# Simulation of photonuclear reaction in coupled neutron-gamma simulation

**URL:** <https://openmc.discourse.group/t/simulation-of-photonuclear-reaction-in-coupled-neutron-gamma-simulation/5293>\
**Category:** User Support\
**Created:** [March 5, 2025, 3:58pm UTC](https://openmc.discourse.group/t/simulation-of-photonuclear-reaction-in-coupled-neutron-gamma-simulation/5293 "2025-03-05T15:58:55Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![yieldz](https://avatars.discourse-cdn.com/v4/letter/y/96bed5/32.png) [@yieldz](https://openmc.discourse.group/u/yieldz)\
**Post date:** [March 5, 2025, 3:58pm UTC](https://openmc.discourse.group/t/simulation-of-photonuclear-reaction-in-coupled-neutron-gamma-simulation/5293/1 "2025-03-05T15:58:55Z")

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Hi all,  
I’m trying to simulate a rather simple case of photon induced fission on a bare Uranium sphere (natural composition), with the photon source uniformly distributed within the sphere. The photon energies are binned 100 groups between 1 and 20 MeV (linear steps), with equal probability.

With coupled neutron-photon transport I tried tallies on the spatial distribution of photon flux, neutron flux, fission rate (keyword ‘fission’) and fission neutron yield (keyword ‘nu-fission’).  
While I do see photon flux, the tallies on neutron flux and fission all give 0 ± 0 as if no event is produced.

Do you have any idea on the issue? Maybe I can do tallies on (gamma,n) with another score?

Thank you in advance,

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**Author:** ![paulromano](https://yyz2.discourse-cdn.com/free1/user_avatar/openmc.discourse.group/paulromano/32/486_2.png) [@paulromano](https://openmc.discourse.group/u/paulromano)\
**Post date:** [March 5, 2025, 4:34pm UTC](https://openmc.discourse.group/t/simulation-of-photonuclear-reaction-in-coupled-neutron-gamma-simulation/5293/2 "2025-03-05T16:34:03Z")

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Unfortunately photonuclear reactions are not yet supported in OpenMC.