Effects of Highly Anisotropic Scattering on Monoenergetic Neutron Transport at Deep Penetrations

The sensitivity of the flux in deep-penetration problems to anisotropic scattering was studied within the framework of monoenergetic transport theory. Several parameterized, anisotropic scattering kernels were used to represent a general class of anisotropies. The representation of these kernels in Legendre polynomial series of various orders was explored to determine their effect on calculated discrete eigenspectra and infinite medium fluxes. Eigenspectra for several kernels are presented as a function of the kernel parameter. Conclusions were drawn about the order of the Legendre expansion of the kernels required for accurate deep-penetration calculations, and the possible existence of multiple diffusion decay modes in realistic problems. In general, rather low order Legendre expansions were found to be adequate for problems in which the scalar flux was the primary quantity of interest.