Resolution of Generic Safety Issues: Issue 199: Implications of Updated Probabilistic Seismic Hazard Estimates in Central and Eastern U.S. for Existing Plants ( NUREG-0933, Main Report with Supplements 1–35 )

DESCRIPTION

On May 26, 2005, the Office of Nuclear Reactor Regulation (NRR), Division of Engineering, recommended that issues related to closed Generic Issue (GI)-194, "Implications of Updated Probabilistic Seismic Hazard Estimates," dated September 23, 2003, and the impact of higher seismic hazard on current nuclear power plants (NPPs) in the Central and Eastern United States (CEUS) region be examined under the GI identification and resolution process.¹⁹³⁰ On June 9, 2005, the staff initiated GI-199, "Implications of Updated Probabilistic Seismic Hazard Estimates in Central and Eastern United States."¹⁹³¹

On March 12, 2012, the U.S. Nuclear Regulatory Commission (NRC) issued Title 10 of the Code of Federal Regulations (10 CFR) 50.54(f) letters,²⁰⁵⁴ requesting every U.S. nuclear power plant to reevaluate its seismic hazard using present -day information and guidance.

The NRC worked with stakeholders to establish guidance for screening, prioritization, and implementation details (SPID) (Electric Power Research Institute (EPRI) Report 1025287, “Seismic Evaluation Guidance: Screening, Prioritization and Implementation Details (SPID) for the Resolution of Fukushima Near-Term Task Force Recommendation 2.1: Seismic,” issued November 2012,²⁰⁹⁴ and endorsed by the NRC on February 15, 2013.²⁰⁹⁵ The NRC staff issued letters with screening and prioritization results to licensees. In cases where a licensee’s reevaluated hazard exceeds the design basis, more detailed evaluations and actions are required. The NRC issued guidance for the additional seismic evaluations that would be required if the reevaluated hazard exceeds the design basis:

• Expedited approach for seismic reevaluations, EPRI Draft Report 3002000704, "Seismic Evaluation Guidance: Augmented Approach for the Resolution of Fukushima Near- Term Task Force Recommendation 2.1," dated May 7, 2013²⁰⁹⁶
• Seismic margin assessment, JLD-ISG-2012-04, “Guidance on Performing a Seismic Margin Assessment in Response to the March 2012 Request for Information Letter,” dated November 16, 2012
• Seismic probabilistic risk assessment (SPRA).

Safety Significance

Recent data and models indicate that estimates of the potential for earthquake hazards for some NPPs in the CEUS may be larger than previous estimates. While it has been determined that currently operating plants remain safe, the recent seismic data and models warrant further study and analysis. This further analysis will allow the U.S. Nuclear Regulatory Commission (NRC) to better understand the current margins at plants for earthquakes.

Regulatory Guide 1.165, "Identification and Characterization of Seismic Sources and Determination of Safe Shutdown Earthquake Ground Motion,"¹⁹³² developed in the early 1990s, specifies a reference probability for exceedance of a safe-shutdown earthquake (SSE) ground motion (i.e., seismic hazard) at a median annual value of 1E-5. This reference probability value is based on the annual probability of exceeding the SSEs for 29 CEUS nuclear power sites and is used to establish the SSEs for future nuclear facilities. Based on preliminary results from work performed by the United States Geological Survey (USGS) in 2004, it appears that the reference probability for the 29 CEUS sites has increased to about 6 to 7E-5. The increase in the reference probability value is primarily due to recent developments in the modeling of earthquake ground motion in the CEUS. When the staff first identified this issue, no new plants had applied for a construction permit or early site permit (ESP) since 10 CFR Part 100, "Reactor Site Criteria," was revised and Regulatory Guide 1.165 issued in 1997. When the staff began review of the ESP applications, the staff realized the impact of the revised regulation and the regulatory guide as they relate to future plants and operating reactors.

From the staff’s review of the ESP applications with support from the 2004 USGS draft report, it appeared that the perception of seismic hazard for operating plants in the CEUS region had increased. Based on the evaluations of the Individual Plant Examination of External Events (IPEEE) Program, the staff had determined that seismic designs of operating plants in the CEUS provided an adequate level of protection. However, in light of the preliminary results from the USGS work of 2004 and the ESP applications, the staff also recognized that the probability of exceeding the SSE at some of the currently operating sites in the CEUS is higher than previously understood. Therefore, the staff initiated this GI to assess the impact of increased estimates of seismic hazards on selected current NPPs in the CEUS region that might be impacted by the updated seismic research, information, and models.

