Natural Circulation Operational Characteristics Under Ocean Condition

Based on the drift flux model, the natural circulation theory analysis models of nuclear power plant (NPP) under ocean condition were established. The neutron physical activities and the responses of reactivity control systems were described by the two-group, 3-D space and time dependent neutron kinetic model. Using the code developed, the natural circulation operating characteristics of NPP and the transition process from forced circulation to natural circulation under rolling condition were analyzed. The results show that the shorter the rolling period is, the more the influence is, and that the bigger the rolling amplitude is, the more the influence is. With the same rolling period and amplitude, the effect of pitching on natural circulation is greater than that of rolling. The fact is that the parameter oscillation period for pitching is the same as the pitching period, and half of the rolling period. In the ocean environment, excessive flow oscillation of the natural circulation may cause the control rods response so frequently that the transition can’t be realized steadily.