The Probability Table Method and Correlated Data

The probability table method (PTM), used in unresolved resonance region calculations, assumes that cross sections are not energy correlated. Strong cross-section energy auto-correlations are noted for some heavy nuclides that could affect the use of the PTM in the unresolved resonance region or its extension to the resolved resonance region. Uranium-238 has strong cross-section auto-correlations and is considered a severe test material for the PTM. Monte Carlo calculations of capture rates in ²³⁸U at 500, 1000, and 2000 eV do not show differences between the PTM and exact methods within an ∼1% calculational uncertainty. These results show that strong auto-correlations do not interfere with the use of the PTM in the resolved and unresolved resonance regions.