Neutron Transport Theory

Abstract

The general concept of “transport theory” refers to a physical process whereby a particle migrates through a lattice composed of scattering centers. The first important part of this concept is that the migrating material can be considered to be a particle, in the case of interest a neutron which changes its speed of travel as its total energy changes. The second part of the transport concept is that the material through which the particle moves interacts with the particle in a scattering-like process. When the migrating material can be considered a particle the idea of a scattering collision is natural; however, only the net overall result of the interaction needs to “look-like” a scattering process. For instance, a neutron may suffer an elastic collision with an atomic nucleus and undergo an elastic scattering; on the other hand it may be absorbed by the nucleus and then it or a like neutron be readmitted at a lower energy level in a different direction and thus suffer an inelastic scattering. From the overall view both of the processes appear to be a scattering phenomenon. In order to include all transport processes it is necessary to generalize the concept of scattering to include absorption as a special case.