Hello, I am benchmarking OpenMC against a Serpent code for a LWR and after extensive examination of both codes (same ENDF librabry used, same running parameter, geometry defined exactly the same way, etc) I still have pcm errors of ~50 (for 10pcm uncertainties) for diff core confugurations. Last check I did was run a general material volume calculation on both codes, I get a sigma of 0.81% I have defined >300 materials, and only 70% of my materials lie within one sigma deviation, I have like 6 materials that present differences of 2% with respect to the serpent volume and my question is, is this normal? I have not yet found any report on volume calculation comparisons that would be uselful for me, and I don’t know if this is acceptable/normal difference between codes or if this indicates something is wrong with my geometry? and if this is maybe the reason for my 50pcm discrepancy on the keff calculations? I know for some simpler geometries the keff difference is ~10pcm but I just don’t knwo what else to check in my model to find out what is causing the ~50pcm error.