ML19140A307

Treatment of Reevaluated Seismic Hazard Information Provided Under Title 10 of the Code of Federal Regulations 50.54(f) Regarding Recommendation 2.1 of the Near-Term Task Force Review of Insights from Fukushima Dai-Ichi Accident

ML19140A307
Person / Time
Issue date:	07/03/2019
From:	Louise Lund Division of Licensing Projects
To:
Valentin-Olmeda M, NRR/DLP, 415-2864
References
Download: ML19140A307 (25)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C 20555-0001 July 3, 2019 The Licensees of Operating Power Reactors on the Enclosed List

SUBJECT:

TREATMENT OF REEVALUATED SEISMIC HAZARD INFORMATION PROVIDED UNDER TITLE 10 OF THE CODE OF FEDERAL REGULA T/ONS 50.54(1) REGARDING RECOMMENDATION 2.1 OF THE NEAR-TERM TASK FORCE REVIEW OF INSIGHTS FROM THE FUKUSHIMA DAI-ICHI ACCIDENT This document describes the U.S. Nuclear Regulatory Commission (NRG) staff's treatment of reevaluated seismic hazard information. The treatment of seismic hazard information reflects the Commission's direction in the Affirmation Notice and Staff Requirements Memorandum (SRM) dated January 24, 2019 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML19023A038), associated with SECY-16-0142, "Draft Final Rule- Mitigation of Beyond-Design-Basis Events [MBDBEJ (RIN 3150-AJ49)," (ADAMS Accession No. ML16291A186). Based on the reevaluated seismic hazard information that has been provided to date, only seismic probabilistic risk assessment (SPRA) report reviews that have not yet received a staff assessment could potentially lead to the staff identifying a need for modifying, suspending or revoking a license. The staff has evaluated the status of each site and placed sites into one of four categories: category 1 (no additional regulatory action is warranted); category 2 (additional insights needed); category 3 (ongoing review): and category 4 (deferred). Enclosure 1, Table 1 provides the status of sites based on the staffs review of the reevaluated seismic hazard information and backfit determinations to date. The NRG staff has suspended its review of seismic mitigation strategies assessments (MSAs).

Summary By letter dated March 12, 2012 (ADAMS Accession No. ML12053A340), the NRC issued a request for information to all power reactor licensees and holders of construction permits in active or deferred status, under Title 1O of the Code of Federal Regulations (1 O CFR),

Section 50.54(f) (hereafter referred to as the "50.54(f) letter"). The request was issued in connection with implementing lessons learned from the 2011 accident at the Fukushima Dai-ichi nuclear power plant, as documented in the NRC's Near-Term Task Force (NTTF) report (ADAMS Accession No. ML111861807). Enclosure 1 of the 50.54(!) letter requested that licensees reevaluate seismic hazards for their sites using present-day methods and regulatory guidance used by the NRC staff when reviewing applications for early site permits and combined licenses.

The 50.54(f) letter describes a two-phase process for providing and assessing this information.

Phase 1 of the process is defined in the 50.54(f) letter as licensees reevaluating the seismic hazards at their sites using updated seismic hazard information and present-day regulatory guidance and methodologies, and, if necessary, to request they perform a risk evaluation.

Phase 2 of the process is outlined by the 50.54(f) letter and is defined as the NRG staff determining whether additional regulatory actions are necessary (e.g., update the design basis and structures, systems, and components (SSCs) important to safety) to provide additional

protection against the updated hazards. In implementing the NRC's Phase 2 process, the staff will follow the guidance provided in a memorandum dated September 21, 2016 (ADAMS Accession No. ML16237A103), which remains in accordance with the most recent Commission direction provided in SRM-SECY-18-0049, "Management of Facility-Specific Backfitting, Issue Finality, and Information Collection," (ADAMS Accession No. ML19149A294).

The staff's treatment of the reevaluated hazard information outlined in this document used information provided in response to the 50.54(f) letter and describes how the staff is using this information for its Phase 2 decisionmaking. Highlights of the staff's progress in this area are as follows:

• Only SPRA report reviews that have not yet received a staff assessment could potentially lead to the staff identifying a need for modifying, suspending or revoking a license in accordance with the Phase 2 process. The staff will continue its assessment of SPRA reports and will use these results in the Phase 2 process described in the 50.54(f) letter and by the memorandum dated September 21, 2016.

• The staff has suspended its review of seismic MSAs. The majority of these MSAs have previously been evaluated by the staff. For the reviews not yet completed, or not yet submitted, the staff will evaluate the mitigation strategies, as appropriate, as part of its review of SPRA reports. Licensees are no longer expected to submit MSAs associated with their reevaluated seismic hazard.

• To provide clarity regarding the status of each site's response to the 50.54(f) letter, this letter bins sites in one of the following four categories:

o Category 1 - No additional regulatory action is warranted. This Category groups the sites where licensees and NRC staff are done with the seismic reevaluation assessments and backfit decisions. There are 47 sites in this category.

o Category 2 - Additional insights are needed before a backfit decision is made.

There are no sites in this category.

o Category 3 - Corresponds to sites that have reevaluated seismic information that will be reviewed by the staff. This Category includes sites that have active SPRA report reviews or that will submit an SPRA report before the end of 2019. The NRC staff has not make a final backfit determination on these sites. There are 9 sites in this category.

o Category 4 - Corresponds to sites that have had, or requested that, reevaluated hazard information submittals be deferred to a date after the licensee's proposed date to shut down its reactor(s). There are three sites in this category.

Background

The seismic reevaluated hazard information provided in response to the 50.54(f) letter was the focus of the seismic hazard screening reports. Depending on the site-specific reevaluated seismic hazard, other necessary licensee submittals may have included: 1) an expedited seismic evaluation process (ESEP) report, 2) seismic MSA; 3) spent-fuel pool (SFP) seismic integrity evaluation; 4) seismic high frequency confirmation; and/or 5) SPRA report.

The staff's discussion of the reevaluated hazard information that has been provided by licensees in response to the 50.54(f) letter is found in Enclosure 1 of this document.

