The central problem in reactor analysis is the determination of the spatial flux and power distribution in the reactor core under steady state as well as transient operating conditions. There is, however, a considerable variation in the degree of accuracy and spatial details of the power distribution required in different facets of reactor analysis and design. Basically, the behavior of neutrons in a nuclear reactor is adequately described by the time-dependent Boltzmann transport equation [24, 38]. However, numerical solutions of the coupled time-dependent transport and delayed neutron precursors’ equations for reactor kinetics problems of practical interest are prohibitively difficult. © 2013, Springer-Verlag Berlin Heidelberg.