SCREENING ANALYSIS

In December 2007, the staff completed the screening analysis using guidance contained in Management Directive 6.4, "Generic Issues Program,"¹⁸⁵⁸ and SECY-07-0022, "Status Report on Proposed Improvements to the Generic Issues Program," dated January 30, 2007.¹⁸⁸⁸ The screening panel reviewed the analysis in January 2008. On February 1, 2008, the Director of the Office of Nuclear Regulatory Research (RES) approved the screening panel recommendation¹⁹³³ to begin the safety/risk assessment stage of the generic issue process.

The screening panel’s recommendation was based on the screening analysis, which showed that GI-199 passed the seven GI screening criteria. The discussion under each criterion below provides the screening analysis for GI-199.

• The issue affects public health and safety, the common defense and security, or the environment. The estimated risk to public health and safety and the environment associated with the occurrence of seismic events at some NPP sites might have increased from previous estimates. The issue stems from ongoing research being conducted by a number of scientists into the seismic history of the CEUS and the details of wave propagation and attenuation in this region. In particular, information submitted to the NRC by ESP applicants contained updated seismic information that included new models to estimate earthquake ground motion and updated models for earthquake sources in seismic regions such as eastern Tennessee and around both Charleston, South Carolina, and New Madrid, Missouri. In addition, information summarized by the USGS as part of the National Seismic Hazard Mapping Program indicates that the estimated likelihood of seismic activity (i.e., seismic hazard) in some CEUS locations has increased from previous estimates. Some of these locations are near existing NPP sites. An increase in the seismic hazard at these sites has the potential to adversely impact public health and safety if the estimated increased seismic hazard were to significantly exceed plant design capabilities; substantially reduce perceived safety margins for plant structures, systems, and components (SSCs) important to safety; or appreciably increase the risk associated with the plant’s response to a seismic event. From a qualitative perspective, if the increased hazard is significant at sites that have relatively small safety margins for seismic events, then the estimated risk for these sites could increase.

• The issue applies to two or more facilities and/or licensees/certificate holders or holders of other regulatory approvals. The updated information described above results in increased estimates of the seismic hazard that could occur at multiple, although not all, NPP sites in the CEUS. Specifically, updated models for earthquake sources in seismic regions such as eastern Tennessee and around both Charleston, South Carolina, and New Madrid, Missouri, indicate that the rate of earthquake occurrence in these regions is greater than previously recognized. Because this change applies to several large regions, it has the potential to affect more than one NPP site. Further, new models used to estimate earthquake ground motion have been revised relative to those used in the 1980s. This change also has the potential to affect more than one NPP site. Updated estimates of seismic hazard values at some of the sites could potentially exceed the design basis as well as the review-level earthquake spectrum used as part of the IPEEE Program.

• The issue cannot be readily addressed through other regulatory programs and processes; existing regulations, policies, or guidance; or voluntary industry initiatives. In a memorandum to RES dated May 26, 2005, NRR identified this issue and recommended that it be examined under the Generic Issues Program.¹⁹³⁴ In this memorandum, the staff concluded that the seismic designs of operating plants in the CEUS still provide adequate safety margins while the staff continues to evaluate new seismic hazard data and models and their potential impact on plant risk estimates. At the same time, the staff also recognized that these new seismic data and models could reduce available safety margins due to increased estimates of the probability associated with seismic hazards at some of the currently operating sites in the CEUS. Therefore, to help assess the potential reduction in available safety margins using a probabilistic approach, the NRR staff recommended that the new data and models on CEUS seismic hazards be examined under the Generic Issues Program. Accordingly, at that time, the NRR staff determined that this issue was not sufficiently characterized to be addressed under existing licensing processes for licensees of plants that might be impacted. Based on the limited evaluation of available information, this issue does not appear to be adequately characterized for complete treatment under existing regulatory programs and processes. Additional analysis will help determine whether this issue is amenable to these or other regulatory programs or industry initiatives.

