Derivation of variance-to-mean formula for periodic and pulsed neutron source

Derivation of a variance-to-mean formula was performed to obtain the prompt neutron decay constant α of the subcritical reactor system that is driven by the periodic and pulsed neutron source. The formula was derived for an experimental technique where the Y value is measured by choosing an injection of pulsed neutrons as the origin of the counting gate. By using the derived formula, it was indicated that the α value can be easily determined. From this fact, it was concluded that the present formula was useful to measure the α value for future experiments with the accelerator driven system.