- Practical Implementation Guidelines for SSHAC Level 3 and 4 Hazard Studies (NUREG-2117, Revision 1)
- A. Kammerer ; J.P. Ake
- Book Title / Journal: Office of Nuclear Regulatory Research
- Year: 2012 , Series: NUREG-2117
- Risk & Reliability
- Description
- 10 CFR 100.23, paragraphs (c) and (d) require that the geological, seismological, and engineering characteristics of a site and its environs be investigated in sufficient scope and detail to permit an adequate evaluation of the Safe Shutdown Earthquake (SSE) Ground Motion for the site. In addition, 10 CFR 100.23, paragraph (d)(1), “Determination of the Safe Shutdown Earthquake Ground Motion,” requires that uncertainty inherent in estimates of the SSE be addressed through an appropriate analysis such as a probabilistic seismic hazard analysis (PSHA). In response to these requirements, in 1997, the U.S. Nuclear Regulatory Commission published NUREG/CR-6372, Recommendations for Probabilistic Seismic Hazard Analysis: Guidance on Uncertainty and the Use of Experts. Written by the Senior Seismic Hazard Analysis Committee (SSHAC), NUREG/CR-6372 provides guidance regarding the manner in which the uncertainties in PSHA should be addressed using expert judgment. In the 15 years since its publication, NUREG/CR-6372 has provided many PSHA studies with the framework and guidance that have come to be known simply as the “SSHAC Guidelines.” The information in this NUREG is based on recent efforts to capture the lessons learned in the PSHA studies that have been undertaken using the SSHAC Guidelines. As a companion to NUREG/CR-6372, this NUREG provides additional practical implementation guidelines consistent with the framework and higher-level guidance of the SSHAC Guidelines.
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- Advances on Seismic Hazard Assessment for Nuclear Facilities in the Central and Eastern United States
- A. Kammerer ; J.P. Ake ; C.G. Munson
- Book Title / Journal: Transactions Structural Mechanics in Reactor Technology (SMiRT) Conference, New Delhi, India
- Year: 2011
- Risk & Reliability
- Description
- The United States Nuclear Regulatory Commission (NRC) is currently sponsoring three key projects in the
area of probabilistic seismic hazard analysis (PSHA) for the central and eastern United States (CEUS). These projects will provide both new guidance describing the methods to be used for PSHA model development and actual updated seismic hazard assessment input models for the CEUS. These three projects, taken together, will result in an advanced regional PSHA model for critical facilities in the CEUS. They will also provide guidance, a welldocumented case study, and a significant number of useful research products, for undertaking PSHA in the US and globally, particularly in low-to-moderate seismicity regions. The first project is the nearly complete NRC Development Project for Practical Procedures for Implementing the Senior Seismic Hazard Analysis Committee (SSHAC) Guidelines and Updating Existing PSHAs. This research program will provide new implementation guidance to complement the original SSHAC guidelines (which are more formally known as NUREG/CR-6372 [1]). The new guidance will be documented in a new NUREG-series report currently in publication [2]. The NUREG provides guidance on the process used to develop Seismic Source Characterization (SSC) and Ground Motion Characterization (GMC) models. The second project, also nearly complete, is the Central and Eastern United States Seismic Source Characterization (CEUS SSC) for Nuclear Facilities Project. The CEUS SSC project will develop an advanced regional SSC model for approximately half of the United States. Lastly, the Next Generation Attenuation Relationships for Central and Eastern North America (NGA-East) Project will produce a suite of ground motion prediction equations that will form the basis for a new GMC model for low-to-moderate seismicity regions. Both the CEUS SSC project and the NGA-East project are being conducted as SSHAC Level 3 studies utilizing the original and new guidance.
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- Development of Implementation Guidance for SSHAC Level 3 & 4 Assessments used in Probabilistic Seismic Hazard Analyses for Nuclear Facilities
- A. Kammerer ; J.J. Bommer ; K.J. Coppersmith ; J.P. Ake
- Book Title / Journal: Transactions Structural Mechanics in Reactor Technology (SMiRT) Conference, New Delhi, India
- Year: 2011
- Risk & Reliability
- Description
- Seismic risk analysis for nuclear facilities requires probabilistic characterization of both the earthquake loading and the fragility of structures, systems and components, including consideration of the important contributors to uncertainty. The seismic hazard is determined through a probabilistic seismic hazard analysis (PSHA), which requires demonstration that the analyses have identified, quantified and incorporated both aleatory and epistemic uncertainties. The explicit characterization of uncertainty contributes to regulatory assurance by reducing the likelihood of unforeseen circumstances that have not been considered in the safety evaluation. Aleatory (random) variability in both the degree and timing of future seismicity and the ground shaking generated by specific earthquakes is accounted for through an integration process within PSHA. However, the associated epistemic (modeling or interpretation) uncertainty requires expert judgment and the use of logic trees. For critical facilities such as nuclear power plants (NPPs), the judgments of multiple experts are required to capture the complete distribution of technically defensible interpretations of the available Earth science data. The guidelines developed by the Senior Seismic Hazard Analysis Committee (SSHAC) as described in NUREG/CR-6372 provide a structured framework for conducting multiple expert assessments. Following 15 years of experience in applying the SSHAC guidelines for hazard studies for critical facilities, the US Nuclear Regulatory Commission (NRC) conducted a study of the lessons learned from practice. These lessons have now been distilled into a new US NRC NUREG-series report that provides additional practical guidance on implementing the SSHAC assessment process. The NUREG focuses primarily on the higher levels of SSHAC process (Levels 3 and 4), which are the most complex but provide a higher degree of regulatory assurance. The new NUREG gives clear guidance on the requirements for such studies, particularly SSHAC Level 3, which received relatively little attention in the original SSHAC guidelines (where the emphasis was on Level 4 studies). This NUREG also corrects the misperception that the most significant increase in complexity and likelihood of regulatory assurance occurs between Levels 3 and 4. The actual increase occurs between Levels 2 and 3. Indeed, for new nuclear sites the NRC makes no distinction between Level 3 and 4 studies, both of which are viewed as appropriate processes for conducting new PSHA studies.
