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Comparative analysis of the international regulations and guidelines related to the seismic hazard assessment for nuclear facilities

Güner, Barı
Turkey intends to build and operate twelve nuclear reactor units in the next ten years; therefore, the regulatory body of Turkey needs a systematic, comprehensive, and up-to-date seismic hazard assessment (SHA) guideline that is applicable for all candidate designs and compatible with the international legislative structures. To facilitate towards this goal, current SHA practice and related regulatory requirements of the leading countries, international organizations, and Turkey are evaluated and compared by focusing on the critical aspects of seismic source and ground motion characterization. Discussions are qualitatively supported by the good practice implemented in the previous nuclear power plant (NPP) projects and the lessons learned from the past experiences. Considerable differences in practical applications and regulatory requirements have been identified in the definition of spatial scales, capable fault terminology, estimation of magnitude recurrence parameters, considered minimum magnitude, assigned maximum magnitude, selection of ground motion models, and truncation of ground motion variability. Quantitative comparisons in terms of the hazard curves are provided to further underline the range and extend of the differences in international approaches for a reference NPP site. Analysis results revealed that the selection and level of truncation for the uncertainty of ground motion models and the possibility of existence for a relatively small capable fault in near region scale have a higher impact (up to 2-fold increase) on the design-basis ground motion, compared to the other parameters. Tangible recommendations are provided for Turkey’s and other embarking countries’ future SHA guidelines and applications based on the comparison results.