Study Of Water Hammer And Simulation Of Nuclear Power Plants Primary System

Water hammer is a kind of shock wave pressure caused by the sudden change of pressure and the compressibility of water and pipe, harmful for water conveyance system. If we can't predict in time or handle correctly, pipe line will vibrate, the connection of equipments will loose, pumps and valves will be destroyed. When it is severe, the whole pipeline will be fracture and the system will be interrupted. The most important part of nuclear power plant is primary system which is also primary coolant loop. The sudden opening and closing of valves and pumps, the accident fracture of pipe in the loop can make it possible to cause water hammer. So it is very important for studying the theory and calculation of water hammer.The paper is based on hydraulic character unit of a nuclear power plant primary system. Make a further study about the theory and calculation methods of water hammer and find proper mathematical simulation model, then make simulation on some conditions. Firstly, give the deducing process of the formula for wave velocity and pressure of water hammer, the dynamic equation and the continuous equation, by comparing with other kinds of equations and methods, realize that equations deduced are the more proper ones relatively. At the same time, get that the characteristic method of numerical method is the proper one. Secondly, according to actual situation of the nuclear power plant primary system, give the boundary equations after reasonable simplification for every part in the whole loop. Finally, use the language of the soft ware 'MATLAB' to develop a program and make simulation calculation for four conditions, get the corresponding results mainly including flow of pipes and pressure before and after valve. The pressure range before valve and after valve, the biggest difference between them, when the pump starts with high velocity, is higher than the ones when the pump starts with low velocity, when the first pump and the second pump starts by turns is higher than the ones when the single pump starts. Among them, the condition which is that the first pump starts with low velocity, runs steadily and then stops, at the same time, the second pump starts with high velocity has the highest pressure fluctuation before and after the first valve, has the most obvious water hammer relatively.On the basis of the occurrence mechanism of water hammer and the simulation results, also according to the actual situation of nuclear power plants in ships and electric power plants, some suggestions are given to prevent and weaken the water hammer, which can supply some technical support for the optimizing design and the safe run of nuclear power plant primary system.