Sensitivity of the scalar and the angular neutron flux to the anisotropic scattering in Monte Carlo calculations

The anisotropic scattering influences both the transport and slowing processes of neutrons. Since Practical shields are usually anisotropic scatters, several parameterized, anisotropic scattering kernels were used to present a general class of anisotropies. To study the anisotropic sensitivity of the flux in thick shield medium, the feasibility of track- length distribution biasing for calculations of scalar and angular neutron flux and their sensitivity to anisotropic scattering was investigated. To represent more realistic angular distribution in a parameterized functional form, an exponential angular density for sampling the scattering angle is proposed, also an empirical formula for the choice of optimal parameter for track length biasing depending on the anisotropic scattering is proposed. The calculations are performed for a particle transport model having an exact solution. The results show that this distribution covers also isotropic and the anisotropic scattering case. The anisotropic effect has a great influence on the behavior of neutron distribution particularly in thick shield. (author)