Regulatory Guide 1.166: Difference between revisions

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{{Adams
{{Adams
| number = ML003740089
| number = ML19266A616
| issue date = 03/31/1997
| issue date = 02/13/2020
| title = (Draft Was DG-1034) Pre-Earthquake Planning & Immediate Nuclear Power Plant Operator Postearthquake Actions
| title =  
| author name =  
| author name = Graizer V, Weaver T
| author affiliation = NRC/RES
| author affiliation = NRC/RES
| addressee name =  
| addressee name =  
Line 9: Line 9:
| docket =  
| docket =  
| license number =  
| license number =  
| contact person =  
| contact person = SJG1
| case reference number = DG-1034
| case reference number = RG 1.166, Rev. 1
| document report number = RG-1.166
| package number = ML19266A614
| document type = Regulatory Guide
| document type = Regulatory Guide
| page count = 8
| page count = 12
}}
}}
{{#Wiki_filter:U.S. NUCLEAR REGULATORY COMMISSION                                                                                         March 1997 REGULATORY GUIDE
{{#Wiki_filter:U.S. NUCLEAR REGULATORY COMMISSION  
    ÷o *OFFICE                                            OF NUCLEAR REGULATORY RESEARCH
REGULATORY GUIDE 1.166, REVISION 1
                                                                  REGULATORY GUIDE 1.166 (Draft was DG-1034)
 
      PRE-EARTHQUAKE PLANNING AND IMMEDIATE NUCLEAR POWER PLANT OPERATOR
Issue Date: February 2020
                                                                  POSTEARTHQUAKE ACTIONS
Technical Leads: Vladimir Graizer Thomas Weaver
 
Written suggestions regarding this guide or development of new guides may be submitted through the NRCs public Web site in the NRC Library at https://nrcweb.nrc.gov/reading-rm/doc-collections/reg-guides/, under Document Collections, in Regulatory Guides, at https://nrcweb.nrc.gov/reading-rm/doc-collections/reg-guides/contactus.html.
 
Electronic copies of this RG, previous versions of RGs, and other recently issued guides are also available through the NRCs public Web site in the NRC Library at https://nrcweb.nrc.gov/reading-rm/doc-collections/reg-guides/, under Document Collections, in Regulatory Guides. This RG is also available through the NRCs Agencywide Documents Access and Management System (ADAMS) at http://www.nrc.gov/reading-rm/adams.html, under ADAMS Accession Number (No.)
ML19266A616. The regulatory analysis may be found in ADAMS under Accession No. ML18268A187. The associated draft guide DG-1337 may be found in ADAMS under Accession No. ML18268A185, and the staff responses to the public comments on DG-1337 may be found under ADAMS Accession No. ML19266A619.
 
PRE-EARTHQUAKE PLANNING, SHUTDOWN, AND  
RESTART OF A NUCLEAR POWER PLANT
FOLLOWING AN EARTHQUAKE


==A. INTRODUCTION==
==A. INTRODUCTION==
This guide provides guidance acceptable to the NRC staff for a timely evaluation after an earthquake of Paragraph IV(a)(4) of Appendix S, "Earthquake                                        the recorded instrumentation data and for determining Engineering Criteria for Nuclear Power Plants," to                                           whether plant shutdown is required by 10 CFR Part 50.
Purpose This regulatory guide (RG) describes guidance acceptable to the staff of the U.S. Nuclear Regulatory Commission (NRC) regarding pre-earthquake planning actions; actions necessary to determine the need to shut down a nuclear power plant; and the short- and long-term processes, inspections, and tests to demonstrate that a nuclear power plant is safe for restarting after a shutdown in response to an earthquake.
 
Applicability This RG applies to applicants and licensees under Title 10 of the Code of Federal Regulations
(10 CFR) Part 50, Domestic Licensing of Production and Utilization Facilities (Ref. 1),
10 CFR Part 52, Licenses, Certifications, and Approvals for Nuclear Power Plants (Ref. 2), and 10 CFR
Part 100, Reactor Site Criteria (Ref. 3).
 
Applicable Regulations
*
10 CFR 50.54(ff), Conditions of licenses, requires plant shutdown if the Operating Basis Earthquake has been exceeded or if significant plant damage occurs for licensees of nuclear power plants that have implemented the earthquake engineering criteria in Appendix S of Part 50.
 
Prior to resuming operations, the licensee is required to demonstrate to the Commission that no functional damage has occurred to those features necessary for continued operation without undue risk to the health and safety of the public, and that the licensing basis is maintained.
 
*
10 CFR Part 50, Appendix A, provides the General Design Criteria for Nuclear Power Plants, and establishes design, fabrication, construction, testing, and performance requirements for structures, systems, and components (SSCs) important to safety through general design criteria (GDC). The GDC applicable to this RG include GDC 2, Design Bases for Protection against
 
RG 1.166, Page 2 Natural Phenomena, which requires, in part, that SSCs important to safety shall be designed to withstand the effects of natural phenomena such as earthquakes, without loss of capability to perform their safety functions.
 
*
10 CFR 50, Appendix S, Earthquake Engineering Criteria for Nuclear Power Plants, for plants licensed on or after January 10, 1997, requires, in part, plant shutdown if the Operating Basis Earthquake Ground Motion is exceeded or if significant plant damage occurs. Prior to resuming operations, the licensee must demonstrate to the Commission that no functional damage has occurred to those features necessary for continued operation without undue risk to health and safety of the public, and that the licensing basis is maintained.
 
*
10 CFR 100, Appendix A, Seismic and Geologic Siting Criteria for Nuclear Power Plants, Section V(a)(2), requires plant shutdown if vibratory ground motion exceeding that of the Operating Basis Earthquake occurs. Prior to resuming operations, the licensee must demonstrate to the Commission that no functional damage has occurred to those features necessary for continued operation without undue risk to the health and safety of the public.
 
Related Guidance
*
RG 1.12, Nuclear Power Plant Instrumentation for Earthquakes (Ref. 4), provides guidance for seismic instrumentation that is acceptable to the NRC staff. RG 1.12 endorses, in part, American National Standards Institute/American Nuclear Society (ANSI/ANS)-2.2-2016, Earthquake Instrumentation Criteria for Nuclear Power Plants (Ref. 5), as an acceptable method for placement of seismic sensors for various nuclear power plant configurations.
 
*
RG 1.208, A Performance-Based Approach to Define the Site-Specific Earthquake Ground Motion (Ref. 6), provides guidance on the development of a site-specific ground motion response spectrum (GMRS).
 
*
NRC Inspection Manual Chapter (IMC) 0326, Operability Determinations & Functionality Assessments for Conditions Adverse to Quality or Safety (Ref. 7), provides guidance to NRC
inspectors in their review of licensees operability determinations and resolution of degraded or nonconforming conditions.
 
Purpose of Regulatory Guides The NRC issues RGs to describe to the public methods that the staff considers acceptable for use in implementing specific parts of the agencys regulations, to explain techniques that the staff uses in evaluating specific problems or postulated events, and to provide guidance to applicants. Regulatory guides are not substitutes for regulations and compliance with them is not required. Methods and solutions that differ from those set forth in RGs will be deemed acceptable if they provide a basis for the findings required for the issuance or continuance of a permit or license by the Commission.
 
Paperwork Reduction Act 
 
This RG provides voluntary guidance for implementing the mandatory information collections in
10 CFR Parts 50, 52, and 100 that are subject to the Paperwork Reduction Act of 1995
(44 U.S.C. 3501 et seq.). These information collections were approved by the Office of Management and Budget (OMB), approval numbers 3150-0011, 3150-0151, and 3150-0093. Send comments regarding this information collection to the Information Services Branch (T6-A10M), U.S. Nuclear Regulatory
 
RG 1.166, Page 3 Commission, Washington, DC 20555-0001, or by e-mail to Infocollects.Resource@nrc.gov, and to the OMB reviewer at: OMB Office of Information and Regulatory Affairs (3150-0011, 3150-0151,
3150-0093), Attn: Desk Officer for the Nuclear Regulatory Commission, 725 17th Street, NW,
Washington, DC 20503; e-mail: oira_submission@omb.eop.gov.
 
Public Protection Notification 


10 CFR Part 50, "Domestic Licensing of Production and Utilization Facilities," requires that suitable instru                                            The information collections contained in this regu mentation 1 be provided so that the seismic response of                                      latory guide are covered by the requirements of 10 CFR
The NRC may not conduct or sponsor, and a person is not required to respond to, a collection of information unless the document requesting or requiring the collection displays a currently valid OMB  
nuclear power plant features important to safety can be                                      Part 50,which were approved by the Office of Manage evaluated promptly. Paragraph IV(a)(3) of Appendix S                                          ment and Budget, approval number 3150-0011. The to 10 CFR Part 50 requires shutdown of the nuclear                                            NRC may not conduct or sponsor, and a person is not power plant if vibratory ground motion exceeding that                                        required to respond to, a collection of information un of the operating basis earthquake ground motion (OBE)                                        less it displays a currently valid OMB control number.
control number.


or significant plant damage occurs. If systems,, struc                                                                     
RG 1.166, Page 4


