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NUREG/CR-7253 Technical Consideration for Seismic Isolation of Nuclear Facilities.
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Issue date:	02/28/2019
From:	Constantinou M, Gascot R, Kammerer A, Whittaker A; Office of Nuclear Regulatory Research, University of Buffalo
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	Meyd, Donald
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NUREG/CR-7253 Technical Considerations for Seismic Isolation of Nuclear Facilities Office of Nuclear Regulatory Research

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NUREG/CR-7253 Technical Considerations for Seismic Isolation of Nuclear Facilities Manuscript Completed: February 2013 Date Published: February 2019 Prepared by A. M. Kammerer1, A. S. Whittaker2, and M. C. Constantinou2 1Formerly, Office of Nuclear Regulatory Research US Nuclear Regulatory Commission 2MCEER, University at Buffalo State University of New York, 212 Ketter Hall Buffalo, NY 14260 Ramón L. Gascot, Scott P. Stovall, and Richard Rivera-Lugo, NRC Project Managers Office of Nuclear Regulatory Research

ABSTRACT Seismic isolation (SI) is a technology that has proven useful in constructing structures capable of withstanding intense earthquake ground motions. Although various techniques for isolating a structure from the effects of earthquake shaking have been known for centuries, the global use of modern seismic (or base) isolation devices has greatly expanded in recent decades.

Seismically isolated structures now number in the thousands around the world and the technology has been shown to meet the performance needs of important non-nuclear structures. SI has been used in the design and construction of nuclear power plants (NPPs) in France and South Africa and was recently used to isolate new emergency response centers at NPPs in Japan. As a result, SI is currently being considered for nuclear facilities in the United States.

Base isolation, an application of SI, reduces the response of a structure to horizontal ground motion through the installation of horizontally flexible and vertically stiff seismic isolators between the superstructure and its foundation. The dynamics of the supported structure change such that the fundamental vibration period of the isolated structural system is significantly longer than that of the fixed-base (non-isolated) structure. This leads to significant reductions in the horizontal accelerations and forces transmitted to the isolated superstructure (and the systems and components therein). The reduction in horizontal acceleration is accompanied by an increase in lateral displacement between the foundation and the superstructure, which is accommodated by deformation of the isolators. SI devices are designed and tested to undergo safely and with significant margin the large horizontal deformations expected in design basis shaking.

This report was developed under the NRCs Seismic Research Program Plan with the goal of providing technical information necessary for NRC staff to develop regulatory guidance on the use of SI technology. This report develops a performance-based and risk-informed design philosophy for SI derived based on NRC objectives and approaches. This design philosophy, in turn, leads to a set of recommended performance objectives and criteria that can serve as the foundation for future NRC guidance on the use of SI and related technology.

This report is the first comprehensive NRC technical document related to SI. As such, it provides background information on seismic isolators and isolation systems, a discussion of the history and performance of seismically isolated structures during earthquakes, and a summary of SI provisions in relevant existing codes and standards. It also provides a series of preliminary recommendations that have resulted from the NRCs research program on SI.

The focus of this NUREG/CR is surface-mounted or near-surface-mounted large light water reactors. Although vertical isolation systems, the isolation of individual systems or components, and the isolation of deeply embedded reactors are not discussed in detail in this NUREG/CR, there is no technical reason that the principles and recommendations contained herein cannot be extended to these and other cases. However, additional considerations, constraints and recommendations may be needed. Some are discussed briefly in this report.

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FOREWORD Appendix A, General Design Criteria for Nuclear Power Plants, to 10 CFR Part 50, General Design Criterion (GDC) 2, Design Bases for Protection Against Natural Phenomena, requires, in part, that nuclear power plant structures, systems, and components (SSCs) important to safety must be designed to withstand the effects of natural phenomena (such as earthquakes) without loss of capability to perform their safety functions. Such SSCs must also be designed to accommodate the effects of, and be compatible with, the environmental conditions associated with normal operation and postulated accidents.

