Creating a cross_section.xml file

User Support
1

Hi! this is probably an extremely simple question but Im brand new with OpenMC and not a very expert linux user. I followed all the install guide and read through the whole User’s guide, nonetheless I run the first example “Pin-cell” and I get the error that there’s no file containing the cross sections. The example says:

“First, it checks whether Materials.cross_sections has been set, indicating the path to a cross_sections.xml file.
If Materials.cross_sections isn’t set, it looks for the OPENMC_CROSS_SECTIONS environment variable.”

But I don not understand where to get the cross section information from? What is cross_section.xml suppose to have? what is OPENMC_CROSS_SECTIONS?.

Again sorry for the “dumb” question…

2

@LilianaQuintero welcome to the community! I know you said you read the whole user’s guide, but nevertheless I’m going to point you to the section on Data configuration which explains this at length. The easiest thing to do is to download and unpack one of the pregenerated nuclear data libraries from https://openmc.org and then set the OPENMC_CROSS_SECTIONS environment variable to the cross_sections.xml file from the unpacked archive.

3

Thanks a lot, I must have overlooked that part. Didn’t know there were pregenerated data files