日本福岛核电站事故发生以后，人们更深刻认识到核电厂安全的重要性。重要厂用水系统（SEC）作为核岛的最终热阱，关系到核电厂设备的安全运行，对其进行水锤分析是非常必要的。本文用Flowmaster软件对某核电厂重要常用水系统做了较为全面的建模，并研究了止回阀阻力特性曲线对停泵水锤模拟的影响。结果表明止回阀阻力特性曲线的改变可能会对停泵水锤模拟结果产生较显著的影响。由于厂家没有提供止回阀的阻力特性曲线，为了更准确模拟止回阀关闭所引起的水锤现象，本文用CFD软件Fluent对原设计止回阀进行了模拟计算，并得到了该阀不同开度时的损失系数。之后本文用Flowmaster对不同运行工况进行了计算，并对影响重要常用水系统停泵水锤的各要素进行了讨论，比如：泵转动惯量、海潮位、管路阻力特性、止回阀动作特性等。结果表明该SEC系统断电停泵时存在较严重的水锤隐患，需要采取水锤防护措施。经比较分析，本文采用阀调节的方式来改善系统水锤性能，水锤隐患可以通过改变止回阀并优化其关闭特性来消除。

After the Fukushima Nuclear Power Plant Accident, people realize the importance of the nuclear plant safety more deeply. The essential service water system (SEC) is the final heat sink of the nuclear island, it’s related to the safe operation of nuclear equipment, so it’s necessary to research on the water hammer characteristics of this system.This thesis uses the software of Flowmaster to set up the model of the SEC system of a power plant comprehensively, and studies the influence which the check valve’s resistance characteristic curve has on the pump-off water hammer simulation. The results show that a small change of the check valve’s resistance characteristic curve may lead to a significant change in the simulation results. However the manufacturer can’t provide the check valve’s resistance curve, in order to simulate the water hammer phenomenon caused by the valve closure more accurately, the thesis uses the CFD software Fluent to simulate the check valve and gets the loss coefficients of different valve openings. Then this thesis uses Flowmaster to simulate several working conditions of SEC system, and discusses several essential factors that affect the water hammer characteristics of the SEC system, such as: pump moment of inertia, the height of the tide, the resistance characteristics of the pipe system, valve operation characteristics and so on. The results show that this SEC system may have hidden dangers caused by water hammer when the pump is powered off unexpectedly, and protection measures need to be taken. After comparison, this thesis uses the method of valve-stroking to improve the water hammer characteristics of the SEC system, the hidden dangers caused by water hammer can be Eliminated by changing the check valve and optimize it’s operating characteristics.