On the Effect of Delayed Neutrons in Reactor Dynamics

A study of linearized reactor dynamics equations shows that delayed neutrons do not always “improve” the stability of nuclear reactors at power level and that a reactor may be unstable although it is stable when delayed neutrons are neglected. The critical power for instability and the damping of natural oscillations are larger when delayed neutrons are taken into account in the case of low-pass phase lagging reactivity feedbacks, but this property is not true for all types of feedbacks.