Study On Flow Induced Vibration Analysis And Evaluation For U-tubes In Steam Generator

In pressurized water reactor nuclear power plant,the vertical,natural circulation,inverted U-tube steam generators are adopted widely.U-tubes in nuclear steam generator are key structure to separate primary circuit and second circuit,and important parts of the primary circuit pressure boundary,whose safety and reliability are very important for the operation of nuclear power plants.The flow-induced vibration is easy to take place in heat exchange tubes of steam generator,which are scoured by the secondary circuit coolant.The flow-induced vibration will cause consequences such as fatigue and wear even failure of structure,which may cause leakage of radioactive material.It has a harmful effect on the operation of the reactor,resulting in economic losses and social impact.Therefore,the research of U-shaped tubes in flow-induced vibration phenomena is necessary.The flow-induced vibration behavior of heat exchange tubes under the condition of different feed water ratio in single phase and different void fraction in two phase is studied in this paper,hoping to provide some reference to the design and safety analysis of the structure in steam generator in nuclear power plant.Experiments and numerical calculations are performed in this paper.In experiment,as the most widespread method currently,using air-water mixture has a lot of advantages,it is simple,inexpensive and environmentally friendly.What’s more,it is convenient to control the void fraction,which meets the requirement of high void fraction of experiment.Pertaining to the structural characteristics of the U-tubes of SG in PWR,this paper used a part model based on the ratio of 1:1,with water and air-water as working fluid separately,to carry out single-phase and two-phase experimental study.In numerical calculation,some work has been done by ANSYS,with k-ε turbulence model and none heat transfer,by which the distribution of flow field in the steam generation simulator can be studied.The maximum lateral velocity presents to inlet area and bend area,in which the tubes of SG are effected by the lateral flow more serious.The displacements of these area caused by flow-induced vibration are larger.The experiment is based on numerical calculation.This paper provides some reference for experimental study and program development of nuclear SG in future.This paper gives the vibration displacement response of U-tubes in SG in single and two phase,and the distribution of excitation energy in frequency domain is obtained through Fast Fourier Transform.The relationship about the vibration displacement of U-tubes and the flow rate and void fraction is obtained finally.The study can provide data support of the development of flow-induced vibration program and technical reference for structure design and safety assessment of steam generator in nuclear power plant under the effect of flow-induced vibration.