Pointing to Cross Sections on Mac from Jupyter

User Support
1

Hello all,

I am a brand new OpenMC user and am using it on a Mac computer in conda. The installation all went fine and I can import OpenMC into python (I have been trying to use this just from a Jupyter notebook) without any issue. I can’t seem to get the pointing to the cross section data bases to work right though.

I downloaded mcnp_endfb70 from the data bases website and ended up with a file full of HD5 files. I try and point to it with the following:

materials.cross_sections = '/Users/gbru/Desktop/UR/OpenMC/mcnp_endfb70' 
materials.export_to_xml()

This doesn’t work and gives me the following when I run the program:

 Reading settings XML file...
 ERROR: Cross sections XML file '/Users/gbru/Desktop/UR/OpenMC/mcnp_endfb70' does not exist.

I assume I am doing something extremely stupid here, but can’t figure it out for the life of me. Can someone help alleviate the mistake?

Thank you!

2

Welcome to the community.

The path used for the cross sections appears a little unusual. This should point to a xml file. Normally the xml file is called cross_sections.xml. By any chance are you missing the extension from the filename?

3

Thanks!

Am I supposed to make the xml file or is that what I should have downloaded? The file it points to is just a normal file full of HDF5 files with cross sections in them.

4

when you download the openmc nuclear data it includes the cross_sections.xml and the h5 cross section files. Both types of file are in the downloaded compressed archive downloadable from openmc.org

5

I have no idea what changed, but I redownloaded the cross section library a couple of times and finally got one with the cross_sections.xml file! Everything worked the first time after that. Thanks for your help!