# Difference between revisions of "Pitfalls and troubleshooting"

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Probability table sampling is switched on using the [[Input syntax manual#set ures|set ures]] option. | Probability table sampling is switched on using the [[Input syntax manual#set ures|set ures]] option. | ||

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+ | === Mass vs. atomic densities === | ||

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+ | The densities and compositions of materials can be entered in atomic (positive values) or mass units (negative values). Using incorrect units can lead to unexpected results. The difference may not be clearly noticeable if the material consists nuclides with similar atomic weight, but |

## Revision as of 18:30, 19 November 2015

## Things to check in case of suspicious results

### Unresolved resonance probability table sampling

Unresolved resonance probability table sampling is not used by default. This method is needed to account for self-shielding effects in the unresolved resonance region. The effect is usually not significant in thermal systems, but can lead to noticeable discrepancies in fast-spectrum systems.

Probability table sampling is switched on using the set ures option.

### Mass vs. atomic densities

The densities and compositions of materials can be entered in atomic (positive values) or mass units (negative values). Using incorrect units can lead to unexpected results. The difference may not be clearly noticeable if the material consists nuclides with similar atomic weight, but