In this chapter, we shall extend the elementary diffusion theory that was developed in Secs. 5.2. and 5.3 and apply it to some important special problems. We shall mainly be interested in the diffusion of thermal neutrons in weakly absorbing “good” moderators, such as H2O, D2O, graphite, beryllium, beryllium oxide, and various hydrogenous materials (paraffin, plexiglass, etc.). In these media, the conditions for the application of diffusion theory are well fulfilled ; as long as we stay one or two mean free paths away from boundaries and sources, the results of diffusion theory will be quite accurate. We specifically assume that the neutron sources emit neutrons with a thermal energy distribution.
KeywordsDiffusion Equation Neutron Flux Thermal Neutron Line Source Source Distribution
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Special Solution of the Diffusion Equation
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