Measurements and analyses of neutron transport through iron

Integral experiments have been performed using a thick homogeneous spherical shell of iron to test existing neutron cross section data. Neutron leakage spectra were measured for Cf-252-fission and DT-fusion neutron sources using an NE-213 spectrometry system. An associated particle detector monitored the absolute DT neutron source strength and the amount of DD neutron contamination in the DT source spectrum. The leakage spectra were calculated using the continuous-energy Monte Carlo code VIM and the discrete-S/sub n/ code ANISN. For neutron energies between 1 and 5 MeV, the calculations underpredicted the leakage spectrum by factors of 2 to 1.4 for the Cf neutron source and of 3 to 2 for the DT neutron source. The large discrepancies are attributed to inadequate representation of cross-section resonance structure (viz., minima); inadequate representation of the angular and secondary energy distributions for continuum inelastic scattering and (n, 2n) reactions may also contribute to these discrepancies