The U.S. Nuclear Regulatory Commission (NRC) initiated the current research investigating the use of seismic isolation (SI) technology in nuclear power plants in 2008 in response to activities ongoing within the US nuclear industry focused on using SI technology as a way to meet the seismic requirements noted above. The importance of developing specific criteria for applying this technology has been highlighted by lessons learned from recent large magnitude earthquakes that have strongly shaken both isolated structures and non-isolated operating nuclear power plants, especially in Japan. The NRC research program on SI has been conducted jointly by the NRCs Office of Nuclear Regulatory Research, the Lawrence Berkeley National Laboratory, and MCEER (www.buffalo.edu/mceer.html) at the University at Buffalo, State University of New York. The research program focused on several technical topics and the resulting recommendations are included in this document.

The research that resulted in this NUREG/CR was intended to meet two key objectives:

1. Collect and summarize existing technical information on seismic isolation (SI) technology to inform NRC staff.

2. Develop performance and design recommendations and technical considerations addressing the design, construction, and operational needs for SI systems that consider the seismic performance of structures, systems, and components (SSC)

The emphasis of the NUREG/CR is the seismic isolation of nuclear facilities, with a focus on base isolation of surface-mounted or near-surface-mounted large light water reactors. Issues relevant to the analysis and design of isolation systems for deeply embedded reactors, non-light water reactors, and for individual systems and components are not addressed in detail in this NUREG/CR. Similarly, vertical isolation is not discussed in detail in this NUREG/CR. For uses of SI technology beyond those considered in this NUREG/CR, additional constraints, recommendations and studies may be needed. Additional studies would address further development of the technical bases for guidance for those uses as their necessary details become known.

To maximize the utility of the NUREG/CR, references are made to relevant consensus standards such as those for seismic analysis of safety-related nuclear structures (ASCE 4) and for seismic design criteria for structures, systems and components in nuclear facilities (ASCE 43). Elements of the standards have been included into the recommendations and options proposed in this report where appropriate. Additional performance criteria were developed to meet the risk-informed goals of the NRC. The technical considerations, recommendations and performance criteria provided in this report, coupled with the applicable provisions in the standards referenced in this document, provide a technical basis to inform development of regulatory guidance on the use of SI technology in nuclear facilities.

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TABLE OF CONTENTS ABSTRACT ...............................................................................................................................iii FOREWORD ............................................................................................................................. v TABLE OF CONTENTS .......................................................................................................... vii LIST OF FIGURES ................................................................................................................. xii LIST OF TABLES ....................................................................................................................xv ACKNOWLEDGMENTS ........................................................................................................ xvii ABBREVIATIONS, ACRONYMNS, AND PARAMETERS ......................................................xix 1 INTRODUCTION............................................................................................................... 1-1 1.1 Potential Benefits of Seismic Isolation ............................................................................ 1-2 1.2 Objective of the NUREG/CR ........................................................................................... 1-2 1.3 Scope .............................................................................................................................. 1-3 2 A BRIEF HISTORY OF SEISMIC ISOLATION ................................................................. 2-1 2.1 Seismic Isolation of Non-Nuclear Structures................................................................... 2-1 2.1.1 Seismic Isolation of Non-Nuclear Structures in the United States ........................ 2-1 2.1.2 Seismic Isolation of Non-Nuclear Structures in Japan ......................................... 2-2 2.1.3 Seismic Isolation of Non-Nuclear Structures in Other Countries .......................... 2-2 2.2 Response of Isolated Non-Nuclear Structures during Past Earthquakes ....................... 2-3 2.2.1 1994 Northridge Earthquake, California ............................................................... 2-3 2.2.2 1995 Kobe Earthquake, Japan ............................................................................. 2-4 2.2.3 1999 Duzce earthquake, Turkey .......................................................................... 2-5 2.2.4 2003 Tokachi-Oki Earthquake, Hokkaido, Japan ................................................. 2-5 2.2.5 2004 Chuetsu Earthquake, Niigata, Japan ........................................................... 2-5 2.2.6 2005 Fukuoka Earthquake, Japan ....................................................................... 2-5 2.2.7 2011 Tohoku Earthquake and Tsunami, Miyagi, Japan ....................................... 2-6 2.2.8 Summary of Earthquake Experience in Non-Nuclear Structures ......................... 2-7 2.3 Nuclear Applications of Seismic Isolation ....................................................................... 2-7 2.3.1 Introduction ........................................................................................................... 2-7 2.3.2 France and South Africa ....................................................................................... 2-8 2.3.3 United States ........................................................................................................ 2-8 2.3.4 Japan .................................................................................................................... 2-9 3 BASICS OF SEISMIC ISOLATION ................................................................................... 3-1 3.1 Introduction ..................................................................................................................... 3-1 3.2 Seismic Design Practice ................................................................................................. 3-4 vii

