C5G7 benchmark: total vs transport XS

User Support
1

I am learning OpenMC and I am going over the C5G7 benchmark example. I see that when creating the cross-sections for UO2, the code in the jupyter notebook does:

uo2_xsdata.set_total([1.77949E-1, 3.29805E-1, 4.80388E-1, 5.54367E-1, 3.11801E-1, 3.95168E-1, 5.64406E-1], temperature=294.)

However, in the benchmark specification document[1] they list:

Total cross-sections: 2.12450E-01, 3.55470E-01, 4.85540E-01, ... 5.70610E-01.
Transport cross-sections: 1.77949E-01, 3.29805E-01, 4.80388E-01, ... 5.64406E-01

So the transport XS are entered as total? Why is that?

–
David

[1] Lewis, E. E. et al. Benchmark specification for Deterministic 2-D/3-D MOX fuel assembly transport calculations without spatial homogenization (C5G7 MOX). NEA/NSC 280 , 2001 (2000).

2

I missed the note in the notebook:

Note : The C5G7 benchmark uses transport-corrected cross sections. So the total cross section we input here will technically be the transport cross section.

3

The total cross sections need to be used with anisotropic scatter cross sections, and the transport cross section is transport corrected to isotropic scattering.

So if you use isotropic scatter cross section, you may need use transport cross section.

you can get more information from IAEA document.

WIMS-D library update, IAEA, Vienna, 2007. Pub1264_web.pdf.