==B. DISCUSSION==
==B. DISCUSSION==
tures, or components necessary for the safe shutdown                                                 When an earthquake occurs, ground motion data of the nuclear power plant are not available after occur                                      are recorded by the seismic instrumentation. 1 These rence of the OBE, the licensee must consult with the                                         data are used to make a rapid determination of the de NRC and must propose a plan for the timely, safe shut                                        gree of severity of the seismic event. The data from the down of the nuclear power plant. Licensees of nuclear                                        nuclear power plant's free-field seismic instrumenta power plants that are subject to the earthquake engi                                          tion, coupled with information obtained from a plant neering criteria in Appendix S to 10 CFR Part 50 are re                                      walkdown, are used to make the initial determination of quired by 10 CFR 50.54(ff) to shut down the plant if                                          whether the plant must be shut down, if it has not al the criteria in Paragraph IV(a)(3) of Appendix S are ex                                        ready been shut down by operational perturbations ceeded.
Reason for Revision This guide merges two related RGsRG 1.166, Pre-Earthquake Planning and Immediate Nuclear Power Operator Postearthquake Actions, issued March 1997 (Ref. 8), and RG 1.167 Restart of a Nuclear Power Plant Shut Down by a Seismic Event, issued March 1997 (Ref. 9)into one and revises their technical content. The staff decided to combine these existing RGs because they are similar in nature and contain overlapping guidance. Both guides reference and endorse the same industry guidelines, which more recent standards have superseded. The merged RG incorporates lessons learned following the shutdown and restart of nuclear power plants in response to earthquake ground motion and post-earthquake evaluations since issuance of the two RGs in 1997, through endorsement of ANSI/ANS-
2.10-2017, Criteria for Retrieval, Processing, Handling, and Storage of Records from Nuclear Facility Seismic Instrumentation (Ref. 10), and ANSI/ANS-2.23-2016, Nuclear Power Plant Response to an Earthquake (Ref. 11), with exceptions and clarifications.
 
Background The NRC endorsed Electric Power Research Institute (EPRI) NP-6695, Guidelines for Nuclear Power Plant Response to an Earthquake, dated December 1, 1989 (Ref. 12), in the initial version of RG 1.166 (Rev. 0) and RG 1.167 (Rev. 0), issued in 1997. Following the issuance of EPRI
NP-6695 in 1989, a significant amount of experience has been gained on the effects of earthquakes on nuclear power plants worldwide and the actions needed to restart a nuclear power plant after an earthquake. Based on these lessons learned, in 2015 EPRI significantly updated EPRI NP-6695 and the lessons were captured in EPRI Report 3002005284, Guidelines for Nuclear Plant Response to an Earthquake (Ref. 13). In addition, experience has been gained from the shutdown and restart of the Virginia Electric and Power Company (VEPCO) North Anna Power Station following the August 23,
2011, earthquake in Mineral, Virginia. For example, the plant used older analogue recording instrumentation that took longer to process than modern digital instrumentation. This equipment contributed to the delay in determining if the OBE and SSE were exceeded. in contrast, modern digital recording instrumentation would have facilitated the determination earlier. In response to the earthquake, VEPCO committed to a number of long-term actions to address exceeding the design basis as a result of the August 23, 2011, seismic event in a letter to the NRC dated November 7, 2011 (Ref. 14). NRC responded to the VEPCO letter with a Confirmatory Action Letter (CAL) on November 11, 2011 (Ref. 15), which remained in effect until NRC concluded that all the actions in the enclosure to the CAL were completed.
 
ANSI/ANS-2.23-2016 incorporates the significant changes and additions included in EPRI
Report 3002005284. ANSI/ANS-2.23-2016 provides guidance that implements both the observed damage level (DL) and earthquake shaking level (EL) to determine post-earthquake actions for an event that exceeds the OBE, whereas EPRI NP-6695 considers only the observed damage level to determine post- earthquake actions. In addition, ANSI/ANS-2.23-2016 builds on EPRI NP-6695 by adding guidance on action levels that clarify what actions should be taken, when they should be taken, and who should perform them. It also provides more comprehensive guidance than EPRI NP-6695 for short-term actions that a licensee should perform following an earthquake and for long-term post-earthquake evaluations.
 
Therefore, this RG endorses ANSI/ANS-2.23-2016.
 
This guide also endorses ANSI/ANS-2.10-2017, Criteria for Retrieval, Processing, Handling, and Storage of Records from Nuclear Facility Seismic Instrumentation, because the standard provides guidance on the retrieval of recorded data from seismic instrumentation in the event that an earthquake occurs with sufficient ground motion to activate the instrumentation, and because of the importance of the
 
RG 1.166, Page 5 storage, handling, and maintenance of recorded data and calculations. This information is important because it is used to assess the short-term and long-term actions needed to ensure the plant can be operated safely.
 
Harmonization with International Standards The International Atomic Energy Agency (IAEA) works with member states and other partners to promote the safe, secure, and peaceful use of nuclear technologies. The IAEA develops safety standards for protecting people and the environment from harmful effects of ionizing radiation. These standards provide a system of safety fundamentals, safety requirements, and safety guides reflecting an international consensus on what constitutes a high level of safety. Pertinent to this RG are: 
 
*
IAEA Safety Reports Series No. 66, Earthquake Preparedness and Response for Nuclear Power Plants (Ref. 16), which draws upon insights from three multiunit nuclear power plants in Japan and one in Armenia that experienced beyond-design-basis earthquakes. It addresses pre-earthquake planning, actions to follow when an earthquake is felt, actions to take before the restart of the nuclear power plant, and short- and long-term post-earthquake actions.
 
*
IAEA Safety Guide NS-G-1.6, Seismic Design and Qualification for Nuclear Power Plants (Ref. 17), which provides guidance on seismic instrumentation.
 
This RG incorporates guidelines on actions by licensees to demonstrate plant readiness for restart similar to those in IAEA Safety Reports Series No. 66 and seismic instrumentation similar to IAEA
Safety Guide NS-G-1.6.
 
Documents Discussed in Staff Regulatory Guidance This RG endorses the use of one or more codes or standards developed by external organizations, and other third-party guidance documents. These codes, standards, and third-party guidance documents may contain references to other codes, standards, or third party guidance documents (secondary references). If a secondary reference has itself been incorporated by reference into NRC regulations as a requirement, then licensees and applicants must comply with that standard as set forth in the regulation. If the secondary reference has been endorsed in a RG as an acceptable approach for meeting an NRC
requirement, then the standard constitutes a method acceptable to the NRC staff for meeting that regulatory requirement as described in the specific RG. If the secondary reference has neither been incorporated by reference into NRC regulations nor endorsed in a RG, then the secondary reference is neither a legally-binding requirement nor a generic NRC approved acceptable approach for meeting an NRC requirement. However, licensees and applicants may consider and use the information in the secondary reference, if appropriately justified, consistent with current regulatory practice, and consistent with applicable NRC requirements.
 
RG 1.166, Page 6 C.  STAFF REGULATORY GUIDANCE
This guide provides methods, approaches, or data that the staff considers acceptable for meeting the requirements of the Applicable Regulations stated in Section A. This guide endorses the following standards subject to the clarifications noted in this section:
 
*
ANSI/ANS-2.10-2017, Criteria for Retrieval, Processing, Handling, and Storage of Records from Nuclear Facility Seismic Instrumentation. The standard addresses the recording, retrieval, documentation and archiving of data from seismic instrumentation, subsequent to an earthquake sufficient to activate the instrumentation.
 
*
ANSI/ANS-2.23-2016, Nuclear Power Plant Response to an Earthquake. The standard provides guidance regarding pre-earthquake planning actions; actions necessary to determine the need to shut down a nuclear power plant; and the short- and long-term processes, inspections, and tests to demonstrate that a nuclear power plant is safe for restarting after a shutdown in response to an earthquake.
 
C. 1 Clarification of Post-shutdown Inspection and Test Documentation Requirements in Section
 
ANSI/ANS-2.23-2016, Section 8.8
 
The documentation described in Section 8.8 of ANSI/ANS-2.23-2016 should be available for NRC inspection prior to restart. The documentation should include the condition report methodology, assumptions, assessments, technical specification (TS) surveillance requirement number for each surveillance test, and other inspections that demonstrated that the operability of all safety-related SSCs was not affected. In addition, the documentation should demonstrate that any nonsafety-related SSC impacts are corrected or that the risk is properly managed in accordance with 10 CFR 50.65, Requirements for monitoring the effectiveness of maintenance at nuclear power plants. Specifically, if the plant is restarted with nonsafety-related equipment impacts left uncorrected or unevaluated, the increase in risk must be monitored and accounted for as required by 10 CFR 50.65.
 
C. 2 Clarification of Seismic Reevaluations in ANSI/ANS-2.23-2016, Section 9.1.3
 
Sections 9.1.3 provides guidance in selecting items for seismic reevaluations which include selecting items with the highest calculated stresses based on previous stress analysis results.  The staff position is that items should also be selected where the fatigue Cumulative Usage Factor is highest.
 
C.3 Clarification of Equipment and Structures Qualified by Analysis in ANSI/ANS-2.23-2016, Section 9.1.4.1
 
When evaluating equipment and structures by analysis, staff finds it acceptable to use best estimate damping values and realistic material properties to determine if stresses or strains are greater than allowables.  Strain based allowable values with adequate justification may be used when non-linear analyses are performed.
 
RG 1.166, Page 7 C.4 Clarification of Seismic Evaluation and Verification Plans in ANSI/ANS-2.23-2016, Section
9.5 Section 9.5 of ANSI/ANS-2.23-2016 provides guidance on developing a seismic evaluation and verification plan. Section 9.5 states that the plan should require the new and replacement safety-related SSCs to be qualified to both the licensing-basis design spectra and the observed spectra unless the licensee can demonstrate using appropriate risk-informed or performance-based approaches that the SSCs involved do not pose a significant seismic risk. All new or replacement equipment must meet current or amended site licensing-basis requirements.
 
