Analysis of Key Factors Related to Site Specific Design Ground Motion for NPPs

Based on 46 project data of evaluation of seismic safety for the Chinese nuclear power plant（NPP） siting and construction in the last ten years, the controlling impacts of the calculated results from different seismic hazard analysis methods are analyzed and discussed on the determination of the site specific design ground motion for nuclear power plants, and statistic analyses are made on the results calculated by the probabilistic seismic hazard analysis method and the results induced by tectonic earthquakes and diffuse earthquakes（diffuse seismicity） in the deterministic seismic hazard analysis method. The research result shows that: In the weaker seismicity area, the site specific design ground motion parameters are mainly controlled by the calculated results from the deterministic seismic hazard analysis method, especially the peak ground acceleration（PGA） and high frequency spectral accelerations are controlled by the results induced by the diffuse earthquake, and therefore, the NPP construction based on the site specific design ground motion in the area will have higher seismic safety margin; In relatively strong seismicity area, the site specific design ground motion parameters are more likely to controlled by the calculated results from the probabilistic method, and for some NPP sites, the ground motion parameters from probabilistic method, especially the low frequency spectral accelerations are much bigger than those from the deterministic method; The determination of site specific design ground motion parameters as a whole is very conservative for Chinese NPP sites.