Spectra of leakage neutrons from a Pb–Li spherical shell with central 252Cf and 14 MeV neutron sources and verification of evaluated neutron data

The spectra of leakage neutrons from a Pb83Li17 spherical shell with a 252Cf neutron source at its center have been measured by the time-of-flight method in a neutron energy range of 200 keV to 10 MeV. The outer radius of the spherical shell was 200 mm, and the inner radius was 60 mm. Measurements were performed with the use of a dedicated fast ionization chamber which simultaneously supplied stop pulses for the time-of-flight technique and recorded the total number of 252Cf decays for the experiment time. From the outer surface of the shell, the leakage neutrons were detected by a scintillation counter based on a paraterphenyl crystal with a diameter of 5 cm and a height of 5 cm and a FEU-143 photomultiplier tube. Earlier, spectra of leakage neutrons from the same spherical shell were measured with a 14 MeV neutron source using the same time-of-flight technique [1]. The results of the both measurements have been compared with the MCNP-4 Monte-Carlo code calculations with the ENDF/B-VII.1 and BROND-3 neutron data libraries.