I calculate the neutron spectrum, but the results shows none tallies in the low-energy as figure follow:
Any advice? Thanks a lot !
Any advice? Thanks a lot !
the model is a Lead-cooled Fast Reactors.
You probably shouldnt be expecting much, if any, thermal flux in a LFR. Not sure what energy structure you are using, but that could play a role
It should probably show some tallying at some slightly lower energies, so if you are running few particles - try increasing the amount?
Also, I am not sure why you are dividing your flux values?
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Hi Jiang Jiang.
Various things could affect the neutron spectrum, not only by the reactor type i.e. LFR, but also by which cells you have tallied and how you tally those cells.
I am generally tallying the whole core model to know the core neutron spectrum, but if needed, I could tally specific cells or specific positions on my core, i.e. on the irradiation position or in the radial/axial reflector. So I think you might need to consider that part.
Also, you might want to double-check your tally.out file just to make sure that the flux value on the low neutron energy bin is null or just a small number. If the number was so small, the neutron distribution could be improved by increasing the particle number as JustAnotherNeutron suggests so that the low energy neutron could be reported with a higher neutron history if they exist.
Thank you for giving me advice!
Yes, the proportion of LFR’s thermal neutrons should be less than the PWR… but there should not be zero tallies in the thermal energy zone.?(I think)
The source type I used was IndependeSource, in a k-mode, I try increase the amount of particles in the source, but still.
The reason dividing the flux values is a silly copy from the examples.
At the figure I showed in the question,what I calculated is a cellFilter(a fuel cell). At last, I delete the filter( so the filter be the whole geomtry) the result become normal:
Thanks again!
Thank you for giving advice!
I calculated the whole core spectrum, the thermal neutron’s proportion becoming normal?
I check the tallies, there is a none, I can’t improve by increasing the particles’ number. But I think this is very important in the future calculation, so thanks!
Hi Jiang Jiang, I think your last neutron spectrum for the whole geometry is a lot better at showing the whole core neutron spectrum, congrats.
Also, generally, neutrons generated closer to fuel will have higher energy compared to neutrons that have been scattered to other core components. So if you want to see the neutron energy distribution, you might want to use a mesh tally filter and add the neutron energy filter i.e. thermal, epithermal, and fast range. So you can see which part of your core has more thermal neutrons than fast neutrons, etc. But that will need more script in post-processing. Hehehe
Have a great day
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Looks great! Glad that you got it working as expected. 
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