3.3 Types of Seismic Isolators Used for Base Isolation ........................................................ 3-5 3.4 Construction of Seismic Isolators .................................................................................... 3-6 3.5 Base Isolation of Nuclear Facilities ................................................................................. 3-7 3.6 Floor and Equipment Isolation ........................................................................................ 3-8 4 MECHANICS OF SEISMIC ISOLATORS ......................................................................... 4-1 4.1 Basic Mechanics of Seismic Isolators ............................................................................. 4-1 4.1.1 Elastomeric Bearings............................................................................................ 4-1 4.1.2 Spherical Sliding Bearings.................................................................................... 4-3 4.2 Mechanical Properties of Seismic Isolators .................................................................... 4-3 4.2.1 Low Damping Bearings ........................................................................................ 4-3 4.2.1.1 Mechanical Properties of a Low Damping Rubber Bearing .................... 4-3 4.2.1.1.1 Shear ...................................................................................... 4-3 4.2.1.1.2 Compression .......................................................................... 4-4 4.2.1.1.3 Tension ................................................................................... 4-4 4.2.1.2 Variation in Mechanical Properties of LDR Bearings .............................. 4-5 4.2.1.2.1 Temperature ........................................................................... 4-5 4.2.1.2.2 Axial Load ............................................................................... 4-6 4.2.1.2.3 Load History and Loading Rate .............................................. 4-6 4.2.1.2.4 Aging and Environmental Effects ........................................... 4-6 4.2.2 Lead Rubber Bearings ......................................................................................... 4-6 4.2.2.1 Mechanical Properties of LR Bearings.................................................... 4-7 4.2.2.1.1 Shear ...................................................................................... 4-7 4.2.2.1.2 Compression .......................................................................... 4-8 4.2.2.1.3 Tension ................................................................................... 4-8 4.2.2.2 Variation in Mechanical Properties of LR Bearings ................................. 4-8 4.2.2.2.1 Temperature ........................................................................... 4-8 4.2.2.2.2 Axial Load ............................................................................. 4-10 4.2.2.2.3 Load History and Loading Rate ............................................ 4-10 4.2.2.2.4 Aging and Environmental Effects ......................................... 4-10 4.2.3 High Damping Rubber Bearings ......................................................................... 4-10 4.2.3.1 Mechanical Properties of High Damping Rubber Bearings................... 4-11 4.2.3.1.1 Shear .................................................................................... 4-11 4.2.3.1.2 Compression ........................................................................ 4-11 4.2.3.1.3 Tension ................................................................................. 4-11 4.2.3.2 Variation in Mechanical Properties of HDR Bearings ........................... 4-12 viii