C.5 Clarification of Initial and Short-Term Evaluations in ANSI/ANS-2.23-2016, Section 6 If the seismic event resulted in a plant automatic shutdown, the licensee needs to understand the cause and evaluate the extent of the condition before plant restart to ensure that (1) operability exists for safety-related SSCs and (2) risk is managed as required by 10 CFR 50.65 for both safety- and nonsafety-related SSCs. To accomplish this, as is done after any automatic reactor shutdown, the licensee must assess the performance of both safety- and nonsafety-related SSCs to determine whether all SSCs had performed as designed, installed, and maintained.
 
C.6 Clarification of Long-Term Evaluations in ANSI/ANS-2.23-2016, Section 9 Coincident with the long-term evaluations, as described in ANSI/ANS-2.23-2016, Section 9, the plant SSCs should be restored to match their licensing basis.
 
C.7 Clarification Addressing Exceptions to Restoration of the Licensing Basis When using ANSI/ANS-2.23-2016, licensees or applicants should note that correction of, or operation with, degraded or nonconforming conditions related to SSCs is accomplished, as appropriate, through evaluation, restoration, modification, license amendment, or regulatory relief (e.g., notice of enforcement discretion, emergency TS amendments, exigent TS changes, exemptions, relief requests, or other relief from a regulatory requirement as granted by the Commission). Operation with SSCs that are deemed operable/functional but are degraded or nonconforming is permitted if an analysis is performed and documented and if corrective actions are completed in a manner that meets the expectations of NRC Inspection Manual Chapter (IMC)
0326.
 
C. 8 Clarification Addressing Degraded or Inoperable Instrumentation
 
If the seismic instrumentation or data-processing equipment is degraded or inoperable, Appendix A, Operating-Basis Earthquake Exceedance Guidelines if Instrumentation is Degraded or Inoperable, of this guide should be used to determine whether the OBE ground motion has been exceeded.
 
RG 1.166, Page 8
 
==D. IMPLEMENTATION==
The NRC staff may use this regulatory guide as a reference in its regulatory processes, such as licensing, inspection, or enforcement. However, the NRC staff does not intend to use the guidance in this regulatory guide to support NRC staff actions in a manner that would constitute backfitting as that term is defined in 10 CFR 50.109, Backfitting, and as described in NRC Management Directive 8.4, Management of Backfitting, Forward Fitting, Issue Finality, and
 
===
 
===Information Requests===
===
(Ref. 18), nor does the NRC staff intend to use the guidance to affect the issue finality of an approval under 10 CFR Part
52, Licenses, Certifications, and Approvals for Nuclear Power Plants. The staff also does not intend to use the guidance to support NRC staff actions in a manner that constitutes forward fitting as that term is defined and described in Management Directive 8.4. If a licensee believes that the NRC is using this regulatory guide in a manner inconsistent with the discussion in this Implementation section, then the licensee may file a backfitting or forward fitting appeal with the NRC in accordance with the process in Management Directive 8.
 
===4.      ===
 
RG 1.166, Page 9 REFERENCES1
1.
 
U.S. Code of Federal Regulations (CFR), Domestic Licensing of Production and Utilization Facilities, Part 50, Chapter 1, Title 10, Energy.
 
2.
 
CFR, Licenses, Certifications, and Approvals for Nuclear Power Plants, Part 52, Chapter 1, Title 10, Energy.
 
3.
 
CFR, Reactor Site Criteria, Part 100, Chapter 1, Title 10, Energy.
 
4.
 
U.S. Nuclear Regulatory Commission (NRC), Regulatory Guide (RG) 1.12, Nuclear Power Plant Instrumentation for Earthquakes, Washington, DC.
 
5.
 
American National Standards Institute/American Nuclear Society (ANSI/ANS)-2.2-2016, Earthquake Instrumentation Criteria for Nuclear Power Plants, LaGrange, Illinois.2
 
6.
 
NRC, RG 1.208, A Performance-Based Approach to Define the Site-Specific Earthquake Ground Motion, Washington, DC.


resulting from the seismic event. If on the basis of these initial evaluations (instrumentation data and
7.
1 Regulatory Guide 1.12, Revision 2, "Nuclear Power Plant Instrumen                          walkdown) it is concluded that the plant shutdown cri tation for Earthquakes," describes seismic instrumentation that is ac ceptable to the NRC staff.                                                                  teria have not been exceeded, it is presumed that the USNRC REGULATORY GUIDES                                        The guides wa issued In the following ten broad divisions:
  Regulatory Guides we Issued to'describe n make available to the public such Informa tlon as methods acceptable to Vie NRC staff for Implementing specific pats of the Com        1.  Power Reactors                              &  Products
                                                                                              2.  Research and Test Reactors                  7.  Transportation mission's regulations, techniques used by the staff inevaluating specific problems or pos                                                    S.  Occupaional Health tulated accidents, and data needed by the NRC staff inits review of applications for per    3    Fuels erd Materials Facilities
                                                                                              4.  Environmental ard Siting                    9.  Antitrust and Financal Review mits and icensee. Regulory guldes are not substitutes for regulations, and compllance                                                      10.. General with them Is not required. Methods aid solutions different from those set out Inthe guides  s  Materials and Plant Protection will be acceptable Ifthey provide a basis for the findings requisite to the Issuance or con tinuence of a permit or lcense by te Commission.                                            Single copies oaregulatory guides may be obtained free of charge by writing the Office of This guide was issued alter consideration of comments received from the public Com          Administration, Attention: Distribution and Mail Services Section. US. Nudear Regulatory merts and suggestions for improvements Inthese guides we encouraged at all imes, and        Commission, Washington. DC 20555-0001; or by fax at (301)415-2280.


guides will be revised, as appropriate, to accommodate comments " to reflect new In formation or aspedence.                                                                      Issued guides may also be purchased from the National Technilcal Information Service on a standing order basis. Details on this service may be obtained by writing NTIS, 6285 Port Written comments may be submitted to the Rules Revew and Directives Branch, DFIPS,          Royal Road, Springfield, VA 22161.
NRC, Inspection Manual Chapter 0326, Operability Determinations & Functionality Assessments for Conditions Adverse to Quality or Safety, Washington, DC.


ADM, U.S. Nulear Regulatory Commission, Washington, DC 20555-0001.
8.


plant will not be shut down (or could restart following a                mends 1.0 to 2.0 Hz for the range of the spectral veloc post-trip review, if it tripped off-line because of the                  ity limit since some structures have fundamental earthquake). Guidance on postshutdown inspections                        frequencies below 1.5 Hz. This is instead of the 1.5 to and plant restart is contained in Regulatory Guide                      2.0 Hz range proposed by EPRI.                            K
NRC, RG 1.166, Pre-Earthquake Planning and Immediate Nuclear Power Plant Operator Postearthquake Actions, Washington, DC.
1.167, "Restart of a Nuclear Power Plant Shut Down by Because free-field seismic instrumentation data a Seismic Event."                                                        are used in the plant shutdown determiniation, it is im The Electric Power Research Institute has devel                    portant to ascertain that the time-history analysis hard oped guidelines that will enable licensees to quickly                    ware and software were functioning properly. There identify and assess earthquake effects on nuclear power                  fore, the response spectrum and CAV should be plants. These guidelines are in EPRI NP-5930, "A Cri                    calculated using a suitable earthquake time-history or terion for Determining Exceedance of the Operating                      manufacturer's calibration standard after the initial in Basis Earthquake," July 19882; EPRI NP-6695,                            stallation and each servicing of the free-field instru
"Guidelines for Nuclear Plant Response to an Earth                      mentation. After an earthquake at the plant site, the re quake," December 19892; and EPRI TR-100082,                            sponse spectrum and CAV should be calculated using
"Standardization of the Cumulative Absolute Veloc                      the time-history or calibration standard that was used ity," December 1991.2                                                  during the last servicing (or initial instrumentation in This regulatory guide is based on the assumption                  stallation if no servicing has been performed) and the that the nuclear power plant has operable seismic in                    results compared with the latest data on file at the plant.


strumentation, including the computer equipment and                          The NRC staff does not endorse the philosophy software required to process the data within 4 hours af                discussed in EPRI NP-6695, Section 4.3.4 (first para ter an earthquake. This is necessary because the deci                  graph, last sentence), pertaining to plant shutdown con sion to shut down the plant will be made, in part, by                  siderations following an earthquake based on the need comparing the recorded data against OBE exceedance                      for continued power generation in the region. If a li criteria. The decision to shut down the plant is also                    censee determines that plant shutdown is required by based on the results of the plant walkdown inspections                  the NRC's regulations, but the licensee does not con        L
9.
that take place within 8 hours of the event. If the seismic              sider it prudent to do so, the licensee would be required  \
instrumentation or data processing equipment is inop                    to consult with the NRC and propose a plan for the erable, the guidelines in Appendix A to this guide                      timely, safe shutdown of the nuclear power plant.


should be used to determine whether the OBE has been                          Because earthquake-induced vibration of the reac exceeded.                                                               tor vessel could lead to changes in neutron fluxes, a Shutdown of the nuclear power plant is required if                prompt check of the neutron flux monitoring sensors the vibratory ground motion experienced exceeds that                    would provide an indication that the reactor is stable.
NRC, RG 1.167, Restart of a Nuclear Power Plant Shutdown by a Seismic Event, Washington, DC.


of the OBE. A criterion for determining exceedance of                          Since the containment isolation valves may have the OBE (based on data recorded in the free-field) is                    malfunctioned during an earthquake, inspection of the provided in EPRI NP-5930: a threshold response spec                      containment isolation system is necessary to ensure trum ordinate check and a cumulative absolute velocity                  continued containment integrity.
10.


