Fast-reactor neutron sources in evaluated nuclear data library validation

Abstract

Two different neutron sources, based on $^{235}$U-fission neutrons with different average energies, provide integral benchmark data for validation of $γ$-ray production data in the evaluated nuclear data libraries corresponding to fast-neutron-induced inelastic-neutron scattering reactions. Firstly, we consider the IRT-M Research Reactor, formerly located at the Nuclear Research Institute just outside of Baghdad, Iraq, to demonstrate the validation methodology using the associated $γ$-ray data in the Evaluated Nuclear Data File, version VIII.0 (ENDF/B-VIII.0), for several $γ$-ray transitions over a wide range of nuclides including $^{28}$Si, $^{32}$S, $^{56}$Fe, and $^{186}$W. Using the characterized neutron flux of the Baghdad IRT-M Reactor, we find flux-weighted cross-sections deduced using the ENDF/B-VIII.0 $γ$-ray data to be in good agreement with the integral measurements performed at the Baghdad Research Reactor in addition to the corresponding results of different reaction-model calculations, {\tt CoH$_{3}$} and {\tt EMPIRE}. Given the excitation thresholds for the $γ$-ray transitions involved in this investigation, these observations lend further support to the characterization of the IRT-M flux in the fast-neutron energy region $0.862 \leq E_{n} \leq 5.0$ MeV. The additional detail devoted to the IRT-M source reflects the broader scope of the validation work carried out at that facility. A second neutron source considered for this validation work is the Forschungsreaktor M{ü}nich (FRM-II), Garching, Germany. Again, the flux-weighted $γ$-ray data from ENDF/B-VIII.0 for $^{56}$Fe compare well to the integral FRM-II measurement and reaction-model calculations.