• The issue can be resolved by new or revised regulation, policy, or guidance. Further analysis of the risk or safety impact would provide sufficient additional information to properly characterize the issue and its potential impact on CEUS plants and support consideration under other existing regulatory programs or industry initiatives. The regulatory office has authority to take appropriate regulatory action(s) as necessary to protect the public health and safety and the environment. Depending on the outcome of the additional analysis, as well as industry initiatives to address any safety issues, the regulatory office could address this issue through one or more actions involving regulation, policy, or guidance.

• The issue’s risk or safety significance can be adequately determined (i.e., it does not involve phenomena or other uncertainties that would require long-term studies and/or experimental research to establish the risk or safety significance). The screening analysis was performed based on the staff’s review of updated seismic data and models submitted by ESP applicants and also updated seismic hazard data and models available from the USGS as part of the National Seismic Hazard Mapping Program. The seismic hazard at CEUS plant sites of interest can be evaluated using an approach like the detailed assessment performed by the EPRI¹⁹³⁵ for 28 of the 29 sites included in Regulatory Guide 1.165.¹⁹³² This study used updated attenuation models and incorporated updates to the EPRI seismic source model developed during the preparation of the ESPs. The risk significance of the updated seismic hazard information can be evaluated for CEUS plant sites of interest by performing a comparison of uniform hazard spectra or other hazard results to the beyond-design-basis review-level earthquake or hazard curve used as part of the IPEEE evaluation.¹⁷⁹⁸ The available IPEEE Program results would allow a general assessment of the potential safety impact of increases in seismic hazard at specific sites. This analysis was performed later as part of the safety/risk assessment under the Generic Issues Program.

• The issue is well defined, discrete, and technical. The seismic hazard will be adequately defined upon detailed assessment of available updated seismic data and models submitted by ESP applicants and also updated seismic hazard data and models available for other CEUS plant sites of interest using an approach like that performed by EPRI for 28 of the 29 sites included in Regulatory Guide 1.165. This will allow the seismic hazard estimates for CEUS plant sites of interest to reflect the state of current knowledge. As new information and research becomes available, future updates might be warranted. The plants’ response to seismic hazards involves technical analyses using established techniques.

• Resolution of the issue may potentially involve review, analysis, or action by the affected licensees, certificate holders, or holders of other regulatory approvals. After further characterization of site-specific seismic hazards and an analysis of the plant’s response to the increased seismic hazard, some plants may be identified as having a vulnerability that must be addressed to maintain adequate safety margins. Determining a plant’s margin and potential need for action to maintain an adequate margin could involve regulatory actions (e.g., requests for information from plant licensees, reviews, additional analysis, mitigation actions, physical enhancements, administrative controls) for some plant licensees or could involve actions by industry stakeholders. The screening analysis showed that the estimated increase in spectral acceleration for some existing CEUS plant sites might exceed the design basis and values used for the NRC’s review of IPEEE submittals. This translates into an equivalent increase in seismic demand on plant SSCs. As a result, this issue has the potential to result in increased seismic core damage frequency (SCDF) estimates for some plants. However, the screening analysis provided a limited evaluation that did not assess the safety response of the plants. The limited scope screening analysis concluded that the seismic designs of operating plants in the CEUS provided adequate safety margins while the staff continued to evaluate new seismic hazard data and models and their potential impact on plant risk estimates. Specific reasons for this conclusion included the following:

• The estimated annual probability of exceedance of seismic hazard is small in an absolute sense.
• Earthquakes cause ground motion over a range of frequencies. Lower frequency motions are more damaging to buildings and equipment than higher frequency motions. Based on the NRC staff’s reviews associated with ESPs, the staff was confident that the recent seismic data and models would show that increased estimates of the seismic hazards would occur primarily in the higher ground motion frequencies. Accordingly, the staff anticipated that these increased estimates of seismic hazards would primarily have little impact on previous estimates of the potential damage to buildings and equipment.
• The plants are designed to withstand anticipated earthquakes with substantial design margins. Plants may have seismic margins beyond those reflected in their IPEEE submittals, and these could compensate for the increase in estimated seismic load. Such additional seismic margins at plants may be inherent in the design and construction, realized from improved data and analysis methods, or result from plant modifications or enhancements completed since the IPEEE submittals.

Based on the knowledge of this issue at the time of the screening analysis and its potential effect on CEUS plants, this issued passed the seven GI screening criteria and, therefore, warranted further analysis under the Generic Issues Program.

