Spontaneous fission of uranium fuel


I’m trying to calculate the neutron source (energy-dependent) due to spontaneous fission of uranium fuel. I have taken the rdecay01 example and changed the homogeneous region to uranium fuel. I had a few questions about how to set up the model:

  1. Since I’m only interested in neutron source and no decay products, do I just need the neutron macro?
  2. If I’m modelling spontaneous fission do I still need a primary particle source?
  3. Is it possible to obtain the output in a tabular format rather than visual?

_Geant4 Version:_geant4-11-01-patch-02 [MT] (15-June-2023)
_Operating System:_Red Hat Enterprise Linux version 8.5 (Ootpa)
_Compiler/Version:_gcc (GCC) 8.5.0 20210514 (Red Hat 8.5.0-20)
_CMake Version:_3.26.5

Thanks in advance,


Yes. You would make your primary particle a U-238 nucleus. I am not certain whether G4 includes spontaneous fission of U-235 in its models (that starts to encroach on ITAR stuff).

Do you mean like a CSV or tab-separated file? Sure, you can specify which G4Analysis manager you want in your simulation code.

Thanks for getting back to me. In terms of the output, I have seen in the manual that you can plot results but is it possible to just get a table of results. It doesn’t matter if it’s .csv or .txt etc. I will have a look at the G4Analysis manager.

Hello, I’ve taken the rdecay01 example and made some changes for the specific problem I am modelling. I have set the histograms to be .csv and I can see the files have been created. I have also deleted some macros which are not relevant to this problem. Specifically I’m interested in the energy-dependent neutron source due to SF and (alpha,n) reactions. I have run the model using the neutron macro and alpha macro but I’m struggling to understand what this means. Would running with the neutron macro specifically give me the neutron source? Looking at the syntax I’m unsure as to how the code differentiates between neutron emission and emission of other particles. I’m also struggling to interpret the data in the csv files.

Best wishes,


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