Conditions for the existence of chaotic oscillations in nuclear reactors

It is shown on the basis of point kinetics equations with delayed neutrons that if the impulse feedback function is negative, nonmonotonic, and possesses several maxima and the coefficient of amplification of feedback is sufficiently large, then chaotic self-excited oscillations of the following type arise in nuclear reactors. Neutron bursts with random intensity occur in random time interals in the reactor, and the neutron density between the bursts oscillates at a low level. The mechanism for the appearance of chaos is described and one-dimensional mappings which approximately determine the chaotic dynamics are constructed. Three types of reactors (boiling water, with gaseous core, pulsed) where such chaotic oscillations can arise are indicated. The results obtained point the way to determining other types of reactors with stochastic behavior. 4 figures, 10 references.