Hi, I have been working with the example depletion chain file chain_simple.xml from the OpenMC notebooks, which includes a few isotopes like Cs-137 and Ba-137m with their gamma decay data. However, I need a more comprehensive depletion chain file that contains the full gamma (photon) decay data for all uranium-series isotopes, such as U-238, Th-234, Pa-234m, Bi-214, Pb-214, Ra-226, and others. I would like to know if there is a pre-existing OpenMC chain file, based on ENDF/B-VII.1 or VIII.0 libraries, that already includes detailed photon source terms for these isotopes. If such a file does not exist, could someone guide me on how to generate one myself, including the proper use of tools like openmc-ace-to-hdf5 or something, and which decay data libraries should I use? Any recommendations on data sources or scripts to create a full uranium decay chain with gamma emissions would be very helpful. Thank you!!! 
Hi Peshwah Rafi, welcome to the openmc community.
You can download the official openmc chain files from openmc.org. They have created a specific chain file either for a typical fast reactor spectrum (SFR) with fast chain, or a typical thermal reactor spectrum (PWR) with thermal chain. Both chain differs in the branching ratio for the capture reaction of some isotopes. If the full chain is too much for you, you can also try to use the simplified chain.
Thanks, but in my case, for running a gamma detector simulation, for some reason, those chain files don’t work, and they throw an error, as shown below. Could you please figure out the reason why this is happening? Any suggestion regarding this is much appreciated.
Hi Peshwah Rafi, sorry for the misunderstanding of your message. I haven’t tried to use the depletion chain for that kind of calculation, but I think the chain file was used for declaring decay photon energy and its probability, i.e., openmc.data.decay_photon_energy("Ba137_m1")
np.sum(openmc.data.decay_photon_energy("Ba137_m1").p)
So I think you can manually add the photon energy and its probability to the source definition if you already know both parameters for the radioisotope you consider. I don’t think that the chain file has the photon energy for each radioisotope, since not all decay modes listed in the chain file were emitting photons. i.e., the Ba137m in the chain files undergoes an IT while U235 in general emits alpha particles.
I hope other readers that has some experience with it can help you later.