A MONTE CARLO CALCULATION OF SCATTERED NEUTRON FLUXES AT AN AIR-GROUND INTERFACE DUE TO POINT ISOTROPIC SOURCES ON THE INTERFACE

摘要

The validity of the method was established by comparing Monte Carlo results for an infinite air medium with moments method results. The two methods were found to yield fluxes that were in good agreement out to 8 source mean free paths for a 2-Mev source. At higher source energies the treatment of inelastic scattering as isotropic elastic scattering overestimated the high-energy flux and underestimated the low-energy flux, while allowing only P1 anisotropic elastic scattering overestimated the flux near the source and underestimated it far from the source. Scattered neutron fluxes at the interface of black ground and air, which is a useful limiting case, were also calculated.