The draft final MBDBE rule, provided in SECY-16-0142, contained provisions that would have required mitigation strategies to address the reevaluated seismic hazard information on a generic basis. As reflected in the Affirmation Notice and SRM dated January 24, 2019, the Commission determined that addressing the reevaluated hazards in their mitigation strategies

on a generic basis was not needed for adequate protection of public health and safety but would instead be assessed on a plant-specific, case-by-case basis under the requirements of 10 CFR

§ 50.109, "Backfitting," and§ 52.98, "Finality of combined licenses; information requests."

The January 24, 2019, SRM directs the staff to use the 50.54(f) process to ensure that the NRC and its licensees will take the needed actions, if any, to ensure there is no undue risk to public health and safety due to the potential effects of the reevaluated seismic hazards. The SRM further directs that the staff should continue these efforts, utilizing existing agency processes to determine whether an operating power reactor license should be modified, suspended, or revoked in light of the reevaluated hazard.

Determination As described in Enclosure 1, the staff has reviewed the reevaluated seismic hazard information that has been provided to date and issued corresponding staff assessments for many sites.

The conclusions documented in those assessments remain valid based on the demonstrated inherent capacity of SSCs and portable equipment. Furthermore, the staff has determined that only SPRA report reviews that have not yet received a staff assessment could potentially lead to the staff identifying a need for modifying, suspending or revoking a license in accordance with the Phase 2 process.

Stakeholder Interactions Treatment of the reevaluated hazard information was discussed in a February 28, 2019 (ADAMS Accession No. ML19052A511 ), public meeting. During this meeting, the staff provided an overview of the preliminary determination process (ADAMS Accession No. ML19037A443) and sought questions and comments from interested stakeholders. The NRC meeting materials are available under ADAMS Accession No. ML19042A683. The staff's treatment of reevaluated seismic hazards reflected in this letter considers the comments received at the February 28, 2019, public meeting, as well as comments submitted to the staff by letter dated March 27, 2019 (ADAMS Accession No. ML190958537) from the Nuclear Energy Institute.

Conclusion Based on the staff's evaluation provided in Enclosure 1, the staff has determined that the conclusions documented in each of the reevaluated seismic hazard staff assessments issued to date remain valid and additional regulatory actions are not warranted for those sites. Reviews will continue to be performed for SPRA reports that have been received by the staff and are currently under review. Additionally, the staff will continue to use the same process to review SPRA reports that are scheduled to be submitted through the end of 2019. A small number of sites have received SPRA report deferral approvals corresponding to planned plant closures. , Table 1 provides a status of the staff's review of the reevaluated seismic hazard information and the seismic binning for each site.

If you have any questions, please contact Milton Valentin-Olmeda at 301-415-2864, or by e-mail at Milton.Valentin-Olmeda@nrc.gov.

Sincerely, Louise Lund, Director Division of Licensing Projects Office of Nuclear Reactor Regulation

Enclosures:

1. Treatment of Reevaluated Seismic Hazard Information

2. List of Licensees cc w/encls: Distribution via list serv

Treatment of Reevaluated Seismic Hazard Information Contents 1.0 Introduction and Summary .. . ................. 1 2.0 Background .. 2 3.0 Process . .. 2 4.0 Seismic Reevaluated Hazards .... . ...... 4 4.1 Expedited Seismic Evaluation Process .. . ........................................... 4 4.2 Seismic Spent Fuel Pool Evaluations . . ............... 5 4.3 Seismic High Frequency Confirmations . . ...... 6 4.4 Mitigation Strategies Assessments . . .................. 6 4.5 Seismic Probabilistic Risk Assessments . . ... .7 5.0 Conclusion . .7 Enclosure 1

1.0 Introduction and Summary This document describes the U.S. Nuclear Regulatory Commission (NRC) staff's process for reviewing the reevaluated seismic hazard information in backfit determinations. The process reflects the Commission's direction in the Affirmation Notice and Staff Requirements Memorandum (SRM) dated January 24, 2019 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML19023A038), associated with SECY-16-0142, "Draft Final Rule- Mitigation of Beyond-Design-Basis Events [MBDBE] (RIN 3150-AJ49)," (ADAMS Accession No. ML16291A186). The preliminary process was first described in a discussion paper (ADAMS Accession No. ML19037A443), which was the subject of a public meeting held on February 28, 2019 (ADAMS Accession No.

ML19052A511 ). Stakeholder feedback from that meeting submitted in a letter dated March 27, 2019 (ADAMS Accession No. ML190956537) has been considered in the development of this process for reviewing reevaluated seismic hazard information.

By letter dated March 12, 2012 (ADAMS Accession No. ML12053A340), the NRC issued a request for information to all power reactor licensees and holders of construction permits in active or deferred status, under Title 1O of the Code of Federal Regulations (10 CFR),

Section 50.54(f) (hereafter referred to as the "50.54(f) letter"). The request was issued in connection with implementing lessons learned from the 2011 accident at the Fukushima Dai-ichi nuclear power plant, as documented in the NRC's Near-Term Task Force (NTIF) report (ADAMS Accession No. ML111861807). Enclosure 1 of the 50.54(1) letter requested that licensees reevaluate seismic hazards for their sites using present-day methods and regulatory guidance used by the NRG staff when reviewing applications for early site permits and combined licenses.

The 50.54(f) letter describes a two-phase process for providing and assessing this information. Phase 1 of the process is defined in the 50.54(f) letter as licensees reevaluating the seismic hazards at their sites using updated seismic hazard information and present-day regulatory guidance and methodologies, and, if necessary, perform a risk evaluation. These evaluations associated with the requested information do not revise the design basis of the plant. Phase 2 of the process is outlined by the 50.54(f) letter and is defined as the NRG staff determining whether additional regulatory actions are necessary (e.g., update the design basis and structures, systems, and components (SSCs) important to safety) to provide additional protection against the updated hazards. In implementing the NRC's Phase 2 process, the staff will follow the guidance provided in a memorandum dated September 21, 2016 (ADAMS Accession No. ML16237A103), which remains in accordance with the most recent Commission direction provided in SRM-SECY-18-0049, "Management of Facility-Specific Backfitting, Issue Finality, and Information Collection," (ADAMS Accession No. ML19149A294).

The process outlined in this letter used information provided in response to the 50.54(f) letter and describes how the staff used this information for its Phase 2 decisionmaking. Highlights of the staff's progress in this area are as follows:

• Based on the reevaluated seismic hazard information that has been provided to date, only SPRA report reviews that have not yet received a staff assessment could potentially lead to the staff identifying a need for modifying, suspending or revoking a license in accordance with the Phase 2 process. The staff will continue its assessment of SPRA reports and will use the results of these assessments in the Phase 2 process described in the 50.54(f) letter and by the memorandum dated September 21, 2016.

