Seismic Margin Analysis Of Nuclear Containment Structure Based On Reliability Theory

Nuclear power is an economic and efficient clean energy,and the development of nuclear power has become an important part of the energy strategy of all countries.Japan's 311 fukushima nuclear disaster has caused heavy personal injury,property losses and social impact,highlighting the huge threat of earthquakes to the safe operation of nuclear power plants.Nuclear containment structure is the last Class I structure to prevent nuclear leakage.Its seismic safety is the key to ensure the safe operation of nuclear power plants.Therefore,it is great theoretical significance and practical value to study the seismic capacity of high confidence of a low probability of failure of nuclear containment structure under strong earthquake and evaluate the structural seismic margin.In this paper,a three-dimensional finite element analysis model of the containment structure is established in the finite element analysis software ABAQUS,based on the CNP1000 nuclear power containment.The dynamic response of the containment structure under the action of strong earthquake is analyzed.The seismic vulnerability curves of nuclear containment structure were established by incremental dynamic analysis and response surface method respectively to evaluate the seismic margin of the structure.The main research work and conclusions are as follows:(1)The three-dimensional finite element model of nuclear containment structure is built by ABAQUS.Modal analysis of the nuclear containment structure is carried out,and the natural frequency of nuclear containment structure is obtained,and the Rayleigh damping coefficient is determined.The dynamic time-history analysis and Pushover analysis of nuclear containment structure were carried out to obtain the structural seismic response and determine the horizontal displacement damage index of structure.(2)15 actual vibration records were selected for incremental dynamic analysis of nuclear containment structure,and IDA curve cluster with horizontal displacement of vertices as horizontal coordinates and PGA as vertical coordinates was obtained.Through linear regression analysis of IDA data,the seismic probability demand model of nuclear containment structure was determined,and the seismic vulnerability curve of nuclear containment structure cracking based on IDA method was obtained.(3)A quadratic polynomial with cross terms is selected as the response surface function form,and the center composite design is selected to select test points.The functional function of nuclear containment structure under different intensity earthquakes is obtained by using Design Expert.Combined with the monte carlo method two nuclear containment structure cracking failure probability is given and two kinds of cracking seismic fragility curves of nuclear containment structures based on response surface method are obtained.(4)Based on the incremental dynamic analysis method and response surface method,the seismic fragility curve data of the nuclear containment structure are obtained.Logarithmic normal seismic fragility analysis model was used,and the number of various lines in the seismic fragility analysis model are determined by the nonlinear regression analysis function of the SPSS software.The seismic fragility curves of structural cracking with different confidence levels are obtained.The results of the calculation are compared and analyzed,and the HCLPF value of the nuclear containment structure is determined to evaluate the seismic margin of the structure.