核电站凝汽器的压力瞬态变化特性

Transient Characteristics of Pressure Variation in Condensers of Nuclear Power Station

为了掌握事故工况下核电凝汽器压力的瞬态变化特性,建立了循环冷却水系统和凝汽器瞬态传热与压力的数学模型,采用Fortran语言编制了瞬态变化特性的计算程序。冷却水流动模型中涉及到水泵参数、管道布置、止回阀门特性及虹吸井参数等,根据凝汽器稳态运行工况可以确定控制容积的初始条件。针对某1 000 MW核电机组凝汽器,数值研究了冷却水流动和凝汽器压力的瞬态变化,结果表明:在突然断电停泵时,冷却水的流速快速降低且波动性地降至零,同时出现了逆流现象;凝汽器传热系数经历了急剧减小、先增大后减小和基本不变的3个阶段;凝汽器在设计、冬季和夏季3种工况下的压力曲线均呈现出波动性增大的趋势,汽轮机紧急停机压力信号和凝汽器不可用压力信号的时间间隔均为26.4s,能够满足核电站运行的要求。

To reveal the characteristics of transient variation of pressure in a nuclear power station condenser meeting accident condition, a mathematical model is established to simulate the cycling cooling water system and the heat transfer and pressure in condenser. A Fortran program for transient variation characteristics is coded. The pump parameter, cooling line organization, check valve feature and the parameter of siphonic water-collecting are considered in the cooling water flow model. The initial conditions of control volume are determined according to steady state of the condenser. The transient characteristics of a 1 000 MW nuclear power station condenser and cooling water system are examined. It is found that under the condition of plant- power-suspension of pump, the cooling water flow rate decreases rapidly with reflux appearing, then fluctuates to zero. The heat transfer coefficient in condenser firstly decreases sharply, then increases, decreases, and keeps constant finally. Under designing, winter, and summer conditions, the condenser pressure goes up in fluctuation, and the time interval between condenser pressure signal and failing signal reaches 26.4 s, which meets the requirement for safe operation of nuclear power station.