Power Peaking Factor

User Support
1

Hi forum,

I’m relatively new to OpenMC and working on a research about reactor’s power peaking factor. Could I calculate power peaking factor (both radially and axially) from fission-q-prompt tally score?

Best regards,
Fadil

2

Hi @fadilnaufalwahas and welcome to the forum. I would recommend using the fission-q-recoverable score because it includes energy from delayed neutrons, photons, and electrons whereas fission-q-prompt does not. Be aware that these scores don’t account for non-fission energy deposition (such as production of photons from (n,γ) reactions and their subsequent deposition), so if you really want to do this rigorously, you need to run a coupled neutron–photon simulation and tally the heating score.

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3

Thank you @paulromano :relaxed:
Referring to the posts you made [1] [2], I would like to know if I understood the calculation. The power of fuel (in watt) could be calculated by:

P (watt) = ( F * Pr * (vf / f) * c ) / ( Q * keff )

with
F = tally fission-q-recoverable (eV/source)
vf = tally nu-fission (neutron/source)
f = tally fission (fission/source)
Pr = known reactor power (J/s)
Q = 3.2E-11 J/fission (for U-235)
keff = neutron multiplication factor (neutron/source)
c = 1.6E-19 watt.s/eV

Is my interpretation correct?

Best regards,
Fadil

4

@fadilnaufalwahas The method I had outlined in those earlier posts is probably not the best, or most straightforward, way to perform a power normalization. There is now a section in our user’s guide about normalizing tally results that gives good advice about how to do this.

1 Like
5

Thank you @paulromano.

6

@paulromano Can you please help me clear my calculation gap on the power peaking factor? I have ‘fission’ tally values which gives me the results in fission/src. After calculating the f value of normalization from here, I multiplied with the fission/src value. I think I have my value in units of fission/s. I don’t know if it works if I multiply this value with Q=200MeV/fission, do I get the power in eV/s and convert into W? Also, I am using MOX fuel, the value of Q will be different, is there a way to calculate it using tallies?