This standard provides criteria and guidance for performing a Probabilistic Seismic Hazard Analysis (PSHA) for the design and construction of nuclear facilities. As defined in ANSI/ANS-2.26-2004, a nuclear facility is a facility that stores, processes, tests, or fabricates radioactive materials in such form and quantity that a nuclear risk to the workers, to the off-site public, or to the environment may exist. These include, but are not limited to, nuclear fuel manufacturing facilities; nuclear material waste processing, storage, fabrication, and reprocessing facilities; uranium enrichment facilities; tritium production and handling facilities; radioactive materials laboratories; and nuclear reactors. Criteria provided in this standard address various aspects of conducting PSHAs, including:
1. Selection of the process, methodology and the level of seismic hazard analysis appropriate for a given Seismic Design Category (SDC) structure, system, or component (SSC) or facility (hereafter, the SDC of a facility is considered synonymous with the highest SDC SSC in the facility) and the geotechnical and seismological characteristics of the site;
2. Seismic sources characterization;
3. Ground motion estimation;
4. Site response assessment;
5. Assessment of aleatory and epistemic uncertainties in a PSHA;
6. PSHA documentation requirements;
This standard does not specify methods for estimating the probability of fault displacement, or other seismically induced hazards such as soil liquefaction, soil settlement, land sliding, and earthquake-induced flooding. These hazards may be applicable for certain sites and need to be evaluated and included in SSC design requirements. Methods for doing this are included in ANSI/ASCE/SEI 43-05.
This standard does not address criteria, procedures or methods for collecting information and data required to perform a PSHA. These are specified in ANSI/ANS-2.27-2008, “Criteria for Investigations of Nuclear Facility Sites for Seismic Hazard Assessments.” In addition, this standard does not address the use of PSHA results or the selection of design basis earthquakes (DBEs) for nuclear facilities. This topic is covered in ANSI/ANS-2.26-2004 and ANSI/ASCE/SEI 43-05.
The use of this standard shall be coordinated with the other three seismic standards named above. This coordination is vital to the collection and evaluation of data required to perform the PSHA, to establish the level and scope of the analysis consistent with an application, and for consistency with the intended use of the PSHA results.
The guidelines and requirements provided in this standard are applicable for the design and evaluation of SDC 3, 4, and 5 facilities. These can also be applied to SDC 1 and 2, or other non-DOE facilities if, for safety, economy, or other reasons, a site-specific seismic hazard determination becomes necessary.