Safety/Risk Assessment

RES staff developed and implemented a methodology to determine the implications of updated probabilistic seismic hazard estimates in the CEUS on existing plants. The methodology, analyses, results, and limitations of the safety risk assessment are summarized below. A detailed discussion of the safety/risk assessment is documented in the NRC’s "Safety/Risk Assessment Results for Generic Issue 199, Implications of Updated Probabilistic Seismic Hazard Estimates in Central and Eastern United States on Existing Plant: Safety/Risk Assessments," dated August 2010. ¹⁹⁷⁴

Risk Methodology

SCDF was chosen as the appropriate risk metric because it is expected to be more sensitive than other metrics (either large early release fraction or public dose) to changes in the seismic hazard. In addition, SCDF can be estimated using IPEEE information. Conversely, the IPEEE Program did not produce sufficient quantitative information to estimate alternate risk metrics.

The staff performed a two-stage assessment to determine the implications of updated probabilistic seismic hazards in the CEUS on existing NPPs. The first stage involved evaluating the change in seismic hazard with respect to previous estimates at individual plants. The second stage estimated the change in SCDF as a result of the change in the seismic hazard for each operating plant in the CEUS. The seismic hazard at each NPP site depends on the unique seismology and geology surrounding the site, which necessitated separately determining the implications of updated probabilistic seismic hazard for each of the 96 operating NPPs in the CEUS.

Evaluation of Changes in Seismic Hazard Estimates

In the first stage of the assessment, the NRC staff evaluated the potential significance of changes in seismic hazards in a stepwise fashion by assessing the degree to which the seismic hazard estimates developed using the most recent seismic hazard information and NRC staff guidance deviate from previously developed assessments. The comparison of results indicated an increase in the seismic hazard estimates relative to previous assessments for a number of plants.

Evaluation of Changes in Seismic Core Damage Frequency

In the second stage, the NRC staff developed SCDF estimates using three sets of mean seismic hazard curves (the 1989 EPRI study, the 1994 Lawrence Livermore National Laboratory study, and a 2008 USGS study) and plant-level fragility curves developed from information provided in the IPEEE submittals. This method had previously been used by the staff in the resolution of GI-194 and during reviews of various risk-informed license amendments.¹⁹⁷⁵ The changes in the NRC’s SCDF for a number of plants lie in the range of 10^-4 per year to 10^-5 per year, which meets the numerical risk criteria for an issue to proceed to the regulatory assessment phase of the Generic Issues Program.

Overall seismic risk estimates remain small in an absolute sense. All operating plants in the CEUS have a SCDF less than or equal to 10^-4/year, confirming that there is no immediate concern for adequate protection.

The approach used to estimate SCDF in the safety/risk assessment does not provide insight into which SSCs are important to seismic risk. Such knowledge provides the basis for postulating plant backfits and conducting a value/impact analysis of potential backfits during a regulatory analysis. For a number of plants, especially those that performed reduced-scope seismic margin analysis, detailed information is presently not available to the NRC regarding plant seismic capacity (the ability of a plant’s SSCs to successfully withstand an earthquake) beyond the required design-basis level.

Safety/Risk Assessment Panel Observations

In accordance with Management Directive 6.4, a safety/risk assessment panel was established to determine, on a generic basis, if the risk associated with GI-199 warranted further investigation for potential imposition as a cost-justified backfit and to provide a recommendation for the next step.

The panel completed its independent review of the safety/risk assessment for GI-199 in September 2010.¹⁹⁷⁶ The panel reached the following conclusions and observations:

