Multi-group Reflected Slab

User Support
1

Hello,

I am trying to learn OpenMC and figured I would start with a simple 1D reflected slab, with two energy groups. I followed the example notebook to define my MG cross section libraries, and then defined the geometry, but I get a k=91, while I know that k=1.00914, from MCNP. I am not sure what I am doing wrong however with this system. From plotting the geometry, it looks okay, so I am assuming my problem lies with the cross section definitions, but I am not sure. Any help or advice would be greatly appreciated!

Cordially,

Hunter

Reflected_Slab_2_Group.ipynb (18.2 KB)

2

Hi Hunter,

The issue is that XSData.set_nu_fission expects the product of nu and the fission cross section, not just nu alone. When I change the values to be 2.50.00339 and 2.50.074 and rerun the notebook, I end up with a keff of 1.00906 +/- 0.00077.

Best regards,
Paul