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- Developing & Implementing a Real-Time Earthquake Notification System for Nuclear Power Plant Sites Using the USGS Shakecast System
- A. Kammerer ; A.R. Godoy ; S. Stowall ; J.P. Ake ; A Altinoyollar ; N. Bekiri ; D.J. Wald ; K. Lin
- Book Title / Journal: Transactions Structural Mechanics in Reactor Technology (SMiRT) Conference, New Delhi, India
- Year: 2011
- Soil Dynamics ; Geotechnical Earthquake Engineering
- Description
- When an earthquake occurs near a nuclear power plant (NPP), specific information is quickly needed to support accurate real-time situational awareness, assessment of the potential impact to the installation, informed decision making, and effective communication with key stakeholders. To address this important need, the International Atomic Energy Agency (IAEA) and the United States Nuclear Regulatory Commission (NRC), in collaboration with the United States Geological Survey (USGS), are developing and implementing a custom ShakeCast system for post-earthquake real-time notification of ground shaking at NPP sites. The custom system, called Nuclear ShakeCast, is being developed to meet the unique informational needs of the global nuclear community. The project is currently focused on developing and implementing the Nuclear ShakeCast system within the IAEA and NRC. However, the software will be freely available to the international nuclear community once developed. Nuclear ShakeCast has the potential to incorporate observations, estimates of hazard levels, and plant fragility and license information into real-time automated comparisons of estimated ground motions against plantspecific shut-down criteria and basic NPP damage estimations. The earthquake shaking data used by the ShakeCast system is in the form of a ShakeMap, a map that displays earthquake shaking parameters spatially. If an earthquake occurs and is of sufficient size to trigger automatic creation of a new ShakeMap, the ShakeCast software retrieves the map and automatically begins a series of calculations based on protocols and databases specified a priori by the user. The system then sends an automated notification containing the information needed by key personnel in the response organization. The report includes basic information about the earthquake, the estimated levels of ground shaking calculated for those nuclear installation sites located in the affected region, and NPP design information important in the NPPs licensing basis. All this information–-supported by existing operating international seismological networks—is essential for a quick effective communication and decision making. Depending on the responding organization, communication may be with the effected utilities and NPPs, the regulatory body, the media, the public, and governmental organizations. Rapid and automated information is particularly important because affected organizations are busy dealing with the consequences and disruption caused by the earthquake.
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- Implementation Guidance for SSHAC Level 3 & 4 Processes
- K.J. Coppersmith ; J.J. Bommer ; A. Kammerer ; J.P. Ake
- Book Title / Journal: 10th International Probabilistic Safety Assessment & Management Conference
- Year: 2010
- Risk & Reliability
- Keywords: PSHA ; Epistemic uncertainty ; SSHAC
- Description
- Risk analysis for critical facilities requires a probabilistic assessment of the hazards that could affect the installation. The complexity of the processes that generate geological hazards such as seismic ground shaking and volcanic events is such that there is inevitably large uncertainty associated in the hazard assessment. This uncertainty is reflected in the range of legitimate technical interpretations made by informed technical experts based on the available data. Procedures to develop multiple expert assessments for seismic hazards in a structured process have been established in the SSHAC (Senior Seismic Hazard Analysis Committee) guidelines. The objective of the present paper is to capture and clarify the insights gained from performing a number of detailed assessments using the SSHAC approach over the past 10-15 years. Unlike classical expert elicitation, which attempts to extract information from independent experts, the SSHAC process encourages interaction amongst experts and fosters learning by the experts throughout the process, with the ultimate objective of capturing the full community distribution of technical interpretations. The SSHAC guidelines, written largely in abstract, have now been implemented in practice several times. In these studies valuable lessons have been learned, which are now being distilled into a new U.S. Nuclear Regulatory Commission NUREG-series report to provide practical guidance on implementing SSHAC processes for hazard assessments. A key lesson from these studies is that higher level SSHAC processes (Levels 3 and 4) which specify the use of a Participatory Peer Review Panel (PPRP), provide a higher degree of regulatory assurance and stability for the initial development of hazard models for safety-critical installations. Also, significant technically-informed participation by project sponsors and regulators throughout the process enhances the likelihood of regulatory acceptance.
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