• The staff has suspended its review of seismic mitigation strategies assessments (MSAs). The majority of these MSAs have previously been evaluated by the staff. For the reviews not yet completed, or not yet submitted, the staff will evaluate the

mitigation strategies, as appropriate, as part of its review of SPRA reports. Licensees are no longer expected to submit MSAs associated with their reevaluated seismic hazard.

• To provide clarity regarding the status of each site's response to the 50.54(f) letter, the NRC staff is binning sites in one of four categories as described in the section 3 of this Enclosure. Table 1 provides the site binning described in section 3.

2.0 Background

The seismic reevaluated hazard information provided in response to the 50.54(f) letter was the focus of the seismic hazard screening reports. Depending on the site-specific reevaluated seismic hazard, other necessary licensee submittals may have included: 1) an expedited seismic evaluation process (ESEP) report, 2) seismic MSA; 3) spent-fuel pool (SFP) seismic integrity evaluation; 4) seismic high frequency confirmation; and/or 5) SPRA report.

The staff's detailed assessment of the reevaluated seismic hazard information that has been provided in response to the 50.54(f) letter can be found in Section 4 of this Enclosure. A key guidance document that was used by the staff to evaluate seismic MSAs was Appendix H, of Nuclear Energy Institute (NEI) 12-06, Revision 4, "Diverse and Flexible Coping Strategies (FLEX) Implementation Guide" (ADAMS Accession No. ML163548421). The NRC's endorsement of NEI 12-06, Revision 4, is described in Japan Lessons-Learned Division (JLD)

Interim Staff Guidance (ISG) JLD-ISG-2012-01, Revision 2, "Compliance with Order EA 049, Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events" (ADAMS Accession No. ML17005A182). 1 Section 6 of JLD-ISG-2012-01, Revision 2, provides guidance regarding the treatment of reevaluated seismic hazard information in mitigation strategies developed in response to Order EA-12-049, "Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events" (ADAMS Accession No. ML12054A735).

The draft final MBDBE rule, provided in SECY-16-0142, contained provisions that would have required mitigation strategies to address the reevaluated seismic hazard information on a generic basis. As reflected in the Affirmation Notice and SRM dated January 24, 2019, the Commission determined that addressing the reevaluated hazards in licensees' mitigation strategies on a generic basis was not needed for adequate protection of public health and safety but would instead be assessed on a plant-specific, case-by-case basis under the requirements of 1O CFR § 50.109, "Backfitting," and § 52.98, "Finality of combined licenses; information requests."

The January 24, 2019, SRM directs the staff to use the 50.54(1) process to ensure that the NRC and its licensees will take the needed actions, if any, to ensure there is no undue risk to public health and safety due to the effects of the reevaluated seismic hazards. The SRM further directs that the staff should continue these efforts, utilizing existing agency processes to detennine whether an operating power reactor license should be modified, suspended, or revoked in light of the reevaluated hazard.

3.0 Process As described in Section 4.0 of this Enclosure, the staff has reviewed the reevaluated seismic hazard information that has been provided to date and issued corresponding staff 1 Appendix H was first introduced in Revision 2 of NEI 12-06, endorsed by Revision 1 of the ISG.

assessments for many sites. The conclusions documented in those assessments remain valid based on the demonstrated inherent capacity of SSCs and portable equipment.

Furthermore, the staff has determined that only SPRA report reviews that have not yet received a staff assessment could potentially lead to the staff identifying a need for modifying, suspending or revoking a license in accordance with the Phase 2 decisionmaking process.

In their submittals, some licensees stated that changes would be pursued to mitigate the impact that the reevaluated seismic hazard could have at their sites, and these changes were not identified as regulatory commitments. Other licensees identified such changes as regulatory commitments as defined in Section 4.2 of NEI 99-04, "Guidelines for Managing NRC Commitment Changes," Revision 0, dated July 1999 (ADAMS Accession No.

ML003680088). Depending on the site-specific details, the staff appropriately credited changes that licensees have planned or implemented at the site such as:

• Physical modifications to the plant that have been planned or implemented that would address a reevaluated seismic hazard.

• Changes to procedures to ensure relay chatter due to a seismic event do not adversely impact a plant's capability to shut down, or its ability to ensure adequate core cooling, containment integrity or SFP cooling.

In an effort to provide clarity regarding the status of each site's response to the 50.54(f) letter, the staff has binned all sites into four different categories. The binning is based on existing and proposed plant capabilities, as reflected in the licensee submittals and staff assessments associated with the reevaluated seismic hazards. The NRC staff binned sites into one of the following four categories:

• Category 1: Corresponds to sites where no additional regulatory action is warranted. This category includes sites that where the reevaluated seismic hazard is bounded by the current design basis, or sites where the licensee has demonstrated that existing seismic capacity and plant procedures will address the unbounded reevaluated hazard. This means that both licensees and staff are finished with the 50.54(f) letter seismic reevaluation assessments and backfit decisions for these sites. There are currently 47 sites in this category.

• Category 2: Corresponds to sites where additional insights are needed before a backfit determination is made. This category includes sites where the NRC does not have all the information needed to make a Phase 2 determination for such a site. There are currently no reevaluated seismic hazard sites in this category.

• Category 3: Corresponds to sites where an SPRA report is under review or is expected to be submitted. Therefore, the staff's review is ongoing and will be conducted in accordance with the recent Commission direction and be documented in the corresponding SPRA report staff assessment. There currently are nine sites in this category.

• Category 4: Corresponds to sites that have requested a deferral from completing seismic work related to the 50.54(f) letter based on impending plant closure. The staff concluded that each site's corresponding deferral letter adequately addressed the site's plan to address the seismic hazard up to the period of plant closure. The NRC staff issued assessments for each deferral. In these assessments, the staff stated that if a deferred

site remains in operation longer than previously communicated, the licensee would be expected to respond to the 50.54(f) letter by completing the deferred seismic reevaluation report(s). There are currently three sites in this category.

