Sensitivity of Subcritical Measurement Simulations to Neutron Cross-Section Data

Abstract

Evaluation of nuclear data typically includes validation of the data through computation of k_eff for critical assemblies. The sensitivity of the computed k_eff values to the nuclear data is used as an indicator in determining the adequacy of an evaluation. Subcritical measurements offer an alternative to critical experiments as a means to evaluate nuclear data through direct computation of subcritical measurement quantities. In some instances, the subcritical measurement quantities are more sensitive to nuclear data changes than the computed k_eff values. Simulations of subcritical source-driven noise measurements were performed for highly enriched uranium metal cylinders and highly enriched uranyl nitrate solutions to demonstrate the sensitivity of the computed subcritical quantities to nuclear data. A particular ratio of spectral quantities from the source-driven noise measurements is of interest because of its independence of detection efficiency and source intensity. These simulations indicate that the spectral ratio is more sensitive to nuclear data evaluations than the computed k_eff values for these systems. Direct simulation of subcritical measurements offers additional means to validate nuclear data evaluations.

Keywords:

• subcritical measurement
• evaluation
• high enriched uranium
• cross sections