WARNING: Negative value(s) found on probability table for nuclide Cs136 at 250K

[paulromano]

The first question was answered here:

Warning while reading from ENDF/B-VII.1

These are both data-related issues. Probability tables are used for unresolved resonance region cross sections to account for energy self-shielding effects. These tables are generated by NJOY and should not have negative probabilities, but this does sometimes occur. OpenMC will zero out those values, but it is telling you that the data produced by NJOY may be suspect. The second message about the maximum neutron energy is due to an erroneous evaluation of Be7 in ENDF/B-VII.1 that has an upper l…

It’s important for OpenMC to know the correct volume of burnable materials for a depletion problem. If the volume is wrong, your results will be wrong too. Using a stochastic volume calculation seems like a good approach for this – what error are you seeing when you try running the stochastic volume calculation?