Table 1 includes the binning of all nuclear power plant sites. The staff's binning is intended to confirm the completion of the 50.54(f) seismic activities for Category 1 sites and the proposed path forward for sites in Categories 3 and 4. Also, the binning process considers all reevaluated seismic hazard reports, the respective staff assessments, and the ongoing MBDBE rulemaking. Category 4 (deferred) sites will follow the process described in the site's corresponding deferral letter, and either provide a submittal by the deferred date that the 50.54(f) activities are no longer necessary based on the conditions of the plant (e.g., fuel being permanently removed from the reactor vessel in accordance with 10 CFR 50.82(a)(1 )(ii), and SFP capabilities) or provide the remaining information should they decide to remain in operation past the planned shutdown date. At such a point, the staff would evaluate those sites based on the process described in this document.

4.0 Seismic Reevaluated Hazards The NRG staff has revisited previously completed reevaluated seismic hazard staff assessments, particularly those where licensee actions were identified to ensure that key safety functions (core cooling, containment, and SFP cooling) are maintained to determine the need for further regulatory actions. The seismic reevaluations in response to the 50.54(f) letter include interim actions associated with the ESEP, SFP integrity evaluations, HF confirmations, seismic MSAs, and SPRA reports. Except for the SFP integrity evaluations, these activities had the potential to propose actions to ensure that key safety functions are maintained. For sites where no SPRA reports were expected, activities identified during the ESEPs, HF confirmations, and seismic MSAs have been revisited to support the previous Phase 2 determination. For sites where SPRA reports will be, or have been, performed, the SPRA report will support the Phase 2 determination.

The staff has completed all seismic MSA staff reviews for plants not requiring an SPRA report.

Additionally, the staff did complete seismic MSA staff reviews for three sites that submitted an SPRA report. However, as described in the seismic MSA section below, future seismic MSA submittals are not warranted, given the recent Commission decision on the MBDBE rule.

Instead, appropriate backfit decisions can be made based on the information that licensees provide in their SPRA reports. If additional information relative to mitigation strategies capabilities associated with a seismic event are needed to support a staff backfit decision, the staff wilt pursue obtaining such information on an individual plant basis as part of its SPRA report reviews. Sites in Category 3 are those with SPRA reports currently under review or that are yet to be submitted.

4.1 Expedited Seismic Evaluation Process By letter dated April 12, 2013 (ADAMS Accession No. ML13102A142), the Electric Power Research Institute (EPRI) staff submitted EPRI Report 3002000704 "Seismic Evaluation Guidance: Augmented Approach for the Resolution of Fukushima Near-Term Task Force

{NTIF) Recommendation 2.1: Seismic" {ADAMS Accession No. ML13102A142). The Augmented Approach proposed that licensees would use the ESEP to address the interim actions as requested by Information Item (6) in the 50.54(f) letter. The ESEP is a simplified seismic capacity evaluation with a focused scope of certain key installed mitigating strategies equipment that is used for core cooling and containment functions to cope with scenarios that involve a loss of all alternating current (ac) power and loss of access to the ultimate heat sink

to withstand the review level ground motion {RLGM), which is up to two times the safe shutdown earthquake (SSE). By letter dated May 7, 2013 (ADAMS Accession No. ML13106A331 ), the NRG staff endorsed the ESEP guidance.

The staff's reviews assessed whether the intent of the guidance was implemented. All sites to which the ESEP was applicable have received a corresponding staff assessment that concludes that licensees have demonstrated adequate implementation of the augmented approach. Part of the staff's assessment included checklist item VII, "Modifications to Plant Equipment." This section of the staff's assessment addressed whether licensees identified actions to resolve modifications to achieve high confidence of low probability of failure

{HCLPF) values that bound the RLGM. In their docketed submittals, some sites identified actions and/or plant modifications needed to achieve HCLPF values. These actions and/or plant modifications resulting from the ESEP have either been completed or will be addressed as part of the SPRA. The staff credited (or will credit as appropriate) these actions and modifications as part of its Phase 2 determination and the conclusions documented in this letter.

4.2 Seismic Spent Fuel Pool Evaluations By letter dated January 31, 2017 (ADAMS Accession No. ML17031A171 ), NEI submitted the EPRI Report No. 3002009564 entitled, "Seismic Evaluation Guidance: Spent Fuel Pool Integrity Evaluation" (SFP Evaluation Guidance Report) (ADAMS Accession No. ML16055A017). The SFP Evaluation Guidance Report provides criteria for evaluating the seismic robustness of an SFP to the reevaluated ground motion response spectrum (GMRS) hazard levels. This report supplements the guidance in EPRI Report 1025287, "Seismic Evaluation Guidance: Screening, Prioritization and Implementation Details (SPID)" (ADAMS Accession No. ML12333A170). The NRG endorsed the SFP Evaluation Guidance Report by letter dated February 28, 2017 (ADAMS Accession No. ML17034A408), as an acceptable method for licensees to use when responding to Item (9) in Enclosure 1 of the 50.54(f) letter.

The staff's guidance was developed to support completion of SFP evaluations for sites with a reevaluated seismic hazard exceedance in the 1-10 Hertz (Hz) frequency range (i.e., the frequency range of structural significance). The staff's evaluations of the 38 sites with an exceedance in this frequency range were grouped based on whether the reevaluated GMRS peak spectral accelerations were above or below 0.8 g. These 38 operating reactor sites have each received a staff SFP structural evaluation that concluded that licensees have demonstrated adequate seismic margin to preclude a potential drain-down of the SFP in the unlikely occurrence of a seismic event up to the magnitude of the reevaluated seismic hazard occurring at their respective sites. The staff has confirmed that conclusions reached in these assessments are not affected by the Commission's Affirmation Notice and SRM on the MBDBE rule.

4.3 Seismic High Frequency Confirmations By letter dated July 30, 2015 (ADAMS Accession No. ML15223A095), NEI submitted EPRI Report 3002004396, "High Frequency Program: Application Guidance for Functional Confirmation and Fragility Evaluation" (hereafter referred to as the HF guidance) (ADAMS Accession No.ML15223A095}. The HF guidance proposes methods for applying HF seismic testing results to support plant-specific analyses of potential HF effects. Specific guidance is given for plants performing a limited-scope HF confirmation to address the information requested in Item (4) in Enclosure 1 of the 50.54(1) letter.

accordance with this enclosure. Specifically, in their docketed submittals, two licensees identified actions (such as operator actions needed to address relay chatter) needed to implement the mitigation strategies under the reevaluated seismic hazard conditions. The staff credited such actions in its Phase 2 determination such that additional information or actions are not warranted.

