Streaming of 14-MeV Neutrons Through an Iron Duct—Comparison of Measured Neutron and Gamma-Ray Energy Spectra with Results Calculated Using the Monte Carlo MCNP Code

Neutron and gamma-ray energy spectra resulting from the streaming of 14-MeV neutrons through a 0.30-m-diam duct (length-to-diameter ratio = 2.83) have been calculated using the Monte Carlo MCNP code. The calculated spectra are compared with measured data and data calculated previously using a combination of discrete ordinates and Monte Carlo methods. Comparisons are made at 12 detector locations on and off the duct axis for neutrons with energies above 850 keV and for gamma rays with energies above 750 keV. The neutron spectra calculated using MCNP agree with the measured data within ∼5 to ∼50%, depending on detector location and neutron energy. Agreement with the measured gamma-ray spectra is also within ∼5 to ∼50%. The spectra obtained with MCNP are also in favorable agreement with the previously calculated data and were obtained with less calculational effort.