Seismic Response And Parameter Analysis Of Nuclear Power Plant Multilevel Isolation

Nuclear energy is a kind of pure and no pollution resource, at 2007, the state council approves nuclear power long-term development program(at year 2005-2020), it shows a long time in the future, we will vigorously develop nuclear energy. Isolation technology has been greatly used in the civil construction field, but few in the nuclear power plant. It is especially important to promote the development of isolation technology engineering since our country are located in circum-Pacific and Eurasia seismic zone. The nuclear design reference classify two grad, for low level seismic wave the nuclear power plant must keep normal sa fe operation,(C hinese code: operational safety ground motion SL1); for high level the nuclear power plant can keep safe, to prevent the leakage of radioactive material(C hinese code: ultimate safety ground motion SL2). The nuclear power isolation is single stage isolation system, multilevel isolation control should be used to protect nuclear power plant structure. There is no study of nuclear power plant multilevel isolation system in our country. The multilevel isolation theory, analysis method, the design and verify of seismic isolation device of nuclear power plant still need sufficient research.In view of that, this paper is based on the national natural science foundation “Dynamic behavior and response control of multilevel isolation of nuclear island under strong earthquakes”, to study the nuclear structures’ reaction when using multilevel isolation, the main works are as follow:1. According to Chinese nuclear design reference, multilevel isolation theory and multilevel isolation goals are put forward. A new kind of variable stiffness isolation device is designed to realize the goal, and analysis of its’ work principle and mechanics have been made.2. A simple single node model for nuclear island isolation structure reactor is studied. Use MATLAB to build up the multilevel isolation analysis program, study the influence of two stage stiffness change(traditional isolation) and three stage stiffness change(multilevel isolation), when changing the second period(isolation period) T2 and yield coefficient β,and the result shows the reasonable range of parameters.3. According to the parameter analysis result of nuclear structure single model, build up the multi- mass model in sap2000 according to nuclear power plant pressurized water reactor model, and analysis the respond result of different isolation with different peak value of acceleration input. The result shows multilevel and traditional isolation can decrease the upper structure’s acceleration under small and moderate earthquake, but under strong earthquake, traditional isolation can decrease acceleration meanwhile increase displacement beyond limit, multilevel isolation can both decrease the acceleration and displacement, prevent the big displacement destroy.4. Build the random vibration equation of eccentric nuclear structure under non stationary random earthquake, using the state space method to solve the non-classical damping vibration. The response for nuclear island structure under non stationary random earthquake is studied, and relevant parameters are researched. The result shows under non stationary random earthquake, the displacement and acceleration increase with the nuclear island structure’s eccentricity increase, but the change of acceleration range is small, the displacement decrease and the acceleration increase with the isolation stiffness increase, the displacement and acceleration decrease with the nuclear island structure damping ratio increase.