Study Of Seismic Hazard Analysis Method For Nuclear Facility

The Fukushima nuclear accident revealed the possibility of a serious nuclear accident caused by external natural disasters,sounded the alarm for the nuclear engineering community.Under this background,operational and constructing nuclear power plant sites in China,were progressively carried out Seismic Margin Assessment(SMA)or Seismic Probabilistic Safety Assessment(SPSA).Focused on seismic hazard analysis method applied in nulcear utility,the problems in determination of design basis ground motion,SPSA and SMA were studied in this paper.Firstly,the significant difference between assess results analyzed per deterministic(DSHA)and probabilistic(PSHA)method of a few nuclear power plant(NPP)sites is an evident problem in the determination of design basis ground motion.Analyzed the seismic hazard of several NPP sites to locate the essential factors of DSHA and PSHA.The nearby seismogenic structures,seismotectonic provinces and potential seismic source zones govern seismic hazard of site when the natural period of spectrum is relatively short;the faraway regional seismogenic structures,high magnitude potential seismic source zones take great influence when natrual period increased.Provided the marginal distributions of variables M,R and ?,per seismic hazard disaggregation of ground motion whose annual probability of exceedance is 10 minus 4.The distribution of variables M,R and ?,demonstrate the substantial components are occurance ratio of earthquakes in high magnitude bins on unit area and truncate levle of attenuation relationship.It's need to develope design factor of spectrum for taking advantage of performance based seismic desgin method.After derived the exact equation of design factor,and contracted the characteristics of seismc hazard curve of Chian to US,developed the approximate equation of design factor adhere to China.Secondly,How to treat and display uncertainty in PSHA is the leading difficulty in SPSA of NPP in China.Analyzed the effect of truncate level on the results of PSHA,discussed the distribuiton of them.Verfied the applicability of random vibration theory(RVT)in soil site response analysis,then evaluated the impact of aleatory in soil profile parameters on soil site response.Introduced how to weight the branch in logic tree model in CEUS,and compared with the situation in China,examined the applicable range of this method.Based on the frontier research of maximum magnitude of stable continent region(SCR),generated huge complete earthquake catalogs and then sampled hunderds records from every catalogs,analyzed the deliver range of b value and occurance ratio of earthquakes in high magnitude bins,to research the combination rule of branches from relative nodes on logic tree model.Preliminarily estimated the distribution of maximum magnitude in the middle reaches of the Yangtze River seismic belt by Bayesian method,depended on prior distribution of the maximum magnitude of SCR and likelihood function of earthquakes in this seismic belt which three inland NPP sites in or nearby.Lastly,analyzed seismic hazard of NPP sites and standard seismic design of reactors in China,and taken the determination of seismic margin earthquake by multi methods of a NPP site as an example,clarified which method is the appropriate one and the proper spectrum shape.