• Overall seismic core damage risk estimates are consistent with the Commission’s safety goal policy statement because they are within the subsidiary objective of 10^-4/year for core damage frequency. The GI-199 safety/risk assessment, based in part on information from the NRC’s IPEEE Program, indicates that no concern exists about adequate protection and that the seismic design of operating reactors provides a safety margin to withstand potential earthquakes exceeding the original design basis.
• The changes in SCDF estimated in the safety/risk assessment stage of GI-199 for numerous plants lie in the range of 10^-4/year to 10^-5/year, which meet the numerical risk criteria for an issue to proceed to the regulatory assessment stage of the generic issues program.
• New consensus seismic-hazard estimates will become available in 2011 (these are a product of a joint NRC, U.S. Department of Energy, USGS, and EPRI project). These consensus seismic hazard estimates will supersede the existing EPRI, Lawrence Livermore National Laboratory, and USGS hazard estimates used in the GI-199 safety/risk assessment.
• Certain factors that affect the development of realistic SCDF estimates will remain unresolved even after the new consensus seismic hazard estimates are developed. The issue is primarily that many IPEEEs did not produce SCDF estimates and so lack some of the information needed to produce such estimates.
  • For a number of the plants that performed reduced-scope seismic margin analyses as part of the IPEEE Program, limited detailed information exists about plant seismic capacity (the ability of a plant’s SSCs to successfully withstand an earthquake) beyond the required design-basis level.
  • The approach used in the safety/risk assessment to estimate SCDF considered the plant-level seismic capacity and, therefore, did not provide insight into which SSCs were important to seismic risk. Such knowledge would be required in order to postulate potential cost-beneficial backfits.
• IPEEE submittals generally provided limited, qualitative information about the seismic capability of containments. Any regulatory analysis of GI-199 should consider potential plant modifications for reducing the probability of seismically induced containment failure as discussed in Section 3.3.1 of NUREG/BR-0058, "Regulatory Analysis Guidelines of the U.S. Nuclear Regulatory Commission," Revision 4, issued September 2004. ¹⁹⁷⁷

Safety/Risk Assessment Panel Conclusion

The panel recommended transferring the lead responsibility for subsequent GI-199 actions to NRR for regulatory office implementation and taking further actions to address GI-199 outside the Generic Issues Program (i.e., obtain information and develop methods, as needed, to complete plant-specific value/impact analyses of potential backfits to reduce seismic risk).

On September 2, 2010, the safety/risk assessment panel issued its report. ²⁰⁵⁵ The panel recommended that responsibility for subsequent actions on GI-199 be transferred to NRR for regulatory office implementation. The panel also recommended further actions be taken to address GI-199 (i.e., obtain information and develop methods, as needed, to complete plant specific value impact analyses of potential backfits to reduce seismic risk). The issue was transferred to NRR, and work associated with GI 199 was incorporated into the work being done by the Japan Lessons Learned Division (JLD) in response to the March 2011, nuclear event at Fukushima Dai-ichi, Japan.

Significant Activities and Milestones during Regulatory Implementation Stage

The NRC asked U.S. nuclear power plant licensees to develop a new ground motion response spectrum, or "hazard curve," using present-day guidance and methods. Plants were to compare the new hazard curve to their SSE. If the new hazard exceeds the SSE, additional actions were required. These actions could include an expedited seismic evaluation process to determine whether interim actions were needed until a more detailed assessment could be completed, high- or low-frequency motion evaluations, spent fuel pool seismic evaluations, or a detailed seismic probabilistic risk assessment (or a combination of these). The spent fuel pool and high- or low-frequency evaluations cover limited areas of a plant. Plants will perform expedited approach evaluations to determine if key plant safety systems require enhancements while the more detailed risk evaluation is done.

The NRC staff used these comparisons in a graded, risk-informed approach to determine the scope of, and prioritization of, any required plant-specific evaluations. The NRC expects U.S. plants to propose any needed corrective actions (and plans to implement them) identified by the detailed seismic risk evaluations. The NRC staff will evaluate the detailed evaluations and determine the need for further regulatory actions. The expedited seismic evaluation process (ESEP) determines if key plant safety systems require enhancements while the more detailed seismic evaluations are completed.  The spent fuel pool and high or low frequency evaluations cover limited seismic exceedances.

Generic Communications Issued

The NRR staff issued two Information Notices (INs) to inform stakeholders of the results of the GI 199 safety/risk assessment report:

• IN 2010-18, “Generic Issue 199, ‘Implications of Updated Probabilistic Seismic Hazard Estimates in Central and Eastern United States on Existing Plants,’”¹⁹⁷⁸ dated September 2, 2010, for all nuclear power plants.
• IN 2010-19, “Updated Probabilistic Seismic Hazard Estimates in Central and Eastern United States,”¹⁹⁷⁹ dated September 16, 2010, for fuel cycle facilities.

The NRC also issued a Generic Letter, "Seismic Risk Evaluation for Operating Reactors," dated September 15, 2011²⁰³², for public comments. The public comment period ended on December 15, 2011.