For sites following Path 5 of NEI 12-06, Revision 4, Appendix H, licensees submitted or are scheduled to submit SPRA reports that include evaluations of HF effects on the plant. The SPRA report review process will identify if additional regulatory actions are warranted in accordance with the NRC's backfit process. Most SPRAs model FLEX equipment: however, neither SFPs nor SFP cooling are modeled in SPRAs. As described above, operating reactor sites have either screened out of the need for conducting a SFP structural evaluation or have received a staff SFP structural evaluation that concluded that licensees have demonstrated adequate seismic margin to preclude a potential drain-down of the SFP in the unlikely occurrence of a seismic event up to the magnitude of the reevaluated seismic hazard taking place at their respective sites.

If the staff has clarification questions regarding the modeling of mitigation strategies capabilities in the context of the SPRA report review, the staff will pursue these questions on an individual plant basis as part of the SPRA report reviews. Table 1 provides the results of the staff's binning of reevaluated seismic hazard submittals that have been provided to the staff.

4.5 Seismic Probabilistic Risk Assessments The NRG staff will continue to review the SPRA reports to complete the Phase 2 process as described in the 50.54(f) letter and in the memorandum dated September 21, 2016, to determine if additional regulatory actions are warranted. The NRG staff has confirmed that pending work on SPRA reports in response to the 50.54(f) letter is not affected by the Commission's Affirmation Notice and SRM on the MBDBE rule. The NRG staff has completed the review of some SPRA reports and concluded that no further regulatory action is warranted for those sites. Those sites have been binned in Category 1. Other sites whose SPRA reports are still under review or sites soon to submit their SPRA reports are binned in Category 3. A limited number of sites have deferred their SPRA report submittal to a date after their proposed shutdown and are binned in Category 4. Those sites are to follow the guidance provided in the NRC staff response to the deferral request.

5.0 Conclusion Based on the staff's assessment provided in this Enclosure, the staff has determined that the conclusions documented in each of the reevaluated seismic hazard staff assessments issued to date remain valid and additional regulatory actions are not warranted for those sites.

Reviews will continue to be performed for SPRA reports that have been received by the staff and are currently under review. Additionally, the staff will continue to use the same process to review SPRA reports that are scheduled to be submitted through the end of 2019. A small number of sites have received SPRA report deferral approvals corresponding to planned plant closures. Table 1 provides a status of the staff's review of the reevaluated seismic hazard information and the site binning as described in Section 3 of this Enclosure.

Table 1 - Status of 50.54(f) Letter (Seismic) - Site Binning Site No additional Additional Ongoing Deferred regulatory action Insights Needed Review is warranted

/Category 1) /Category 2) (Category 3) (Category 4)

Arkansas Nuclear X Beaver Valley X Braidwood X Browns Ferry X Brunswick X Byron X Callaway X Calvert Cliffs X Catawba X Clinton X Columbia X Comanche Peak X Cooper X Davis-Besse X DC Cook X Diablo Canyon X Dresden X Duane Arnold X Farley X Fermi X FitzPatrick X Ginna X Grand Gulf X Harris X Hatch X Hope Creek X Indian Point X LaSalle X Limerick X McGuire X Millstone X Monticello X Nine Mile Point X North Anna X Oconee X Palisades X Palo Verde X Peach Bottom X Perry X Pilgrim X

Point Beach X Prairie Island X Quad Cities X River Bend X Robinson X Salem X Seabrook X Sequoyah X St. Lucie X South Texas X Summer X Surry X Susquehanna X TMI X Turkey Point X Vogtle X Waterford X Watts Bar X Wolf Creek X Total 47 0 9 3

LIST OF APPLICABLE POWER REACTOR LICENSEES Arkansas Nuclear One Units 1 and 2 Browns Ferry Nuclear Plant, Units 1, 2, Entergy Operations, Inc. and 3 Docket Nos. 50-313 and 50-368 Tennessee Valley Authority License Nos. OPR-51 and NPF-6 Docket Nos. 50-259, 50-260, and 50-296 License Nos. DPR-33, DPR-52, and DPR-ANO Site Vice President 68 Arkansas Nuclear One Entergy Operations, Inc. Mr. Joseph W. Shea N-TSB-58 Vice President, Nuclear Regulatory Affairs 1448 S.R. 333 and Support Services Russellville, AR 72802 Tennessee Valley Authority Browns Ferry Nuclear Plant Beaver Valley Power Station, Units 1 and 2 1101 Market Street, LP 4A FirstEnergy Nuclear Operating Company Chattanooga, TN 37402-2801 Docket Nos. 50-334 and 50-412 License Nos. DPR-66 and NPF-73 Brunswick Steam Electric Plant, Units 1 and 2 Mr. Richard D. Bologna Duke Energy Progress, LLC Site Vice President Docket Nos. 50-325 and 50-324 FirstEnergy Nuclear Operating Company Licensee Nos DPR-71 and DPR-62 Beaver Valley Power Station Mail Stop A-BV-SSB Mr. William R. Gideon P.O. Box 4, Route 168 Site Vice President Shippingport, PA 15077 Brunswick Steam Electric Plant 8470 River Rd. SE (M/C BNP001)

Braidwood Station Units 1 and 2 Southport, NC 28461 Exelon Generation Company, LLC Docket Nos. STN 50-456 and STN 50-457 Byron Station, Units 1 and 2 License Nos. NPF-72 and NPF-77 Exelon Generation Company, LLC Docket Nos. STN 50-454 and STN 50-455 Mr. Bryan C. Hanson License Nos. NPF-37 and NPF-66 Senior Vice President Exelon Generation Company, LLC Mr. Bryan C. Hanson President and Chief Nuclear Officer (CNO) Senior Vice President Exelon Nuclear Exelon Generation Company, LLC Braidwood Station President and Chief Nuclear Officer (CNO}

4300 Winfield Road Exelon Nuclear Warrenville, IL 60555 Byron Station 4300 Winfield Road Warrenville, IL 60555 Enclosure 2

