Comparative Study Of Base Isolation With Story Isolation On AP1000 NPPs Shield Building

The shielding building of AP1000 nuclear power plants(NPPs)plays an important role in ensuring the safety and the function of NPPs.The shielding building is the last barrier to keep radioactive material inside the plant,and is also the first barrier to prevent missile out of the plant.In addition,the shielding building not only provides the heat exchange channel,but also supports the cooling water storage tank for the Passive Containment Cooling System.Therefore,it is of significance in theoretic research and engineering practice to study the seismic performance of AP1000.Earthquake is one of the main natural disasters that threatens the safety of NPPs.As the earthquake is a random event,NPPs may suffer earthquake beyond design basis level during the normal operation.Once the AP1000 shielding building damages under the seismic action,it may cause a serious environmental pollution.Based on the isolation mechanism of NPPs,the isolation mechanism of structure is apply to the AP1000 shielding building in this paper.The seismic response and dynamical mechanism of the traditional structure,the basic isolation structure and story isolation structure are studied respectively.The study details are as follows:Firstly,using finite element method ANSYS,the numerical simulation is applied to research the dynamic characteristics of the gravity tank in AP1000 shielding building.The comparison between the numerical simulation results and Housner theoretical computation results of the modal of the water tank proves that numerical simulation by ANSYS has high accuracy.Those studies above give the base foundation for the establishment of AP1000 shielding building model in ANSYS system.Secondly,based on the actual size of AP1000 shielding building and the similarity theory of dynamic characteristic,the equivalent simplified model of AP1000 shielding building is shown in this article.Comparing the dynamic analysis results of simplified model with finite element model proves that the simplified model has high accuracy in the dynamic analysis.Then,According to the code for seismic design of nuclear power plants,the time-history analysis of traditional structure,base isolation structure,and story isolation structure of AP1000 shielding building are completed by the finite element method.The relationship and difference of three models on seismic response are shown by comparing the acceleration,displacement and the base shear force under the safe shutdown earthquake.The comparison results of the seismic response of three structures show that the story isolation structure is one of good method to improve the aseismic performance of AP1000 shielding building.