Nelson's comments

[nelsonag]

• [x] Isn't it normal nomenclature for the LHS onf equation 9 to be \Sigma_{tr} instead of the term on the RHS?

• [x] The paper doesn't discuss the fission production matrix (i.e., nu-fission with both energy and energyout filters). Not realy a problem, just wanted to note that so its omission is on purpose and not just a miss.

• [x] Realizing it won't be trivial, should this discussion and results be updated to OpenMC v0.10?

• [x] Sec IV.C.3, Paragraph 2 refers to universes in an example. is this common enough nomenclature?

[wbinventor]

1. I think you're right, I just defined \Sigma{tr} as the term correcting the total xs rather than the corrected total xs. What do you think about renaming the correction term on the LHS of equation 8 as \Delta\Sigma{tr}, and the LHS of equation 9 modified to \Sigma_{tr}?

2. We can add in the fission production matrix, since there it wasn't omitted for any substantive reason. Most of the math formulation for the tallies is taken from my thesis, which describes only those MGXS which were needed for my OpenMOC simulations. Since OpenMOC uses the vector chi rather than the matrix, it was left out here. But for completeness, I think it would be good to add it in so I will.

3. Since you've been more involved with OpenMC over the last year than I, what would you expect to be different for v0.10? I doubt any of the results would be substantively different unless some major physics bugs were discovered. Has openmc.mgxs changed in any major way?

4. I'll remove mention of universes in that paragraph, since I don't think it adds anything in that context.

[nelsonag]

Regarding #3, my gut was wrong. The filters vs scores distinction for expansion tallies was changed after v0.10.0 (i.e., its on develop and not yet released), therefore there might not be anything of interest between v0.9 and 0.10. So I am ok with leaving it at 0.9.

[wbinventor]

I changed to v0.10.0 since @paulromano brought independently remarked on this, so closing this issue now.