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 crosssection 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.