Studies On Differences And Effects Of Seismic Analysis Of Nuclear Power Plant Building Based On Different Regulations

The NPPs (nuclear power plants) that had been built and will be built inChina are involve many types technique, some are come from domestic, somewere introduced from foreign countries, and the countries that the techniquewas used for design NPPs are difference. So we could use many codes thatwere published in other countries, but this status will lead to NPPs in Chinacould accord different codes to design. For the NPPs seismic analysis, if weuse the different regulations, then we maybe reach to different depths ofdesign in one same phase and receive two distinct design results for one sameNPP which is according to two different codes. In this paper, we do series ofstudies on this discrepancy between codes of NPPs seismic design that couldbe used in China, and we give some results of studies that could be used inactual NPPs project, and provide theoretical guidance on NPPs design, safereview of design reports and renovate code. These studies could help theconstruction and research of the later NPPs.The works in this study include:(1)Based on the process of AP1000licensing process in China andAmerican, comparison and analysis of the difference between the manageprograms of nuclear power plant in China and American. We gained that thereare also some differences in same nuclear power plant under two disparatecodes.(2)The earthquake response analysis of power plant structures underdifferent impendence functions of regulations considering the sensitivity ofparameters of ground soil. Based on impendence functions of foundation thatare calculated by two methods of different regulations, we analyze thestructure earthquake response of CPR1000NPP and give the difference ofearthquake response of NPP building by RCC-G and ASCE4-98impendencefunction. Considering the sensitivity of the impendence function of groundsoil, we study the response behavior of three parameters of velocity of ground,Poisson's ratio of ground, and density of ground change. The results showthat:the computational method of impendence functions of ASCE4-98isconservative compared with the method in RCC-Gï¼›The density of ground haslittle impact on the response of NPP; the influence of Poisson's ratio ofground could be neglected to the response of NPP; the ground soil could reduce the response of earthquakes under some conditionsï¼› With theincreasing of the shear wave velocity of ground, the response of NPP changeslittle, and when the velocity varies from1900m/s to2200m/s, there is only2%difference between two horizontal peak acceleration responses of the highestpoint in CPR1000NPP. Considering the uncertainty of the computation, wesuggest that the effect of foundation-structure interaction could be neglectedwhen the shear wave velocity of ground is greater than or is equal to1900m/s.(3)In the process of seismic hazard assessment of nuclear power plant,there are some different requirements in determination of seismic bedrock inthe site model by the related China and America code. In this study, theseismic bedrocks with different shear wave velocities of700m/s,1100m/s,and2438m/s were selected based on the site models for AP1000nuclearpower plant design, and seismic responses of the site models, including thepeak ground accelerations and response spectra, were analyzed by softwareswere widely used in China and America. The results indicated that differentshear wave velocities of seismic bedrocks could lead to a strong difference ofcalculated ground motions of sites for AP1000nuclear power plant design,such as more than2.25times variation of the peak ground accelerations.Therefore, it was suggested that the rock layer with shear wave velocity of2438m/s should be regarded as the seismic bedrock in the seismic safetyanalysis of AP1000nuclear power plant site. When the shear wave velocity ofsoil in certain depth still could not reach2438m/s,then we should select theseismic bedrock based on soil-structure interaction analysis. Based on theintroduction of AP1000Certified Seismic Design Response Spectra,we givethe relationship of difference Response Spectra of definite by differentRegulations, and illuminate that we should compare the site specific ResponseSpectra and AP1000CSDRS on one same ground level. Then, According totwo methods in SSI analysis, utilizing one artificial earthquake waves thatsimulating five damping rations of AP1000CSDRS, calculating two levelsCSDRS of design rock and foundation base on the basis of AP1000designground. We get that the calculated two levels CSDRS of design rock andfoundation base could not envelope RG1.60anchored by0.2g.(4) The main technical requirements in several domestic and foreigncodes involved in the synthesis of design ground motion are interpreted, andthe suggestions could be employed in actual project in China. Based on thepractical engineering requirements of nuclear power plants, we propose anoptimization algorithm for the time history generation to match the multi-damping design spectra. The algorithm could enhance the fittingprecision between the response spectra of time history to target spectra undermulti-damping ratios. In our method, the seed ground motion history could beobtained from actual seismic records or from traditional methods, and then weconsider to superimpose an adjusted ground motion in time domain from aglobal view point, which make the influences of the superimposed signal tothe response spectra be under control. The controllable property isimplemented through adding constraints on the objective function whichneeds to be optimized. In a numerical example, we demonstrate that theground motions generated by our method could match the design spectraunder5different damping ratios in a high precision. The max differencebetween response spectra of artificial time history and design spectra is about5%, and all the response spectra envelope the design spectra.(5)The main technical requirements in several domestic and foreignstandards involved in the methods of seismic analysis of NPPs are different,Based on there is no complex frequency response method in Code for SeismicDesign of Nuclear Power Plants of China, and we do analysis in AP1000nuclear island structure by complex frequency response method and timehistory method. The results of analysis show that the two methods are similaron the basis of the linear analysis of nuclear island. Besides, with thedevelopment of computer science, the complex frequency response methodbecomes much more fast and convenience, and then we suggest that we couldadd complex frequency response method in Code for Seismic Design ofNuclear Power Plants of China.(6)The requirements of vertical ground response of seismic analysis ofNPPs in several domestic and foreign standards are compared,and we do theseismic analysis on the basis of AP1000nuclear island structure and AP1000design response spectrum. The results of analysis show that different methodsof obtaining vertical ground response in seismic evaluation of one site on thehorizontal response of nuclear island structure effect could be neglectedï¼›thepeaks of different vertical ground accelerations are same and the shapes ofvertical response spectrum are different which have a little effect on the peaksof response accelerations of nuclear island structure,the effect on responsespectrums of nuclear island structure but need to be considered. In seismicanalysis of building of nuclear power plant, the vertical peak of designacceleration by scaling the corresponding ordinates of the horizontal peak ofdesign acceleration by two-thirds is un-conservative. In the end, we summarized our studied work, and then pointed out theproblems that need to be studied more deeply.