Neutron Kinetics for Reflected Compact Reactors on Short Periods

The common seventh group approximation for treating the effect of neutron delay due to reflector slowing down and thermalization is presented. Modifications appropriate when reactivity changes are produced by reflector movements are introduced. An improved formulation, allowing distinctions between several different groups of slowing down and thermalizing neutrons, is presented. This formulation is shown to reduce to the seventh group approximation for the case of one atypical neutron group, providing the population and reaction rate of the group are small in comparison to the total neutron population and reaction rate. (auth