Energy deposition for photons and beta particles

User Support
1

Hello everyone,

I’m trying to count energy deposition for photons, beta particles and neutrons.
I learned from the Theory and Mathedology manual that OpenMc obtains all relevant components of fission energy release through modifications to heating reaction.

But I’m not sure whether energy of delayed fission photons and energy of prompt fission photons are both computed from NJOY. Is one of the two types of energies estimated proportionally according to the other?
In addition, how could I get energy deposition for beta particles?

Any help regarding this topic would be very appreciated.

Kimberly

1 Like
2

Hi @Kimberly and welcome to the community!

NJOY does not include delayed fission photon energy in the KERMA values that it produces in the HEATR module.

Because we generally don’t know what the spectrum of delayed fission photons looks like, what we do instead is to artificially increase the yield of prompt photons from fission in order to produce the same amount of energy that would be produced by both prompt and delayed photons. This is done by default, although you can turn it off with settings.delayed_photon_scaling = False.

Most heating-related scores (heating, fission-q-recoverable, and kappa-fission) include the energy from beta particles. I’d recommend taking a look at the description of the scores here.

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Thank you @paulromano for your reply. If my understanding is correct, when I turn the treatment for delayed fission photons off, OpenMC treats photons in the same way as MCNP.
In fact, I had done a test for a cube filled with U235. Here is the input file
U-cube.py (3.9 KB). The energy deposions for photons computed from OpenMC and MCNP are 10.79MeV/source and 7.01MeV/source, respectively. What causes the difference?

Thanks,
Kimberly

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Please @paulromano, do you have any comments on this?

Thank you,
Kimberly

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Hi @Kimberly. The value from MCNP (7.01 MeV/source) sounds like it just includes the prompt photon energy. If you are looking at the heating value from OpenMC, that includes the energy deposited not only by prompt photons produced from fission but also by photons produced from (n,γ) reactions. That is the most likely source of the difference you are seeing.

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Thank you @paulromano for your reply. I will look in to that.
Kind regards,
Kimberly