Fission Yield of Pm149 from U235

Validation and Verification
1

hello everybody

I’m trying to get the fission yield of Pm149 from U235 as follow:

import openmc.data
chain_file = “/home/pc/pychamobjects/OpenMC/ENDF/endfb80_hdf5/chain_casl.xml”
chain = openmc.deplete.Chain.from_xml(chain_file)

def calc_mean_yeald(nucl=‘Pm149’):
# xe135=0
Pm_149_Thermal=chain[‘U235’].yield_data[0.0253][nucl]
Pm_149_Fast=chain[‘U235’].yield_data[500000.0][nucl]
Pm_149_14Mev=chain[‘U235’].yield_data[14000000.0][nucl]
return Pm_149_Thermal,Pm_149_Fast,Pm_149_14Mev

I get this values

Pm_149_Thermal = 3.86973e-08
Pm_149_Fast= 1.63999e-08
Pm_149_14Mev= 1.35185e-05

but when I compared OpenMC results with IAEA data fission yield , there was a big difference.

IAEA fission yield

Has anyone have an explanation about this difference ? Help me, please.
Thank you.

2

@shatnawihamza The chain file used in OpenMC is usually based on independent yields, which is what you see there for Pm149. The IAEA data you’re looking at appears to be cumulative yields, which account for the decay of other nuclides into Pm149. In this case, Pr149 and Ce149 have a combined independent yield of about 1.0e-2, so their decay into Pm149 gives the value you see there in the IAEA data.

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3

Thank you very much D.paul romano.
Know I’m understanding. But how we can get cumulative yields by OpenMC ??.
Actually I saw this class but I don’t well understand.
class openmc.data.FissionProductYields(ev_or_filename )

Thank you.

4

The FissionProductYields class takes an ENDF fission product yield sublibrary file. Getting the cumulative yield would look like:

import openmc

u235 = openmc.data.FissionProductYields('nfy-092_U_235.endf')
thermal = 0
pm149_yield_cumulative = u235.cumulative[thermal]['Pm149']
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