Determination of Neutron Dose-Equivalent Buildup Factors for Infinite Slabs Irradiated by Point Isotropic Neutron Sources Using the MCNP Code

Neutron dose-equivalent buildup factors were calculated for point isotropic neutron sources irradiating infinite slablike shields of lead, iron and water using the MCNP code. The factors are presented for some source neutron energies in the range from 0.025 eV to 14 MeV, and for shield thicknesses from 0.5 to 10 mfp. Since the MCNP code considers all kinds of neutron interactions with matter, and the variance reduction techniques available in this code allows one to reach correct answers, one can say that the buildup factors presented here are accurate enough to be used in neutron shielding and dosimetry calculations. Comparison of the results obtained here with some previously calculated buildup factors, shows good agreements.