4.2.3.2.1 Temperature ......................................................................... 4-12 4.2.3.2.2 Axial Load ............................................................................. 4-12 4.2.3.2.3 Load History and Loading Rate ............................................ 4-12 4.2.3.2.4 Aging and Environmental Effects ......................................... 4-12 4.2.4 Spherical Sliding Bearings.................................................................................. 4-12 4.2.4.1 Mechanical Properties of the FP Bearing ............................................. 4-14 4.2.4.1.1 Shear .................................................................................... 4-14 4.2.4.1.2 Compression ........................................................................ 4-14 4.2.4.1.3 Tension ................................................................................. 4-15 4.2.4.2 Variation in Mechanical Properties of a FP bearing .............................. 4-15 4.2.4.2.1 Temperature ......................................................................... 4-15 4.2.4.2.2 Axial Load ............................................................................. 4-15 4.2.4.2.3 Load History and Loading Rate ............................................ 4-16 4.2.4.2.4 Aging and Environmental Effects ......................................... 4-16 5 GUIDANCE ON ANALYSIS AND DESIGN OF ISOLATION SYSTEMS IN US CODES AND STANDARDS ............................................................................................. 5-1 5.1 Approaches to Analysis and Design ............................................................................... 5-1 5.1.1 Deterministic ......................................................................................................... 5-1 5.1.2 Probabilistic .......................................................................................................... 5-1 5.2 Summary of Design Standards for Non-Nuclear, Seismically Isolated Structures .......... 5-2 5.2.1 ASCE 7-10 ........................................................................................................... 5-2 5.2.1.1 Definitions ............................................................................................... 5-2 5.2.1.2 General Design Requirements................................................................ 5-3 5.2.1.3 Hazard Characterization ......................................................................... 5-4 5.2.1.4 Analysis Procedure Selection ................................................................. 5-4 5.2.1.5 Equivalent Lateral Force Procedure ....................................................... 5-4 5.2.1.6 Dynamic Analysis Procedures ................................................................ 5-5 5.2.1.7 Design Review ........................................................................................ 5-6 5.2.1.8 Testing .................................................................................................... 5-6 5.2.2 AASHTO Guide Specification for Seismic Isolation Design ................................. 5-6 5.3 Summary of Design Standards Applicable to Isolated, Safety-Related Nuclear Structures .................................................................................................................. 5-6 5.3.1 ASCE 43-05 ......................................................................................................... 5-7 5.3.2 ASCE 4-16 ........................................................................................................... 5-8 5.3.3 NRC RG 1.208 ..................................................................................................... 5-9 ix

5.3.4 Concrete Structures.............................................................................................. 5-9 5.3.5 Steel Structures .................................................................................................... 5-9 6 INTERNATIONAL GUIDANCE FOR SEISMIC ISOLATION OF NUCLEAR FACILITIES ...................................................................................................................... 6-1 6.1 Regulatory Guidance for Seismic Isolation of Nuclear Facilities in Japan ...................... 6-1 6.1.1 JNES-RC-2013-1002 ........................................................................................... 6-1 6.1.2 JEAG 4614 ........................................................................................................... 6-3 6.2 Guidance for Seismic Isolation of Nuclear Facilities in France ....................................... 6-4 6.3 Guidance for Seismic Isolation of Nuclear Facilities by the International Atomic Energy Agency .......................................................................................................... 6-4 7 MODELING AND ANALYSIS OF SEISMICALLY ISOLATED NUCLEAR STRUCTURES.................................................................................................................. 7-1 7.1 Analysis of Seismically Isolated Structures ..................................................................... 7-1 7.1.1 Overview............................................................................................................... 7-1 7.1.2 Coupled Time-Domain Analysis ........................................................................... 7-2 7.1.3 Coupled Frequency-Domain Analysis .................................................................. 7-3 7.1.4 Multi-step Analysis................................................................................................ 7-3 7.2 Modeling of Isolator Units ............................................................................................... 7-4 7.2.1 Mechanical Properties of Isolator Units ................................................................ 7-4 7.2.2 Equivalent Linear Models of Isolators................................................................... 7-4 7.2.3 Nonlinear Models of Isolators ............................................................................... 7-5 8 RECOMMENDED PERFORMANCE CRITERIA FOR SEISMICALLY ISOLATED NUCLEAR FACILITIES .................................................................................................... 8-1 8.1 Philosophy in Developing Performance Criteria ............................................................. 8-1 8.2 Performance Matrix......................................................................................................... 8-2 8.3 Hazard Definitions for Analysis of Seismic Isolation Systems ........................................ 8-3 8.4 Performance Expectations for GMRS+ Shaking ............................................................. 8-5 8.5 Performance Expectations for BDB GMRS Shaking ...................................................... 8-6 8.5.1 Clearance to the Stop ........................................................................................... 8-6 8.5.2 Isolators ................................................................................................................ 8-6 8.5.3 Umbilical Lines ..................................................................................................... 8-7 8.5.4 Stop ...................................................................................................................... 8-7 8.6 Seismic Probabilistic Risk Assessment .......................................................................... 8-7 9 ADDITIONAL RECOMMENDATIONS ON DESIGN, CONSTRUCTION AND OPERATION ..................................................................................................................... 9-1 9.1 Additional Considerations ............................................................................................... 9-1 x