Callaway Plant, Unit 1 Columbia Generating Station Union Electric Company Energy Northwest Docket No. 50-483 Docket No. 50-397 License No. NPF-30 License No. NPF-21 Mr. Fadi Oiya Mr. Bradley J. Sawatzke Senior Vice President and Chief Chief Executive Officer Nuclear Officer Energy Northwest Ameren Missouri Columbia Generating Station Callaway Energy Center MD 1023 8315 County Road 459 76 North Power Plant Loop Steedman, MO 65077 PO Box 968 Richland, WA 99352 Calvert Cliffs Nuclear Power Plant Units 1 and 2 Comanche Peak Nuclear Power Plant Calvert Cliffs Nuclear Power Plant. LLC Units 1 and 2 Docket Nos. 50-317 and 50-318 Vistra Operations Company, LLC License Nos. DPR-53 and DPR-69 Docket Nos. 50-445 and 50-446 License Nos. NPF-87 and NPF-89 Mr. Bryan C. Hanson Senior Vice President Mr. Ken J. Peters Exelon Generation Company, LLC Senior Vice President & Chief President and Chief Nuclear Officer Nuclear Officer Exelon Nuclear Attention: Regulatory Affairs 4300 Winfield Road Comanche Peak Nuclear Power Plant Warrenville, IL 60555 Vistra Operations Company, LLC 6322 N FM 56 Catawba Nuclear Station Units 1 and 2 P.O. Box 1002 Duke Energy Carolinas, LLC Glen Rose, TX 76043 Docket Nos. 50-413 and 50-414 License Nos. NPF-35 and NPF-52 Cooper Nuclear Station Nebraska Public Power District Mr. Robert T. Simril Docket No. 50-298 Site Vice President License No. DPR-46 Duke Energy Carolinas, LLC Catawba Nuclear Station Mr. John Dent, Jr.

4800 Concord Road Vice President-Nuclear and CNO York, SC 29745 Nebraska Public Power District Cooper Nuclear Station Clinton Power Station Unit 1 72676 648A Avenue Exelon Generation Company, LLC Brownville, NE 68321 Docket No. 50-461 License No. NPF-62 Mr. Bryan C. Hanson Senior Vice President Exelon Generation Company, LLC President and Chief Nuclear Officer (CNO)

Exelon Nuclear Clinton Power Station 4300 Winfield Road Warrenville, IL 60555

Davis-Besse Nuclear Power Station, Unit 1 Dresden Nuclear Power Station Units 2 FirstEnergy Nuclear Operating Company and 3 Docket No. 50-346 Exelon Generation Company, LLC License No. NPF-3 Docket Nos. 50-237 and 50-249 License Nos. DPR-19 and DPR-25 Mr. Mark Bezilla Site Vice President Mr. Bryan C Hanson FirstEnergy Nuclear Operating Company Senior Vice President c/o Davis-Besse NPS Exelon Generation Company, LLC 5501 N. State Route 2 President and Chief Nuclear Officer (CNO)

Oak Harbor, OH 43449-9760 Exelon Nuclear Dresden Nuclear Power Station Diablo Canyon Power Plant. Unit Nos. 1 4300 Winfield Road and 2 Warrenville, IL 60555 Pacific Gas and Electric Company Docket Nos. 50-275 and 50-323 Duane Arnold Energy Center License Nos. DPR-80 and DPR-82 NextEra Energy Duane Arnold, LLC Docket No. 50-331 Mr. James M. Welsch License No. DPR-49 Vice President, Nuclear Generation and Chief Nuclear Officer Mr. Mano Nazar Pacific Gas and Electric Company President and Chief Nuclear Officer P O Box 56, Mail Code 10416 Nuclear Division Avila Beach, CA 93424 NextEra Energy Duane Arnold. LLC Mail Stop: NT3/JW Donald C. Cook Nuclear Plant Units 1 and 15430 Endeavor Drive 2 Jupiter, FL 33478 Indiana Michigan Power Company Docket Nos. 50-315 and 50-316 Edwin I. Hatch Nuclear Plant Units 1 and 2 License Nos. DPR-58 and DPR-74 Southern Nuclear Operating Company. Inc.

Docket Nos. 50-321 and 50-366 Mr. Joel P. Gebbie License Nos. DPR-57 and NPF-5 Senior Vice President and Chief Nuclear Officer Ms Cheryl A Gayheart Indiana Michigan Power Company Regulatory Affairs Director Nuclear Generation Group Southern Nuclear Operating Company, Inc.

One Cook Place 3535 Colonnade Parkway Bridgman, Ml 49106 Birmingham, AL 35243 Fermi Unit 2 DTE Electric Company Docket No. 50-341 License No NPF-43 Mr. Keith J. Polson, Senior Vice President and Chief Nuclear Officer DTE Electric Company 6400 North Dixie Highway Newport, Ml 48166

. 3.

Grand Gulf Nuclear Station, Unit 1 James A. FitzPatrick Nuclear Power Plant Entergy Operations, Inc. Exelon Generation Company, LLC Docket No. 50-416 Docket No. 50-333 License No. NPF-29 License No. DPR-59 Vice President, Operations Mr. Bryan C. Hanson Entergy Operations, Inc. Senior Vice President Grand Gulf Nuclear Station Exelon Generation Company, LLC P.O. Box 756 President and Chief Nuclear Officer Port Gibson, MS 39150 Exelon Nuclear 4300 Winfield Road H. B. Robinson Steam Electric Plant, Unit Warrenville, IL 60555 No.2 Duke Energy Progress, LLC Joseph M. Farley Nuclear Plant, Units 1 Docket No. 50-261 and 2 License No. DPR-23 Southern Nuclear Operating Company. Inc.

Docket Nos. 50-348 and 50-364 Mr. Ernest J. Kapopoulos, Jr. License Nos NPF-2 and NPF-8 Site Vice President H B Robinson Steam Electric Plant Ms. Cheryl A. Gayheart Duke Energy Progress, LLC Regulatory Affairs Director 3581 West Entrance Road, RNPA01 Southern Nuclear Operating Company, Inc.