(CAV) check. Seismic Category I structures at a nuclear power plant site may be designed using different                              Appendix B to this guide provides definitions to be ground motion response spectra; for example, one used                    used with this guidance.
ANSI/ANS-2.10-2017, Criteria for Retrieval, Processing, Handling, and Storage of Records from Nuclear Facility Seismic Instrumentation, LaGrange Park, Illinois.


for the certified standard design and another for site
11.


==C. REGULATORY POSITION==
ANSI/ANS-2.23-2016, Nuclear Power Plant Response to an Earthquake, LaGrange Park, Illinois.
specific applications. The spectrum ordinate criterion is based on the lowest spectrum used in the design of the                1. BASE-LINE DATA
Seismic Category I structures. A procedure to standard ize the calculation of the CAV is provided in EPRI                      L1 Information Related to Seismic TR-100082. A spectral velocity threshold has also                            Instrumentation been recommended by EPRI since some structures                                A file containing information on all the seismic in have fundamental frequencies below the range speci                      strumentation should be kept at the plant. The file fied in EPRI NP-5930. The NRC staff now recom                          should include:
2                                                                              1. Information on each instrument type such as EPRI reports may be obtained from the Electric Power Research Insti tute, EPRI Distribution Center, 207 Coggins Dr., RO. Box 23205,        make, model, and serial number; manufacturers' data Pleasant Hill, CA 94523.                                              sheet; list of special features or options; performance
                                                                1.166-2


characteristics; examples of typical instrumentation          3. EVALUATION OF GROUND MOTION
12.
  readings and interpretations; operations and mainte                RECORDS
  nance manuals; repair procedures (manufacturers' rec
                                                                  3.1 Data Identification
.. ommendations for repairing common problems); and a list of any special requirements, e.g., for maintenance,            A record collection log should be maintained at the operation, or installation.                                    plant, and all data should be identifiable and traceable with respect to:
        2. Plan views and vertical sections showing the lo
                                                                      1. The date and time of collection, cation of each seismic instrument and the orientation of the instrument components with respect to plant refer              2. The make, model, serial number, location, and ence axes.                                                              orientation of the instrument (sensor) from which the record was collected.


3. A complete service history of each seismic in strument. The service history should include informa          3.2 Data Collection tion such as dates of servicing, description of                    3.2.1 Only personnel trained in the operation of completed work, and calibration records and data              the instrument should collect the data.
Electric Power Research Institute (EPRI) NP-6695, Guidelines for Nuclear Power Plant Response to an Earthquake, Palo Alto, California, December 1, 1989.3


(where applicable). The documentation and retention
1 Publicly available NRC-published documents are available electronically through the NRC Library on the NRCs public web site at http://www.nrc.gov/reading-rm/doc-collections/ and through the NRCs Agencywide Documents Access and Management System (ADAMS) at http://www.nrc.gov/reading-rm/adams.html. The documents can also be viewed online or printed for a fee in the NRCs Public Document Room (PDR) at 11555 Rockville Pike, Rockville, MD. For problems with ADAMS, contact the PDR staff at 301-415-4737 or (800) 397-4209; fax
                                                                      3.2.2 The steps for removing and storing records of these data should be commensurate with the from each seismic instrument should be planned and recordkeeping for other plant equipment.
(301) 415-3548; or e-mail pdr.resource@nrc.gov.


performed in accordance with established procedures.
2 Copies of ANSI/ANS standards may be purchased from the ANS web site (http://www.new.ans.org/store/), or by writing to American Nuclear Society, 555 North Kensington Avenue, La Grange Park, IL 60526 (telephone:
800-323-3044). 


4. A suitable earthquake time-history (e.g., the Oc          3.2.3 Extreme caution should be exercised to tober 1987 Whittier, California, earthquake) or man            prevent accidental damage to the recording media and ufacturer's calibration standard and the corresponding        instruments during data collection and subsequent han response spectrum and cumulative absolute velocity            dling.
3 Copies of EPRI standards and reports may be purchased from Electric Power Research Institute, 3420 Hillview Avenue, Palo Alto, CA 94304 (telephone: (800) 313-3774; fax: (925) 609-1310).  


(CAV) (see Regulatory Positions 4.1 and 4.2). After the initial installation and each servicing of the free-field          3.2A As data are collected and the instrumenta instrumentation, the response spectrum and CAV                tion is inspected, notes should be made regarding the should be calculated and filed (see Regulatory Position        condition of the instrument and its installation, for ex
RG 1.166, Page 10
  4.3).                                                          ample, instrument flooded, mounting surface tilted, or objects that fell and struck the instrument or the instru
13.
  1.2 Planning for Postearthquake Inspections                    ment mounting surface.


3.2.5 For validation of the collected data, the in Sections 4.3.4.1 and 5.3.1 of EPRI NP-6695,
EPRI Report 3002005284, Guidelines for Nuclear Plant Response to an Earthquake, Palo Alto, California, 2015.
  "Guidelines for Nuclear Plant Response to an Earth            formation described in Regulatory Position 1.1(4)
  quake," describe actions, such as selecting equipment          should be provided.


and structures for inspections and the content of the              3.2.6 If the instrument's operation appears to baseline inspections, that are to be taken before an          have been normal, the instrument should remain in earthquake and that are acceptable to the NRC staff for        service without readjustment or change that would de satisfying the requirements in Paragraph IV(a)(3) of          feat attempts to obtain postevent calibration.
14.


Appendix S to 10 CFR Part 50 for ensuring the safety of nuclear power plants.                                      3.3 Record Evaluation Records should be analyzed according to the man
Virginia Electric and Power Company, letter to NRC, November 7, 2011, Virginia Electric and Power Company North Anna Power Station Units 1 and 2, Independent Spent Fuel Storage Installation Revised Long-Term Actions Commitment List, ADAMS Accession number ML11314A069.
  2.    ACTIONS IMMEDIATELY AFTER AN                            ufacturer's specifications and the results of the analysis EARTHQUAKE                                              should be evaluated. Any record anomalies, invalid data, and nonpertinent signals should be noted, along The guidelines for actions immediately after an          with any known causes.


earthquake that are specified in Sections 4.3.1 (with the exception specified below) and 4.3.2 of EPRI NP-6695          4.  DETERMINING OBE EXCEEDANCE
15.
  are acceptable to the NRC staff for satisfying the re              The evaluation to determine whether the OBE was quirements in Paragraph IV(a)(3) of Appendix S to 10
                                                                  exceeded should be performed using data obtained CFR Part 50.


from the three components of the free-field ground mo
NRC letter to Virginia Electric and Power Company, November 11, 2011, Confirmatory Action Letter Regarding North Anna Power Station, Unit Nos. 1 and 2, Long-Term Commitments to Address Exceeding Design Bases Seismic Event (TAC Nos. ME7254 and ME7255), ADAMS
        "InSection 4.3.1, a check of the neutron flux moni      tion (i.e., two horizontal and one vertical). The evalua toring sensors for changes should be added to the spe          tion may be performed on uncorrected earthquake cific control room board checks.                              records. It was found in a study of uncorrected versus
Accession number ML11311A201.
                                                          1.166-3


corrected earthquake records (see EPRI NP-5930) that          and software were functioning properly. The results of the use of uncorrected records is conservative. The          this comparison should be reported to the NRC.
16.


evaluation should consist of a check of the response spectrum and CAV and a check on the operability of the        4.4 Inoperable Instrumentation or Data Processing Hardware or Software K
International Atomic Energy Agency Safety (IAEA) Report Series No. 66, Earthquake Preparedness and Response for Nuclear Power Plants, Vienna, Austria.4
instrumentation. This evaluation should take place within 4 hours of the earthquake.                                  If the response spectrum and the CAV (Regulatory Positions 4.1 and 4.2) cannot be obtained because the
4.1 Response Spectrum Check                                  seismic instrumentation is inoperable, data from the
    4.1.1 The OBE response spectrum check is per            instrumentation are destroyed, or the data processing formed using the lower of:                                    hardware or software is inoperable, the criteria in Ap pendix A to this guide should be used to determine
    1. The spectrum used in the certified standard          whether the OBE has been exceeded.


design, or
17.
                                                              5. CRITERIA FOR PLANT SHUTDOWN
    2.  A spectrum other than (1) used in the design of any Seismic Category I structure.                        If the OBE is exceeded or significant plant damage occurs, the plant must be shut down unless a plan for the
    4.1.2 The OBE response spectrum is exceeded if timely, safe shutdown of the nuclear power plant has any one of the three components (two horizontal and been proposed by the licensee and accepted by the NRC
one vertical) of the 5 percent of critical damping re staff.


sponse spectra generated using the free-field ground motion is larger than:                                        5.1 OBE Exceedance
IAEA Safety Guide NS-G-1.6, Seismic Design and Qualification for Nuclear Power Plants.
    1. The corresponding design response spectral                If the response spectrum check and the CAV check acceleration (OBE spectrum if used in the de        (performed or calculated in accordance with Regulato sign, otherwise 1/3 of the safe shutdown earth      ry Positions 4.1 and 4.2) were exceeded, the OBE was quake ground motion (SSE) spectrum) or              exceeded and plant shutdown is require


====d. If either====
18.
          0.2g, whichever is greater, for frequencies be      check does not exceed the criterion, the earthquake mo tween 2 to 10 Hz, or                                tion did not exceed the OBE. If only one check can be    K
                                                              performed, the other check is assumed to be exceeded;
    2. The corresponding design response spectral if neither check can be performed, see Regulatory Posi velocity (OBE spectrum if used in the design, tion 4.4. The determination of whether or not the OBE
          otherwise 1/3 of the SSE spectrum) or a spec has been exceeded should be performed even if the tral velocity of 6 inches per second (15.24 cen plant automatically shuts down as a result of the earth timeters per second), whichever is greater, for quake.


