Measurements and Calculations of the Neutron Spectra from Iron Bombarded with 14-MeV Neutrons

The neutron spectra emitted from 0.9, 2.9, and 4.8 mfp of iron for a 14-MeV neutron source have been measured between 14 MeV and 10 keV, using the sphere transmission and time-of-flight techniques. The spectra have also been calculated using the Monte Carlo neutron transport code TART. To reproduce the measurements, a revision of the Lawrence Livermore Laboratory neutron library was carried out. The cross sections were obtained from reported measurements, and a discussion of the revised neutron cross sections is presented. Very good agreement between measurements and calculations was obtained as a function of mean-free-path throughout the entire neutron energy spectrum. Calculations were also carried out with the ENDF/B-III neutron library and compared with the measurements.