The complex nonlinear dynamics in the multiple boiling channels coupling with multi-point reactors with constant total flow rate

•The nuclear-coupled effect has a distinct influence on the system dynamic behaviors and oscillation modes.•The effect of channel-to-channel interaction makes the 5-channel system more unstable than a 3-channel one.•Complex nonlinear bifurcation phenomena may appear in the present system.•The unimaginable types of complex periodic oscillations may exist in such a system.

The present study explores the effect of nuclear-coupled feedback on the oscillation modes and nonlinear phenomena of a five nuclear-coupled boiling channel system by a nonlinear dynamic model previously developed by the authors. The results show that the combined effects of stable neutron interaction and unstable void-reactivity feedback generate distinct influence on the system stability, particularly a significant unstable effect as in the 4Cα cases. The effect of channel-to-channel interaction will drive the 5-channel system more unstable than a 3-channel one. Such a nuclear-coupled effect may affect the oscillation modes and nonlinear phenomena among the channels substantially. For the present system with a constant total flow rate, the superimposition of the dominant single-phase frictional pressure drop and strengthening void-reactivity feedback may result in the departure from the out-of-phase mode oscillations at some system states. The results demonstrate the appearance of different bifurcation phenomena in the unstable region and complex nonlinear phenomena, i.e. various periodic oscillations and complex Rossler type of chaotic oscillations, in such a system subject to certain nuclear-coupled feedbacks. A special type of complex P-3 oscillations is identified in this system. It suggests that there may be immeasurable types of the periodic nonlinear oscillations in the limited unstable space of this five nuclear-coupled boiling channel system.