Robin K. McGuire

New seismic design spectra for nuclear power plants

Under a US Nuclear Regulatory Commission-sponsored project recommendations for seismic design ground motions for nuclear facilities are being developed. These recommendations will take several forms. Spectral shapes will be developed empirically and augmented as necessary by analytical models. Alternative methods of scaling the recommended shapes will be included that use a procedure that integrates over fragility curves to obtain approximately consistent risk at all sites. Site-specific soil effects will be taken into account by recommending site-specific analyses that can be used to modify rock hazard curves at a site. Also, a database of strong motion records will be archived for the project, along with recommendations on the development of artificial motions. This will aid the generation of motions for detailed soil- and structural-response studies.

Hazard- and risk-consistent spectra

Under a US Nuclear Regulatory Commission-sponsored project recommendations for seismic design ground motions for nuclear facilities are being developed. These recommendations will take several forms. Spectral shapes will be developed empirically and augmented as necessary by analytical models. Alternative methods of scaling the recommended shapes will be included which use a procedure that integrates over fragility curves to obtain approximately consistent risk at all sites. Site-specific soil effects will be taken into account by recommending site-specific analyses that can be used to modify rock hazard curves at a site. Also, a database of strong motion records will be archived for the project, along with recommendations on the development of artificial motions. This will aid the generation of motions for detailed soil- and structural-response studies.

Assessment of the potential for tectonic fault rupture for high-level nuclear waste repositories

Abstract Active faults that extend to near the Earths surface may pose a direct threat to the safety of engineered structures. Usually the threat can be mitigated by taking appropriate siting or design actions. Such actions require a thorough understanding of the characteristics and magnitude of the faulting hazard based on detailed field investigations of the site locality and an adequate assessment of the characteristics of past faulting in the sites tectonic regime. An active fault may be defined in purely geological terms as one that has exhibited displacement in the present tectonic regime. However, for engineering considerations an active fault is usually defined in terms of a specified time of most recent movement, or a longer time in which multiple movements have taken place. Deterministic or probabilistic approaches are used to assess faulting hazard for the purpose of engineering design consideration. Support is building for the use of probabilistic procedures alone or combined with deterministic procedures to assess faulting hazard for design of critical facilities.

Approaches that use seismic hazard results to address topics of nuclear power plant seismic safety, with application to the Charleston earthquake issue

Abstract Plant seismic safety indicators include seismic hazard at the SSE (safe shut-down earthquake) acceleration, seismic margin, reliability against core damage, and reliability against offsite consequences. This work examines the key role of hazard analysis in evaluating these indicators and in making rational decisions regarding plant safety. The paper outlines approaches that use seismic hazard results as a basis for plant seismic safety evaluation and applies one of these approaches to the Charleston earthquake issue. This approach compares seismic hazard results that account for the Charleston tectonic interpretation, using the Electric Power Research Institute (EPRI)–Seismicity Owners Group (SOG) methodology, with hazard results that are consistent with historical tectonic interpretations accepted in regulation. Based on hazard results for a set of 21 eastern U.S. nuclear power plant sites, the comparison shows that no systematic “plant-to-plant” increase in hazard accompanies the Charleston hypothesis; differences in mean hazards for the two interpretations are generally insignificant relative to current uncertainties in seismic hazard.