Hartsville, SC 29550 3535 Colonnade Parkway Birmingham, AL 35243 Hope Creek Generating Station PSEG Nuclear, LLC LaSalle County Station, Units 1 and 2 Docket No. 50-354 Exelon Generation Company. LLC License No. NPF-57 Docket Nos. 50-373 and 50-374 License Nos. NPF-11 and NPF-18 Mr. Peter P. Sena, Ill President and Chief Nuclear Officer Mr. Bryan C. Hanson PSEG Nuclear LLC - N09 Senior Vice President P 0. Box 236 Exelon Generation Company, LLC Hancocks Bridge, NJ 08038 President and Chief Nuclear Officer (CNO)

Exelon Nuclear Indian Point Nuclear Generating Unit Nos. LaSalle County Station 1 2 and 3 4300 Winfield Road Entergy Nuclear Operations, Inc. Warrenville, IL 60555 Docket Nos. 50-247 and 50-286 License Nos. DPR-26 and DPR-64 Limerick Generating Station, Units 1 and 2 Exelon Generation Company, LLC Vice President, Operations Docket Nos. 50-352 and 50-353 Entergy Nuclear Operations. Inc. License Nos. NPF-39 and NPF-85 Indian Point Energy Center 450 Broadway, GSB Mr. Bryan C. Hanson PO Box 249 Senior Vice President Buchanan, NY 10511-0249 Exelon Generation Company, LLC President and Chief Nuclear Officer Exelon Nuclear 4300 Winfield Road Warrenville, IL 60555

McGuire Nuclear Station Units 1 and 2 Nine Mile Point Nuclear Station Units 1 Duke Energy Carolinas, LLC and 2 Docket Nos. 50-369 and 50-370 Nine Mile Point Nuclear Station, LLC License Nos. NPF-9 and NPF-17 Exelon Generation Company, LLC Docket Nos. 50-220 and 50-41 O Mr. Tom Ray License Nos. DPR-63 and NPF-69 Site-Vice President Duke Energy Carolinas, LLC Mr. Bryan C. Hanson McGuire Nuclear Statron Senior Vice President 12700 Hagers Ferry Road Exelon Generation Company, LLC Huntersville, NC 28078-8985 President and Chief Nuclear Officer Exelon Nuclear Millstone Power Station, Units 2 and 3 4300 Winfield Road Dominion Nuclear Connecticut, Inc. Warrenville, IL 60555 Docket Nos. 50-336 and 50-423 License Nos. DPR-65 and NPF-49 North Anna Power Station Units 1 and 2 Virginia Electric and Power Company Mr. Daniel G. Stoddard Docket Nos. 50-338 and 50-339 Senior Vice President & Chief Nuclear License Nos. NPF-4 and NPF-7 Officer Dominion Nuclear Connecticut, Inc. Mr. Daniel G Stoddard Millstone Power Station Senior Vice President and Innsbrook Technical Center Chief Nuclear Officer 5000 Dominion Boulevard Virginia Electric and Power Company Glen Allen, VA 23060 North Anna Power Station Innsbrook Technical Center Monticello Nuclear Generating Plant 5000 Dominion Boulevard Northern States Power Company Glen Allen, VA 23060 Docket No. 50-263 License No. DPR-22 Oconee Nuclear Station, Units 1, 2 and 3 Duke Energy Carolinas, LLC Mr. Christopher R. Church Docket Nos. 50-269, 50-270, and 50-287 Senior Vice President and Chief License Nos. DPR-38, DPR-47, and DPR-Nuclear Officer 55 Northern States Power Company -

Minnesota Mr. J. Ed Burchfield, Jr.

Monticello Nuclear Generating Plant Site Vice President 2807 West County Road 75 Oconee Nuclear Station Monticello, MN 55362 Duke Energy Carolinas, LLC 7800 Rochester Highway Seneca, SC 29672-0752 Palisades Nuclear Plant Entergy Nuclear Operations, Inc.

Docket No. 50-255 License No. DPR-20 Vice President, Operations Entergy Nuclear Operations, Inc.

Palisades Nuclear Plant 27780 Blue Star Memorial Highway Covert, Ml 49043-9530

Palo Verde Nuclear Generating Station. Point Beach Nuclear Plant Units 1 and 2 Units 1 2 and 3 NextEra Energy Point Beach, LLC Arizona Public Service Company Docket Nos. 50-266 and 50-301 Docket Nos. STN 50-528, STN 50-529, License Nos. DPR-24 and DPR-27 and STN 50-530 License Nos. NPF-41, NPF-51, and NPF- Mr_ Mano Nazar 74 President and Chief Nuclear Officer Nuclear Division Mr. Robert S. Bement NextEra Energy Point Beach, LLC Executive Vice President Nuclear/ Mail Stop: NT3/JW Chief Nuclear Officer 15430 Endeavor Drive Arizona Public Service Company Jupiter, FL 33478 Palo Verde Nuclear Generating Station P 0. Box 52034 MS 7602 Prairie Island Nuclear Generating Plant, Phoenix, AZ 85072-2034 Units 1 and 2 Northern States Power Company -

Peach Bottom Atomic Power Station Units Minnesota 2 and 3 Docket Nos. 50-282 and 50-306 Exelon Generation Company, LLC License Nos. DPR-42 and DPR-60 Docket Nos. 50-277 and 50-278 License Nos. DPR-44 and DPR-56 Mr. Scott Sharp Site Vice President Mr. Bryan C. Hanson Northern States Power Company -

Senior Vice President Minnesota Exelon Generation Company, LLC Prairie Island Nuclear Generating Plant President and Chief Nuclear Officer 1717 Wakonade Drive East Exelon Nuclear Welch, MN 55089 4300 Winfield Road Warrenville, IL 60555 Quad Cities Nuclear Power Station. Units 1 and 2 Perry Nuclear Power Plant. Unit 1 Exelon Generation Company, LLC FirstEnergy Nuclear Operating Company Docket Nos. 50-254 and 50-265 Docket No. 50-440 License Nos. DPR-29 and DPR-30 License No. NPF-58 Mr. Bryan C. Hanson Mr. David B. Hamilton Senior Vice President Site Vice President Exelon Generation Company, LLC FirstEnergy Nuclear Operating Company President and Chief Nuclear Officer Perry Nuclear Power Plant Exelon Nuclear P.O. Box 97 Quad Cities Nuclear Power Station Mail Stop A-PY-290 4300 Winfield Road Perry, OH 44081-0097 Warrenville, IL 60555 Pilgrim Nuclear Power Station Docket No. 50-293 License No. DPR-35 Site Vice President Entergy Nuclear Operations, Inc.