frequencies between 1 and 2 Hz.
NRC,  Management Directive 8.4, Management of Backfitting, Forward Fitting, Issue Finality, and  


5.2 Damage
===
4.2 Cumulative Absolute Velocity Check The plant should be shut down if the walkdown For each component of the free-field ground mo          inspections performed in accordance with Regulatory tion, the CAV should be calculated as follows: (1) the        Position 2 discover damage. This evaluation should absolute acceleration (g units) time-history is divided      take place within 8 hours of the earthquake occurrence.


into 1-second intervals, (2) each 1-second interval that has at least 1 exceedance of 0.025g is integrated over        5.3 Continued Operation time, (3) all the integrated values are summed together            If the OBE was not exceeded and the walkdown in to arrive at the CAy. The CAV check is exceeded if any        spection indicates no damage to the nuclear power CAV calculation is greater than 0.16 g-second. Addi          plant, shutdown of the plant is not required. The plant tional information on how to determine the CAV is pro        may continue to operate (or may restart following a vided in EPRI TR-100082.                                      post-trip review, if it automatically shut down because of the earthquake).
===Information Requests===
4.3 Instrument Operability Check After an earthquake at the plant site, the response      6. PRE-SHUTDOWN INSPECTIONS
===
spectrum and CAV should be calculated using the same              The pre-shutdown inspections described in Sec input as that used in Regulatory Position 1.1(4), and the    tion 4.3.4 of EPRI NP-6695, "Guidelines for Nuclear results should be compared with the latest filed data to      Plant Response to an Earthquake," with the exceptions demonstrate that the time-history analysis hardware          specified below, are acceptable to the NRC staff for
, Washington, DC.
                                                      1.166-4


satisfying the requirements in Paragraph IV(aX3) of                shutdown activities. In order to ascertain possi Appendix S to 10 CFR Part 50 for ensuring the safety of            ble fuel and reactor internal damage, the fol nuclear power plants.                                             lowing checks should be made, if possible, be fore plant shutdown is initiated ..... "
4 Copies of IAEA documents may be obtained through the IAEA Web site at www.iaea.org/ or by writing the International Atomic Energy Agency, P.O. Box 100 Wagramer Strasse 5, A-1400 Vienna, Austria.
6.1 Shutdown Timing


==D. IMPLEMENTATION==
RG 1.166, Appendix A, Page A-1 APPENDIX A
Delete the last sentence in the first paragraph of Section 4.3.4 of EPRI NP-6695.                                     The purpose of this section is to provide guidance to applicants and licensees regarding the NRC staff's
 
6.2 Safe Shutdown Equipment                                  plans for using this regulatory guide.
OPERATING-BASIS EARTHQUAKE EXCEEDANCE GUIDELINES IF
INSTRUMENTATION IS DEGRADED OR INOPERABLE
 
If the seismic instrumentation or data-processing equipment is degraded or inoperable, the following should be used to determine whether the operating-basis earthquake (OBE) ground motion has been exceeded: 
*
For plants at which instrumentally determined data are available only from an instrument installed on a foundation, the cumulative absolute velocity (CAV) check does not apply. In this case, the determination of OBE exceedance is based on a response spectrum check described in Section 6.4.1 of American National Standards Institute/American Nuclear Society (ANSI/ANS)-
2.23-2016, Nuclear Power Plant Response to an Earthquake (Ref. 1). A comparison should be made between the foundation-level design response spectra and data obtained from the foundation-level instruments. If the response spectrum check at any foundation is exceeded, the OBE is exceeded, and the plant must be shut down. At this instrument location, it is inappropriate to use the 0.2g spectral acceleration limit or the spectral velocity limit of 6 inches per second
(15.24 centimeters per second) in Section 6.4.1 of ANSI/ANS-2.23-2016.
 
*
For plants at which no free-field or foundation-level instrumental data are available or the data-processing equipment is inoperable and the response spectrum check and the CAV check cannot be determined, the OBE will be considered to have been exceeded, and the plant must be shut down if one of the following two conditions apply: 
 
(1) 
If instrumental intensity information is not available, the earthquake with moment magnitude M specified in Table B-1 occurred within a distance less than or equal to that specified in Table B-1.
 
Table B-1  Maximum Distance from an Earthquake with Moment Magnitude M at which the OBE Can Be Exceeded
 
Magnitude (M)
 
Distance (km)
5.0-5.5
 
80
5.6-6.0
 
150
6.1-6.5
 
250
6.6-7.0
 
300
7.1-7.5
 
380
7.6-8.0


In Section 4.3.4.1 of EPRI NP-6695, a check of the            Except in those cases in which the applicant pro containment isolation system should be added to the          poses an acceptable alternative method for complying minimum list of equipment to be inspected.                  with the specified portions of the Commission's regula tions, the method described in this guide will be used in
480
6.3 Orderly Plant Shutdown the evaluation of applications for construction permits, The following paragraph in Section 4.3.4 of EPRI        operating licenses, combined licenses, or design certi NP-6695 is printed here to emphasize that the plant           fication submitted after January 10, 1997. This guide should shut down in an orderly manner.                       will not be used in the evaluation of an application for an operating license submitted after January 10, 1997,
If plant shutdown is warranted under the above guidelines, the plant should be shut down in an orderly manner (see Sections 6.2 and 6.5 of ANSI/ANS-2.23-2016).  
    "Prior to initiating plant shutdown following if the construction permit was issued prior to that date.


an earthquake, visual inspections and control board checks of safe shutdown systems should                  Holders of an operating license or construction per be performed by plant operations personnel,              mit issued prior to January 10, 1997, may voluntarily and the availability of off-site and emergency          implement the methods described in this guide in com on-site power sources should be determined.              bination with the methods in Revision 2 to Regulatory The purpose of these inspections is to deter            Guide 1.12, "Nuclear Power Plant Instrumentation for mine the effect of the earthquake on essential          Earthquakes," and in Regulatory Guide 1.167, "Restart safe shutdown equipment which is not normal              of a Nuclear Power Plant Shut Down by a Seismic ly in use during power operation so that any re          Event." Other implementation strategies, such as vol sets or repairs required as a result of the earth        untary implementation of portions of the cited regula quake can be performed, or alternate                    tory guides, will be evaluated by the NRC staff on a equipment can be readied, prior to initiating            case-by-case basis.
RG 1.166, Appendix A, Page A-2 The licensee should conduct a post-earthquake plant walkdown after the earthquake (see Section 6.2 of ANSI/ANS-2.23-2016).


1.166-5
(2) 
The earthquake resulted in Instrumental Intensity VI (Table B-2) or greater within 5 kilometers (km) of the plant.


APPENDIX A
Table B-2 ShakeMap Instrumental Intensity Scale (Ref. 2 and Ref. 3)
              INTERIM OPERATING BASIS EARTHQUAKE EXCEEDANCE GUIDELINES
                                                                                                                        11 This regulatory guide is based on the assumption                be determined (Regulatory Positions 4.1 and 4.2),
that the nuclear power plant has operable seismic in                the OBE will be considered to have been exceeded strumentation and equipment (hardware and software)                  and the plant must be shut down if one of the fol to process the data. If the seismic instrumentation or              lowing applies:
data processing equipment is inoperable, the following
                                                                    1. The earthquake resulted in Modified Mercalli should be used to determine whether the operating                        Intensity (MMI) VI or greater within 5 km of basis earthquake ground motion (OBE) has been the plant, exceeded:
                                                                    2. The earthquake was felt within the plant and
1. For plants at which instrumentally determined data                    was of magnitude 6.0 or greater, or are available only from an instrument installed on a            3. The earthquake was of magnitude 5.0 or great foundation, the cumulative absolute velocity                        er and occurred within 200 km. of the plant.


(CAV) check (see Regulatory Position 4.2 of this guide) is not applicable. In this case, the determina          A postearthquake plant walkdown should be con tion of OBE exceedance is based on a response              ducted after the earthquake (see Regulatory Position 2 spectrum check similar to that described in Regula        of this guide).
Note that the determination of epicentral location, magnitude, and intensity by the U.S. Geological Survey, National Earthquake Information Center, will usually take precedence over other estimates. However, higher quality damage reports or a lack of damage reports from the nuclear power plant site or its immediate vicinity will take precedence over more distant reports.
    tory Position 4.1 of this regulatory guide. A com              If plant shutdown is warranted under the above parison is made between the foundation-level de            guidelines, the plant should be shut down in an orderly sign response spectra and data obtained from the           manner (see Regulatory Position 6 of this guide).
    foundation-level instruments. If the response spec trum check at any foundation is exceeded, the OBE                Note: The determinations of epicentral loca is exceeded and the plant must be shut down. At                tion, magnitude, and intensity by the U.S. Geo this instrument location it is inappropriate to use            logical Survey, National Earthquake Informa        K
    the 0.2g spectral acceleration limit or the 6 inches            tion Center, will usually take precedence over per second (15.24 centimeters per second) spectral              other estimates; however, regional and local velocity limit stated in Regulatory Position 4.1.2.             determinations will be used if they are consid ered to be more accurate. Also, higher quality
2. For plants at which no free-field or foundation                  damage reports or a lack of damage reports level instrumental data are available, or the data              from the nuclear power plant site or its imme processing equipment is inoperable and the re                  diate vicinity will take precedence over more sponse spectrum check and the CAV check can not                distant reports.