9.1.1 Long-Term Changes in Isolator Mechanical Properties ....................................... 9-1 9.1.2 Basemat and Foundation Design ......................................................................... 9-1 9.1.3 Anchorage Design ................................................................................................ 9-1 9.1.4 Other External Events .......................................................................................... 9-2 9.1.5 Accident Conditions and Emergency Response .................................................. 9-2 9.1.6 Moat Cap Design .................................................................................................. 9-2 9.1.7 Near-fault Ground Shaking ................................................................................... 9-2 9.1.8 Peer Review ......................................................................................................... 9-2 9.2 Additional Manufacturing and Construction Considerations ........................................... 9-3 9.2.1 Quality Control and Quality Assurance................................................................. 9-3 9.2.2 Testing of Prototype and Production Isolators ...................................................... 9-3 9.2.3 Construction Assurance ....................................................................................... 9-3 9.3 Operation Considerations ............................................................................................... 9-4 9.3.1 In-service Inspection, Replacement and Maintenance ......................................... 9-4 9.3.2 Additional Seismic Monitoring Equipment ............................................................ 9-4 9.3.3 Monitoring of Foundation Deformations ............................................................... 9-4 9.3.4 Requirements for Safety-related Equipment ........................................................ 9-4 9.3.5 Operating Temperature ........................................................................................ 9-4 10 REFERENCES................................................................................................................ 10-1 xi

LIST OF FIGURES Figure 2.1 Examples of Application of Seismic Isolation of Important and Critical Structures and Infrastructure .................................................................................. 2-3 Figure 2.2 Other Applications of Seismic Isolation in Critical Facilities..................................... 2-4 Figure 2.3 Failed Isolation System in the Bolu Viaduct in Turkey............................................. 2-6 Figure 3.1 Cross Section of a Seismically Isolated Nuclear Structure...................................... 3-2 Figure 3.2 Effect of Seismic Isolation on Spectral Demand (Courtesy of Dynamic Isolation Systems) ................................................................................................... 3-4 Figure 3.3 Force-Displacement Relationship for an Isolator..................................................... 3-6 Figure 4.1 Cross-Section of a Typical Elastomeric Bearing (Constantinou et al. 2007) ........... 4-2 Figure 4.2 Force-Displacement Relationship for a Low Damping Rubber Bearing (Constantinou et al., 2007)....................................................................................... 4-4 Figure 4.3 Effect of Temperature on the Mechanical Properties of a Low Damping Rubber Bearing (Constantinou et al., 2007) ........................................................................ 4-5 Figure 4.4 Cut-Away View of a Lead Rubber Bearing (Courtesy of Dynamic Isolation Systems, Inc.) .......................................................................................................... 4-7 Figure 4.5 Force-Displacement Relationship for a Large Lead Rubber Bearing (Kalpakidis et al., 2010; Kumar et al., 2014) ............................................................ 4-8 Figure 4.6 Effect of Temperature on the Mechanical Properties of a Lead Rubber Bearing (Constantinou et al., 2007) ......................................................................... 4-9 Figure 4.7 Force-Displacement Relationship for a Lead Rubber Bearing Subjected to 25 Cycles of Motion at +/-75% Shear Strain (Reproduced from Kalpakidis et al. (2010)) .......................................................................................................... 4-10 Figure 4.8 Force-Displacement Relationship for a High Damping Rubber Bearing (Thompson et al., 2000)......................................................................................... 4-11 Figure 4.9 Friction Pendulum' Bearings (Courtesy Earthquake Protection Systems, Inc.) .. 4-13 Figure 4.10 Hysteresis Loops for Friction Pendulum Bearings ................................................ 4-14 Figure 4.11 Effect of Ambient Temperature and Velocity on the Coefficient of Sliding Friction (Constantinou et al., 2007) ........................................................................ 4-15 Figure 4.12 Effect of Apparent Pressure on the Coefficient of Sliding Friction (Constantinou et al., 2007)..................................................................................... 4-16 Figure 7.1 Linearization of a Nonlinear Isolator Unit (HITEC, 1999) ......................................... 7-5 xiii