• The NRC determined the priority for nuclear power plants to complete the risk assessments based on the following three factors:

The NRC also sent request for information under 10 CFR 50.54(f)²⁰⁵⁴ to all licensees to respond to Recommendations 2.1 and 2.3 of the Fukushima Near-Term Task Force (NTTF).

• The NRC requested that all operating power reactor licensees reevaluate the seismic hazard at their sites using present-day NRC requirements and guidance and identify actions that are planned to address plant specific vulnerabilities associated with the reevaluated seismic hazard. Each licensee followed a similar two phase process to respond to the hazard reevaluations requested by the 50.54(f) letter. In Phase 1, licensees submitted hazard reevaluation reports using NRC endorsed, industry developed guidance. The guidance specified that a licensee should determine if interim protection measures were needed while a longer term evaluation of the impacts of the hazard was completed. The NRC staff reviewed the reevaluated hazard information. Using the reevaluated hazard information and a graded approach, the NRC identified the need for, and prioritization and scope of, plant specific assessments.
• For those plants that are required to perform a SPRA, the staff issued Phase 2 Decisionmaking for Reevaluated Flooding and Seismic Hazards, dated September 16, 2016²²⁴³ which helped licensees determine if additional plant-specific regulatory actions were necessary

1. The extent to which the reevaluated hazard exceeds the current design basis
2. The absolute seismic hazard based on an examination of the probabilistic seismic hazard curves for the site
3. Previous estimates of plant capacity (e.g., IPEEE insights). Licensee Responses and Actions

Licensees for plants in the CEUS submitted their seismic hazard reevaluations before the end of March 2014, and plants in the western United States (WUS) submitted their seismic hazard reevaluations before the end of March 2015. Depending on the comparison between the reevaluated seismic hazard and the design basis, some licensees had no further evaluations for the plant (screened out), while other licensees were required to perform additional plant risk assessments if the reevaluated hazard exceeded the plant’s design basis (screened in).

For those plants that screened in,

• If the reevaluated hazard show that the ground motion response spectrum exceeds the plant's design-basis safe shutdown earthquake (SSE) only in the region above 10 hertz (Hz), then the license needed to assess the potential impact of high frequency ground motion on plant equipment.
• If the reevaluated hazard exceeded the design basis in the region below 2.5 Hz, then the licensee had to perform a low frequency limited scope evaluation.
• If the reevaluated hazard exceeded the design basis in the 1-10 Hz range, then the licensee had to perform a low hazard spent fuel pool evaluation.
• If the reevaluated hazard exceeded a peak spectral acceleration of 0.8g, a high hazard spent fuel evaluation was required. NRC Staff Reviews

  The NRC staff finished reviewing the hazard reports and issued a final determination letter for seismic risk evaluations on October 27, 2015.²²⁴⁵ The final determination letter updated the preliminary screening letters that the NRC issued on May 9, 2014²²⁴⁶ and October 3, 2014, ²²⁴⁷ for CEUS plants, and May 13, 2015, for WUS plants.²²⁴⁸ The final determination letter included a staggered schedule for licensees to submit their seismic risk evaluations to the NRC for those sites that screen in, with the earliest in March 2017 and the latest in December 2019. All actions associated with low- and high-frequency spent fuel pool seismic evaluations and with low- and high-frequency plant seismic evaluation have been completed.

• Of the original 61 sites (58 CEUS and 3 WUS). 20 operating reactor sites (16 CEUS and 2 WUS) screened in, requiring licensees to complete a SPRA; and two CEUS sites were subsequently screened out, based on additional information provided by the licensee, dated December 22, 2016.²⁰⁵⁷
• Thirty-four sites screened in to perform high frequency limited scope evaluations.
• One site screened in to perform a low frequency limited scope evaluation.
• Thirty sites screened in to perform low hazard spent fuel pool evaluations and eight sites screened in to perform high hazard limited scope evaluations.

 While the additional plant-specific assessments were ongoing, the NRC also required 34 sites (33 CEUS and 1 WUS) to complete near-term ESEP reports of key equipment needed to protect the reactor core following a beyond-design-basis seismic event. The staff received all ESEP reports for CEUS plants by December 2014 and received the ESEP report for the one WUS plant during the second quarter of 2016. The staff completed its evaluation of all 33 CEUS ESEP reports during the second quarter of 2016 and of the one WUS site in May 2016. In some cases, the NRC required plant modifications as a result of the ESEP reviews. Licensees notified the NRC that the 15 plants requiring modifications have completed that task. Plant upgrades not requiring an outage were completed by December 2016 for CEUS plants and by June 2018 for WUS plants.