1.166-6
REFERENCES


APPENDIX B
1.
                                                DEFINITIONS
    Certified Standard Design. A Commission ap                tinued operation without undue risk to the health and proval, issued pursuant to Subpart B of 10 CFR Part 52,        safety of the public will remain functional. The value of of a standard design for a nuclear power facility.            the OBE is set by the applicant.


Design Response Spectra. Response spectra used Spectral Acceleration. The acceleration response to design Seismic Category I structures, systems, and of a linear oscillator with prescribed frequency and components.
ANSI/ANS-2.23-2016, Nuclear Power Plant Response to an Earthquake, LaGrange Park, IL.5


damping.
2.


Operating Basis Earthquake Ground Motion (OBE). The vibratory ground motion for which those                  Spectral Velocity. The velocity response of a lin features of the nuclear power plant necessary for con-        ear oscillator with prescribed frequency and damping.
Wald, D.J., V. Quitoriano, T.H. Heaton, H. Kanamori, C.W. Scrivner, and C.B. Worden, TriNet ShakeMaps: Rapid Generation of Peak Ground Motion and Intensity Maps for Earthquakes in Southern California, Earthquake Spectra, 15(3):537-556, 1991.6
3.


REGULATORY ANALYSIS
U.S. Geological Survey, ShakeMap 3.5 Manual, available at https://usgs.github.io/shakemap/index.html.
    A separate regulatory analysis was not prepared for      benefits of the rule as implemented by the guide. A
this regulatory guide. The regulatory analysis, "Revi          copy of the regulatory analysis is available for inspec sions of 10 CFR Part 100 and 10 CFR Part 50," was pre        tion and copying for a fee at the NRC Public Document pared for these amendments, and it provides the regula        Room, 2120 L Street NW. (Lower Level), Washington, tory basis for this guide and examines the costs and          DC, as Attachment 7 to SECY-96-118.


lPanper Federal Recycling Program
5 Copies of ANSI/ANS standards may be purchased from the ANS Web site (http://www.new.ans.org/store/), or by writing to American Nuclear Society, 555 North Kensington Avenue, La Grange Park, IL 60526 (telephone:
                                                      1.166-7
800-323-3044).  


SJ .      . . ... ..      ... 1.
6 Earthquake Engineering Research Institute, 499 14th Street, Suite 220, Oakland, CA 94612-1934 USA


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ML19266A616
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Issue date: 02/13/2020
From: Vladimir Graizer, Thomas Weaver
Office of Nuclear Regulatory Research
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References
RG 1.166, Rev. 1
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U.S. NUCLEAR REGULATORY COMMISSION

REGULATORY GUIDE 1.166, REVISION 1

Issue Date: February 2020

Technical Leads: Vladimir Graizer Thomas Weaver

Written suggestions regarding this guide or development of new guides may be submitted through the NRCs public Web site in the NRC Library at https://nrcweb.nrc.gov/reading-rm/doc-collections/reg-guides/, under Document Collections, in Regulatory Guides, at https://nrcweb.nrc.gov/reading-rm/doc-collections/reg-guides/contactus.html.

Electronic copies of this RG, previous versions of RGs, and other recently issued guides are also available through the NRCs public Web site in the NRC Library at https://nrcweb.nrc.gov/reading-rm/doc-collections/reg-guides/, under Document Collections, in Regulatory Guides. This RG is also available through the NRCs Agencywide Documents Access and Management System (ADAMS) at http://www.nrc.gov/reading-rm/adams.html, under ADAMS Accession Number (No.)

ML19266A616. The regulatory analysis may be found in ADAMS under Accession No. ML18268A187. The associated draft guide DG-1337 may be found in ADAMS under Accession No. ML18268A185, and the staff responses to the public comments on DG-1337 may be found under ADAMS Accession No. ML19266A619.

PRE-EARTHQUAKE PLANNING, SHUTDOWN, AND

RESTART OF A NUCLEAR POWER PLANT

FOLLOWING AN EARTHQUAKE

A. INTRODUCTION

Purpose This regulatory guide (RG) describes guidance acceptable to the staff of the U.S. Nuclear Regulatory Commission (NRC) regarding pre-earthquake planning actions; actions necessary to determine the need to shut down a nuclear power plant; and the short- and long-term processes, inspections, and tests to demonstrate that a nuclear power plant is safe for restarting after a shutdown in response to an earthquake.

Applicability This RG applies to applicants and licensees under Title 10 of the Code of Federal Regulations

(10 CFR) Part 50, Domestic Licensing of Production and Utilization Facilities (Ref. 1),

10 CFR Part 52, Licenses, Certifications, and Approvals for Nuclear Power Plants (Ref. 2), and 10 CFR

Part 100, Reactor Site Criteria (Ref. 3).

Applicable Regulations

10 CFR 50.54(ff), Conditions of licenses, requires plant shutdown if the Operating Basis Earthquake has been exceeded or if significant plant damage occurs for licensees of nuclear power plants that have implemented the earthquake engineering criteria in Appendix S of Part 50.

Prior to resuming operations, the licensee is required to demonstrate to the Commission that no functional damage has occurred to those features necessary for continued operation without undue risk to the health and safety of the public, and that the licensing basis is maintained.

10 CFR Part 50, Appendix A, provides the General Design Criteria for Nuclear Power Plants, and establishes design, fabrication, construction, testing, and performance requirements for structures, systems, and components (SSCs) important to safety through general design criteria (GDC). The GDC applicable to this RG include GDC 2, Design Bases for Protection against

RG 1.166, Page 2 Natural Phenomena, which requires, in part, that SSCs important to safety shall be designed to withstand the effects of natural phenomena such as earthquakes, without loss of capability to perform their safety functions.

10 CFR 50, Appendix S, Earthquake Engineering Criteria for Nuclear Power Plants, for plants licensed on or after January 10, 1997, requires, in part, plant shutdown if the Operating Basis Earthquake Ground Motion is exceeded or if significant plant damage occurs. Prior to resuming operations, the licensee must demonstrate to the Commission that no functional damage has occurred to those features necessary for continued operation without undue risk to health and safety of the public, and that the licensing basis is maintained.

10 CFR 100, Appendix A, Seismic and Geologic Siting Criteria for Nuclear Power Plants,Section V(a)(2), requires plant shutdown if vibratory ground motion exceeding that of the Operating Basis Earthquake occurs. Prior to resuming operations, the licensee must demonstrate to the Commission that no functional damage has occurred to those features necessary for continued operation without undue risk to the health and safety of the public.

Related Guidance

RG 1.12, Nuclear Power Plant Instrumentation for Earthquakes (Ref. 4), provides guidance for seismic instrumentation that is acceptable to the NRC staff. RG 1.12 endorses, in part, American National Standards Institute/American Nuclear Society (ANSI/ANS)-2.2-2016, Earthquake Instrumentation Criteria for Nuclear Power Plants (Ref. 5), as an acceptable method for placement of seismic sensors for various nuclear power plant configurations.

RG 1.208, A Performance-Based Approach to Define the Site-Specific Earthquake Ground Motion (Ref. 6), provides guidance on the development of a site-specific ground motion response spectrum (GMRS).

NRC Inspection Manual Chapter (IMC) 0326, Operability Determinations & Functionality Assessments for Conditions Adverse to Quality or Safety (Ref. 7), provides guidance to NRC

inspectors in their review of licensees operability determinations and resolution of degraded or nonconforming conditions.

Purpose of Regulatory Guides The NRC issues RGs to describe to the public methods that the staff considers acceptable for use in implementing specific parts of the agencys regulations, to explain techniques that the staff uses in evaluating specific problems or postulated events, and to provide guidance to applicants. Regulatory guides are not substitutes for regulations and compliance with them is not required. Methods and solutions that differ from those set forth in RGs will be deemed acceptable if they provide a basis for the findings required for the issuance or continuance of a permit or license by the Commission.

Paperwork Reduction Act

This RG provides voluntary guidance for implementing the mandatory information collections in

10 CFR Parts 50, 52, and 100 that are subject to the Paperwork Reduction Act of 1995

(44 U.S.C. 3501 et seq.). These information collections were approved by the Office of Management and Budget (OMB), approval numbers 3150-0011, 3150-0151, and 3150-0093. Send comments regarding this information collection to the Information Services Branch (T6-A10M), U.S. Nuclear Regulatory

RG 1.166, Page 3 Commission, Washington, DC 20555-0001, or by e-mail to Infocollects.Resource@nrc.gov, and to the OMB reviewer at: OMB Office of Information and Regulatory Affairs (3150-0011, 3150-0151,

3150-0093), Attn: Desk Officer for the Nuclear Regulatory Commission, 725 17th Street, NW,

Washington, DC 20503; e-mail: oira_submission@omb.eop.gov.

Public Protection Notification

The NRC may not conduct or sponsor, and a person is not required to respond to, a collection of information unless the document requesting or requiring the collection displays a currently valid OMB

control number.

RG 1.166, Page 4

B. DISCUSSION

Reason for Revision This guide merges two related RGsRG 1.166, Pre-Earthquake Planning and Immediate Nuclear Power Operator Postearthquake Actions, issued March 1997 (Ref. 8), and RG 1.167 Restart of a Nuclear Power Plant Shut Down by a Seismic Event, issued March 1997 (Ref. 9)into one and revises their technical content. The staff decided to combine these existing RGs because they are similar in nature and contain overlapping guidance. Both guides reference and endorse the same industry guidelines, which more recent standards have superseded. The merged RG incorporates lessons learned following the shutdown and restart of nuclear power plants in response to earthquake ground motion and post-earthquake evaluations since issuance of the two RGs in 1997, through endorsement of ANSI/ANS-

2.10-2017, Criteria for Retrieval, Processing, Handling, and Storage of Records from Nuclear Facility Seismic Instrumentation (Ref. 10), and ANSI/ANS-2.23-2016, Nuclear Power Plant Response to an Earthquake (Ref. 11), with exceptions and clarifications.