LIST OF TABLES Table 3-1 Definitions of Terms .................................................................................................. 3-3 Table 5-1 Target Probability Goals in ASCE 43-05 for Nuclear Structures ............................... 5-8 Table 6-1 Comparison of JNES-RC-2013-1002 and this NUREG/CR Report .......................... 6-5 Table 8-1 Performance and Design Recommendations for Seismically Isolated Nuclear Power Plants1 ............................................................................................................ 8-8 xv

ACKNOWLEDGMENTS The United States Nuclear Regulatory Commission (NRC), Lawrence Berkeley National Laboratory (LBNL), and MCEER at the State University of New York, University at Buffalo conducted this research project on seismic isolation. This project is a part of a broader NRC initiative at LBNL related to advances in structural analysis and design of nuclear installations.

Dr. Robert Budnitz served as the technical lead at LBNL for the projects that have comprised this initiative.

A broad research review panel, formed to provide input to the various LBNL projects, provided significant and important input to this study. The research review group was composed of Dr. Robert Kennedy (RPK Structural Mechanics Consulting), Dr. Nilesh Chokshi (NRC),

Mr. Donald Moore (Southern Nuclear Operating Company), Dr. James Johnson (James J.

Johnson and Associates), Mr. Antonio Godoy (James J. Johnson and Associates and International Atomic Energy Agency (retired)), and Prof. Jon Stewart of UC Los Angeles.

Dr. Robert Kennedy (RPK Structural Mechanics Consulting) chaired the review group.

Prof. Gregory Fenves of the University of Texas, Austin was a member of the panel early in the project. Prof. Bozidar Stojadinovic (Eidgenssische Technische Hochschule, Zürich) also contributed to the early phases of this project.

Professor Yin-Nan Huang (National Taiwan University) provided significant technical input and also reviewed early drafts of the report. Dr. Sanjeev Malushte (Bechtel) provided information on isolation of NPPs. Dr. Troy Morgan (formerly of Tokyo Institute of Technology, now of Exponent) assisted with review of the translation of JEAG 4614-2000, as well as information on earthquake experience in Japan. Additional external review was also provided at NRC requests by Dr. Cameron Black (SIE), Dr. Claudia Marin (Howard University), Dr. Nebojsa Orbovic (Canadian Nuclear Safety Commission), Dr. Ovidiu Coman (International Atomic Energy Agency), and Dr. Tory Iijima and Dr. Hiroshi Abe (both staff at the former Japan Nuclear Energy Safety (JNES)

Organization, now a part of Japans Nuclear Regulation Authority). Comments were provided by the late Dr. John Stevenson, Dr. Pierre Sollogoub, Dr. Nadim Moussallam, Dr. Renzo Medeot, Massimo Fornia and Hamid Ahmadi. The provision of comments does not imply endorsement by any external reviewer. Dr. Manish Kumar and Dr. Brian Terranova of the University at Buffalo assisted with the preparation of the final draft of this NUREG/CR and their technical contributions are gratefully acknowledged.

The project benefitted from an ongoing bi-lateral seismic research cooperation program between the former JNES and the NRC. Under this bi-lateral agreement, JNES staff attended research review panel meetings to provide seismic isolation insights from a Japanese perspective.

