Quasi-Three-Dimensional Seismic Safety Analysis Of Nuclear Power Plant Structures Under Layered Soil Conditions

As a safe and efficient energy source,nuclear power has unique advantages in meeting energy demand,reducing environmental pollution and promoting economic development.With the continuous development of nuclear power construction in China,the number of excellent sites such as rock foundation is decreasing year by year.In order to speed up the construction of nuclear power plants,it has become an urgent task for the development of nuclear power to build nuclear power plants on the condition that the covering soil is the soil site.In this study,a planned inland nuclear power plant on layered soil site is taken as the research object,and the quasi-three-dimensional safety and seismic numerical analysis of the nuclear power plant engineering structure is studied.On the basis of keeping the true three-dimensional accurate simulation foundation of the superstructure,the calculation efficiency of the non-linear dynamic analysis is improved by simplifying the layered foundation,and combined with the secondary development function of the general finite element software.The embedding of quasi-three-dimensional dynamic calculation time-domain model and seismic response analysis under layered soil site conditions are realized.(1)The rationality and efficiency of the quasi-three-dimensional dynamic interaction analysis model of layered soil foundation-structure is the key technology of seismic safety analysis.Based on the refined three-dimensional simulation of the upper nuclear power plant structure,a quasi-three-dimensional simplified treatment method for layered foundation is proposed to improve the computational efficiency of the non-linear dynamic analysis of the nuclear power plant structure.The equivalent linear method is used to describe the non-linear characteristics of the near-field layered soil foundation,and the viscoelastic artificial boundary is introduced to simulate the radiation damping effect of infinite foundation and infinite foundation.Based on the elastic recovery performance,a quasi-three-dimensional seismic response analysis model of nuclear power plant structure on layered foundation is established in the framework of finite element method.The reliability and rationality of the model are verified by a typical example.(2)Maneuverability and engineering practicability are the necessary conditions to promote the application of pseudo-three-dimensional dynamic calculation model in engineering under the condition of layered soil site.Based on the quasi-three-dimensional dynamic response analysis model under layered soil conditions and the secondary development characteristics of UPFs,the sub-programs UserElem.f and UserXX.f for the quasi-three-dimensional dynamic calculation model are developed on the development platform of ANSYS,which is a large general finite element software.The dynamic calculation process of simplified foundation considering out-of-plane effects is completed,and the quasi-three-dimensional dynamic response analysis model based on APDL is realized.The time domain calculation model is embedded in ANSYS software,and a quasi three-dimensional dynamic calculation and analysis model suitable for layered soil is established.Finally,the accuracy and reliability of the quasithree-dimensional computational time-domain model are verified by comparing the results of typical examples with the true three-dimensional dynamic calculation results.(3)It is widely used in practical engineering to establish a three-dimensional simulation model of layered soil site.Based on the research results of this paper,the quasi-threedimensional dynamic response of an inland nuclear power plant with several CPR1000 MW PWR nuclear power units on layered soil site conditions is analyzed,and the influence of different effective widths on the quasi-three-dimensional dynamic response is considered.Furthermore,the acceleration response spectrum and displacement response of typical parts of nuclear island powerhouse structure under different working conditions are compared and analyzed,and the floor acceleration response spectrum and CPR1000 design spectrum are compared and analyzed.The research results have guiding and reference significance for seismic safety analysis of nuclear power plant structure under layered soil conditions.