The influence of void-reactivity feedback on the bifurcation phenomena and nonlinear characteristics of a single nuclear-coupled boiling channel

This study employs the nonlinear dynamic model developed previously by the authors to investigate the effect of void-reactivity feedback on the bifurcation phenomena and nonlinear characteristics of a single nuclear-coupled boiling channel in an advanced boiling water reactor. The parametric effects on the system stability are evaluated by nonlinear analyses as well. The effects of void-reactivity feedback and outlet flow resistance will both destabilize the system, while the inlet flow resistance will generate a stable effect on the system. The strength of void-reactivity feedback has a great influence on the bifurcation phenomena and nonlinear dynamics of the single nuclear-coupled boiling channel. The system can evolve from stable state, limit cycle, periodic to chaotic oscillation through supercritical Hopf and period-doubled bifurcations as the increase in the absolute value of void-reactivity coefficient. In addition, the system can experience a series of period-doubled bifurcation to present various types of oscillations, from periodic ones to chaos, in the unstable region as the controlling parameter of steady phase change number or subcooling number under some specific conditions with a relatively strong void-reactivity coefficient of Cα=-0.38$/%. The appearance of a periodic cycle of three suggests that there may be immeasurable periodic types of nonlinear oscillations in the limited unstable space of this system.