Background The NRC endorsed Electric Power Research Institute (EPRI) NP-6695, Guidelines for Nuclear Power Plant Response to an Earthquake, dated December 1, 1989 (Ref. 12), in the initial version of RG 1.166 (Rev. 0) and RG 1.167 (Rev. 0), issued in 1997. Following the issuance of EPRI

NP-6695 in 1989, a significant amount of experience has been gained on the effects of earthquakes on nuclear power plants worldwide and the actions needed to restart a nuclear power plant after an earthquake. Based on these lessons learned, in 2015 EPRI significantly updated EPRI NP-6695 and the lessons were captured in EPRI Report 3002005284, Guidelines for Nuclear Plant Response to an Earthquake (Ref. 13). In addition, experience has been gained from the shutdown and restart of the Virginia Electric and Power Company (VEPCO) North Anna Power Station following the August 23,

2011, earthquake in Mineral, Virginia. For example, the plant used older analogue recording instrumentation that took longer to process than modern digital instrumentation. This equipment contributed to the delay in determining if the OBE and SSE were exceeded. in contrast, modern digital recording instrumentation would have facilitated the determination earlier. In response to the earthquake, VEPCO committed to a number of long-term actions to address exceeding the design basis as a result of the August 23, 2011, seismic event in a letter to the NRC dated November 7, 2011 (Ref. 14). NRC responded to the VEPCO letter with a Confirmatory Action Letter (CAL) on November 11, 2011 (Ref. 15), which remained in effect until NRC concluded that all the actions in the enclosure to the CAL were completed.

ANSI/ANS-2.23-2016 incorporates the significant changes and additions included in EPRI

Report 3002005284. ANSI/ANS-2.23-2016 provides guidance that implements both the observed damage level (DL) and earthquake shaking level (EL) to determine post-earthquake actions for an event that exceeds the OBE, whereas EPRI NP-6695 considers only the observed damage level to determine post- earthquake actions. In addition, ANSI/ANS-2.23-2016 builds on EPRI NP-6695 by adding guidance on action levels that clarify what actions should be taken, when they should be taken, and who should perform them. It also provides more comprehensive guidance than EPRI NP-6695 for short-term actions that a licensee should perform following an earthquake and for long-term post-earthquake evaluations.

Therefore, this RG endorses ANSI/ANS-2.23-2016.

This guide also endorses ANSI/ANS-2.10-2017, Criteria for Retrieval, Processing, Handling, and Storage of Records from Nuclear Facility Seismic Instrumentation, because the standard provides guidance on the retrieval of recorded data from seismic instrumentation in the event that an earthquake occurs with sufficient ground motion to activate the instrumentation, and because of the importance of the

RG 1.166, Page 5 storage, handling, and maintenance of recorded data and calculations. This information is important because it is used to assess the short-term and long-term actions needed to ensure the plant can be operated safely.

Harmonization with International Standards The International Atomic Energy Agency (IAEA) works with member states and other partners to promote the safe, secure, and peaceful use of nuclear technologies. The IAEA develops safety standards for protecting people and the environment from harmful effects of ionizing radiation. These standards provide a system of safety fundamentals, safety requirements, and safety guides reflecting an international consensus on what constitutes a high level of safety. Pertinent to this RG are:

IAEA Safety Reports Series No. 66, Earthquake Preparedness and Response for Nuclear Power Plants (Ref. 16), which draws upon insights from three multiunit nuclear power plants in Japan and one in Armenia that experienced beyond-design-basis earthquakes. It addresses pre-earthquake planning, actions to follow when an earthquake is felt, actions to take before the restart of the nuclear power plant, and short- and long-term post-earthquake actions.

IAEA Safety Guide NS-G-1.6, Seismic Design and Qualification for Nuclear Power Plants (Ref. 17), which provides guidance on seismic instrumentation.

This RG incorporates guidelines on actions by licensees to demonstrate plant readiness for restart similar to those in IAEA Safety Reports Series No. 66 and seismic instrumentation similar to IAEA

Safety Guide NS-G-1.6.

Documents Discussed in Staff Regulatory Guidance This RG endorses the use of one or more codes or standards developed by external organizations, and other third-party guidance documents. These codes, standards, and third-party guidance documents may contain references to other codes, standards, or third party guidance documents (secondary references). If a secondary reference has itself been incorporated by reference into NRC regulations as a requirement, then licensees and applicants must comply with that standard as set forth in the regulation. If the secondary reference has been endorsed in a RG as an acceptable approach for meeting an NRC

requirement, then the standard constitutes a method acceptable to the NRC staff for meeting that regulatory requirement as described in the specific RG. If the secondary reference has neither been incorporated by reference into NRC regulations nor endorsed in a RG, then the secondary reference is neither a legally-binding requirement nor a generic NRC approved acceptable approach for meeting an NRC requirement. However, licensees and applicants may consider and use the information in the secondary reference, if appropriately justified, consistent with current regulatory practice, and consistent with applicable NRC requirements.

RG 1.166, Page 6 C. STAFF REGULATORY GUIDANCE

This guide provides methods, approaches, or data that the staff considers acceptable for meeting the requirements of the Applicable Regulations stated in Section A. This guide endorses the following standards subject to the clarifications noted in this section:

ANSI/ANS-2.10-2017, Criteria for Retrieval, Processing, Handling, and Storage of Records from Nuclear Facility Seismic Instrumentation. The standard addresses the recording, retrieval, documentation and archiving of data from seismic instrumentation, subsequent to an earthquake sufficient to activate the instrumentation.

ANSI/ANS-2.23-2016, Nuclear Power Plant Response to an Earthquake. The standard provides guidance regarding pre-earthquake planning actions; actions necessary to determine the need to shut down a nuclear power plant; and the short- and long-term processes, inspections, and tests to demonstrate that a nuclear power plant is safe for restarting after a shutdown in response to an earthquake.

C. 1 Clarification of Post-shutdown Inspection and Test Documentation Requirements in Section

ANSI/ANS-2.23-2016, Section 8.8

The documentation described in Section 8.8 of ANSI/ANS-2.23-2016 should be available for NRC inspection prior to restart. The documentation should include the condition report methodology, assumptions, assessments, technical specification (TS) surveillance requirement number for each surveillance test, and other inspections that demonstrated that the operability of all safety-related SSCs was not affected. In addition, the documentation should demonstrate that any nonsafety-related SSC impacts are corrected or that the risk is properly managed in accordance with 10 CFR 50.65, Requirements for monitoring the effectiveness of maintenance at nuclear power plants. Specifically, if the plant is restarted with nonsafety-related equipment impacts left uncorrected or unevaluated, the increase in risk must be monitored and accounted for as required by 10 CFR 50.65.

C. 2 Clarification of Seismic Reevaluations in ANSI/ANS-2.23-2016, Section 9.1.3

Sections 9.1.3 provides guidance in selecting items for seismic reevaluations which include selecting items with the highest calculated stresses based on previous stress analysis results. The staff position is that items should also be selected where the fatigue Cumulative Usage Factor is highest.

C.3 Clarification of Equipment and Structures Qualified by Analysis in ANSI/ANS-2.23-2016, Section 9.1.4.1

When evaluating equipment and structures by analysis, staff finds it acceptable to use best estimate damping values and realistic material properties to determine if stresses or strains are greater than allowables. Strain based allowable values with adequate justification may be used when non-linear analyses are performed.

RG 1.166, Page 7 C.4 Clarification of Seismic Evaluation and Verification Plans in ANSI/ANS-2.23-2016, Section

9.5 Section 9.5 of ANSI/ANS-2.23-2016 provides guidance on developing a seismic evaluation and verification plan. Section 9.5 states that the plan should require the new and replacement safety-related SSCs to be qualified to both the licensing-basis design spectra and the observed spectra unless the licensee can demonstrate using appropriate risk-informed or performance-based approaches that the SSCs involved do not pose a significant seismic risk. All new or replacement equipment must meet current or amended site licensing-basis requirements.

C.5 Clarification of Initial and Short-Term Evaluations in ANSI/ANS-2.23-2016, Section 6 If the seismic event resulted in a plant automatic shutdown, the licensee needs to understand the cause and evaluate the extent of the condition before plant restart to ensure that (1) operability exists for safety-related SSCs and (2) risk is managed as required by 10 CFR 50.65 for both safety- and nonsafety-related SSCs. To accomplish this, as is done after any automatic reactor shutdown, the licensee must assess the performance of both safety- and nonsafety-related SSCs to determine whether all SSCs had performed as designed, installed, and maintained.

C.6 Clarification of Long-Term Evaluations in ANSI/ANS-2.23-2016, Section 9 Coincident with the long-term evaluations, as described in ANSI/ANS-2.23-2016, Section 9, the plant SSCs should be restored to match their licensing basis.

C.7 Clarification Addressing Exceptions to Restoration of the Licensing Basis When using ANSI/ANS-2.23-2016, licensees or applicants should note that correction of, or operation with, degraded or nonconforming conditions related to SSCs is accomplished, as appropriate, through evaluation, restoration, modification, license amendment, or regulatory relief (e.g., notice of enforcement discretion, emergency TS amendments, exigent TS changes, exemptions, relief requests, or other relief from a regulatory requirement as granted by the Commission). Operation with SSCs that are deemed operable/functional but are degraded or nonconforming is permitted if an analysis is performed and documented and if corrective actions are completed in a manner that meets the expectations of NRC Inspection Manual Chapter (IMC) 0326.

