Problem generating sab for U and O in UO2 using openmc.data.njoy

User Support
1

Hello

I am trying to generate sab cross sections for Uranium and Oxygen in UO2 using openmc.data.njoy. I am getting error message for both of them which i can’t understand.

for Uranium, the error message is

Traceback (most recent call last):
File “test.py”, line 8, in
vari = njoy.make_ace_thermal(‘U238.endf’, ‘UinUO2.endf’, temperatures=[600.], ace=‘c_U_in_UO2.ace’, xsdir=‘c_U_in_UO2.xsdir’)
File “/usr/local/lib/python3.5/dist-packages/openmc-0.9.0-py3.5.egg/openmc/data/njoy.py”, line 348, in make_ace_thermal
data = _THERMAL_DATA[mat_thermal]
KeyError: 76

while for oxygen, the error i am getting is

reconr… 0.0s

—message from lunion—xsec nonzero at threshold for mt=600
adjusted using jump in xsec

broadr… 0.4s

thermr… 0.7s

wrote thermal data for temp = 2.9600E+02 10.1s

thermr… 10.1s

warningmaximum value of beta limits the allowed energy transfer
the sct approx. will be used for transfers larger than 2.024 ev.

wrote thermal data for temp = 2.9600E+02 41.7s

acer… 41.7s

—message from acesix—emax reset to 4.0000E+00
At line 749 of file /home/osboxes/NJOY2016/src/aceth.f90 (unit = 10, file = ‘/tmp/gfortrantmp3un0iN’)
Fortran runtime error: I/O past end of record on unformatted file

i have downloaded the files from https://t2.lanl.gov/nis/data/endf/index.html. Can you please help me with this?

2

Hi Khurrum,

If I’m not mistaken, you are using ENDF/B-VII.0 files. It appears that the material number for U in UO2 actually changed between ENDF/B-VII.0 and ENDF/B-VII.1, and right now OpenMC only recognizes the more recent material number (48). Unfortunately, even when using the more recent file, NJOY still appears to fail (I get the same error you’re seeing for both U in UO2 and O in UO2). I just reported an issue to the NJOY team and we’ll see what they say about this.

Thanks,
Paul