Some Outstanding Problems in Neutron Transport Computation

As more applications are required of the radiations (e.g., neutrons and photons), be it a nuclear reactor, shielding facility, or a radiation treatment apparatus, the demands on the capability and accuracy of design and analysis are increasing ever to a very high degree. One (perhaps the ultimate) task in designing such a nuclear system is to determine the distribution of the neutrons (and/or photons) in the system under design accurately. For that, we have to take into account the motion of the neutrons and their interactions with the host nuclei of various kinds. Thus, we need a mathematical model or theory to describe this particle transport phenomena. As a high-level model that describes the distribution of neutrons in a medium such as a reactor, we usually consider the following Boltzmann transport equation :