectrum inputs

Dear experts,

As a beginner of FLUKA, I came cross a problem when I calculate the activation and the production yield of an alloy. I want to get the residual activity(Bq/kg) of the alloy cooling down for several special (or fixed) decay time followed by 2 years irradiation. Expecting to reproduce the beam imformation in detail, I modified the source routine, input a neutron spectrum file and compiled the executable. I have set the essential cards for source routine and activation, including PHYSICS, SOURCE, IRRPROFI, DCYTIMES, RADDECAY, RESNUCLE and DCYSCORE. But the result is relatively odd. There are few radionuclides produced. I do not know how to solve it.

I guess there are some differences between single energy beam and spectrum and there are some defects in my input. Could you please help me out?Thanks a lot!
Here are some essential files:

activation_exercise.flair (15.1 KB)
activation_exercise.inp (9.6 KB)
PWR.txt (19.5 KB)
source_newgen_neutron_PWR.f (18.8 KB)

Hi Da Chen,

I checked your files, here a few comments:

  • In the source_newgen_neutron_PWR.f you uploaded, you do not call your spectrum but DEMO.txt (line 240)
  • When I opened your .flair project I saw that in the Exe box (on the right in run tab) you were calling the fotran routine rather than the executable file
  • To check if the routine was properly uploading the spectrum of interest I created a source term called PWR3MeV.txt (as you see here attached) where you have only one bin of energy 3 MeV and I compared the results against a monoenergetic 3 MeV neutron beam (expressed as 0.003 GeV in the BEAM card). The results seem consistent with each other in terms of activation (use the attached flair projects to run and plot the results).
  • To this regard, I also added a USRTRACK scorer just in front of the target material to check the neutron spectrum. As you see below, the neutron spectra are similar with each other (of course they are not monoenergetic because you also get the contribution from backscattered neutrons coming from the target). So for me the routine is indeed correctly uploading the requested spectrum.

  • If you can, try to understand what radionuclides you expect to produce with a neutron spectrum as the one in PWR.txt to see if the results make sense.

Let me know if I was not clear,

source_newgen_neutron_PWR.f (18.8 KB)
activation_exercise.flair (10.0 KB)
activation_exercise_3MeV.flair (6.0 KB)
activation_exercise_3MeV.inp (9.8 KB)
activation_exercise.inp (9.9 KB)
PWR3MeV.txt (155 Bytes)

Hi Marco Tisi,
Thanks for your helpful guidance. I checked the fortran routine, Exe box and corrected the mistake. Besides,I used USRTRACK to confirm the neutron spectrum of interest according to your advice. Then, I compared the spectrum produced by FLUKA with the curve produced by Origin. They are consistent. So I conservatively think my spectrum is input correctly.
Best wishes to you!
Da Chen