Dynamic Bearing Characteristics Of Polar Crane In Nuclear Power Plant Under Earthquake Action

In order to solve the problem of energy shortage and achieve the goal of energy saving and emission reduction,China will still develop nuclear power technology efficiently.At present,China is the country with the largest number of nuclear power plants(NPP)to be built in the world.Although nuclear power has the advantages of high energy density,environmental protection and cleanliness,nuclear safety has always been the most prominent and most challenging issue.With the independence and localization of the three generation nuclear power technology in China,the requirements for seismic safety performance of nuclear power structure and equipment have been gradually improved.As a special equipment for NPP,the study of the dynamic bearing characteristics and dynamic response characteristics of a NPP is an important content to ensure the safety of the structure and sufficient seismic margin.In this paper,the first domestic ring crane of A NPP with completely independent intellectual property rights is selected as the research object.Using the finite element method,the three-dimensional model of containment vessel and polar crane is established.The structure of the nuclear polar crane is analyzed as follows:(1)Modal analysis and static analysis under steady state conditions.This paper introduces the method of establishing the finite element model of the nuclear ring crane structure and the setting of the related parameters.The modal analysis theory of the multi-degree-of-freedom system and the numerical modal analysis method are discribed.The maximum response position of the ring crane is determined by modal analysis,and the damping coefficient of the structure is calculated.The maximum deflection of the ring crane is 32.41 mm,and the maximum stress is 71.11 Mpa,which satisfies the specification requirement.(2)Analysis on floor response spectrum of polar crane in NPP under unidirectional ground motion.The acceleration time-history curves are simulated and obtained through the three typical seismic waves by using the time-history analysis method.The seismic response spectrum is generated under the condition of different damping ratio by the Duhamel integral.The obtained numerical results highlight the amplification effect of the steel containment vessel to the ground vibration.Co Mpared with the ground surface response spectrum(GSRS),the peak values of FRS of the crane structure in horizontal direction are increased from 2 to 10 times,and the values in vertical direction are raised from 3 to 9 times.Meanwhile,it is important to select input seismic wave and the damping of polar crane reasonably.(3)Comparison and analysis of the reduced scale model experiment and numerical simulation of the nuclear polar crane under two-direction seismic action.The experimental model has the same natural frequency as the simulation value in the test results of the 1:16 scale model of the nuclear ring.The acceleration response of the experimental model coincides with the simulation.The numerical model is reasonable and effective.(4)Analysis of load capacity and dynamic response of nuclear ring crane under threedirection seismic motion with the Time-history analysis method and response spectrum method.The dynamic response of the response spectrum method is greater than the response result of the Time-history method.Based on the results of the two methods,the maximum stress of the main-beam of the nuclear polar crane is 157.98 Mpa,and the maximum stress of the trolley is 269.77 Mpa.The strength design of the polar crane structure meets the specification requirements.In summary,through the study of the dynamic characteristics of the nuclear ring crane under the action of earthquake,the maximum bearing state and acceleration response of the ring crane are determined,which provides a reference for the design and research of the nuclear ring crane.