Nuclide O-18 is missing from official ENDF7.1 Library

User Support
1

Hi All,

I am a new openMC user. I tried to run some problems in the provided examples using official ENDF7.1 Library and found that the data for nuclide for O-18 is missing (after downloading for long time). Is the library obsolete or should I use other libs?

This problem seems quite trivial so I believe it must have been addressed before, but I couldn't find this information using search feature in this group.

Thanks.

2

O18 is not included in the official ENDF 7.1 data library. See the attached file…

O18.h5 [ from tendl-2019 ACE file to HDF5 file using NJOY2016, temperatures = 250 K, 293.6 K, 600 K, 900 K, 1200 K, and 2500 K ]

Or, you can use convert_lib80x.py script [ O18, C13 included ] from data.

Hope this helps

O18.h5 (541 KB)

convert_lib80x.py (2.96 KB)

3

Thanks Ariful. That is really helpful. I will just simply use the data from TENDL.

Btw, I am wondering why O-18 is not included in the official OpenMC data lib? Is it missing from original ENDF7.1? Or because O-18 content is not significant in typical light water?

4

Hi Muhammad,

One thing you need to know that TENDL did not include any thermal scattering evaluation data. If you want to use it then you need to pick it up from another data library ( ENDF-7.1, ENDF-8, JEFF-3.3 ).

NNDC, LANL did not include neutron reaction sublibrary file for O18, C13. That’s why these nuclides are not in the official OpenMC data library ( endf 7.1 ).

5

Thanks Ariful.

6

One more thing to keep in mind is that when you are generating inputs from the Python API, it will look at your OPENMC_CROSS_SECTIONS environment variable to see what nuclides are available. So, if you run:

mat.add_element(‘O’, …)

and your OPENMC_CROSS_SECTIONS environment variable points to a file that does not include O18, it will not be included in your material (the density of O18 in this case gets replaced with O16)

1 Like
7

Thanks Paul and Jonathan (his email was sent personally).