Discrepancy in Photon Heating Values

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1

I am running a few cases for nuclear heating using the same geometry and materials, then comparing it to MCNP values. My values are:

  1. OpenMC run with heating-local: 10.09682 MeV/sp
  2. OpenMC run with heating (n,p): 9.1556 MeV/sp
    • n: 9.30226 MeV
    • p: 0.0025368 MeV
  3. OpenMC run with heating (n,p,e,e+): 10.57913 MeV/sp
    • n: 9.15309 MeV
    • p: 0.002536 MeV
    • e-: 1.284695 MeV
    • e+: 0.138812 MeV
  4. MCNP run with heating (mode n,p): 10.571 MeV/sp
    • n: 9.79 MeV
    • p: 0.781 MeV

My questions are:

  1. Shouldn’t the heating-local be a more conservative estimate as the photon transport is also included in ‘heating’ simulations whereas in ‘heating-local’ all photon energy deposited + charged particles are deposited locally?
  2. As far as I know OpenMC does not run charged particle transport, so why do the numbers for change between #2 and #3 cases above? Am I double counting contribution if I add up all the numbers in #3 to compare to the MCNP value?

Thank you

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2

There are no charged particles in OpenMC, it is all photon and neutron Kerma.

I never use heating-local, I believe it pertains to lumping the secondary photons from fission into the Kerma. Though the wording/documentations is a bit fuzzy and implies all photon secondaries.

#3 is the correct way.
It’s to do with how OpenMC accounts for different interactions.
This is a frequent hang-up in OpenMC

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