Seismic risk analysis and design of nuclear power plants

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Earthquake is one of the most destructive natural disasters. The Great East Japan earthquake and the tsunami, occurred on March 11, 2011, caused a series of equipment failures, nuclear meltdowns, and releases of radioactive materials at the Fukushima Daiichi Nuclear Power Plant. Since several destructive earthquakes have occurred in recent decades, nuclear energy industries world-wide are launching an unprecedented and extensive re-evaluation of seismic hazards and risk to nuclear power plant (NPP) systems. In a NPP, there are a large number of Structures, Systems, and Components (SSCs), such as main steam line, piping, and equipment, mounted on the primary structural systems. Seismic response analysis, in terms of Floor Response Spectra (FRS), for SSCs is of crucial importance for seismic qualification and seismic safety assessment, which ensures that the NPP has sufficient seismic margin and the frequency of occurrence of adverse consequences due to the potential effects of earthquakes are within the acceptable level. The proposed research will develop comprehensive methodologies for the accurate determination of both second and third level FRS. The method will provide a complete probabilistic characterization of FRS as an integral part of seismic risk analysis. The methods overcome the deficiencies of existing spectrum-to-spectrum approaches and will reduce or eliminate the cumbersome and expensive computation in the time history method. The research will develop efficient and accurate modeling techniques, design methods, and guidelines for structural changes to ensure that SSCs in NPPs are seismic qualified in a cost-effect way. The methodologies developed provide modern tools to assess existing SSCs in refurbishment of existing NPPs and to design new SSCs in new NPPs to comply with standards for seismic safety.