Measuring neutron leakage spectra using spherical benchmarks with 252Cf source in its centers

Abstract

The presented paper summarizes the methodology of fast neutron leakage fluxes measurement using a stilbene scintillation detector on spherical benchmark assemblies. The experiments are realized in a spherically simple geometry, which does not need validation of the neutron transport model. Hence, this type of experiment is suitable for validation of the nuclear cross sections of various isotopes. The 252Cf neutron source is always placed in the center of a sphere of different pure materials. The selection is focused on structural materials used in the nuclear industry. In the presented set, the materials include light water, heavy water and nickel. For example, the light and heavy water spheres can be used to eliminate the effect of hydrogen and estimate the effect of oxygen. The neutron spectra in the region of 1–10 MeV are measured in a room where the background could substantially influence the final result. For this reason, the estimation of the scattered neutrons is crucial for the correct evaluation of the experiment. The comparison of the calculated and measured neutron fluxes and background signal share are presented. Calculations were performed using the MCNP6 program with the ENDF/B-VII.1 nuclear data library.