Sensitivity of Photoneutron Production to Perturbations in Cross-Section Data

The most recent release of photonuclear interaction data for Monte Carlo applications is the ENDF/B-VII library. While this current version offers several improvements over its predecessors, it does not address the observed, sometimes quite significant variance in the measured data. For instance, for ²³⁸U, the cross-section data in the ENDF/B-VII library is consistently larger than all measurements except for those by Caldwell et al., occasionally by as much as 20%. The objective of the work performed here was to investigate the sensitivity of photoneutron production to perturbations in photonuclear cross-section data. The effect of these perturbations on experimental observables in a common setup was assessed using the MCNPX/MCNP-PoliMi code system. A new methodology was developed and implemented to evaluate the sensitivity of commonly measured parameters to perturbations in photonuclear cross-section data. The results of the analysis show that the maximum variation applied to the cross section (20%) results in an integral detector response change that in general varies between 6 and 8% for the exact configuration considered here. However, the methodology is general and may be readily applied to any source-target configuration.