This NUREG/CR also benefitted from on-going interactions with the International Atomic Energy Agency (IAEA) International Seismic Safety Center Special Working Group on Seismic Isolation.

Technical discussions among working group members improved the completeness of the guidance and the discussions of practice in other IAEA Member States.

NRC technical staff provided detailed review comments on this NUREG/CR at different times throughout the term of the project. Special thanks are due to Dr. Jose Pires, Senior Technical Advisor for Civil and Structural Engineering.

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ABBREVIATIONS, ACRONYMNS, AND PARAMETERS A bonded area of the elastomer in a rubber isolator (or bearing or unit)

ACI American Concrete Institute ALMR Advanced Liquid Metal Reactor ANS American Nuclear Society ANSI American National Standards Institute ASCE American Society of Civil Engineers ASME American Society of Mechanical Engineers AASHTO American Association of State Highway and Transportation Officials BDB beyond design basis eff effective damping ratio for an isolator CEN Comité Européen de Normalisation CRIEPI Central Research Institute of the Electric Power Industry CSDR certified seismic design response spectrum D bonded diameter of a rubber bearing DBE Design Basis Earthquake DFBR Demonstration Fast Breeder Reactor max maximum positive horizontal displacement of an isolator during prototype testing min minimum negative horizontal displacement of an isolator during prototype testing EDC energy dissipation per cycle of loading of an isolator EdF Électricité de France EERI Earthquake Engineering Research Institute EFR European Fast Breeder Reactor Fmax horizontal force corresponding to max Fmin horizontal force corresponding to min FOSID first onset of significant inelastic deformation FP Friction Pendulum' isolator Fy effective yield strength of an isolator g acceleration due to gravity (9.81m/s2)

G shear modulus of an elastomer GDC General Design Criteria GE General Electric GMRS ground motion response spectra xix

GMRS+ ground motion response spectra +

HD mean annual hazard exceedance frequency HCLPF high confidence of low probability of failure HDR high damping rubber HITEC Highway Innovation Technology Engineering Center IAEA International Atomic Energy Agency IBC International Building Code IRIS International Reactor Innovate and Secure JAERI Japan Atomic Energy Research Institute JEA Japan Electrical Association JEAG Japan Electrical Association Guide JNES Japanese Nuclear Energy Safety Association Kd post-yield stiffness of an isolator Keff effective (secant) horizontal stiffness of an isolator Ku initial stiffness of an isolator LDR low damping rubber LNG liquefied natural gas LR lead rubber MAFE Mean Annual Frequency of Exceedance MCE Maximum Considered Earthquake MPa Megapascal coefficient of sliding friction n number of isolators in an isolation system nr number of layers of rubber in an elastomeric bearing NUPEC Nuclear Power Engineering Corporation NPP nuclear power plant NRC Nuclear Regulatory Commission NUREG/CR Nuclear Regulatory Report PF* annual frequency of unacceptable performance PF annual frequency of failure for a structure or element PH annual frequency of exceeding a designated hazard level PRISM Power Reactor Innovative Small Module PSHA probabilistic seismic hazard analysis PTFE Polytetraflouroethylene xx

PWR Pressurized water reactor Qd characteristic strength R effective radius of curvature of a sliding isolator RP probability ratio, which is the ratio of HD to PF*

RR risk reduction factor S first shape factor for a rubber bearing SAFR Sodium Advanced Fast Reactor SC-I Seismic Category 1 SC-II Seismic Category 2 SDC Seismic Design Category SI seismic isolation SIDRS seismic isolation design response spectrum SPRA seismic probabilistic risk assessment SSC structures, system, and components SSE safe shutdown earthquake STAR-LM Secure Transportable Autonomus Reactor-Liquid Metal S-PRIM power reactor innovate small module Tb effective period of a seismic isolation system tr thickness of a single layer of elastomer in a rubber isolator Tr total thickness of elastomer in a rubber isolator (= nrxtr )

uy effective yield displacement of an isolator US United States UHRS uniform hazard response spectrum W weight supported by an isolator or the isolation system xxi