The Multi-P N Method : A New Angular Discretization Technique for Neutral-Particle Transport Problems

The accuracy of the angular discretization in the deterministic solution of the transport equation is particularly relevant for radiation shielding calculations. It is demonstrated how the Discrete Ordinates (S N ) method turns out to be inefficient in the presence of geometrically large and low-scattering regions. The here presented Multi-P N method (MP N ) is a new angular discretization technique relying on a solid angle expansion of the interface fluxes, allowing for a local coupling between different angular degrees of freedom within the same solid angle. This coupling enables to solve the equation by means of a standard sweep algorithm. Furthermore, the angular moments are directly integrated without any use of quadrature rules. The MP N numerical solutions are less affected by the ray-effect and the measured convergence rate with respect to the angular degrees of freedom is significantly larger than the one measured with S N