Pilgrim Nuclear Power Station 600 Rocky Hill Road Plymouth, MA 02360-5508

R. E. Ginna Nuclear Power Plant Sequoyah Nuclear Plant, Units 1 and 2 R. E. Ginna Nuclear Power Plant, LLC Tennessee Valley Authority Exelon Generation Company, LLC Docket Nos. 50-327 and 50-328 Docket No. 50-244 License Nos. DPR-77 and DPR-79 License No. DPR-18 Mr. Joseph W. Shea Mr. Bryan C. Hanson Vice President, Nuclear Regulatory Affairs Senior Vice President and Support Services Exelon Generation Company, LLC Tennessee Valley Authority President and Chief Nuclear Officer Sequoyah Nuclear Plant Exelon Nuclear 1101 Market Street, LP 4A 4300 Winfield Road Chattanooga, TN 37402-2801 Warrenville, IL 60555 Shearon Harris Nuclear Power Plant, Unit River Bend Station Unit 1 1 Entergy Operations, Inc. Duke Energy Progress, LLC Docket No. 50-458 Docket No. 50-400 License No. NPF-47 License No. NPF-63 Vice President, Operations Ms. Tanya Hamilton, Site Vice President Entergy Operations. Inc. Shearon Harris Nuclear Power Plant River Bend Station 5413 Shearon Harris Rd.

5485 U.S Highway 61 MIC HNP01 St. Francisville, LA 70775 New Hill, NC 27562-0165 Salem Nuclear Generating Station, Units 1 South Texas Project, Units 1 and 2 and 2 STP Nuclear Operating Company PSEG Nuclear, LLC Docket Nos. 50-498 and 50-499 Docket Nos. 50-272 and 50-311 License Nos. NPF-76 and NPF-80 License Nos. DPR-70 and DPR-75 Mr. G. T. Powell Mr. Peter P. Sena, Ill President and CEO President and Chief Nuclear Officer STP Nuclear Operating Company PSEG Nuclear LLC - N09 South Texas Project Salem Nuclear Generating Station PO Box 289 PO Box 236 Wadsworth, TX 77 483 Hancocks Bridge. NJ 08038 St. Lucie Plant Units 1 and 2 Seabrook Station Unit 1 Florida Power and Light Company NextEra Energy Seabrook, LLC Docket Nos. 50-335 and 50-389 Docket No 50-443 License Nos. DPR-67 and NPF-16 License No NPF-86 Mr. Mano Nazar Mr. Mano Nazar President, Nuclear Division President and Chief Nuclear Officer, and Chief Nuclear Officer Nuclear Division Florida Power & Light Company NextEra Energy Seabrook, LLC Mail Stop EX/JB Mail Stop: EX/JB 700 Universe Blvd.

700 Universe Blvd. Juno Beach, FL 33408 Juno Beach, FL 33408

Surry Power Station, Unit Nos. 1 and 2 Turkey Point Nuclear Generating Units 3 Virginia Electric and Power Company and 4 Docket Nos. 50-280 and 50-281 Florida Power and Light Company License Nos. DPR-32 and DPR-37 Docket Nos. 50-250 and 50-251 License Nos. DPR-31 and DPR-41 Mr. Daniel G. Stoddard, Senior Vice President and Chief Nuclear Officer Mr. Mano Nazar Dominion Nuclear President and Chief Nuclear Officer Virginia Electric and Power Company Nuclear Division Surry Power Station Florida Power & Light Company Innsbrook Technical Center Mail Stop EX/JB 5000 Dominion Boulevard 700 Universe Blvd.

Glen Allen, VA 23060-6711 Juno Beach, FL 33408 Susquehanna Steam Electric Station, Units Virgil C. Summer Nuclear Station, Unit 1 1 and 2 South Carolina Electric & Gas Company Susquehanna Nuclear, LLC Docket No. 50-395 Docket Nos. 50-387 and 50-388 License No. NPF-12 License Nos. NPF-14 and NPF-22 Mr. Daniel G. Stoddard Mr. Kevin Cimorelli Senior Vice President and Site Vice President Chief Nuclear Officer Susquehanna Nuclear, LLC Innsbrook Technical Center 769 Salem Boulevard 5000 Dominion Blvd., Floor: IN-2SW NUCSB3 Glen Allen, VA 29060 Berwick, PA 18603-0467 Vogtle Electric Generating Plant, Units 1 Three Mile Island Nuclear Station, Unit 1 and 2 Exelon Generation Company. LLC Southern Nuclear Operating Company, Inc.

Docket No. 50-289 Docket Nos. 50-424 and 50-425 License No. DPR-50 License Nos. NPF-68 and NPF-81 Mr. Bryan C Hanson Ms. Cheryl A. Gayheart Senior Vice President Regulatory Affairs Director Exelon Generation Company, LLC Southern Nuclear Operating Company, Inc.

President and Chief Nuclear Officer 3535 Colonnade Parkway Exelon Nuclear Birmingham, AL 35243 4300 Winfield Road Warrenville, IL 60555 Waterford Steam Electric Station, Unit 3 Entergy Operations, Inc.

Docket No. 50-382 License No. NPF-38 Site Vice President Entergy Operations, Inc.

Waterford Steam Electric Station 17265 River Road Killona, LA 70057-3093

Watts Bar Nuclear Plant, Units 1 and 2 Wolf Creek Generating Station Tennessee Valley Authority Wolf Creek Nuclear Operating Corporation Docket No. 50-390 and 50-391 Docket No. 50-482 License No. NPF-90 and NPF-96 License No NPF-42 Mr. Joseph W. Shea Mr. Adam C. Heflin Vice President, Nuclear Regulatory Affairs President and Chief Executive Officer and Support Services Wolf Creek Nuclear Operating Corporation Tennessee Valley Authority PO Box 411 Watts Bar Nuclear Plant Burlington, KS 66839 1101 Market Street, LP 4A Chattanooga, TN 37402-2801

. ML1914DA307 concurred *via email NRR-106 OFFICE NRR/DLP/PBMB/PM NRR/DLP/PBMB/LA* NRR/DLP/PMBM/BC (A)

NAME MValentin-Olmeda Slent* BTitus*

DATE 5/24/2019 5/2812019 5131/2019 OFFICE OGc* NRR/DLPID NAME BHarris (NLO) LLund DATE 6112/2019 7/3/2019

DISTRIBUTION:

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