C. 8 Clarification Addressing Degraded or Inoperable Instrumentation

If the seismic instrumentation or data-processing equipment is degraded or inoperable, Appendix A, Operating-Basis Earthquake Exceedance Guidelines if Instrumentation is Degraded or Inoperable, of this guide should be used to determine whether the OBE ground motion has been exceeded.

RG 1.166, Page 8

D. IMPLEMENTATION

The NRC staff may use this regulatory guide as a reference in its regulatory processes, such as licensing, inspection, or enforcement. However, the NRC staff does not intend to use the guidance in this regulatory guide to support NRC staff actions in a manner that would constitute backfitting as that term is defined in 10 CFR 50.109, Backfitting, and as described in NRC Management Directive 8.4, Management of Backfitting, Forward Fitting, Issue Finality, and

=

Information Requests

=

(Ref. 18), nor does the NRC staff intend to use the guidance to affect the issue finality of an approval under 10 CFR Part

52, Licenses, Certifications, and Approvals for Nuclear Power Plants. The staff also does not intend to use the guidance to support NRC staff actions in a manner that constitutes forward fitting as that term is defined and described in Management Directive 8.4. If a licensee believes that the NRC is using this regulatory guide in a manner inconsistent with the discussion in this Implementation section, then the licensee may file a backfitting or forward fitting appeal with the NRC in accordance with the process in Management Directive 8.

4.

RG 1.166, Page 9 REFERENCES1

1.

U.S. Code of Federal Regulations (CFR), Domestic Licensing of Production and Utilization Facilities, Part 50, Chapter 1, Title 10, Energy.

2.

CFR, Licenses, Certifications, and Approvals for Nuclear Power Plants, Part 52, Chapter 1, Title 10, Energy.

3.

CFR, Reactor Site Criteria, Part 100, Chapter 1, Title 10, Energy.

4.

U.S. Nuclear Regulatory Commission (NRC), Regulatory Guide (RG) 1.12, Nuclear Power Plant Instrumentation for Earthquakes, Washington, DC.

5.

American National Standards Institute/American Nuclear Society (ANSI/ANS)-2.2-2016, Earthquake Instrumentation Criteria for Nuclear Power Plants, LaGrange, Illinois.2

6.

NRC, RG 1.208, A Performance-Based Approach to Define the Site-Specific Earthquake Ground Motion, Washington, DC.

7.

NRC, Inspection Manual Chapter 0326, Operability Determinations & Functionality Assessments for Conditions Adverse to Quality or Safety, Washington, DC.

8.

NRC, RG 1.166, Pre-Earthquake Planning and Immediate Nuclear Power Plant Operator Postearthquake Actions, Washington, DC.

9.

NRC, RG 1.167, Restart of a Nuclear Power Plant Shutdown by a Seismic Event, Washington, DC.

10.

ANSI/ANS-2.10-2017, Criteria for Retrieval, Processing, Handling, and Storage of Records from Nuclear Facility Seismic Instrumentation, LaGrange Park, Illinois.

11.

ANSI/ANS-2.23-2016, Nuclear Power Plant Response to an Earthquake, LaGrange Park, Illinois.

12.

Electric Power Research Institute (EPRI) NP-6695, Guidelines for Nuclear Power Plant Response to an Earthquake, Palo Alto, California, December 1, 1989.3

1 Publicly available NRC-published documents are available electronically through the NRC Library on the NRCs public web site at http://www.nrc.gov/reading-rm/doc-collections/ and through the NRCs Agencywide Documents Access and Management System (ADAMS) at http://www.nrc.gov/reading-rm/adams.html. The documents can also be viewed online or printed for a fee in the NRCs Public Document Room (PDR) at 11555 Rockville Pike, Rockville, MD. For problems with ADAMS, contact the PDR staff at 301-415-4737 or (800) 397-4209; fax

(301) 415-3548; or e-mail pdr.resource@nrc.gov.

2 Copies of ANSI/ANS standards may be purchased from the ANS web site (http://www.new.ans.org/store/), or by writing to American Nuclear Society, 555 North Kensington Avenue, La Grange Park, IL 60526 (telephone:

800-323-3044).

3 Copies of EPRI standards and reports may be purchased from Electric Power Research Institute, 3420 Hillview Avenue, Palo Alto, CA 94304 (telephone: (800) 313-3774; fax: (925) 609-1310).

RG 1.166, Page 10

13.

EPRI Report 3002005284, Guidelines for Nuclear Plant Response to an Earthquake, Palo Alto, California, 2015.

14.

Virginia Electric and Power Company, letter to NRC, November 7, 2011, Virginia Electric and Power Company North Anna Power Station Units 1 and 2, Independent Spent Fuel Storage Installation Revised Long-Term Actions Commitment List, ADAMS Accession number ML11314A069.

15.

NRC letter to Virginia Electric and Power Company, November 11, 2011, Confirmatory Action Letter Regarding North Anna Power Station, Unit Nos. 1 and 2, Long-Term Commitments to Address Exceeding Design Bases Seismic Event (TAC Nos. ME7254 and ME7255), ADAMS

Accession number ML11311A201.

16.

International Atomic Energy Agency Safety (IAEA) Report Series No. 66, Earthquake Preparedness and Response for Nuclear Power Plants, Vienna, Austria.4

17.

IAEA Safety Guide NS-G-1.6, Seismic Design and Qualification for Nuclear Power Plants.

18.

NRC, Management Directive 8.4, Management of Backfitting, Forward Fitting, Issue Finality, and

=

Information Requests

=

, Washington, DC.

4 Copies of IAEA documents may be obtained through the IAEA Web site at www.iaea.org/ or by writing the International Atomic Energy Agency, P.O. Box 100 Wagramer Strasse 5, A-1400 Vienna, Austria.

RG 1.166, Appendix A, Page A-1 APPENDIX A

OPERATING-BASIS EARTHQUAKE EXCEEDANCE GUIDELINES IF

INSTRUMENTATION IS DEGRADED OR INOPERABLE

If the seismic instrumentation or data-processing equipment is degraded or inoperable, the following should be used to determine whether the operating-basis earthquake (OBE) ground motion has been exceeded:

For plants at which instrumentally determined data are available only from an instrument installed on a foundation, the cumulative absolute velocity (CAV) check does not apply. In this case, the determination of OBE exceedance is based on a response spectrum check described in Section 6.4.1 of American National Standards Institute/American Nuclear Society (ANSI/ANS)-

2.23-2016, Nuclear Power Plant Response to an Earthquake (Ref. 1). A comparison should be made between the foundation-level design response spectra and data obtained from the foundation-level instruments. If the response spectrum check at any foundation is exceeded, the OBE is exceeded, and the plant must be shut down. At this instrument location, it is inappropriate to use the 0.2g spectral acceleration limit or the spectral velocity limit of 6 inches per second

(15.24 centimeters per second) in Section 6.4.1 of ANSI/ANS-2.23-2016.

For plants at which no free-field or foundation-level instrumental data are available or the data-processing equipment is inoperable and the response spectrum check and the CAV check cannot be determined, the OBE will be considered to have been exceeded, and the plant must be shut down if one of the following two conditions apply:

(1)

If instrumental intensity information is not available, the earthquake with moment magnitude M specified in Table B-1 occurred within a distance less than or equal to that specified in Table B-1.

Table B-1 Maximum Distance from an Earthquake with Moment Magnitude M at which the OBE Can Be Exceeded

Magnitude (M)

Distance (km)

5.0-5.5

80

5.6-6.0

150

6.1-6.5

250

6.6-7.0

300

7.1-7.5

380

7.6-8.0

480

If plant shutdown is warranted under the above guidelines, the plant should be shut down in an orderly manner (see Sections 6.2 and 6.5 of ANSI/ANS-2.23-2016).

RG 1.166, Appendix A, Page A-2 The licensee should conduct a post-earthquake plant walkdown after the earthquake (see Section 6.2 of ANSI/ANS-2.23-2016).

(2)

The earthquake resulted in Instrumental Intensity VI (Table B-2) or greater within 5 kilometers (km) of the plant.

Table B-2 ShakeMap Instrumental Intensity Scale (Ref. 2 and Ref. 3)

Note that the determination of epicentral location, magnitude, and intensity by the U.S. Geological Survey, National Earthquake Information Center, will usually take precedence over other estimates. However, higher quality damage reports or a lack of damage reports from the nuclear power plant site or its immediate vicinity will take precedence over more distant reports.

REFERENCES

1.

ANSI/ANS-2.23-2016, Nuclear Power Plant Response to an Earthquake, LaGrange Park, IL.5

2.

Wald, D.J., V. Quitoriano, T.H. Heaton, H. Kanamori, C.W. Scrivner, and C.B. Worden, TriNet ShakeMaps: Rapid Generation of Peak Ground Motion and Intensity Maps for Earthquakes in Southern California, Earthquake Spectra, 15(3):537-556, 1991.6

3.

U.S. Geological Survey, ShakeMap 3.5 Manual, available at https://usgs.github.io/shakemap/index.html.

5 Copies of ANSI/ANS standards may be purchased from the ANS Web site (http://www.new.ans.org/store/), or by writing to American Nuclear Society, 555 North Kensington Avenue, La Grange Park, IL 60526 (telephone:

800-323-3044).

6 Earthquake Engineering Research Institute, 499 14th Street, Suite 220, Oakland, CA 94612-1934 USA

phone: 510-451-0905 l fax: 510-451-5411 l email: eeri@eeri.org


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