On March 1, 2017, the NRC staff completed a 2-day SPRA orientation session. Approximately 30 NRC staff and contractors from Pacific Northwest National Laboratory and the Southwest Research Institute's Center for Nuclear Waste Regulatory Analyses attended the session. After this orientation session, the infrastructure necessary to review the SPRA submittals was in place. The NRC required 18 sites to submit SPRAs.

Summary of Required Reviews and Actions:

1. All actions associated with low- and high-frequency spent fuel pool seismic evaluations and with low- and high-frequency plant seismic evaluation were complete.
2. All actions associated with ESEP reports have been closed out.
3. All licensees have submitted their SPRAs to the NRC for review. The staff has reviewed and concluded that the nuclear sites have implemented the NRC mandated safety enhancements resulting from the lessons learned from the Fukushima Dai-ichi accident through its implementation of Orders EA-12-049, EA-12-051, EA-13-109, (as applicable) and its response to the 50.54(f) letters. Therefore, the NRC has issued a close out letter for each site, stating that no further regulatory decision making is required related to the Fukushima lessons-learned activities.

• Arkansas Nuclear One (ANO)²⁰⁵⁸
• Braidwood Station²⁰⁵⁹
• Browns Ferry²²⁵⁹
• Bryon Station²⁰⁶⁰
• Calvert Cliffs²⁰⁶¹
• Callaway ²²⁵⁸
• Clinton Power²⁰⁶²
• Columbia²²⁵⁷
• Comanche Peak²⁰⁶³
• Cook ²²⁵⁵
• Dresden²²⁵⁶
• Joseph M. Farley ²⁰⁶⁴
• McGuire ²⁰⁶⁶
• North Anna²²⁵⁴
• Oconee²²⁵³
• Palo Verde²⁰⁶⁷
• Peach Bottom
• Point Beach²⁰⁶⁸
• Prairie Island²⁰⁶⁹
• R. E. Ginna²⁰⁷⁰
• River Bend²⁰⁷¹
• Robinson²²⁵¹
• Salem Nuclear²⁰⁷²
• Sequoyah²²⁵⁰
• Shearon Harris²⁰⁷³
• St. Lucie Plant²⁰⁷⁴
• South Texas Project (STP)²⁰⁷⁵
• Summer²²⁴⁹
• Three Mile Island (TMI)²⁰⁷⁶
• Vogtle Electric²⁰⁷⁷
• Waterford²⁰⁷⁸

4. The following plants deferred submitting SPRA pending permanent shutdown:

• Pilgrim (deferral due to early permanent shutdown)
• Indian Point (deferral due to early permanent shutdown)

• Palisades (deferral due to early permanent shutdown)

NRR is developing a NUREG for capturing knowledge lessons-learned from activities associated with the events at Fukushima Dai-ichi.

The NRC also has established the Japan Lessons Learned page  on the NRC public Web site, found at https://www.nrc.gov/reactors/operating/ops-experience/japan-dashboard.html. The Web site contains links providing the status of post-Fukushima order implementation; flooding and seismic hazard reevaluations; and Tier 2, Tier 3, and nontiered activities.

The Plant-Specific Japan Lessons-Learned Activities Web page, found at https://www.nrc.gov/reactors/operating/ops-experience/japan-dashboard/japan-plants.html, lists operating nuclear power reactors and links to plant-specific actions related to the nuclear accident at Fukushima Dai-ichi.

ADDITIONAL REFERENCES:

1. Management Directive 6.4, "Generic Issues Program," U.S. Nuclear Regulatory Commission, January 2, 2015.²⁰⁸¹
2. SECY-07-0022, "Status Report on Proposed Improvements to the Generic Issues Program," U.S. Nuclear Regulatory Commission, January 30, 2007.²⁰⁸²
3. Memorandum for F. Eltawila from M. Mayfield, "Identification of a Generic Seismic Issue," May 26, 2005.²⁰⁸³
4. Memorandum for M. Mayfield from F. Eltawila, "Generic Issue 199, ‘Implications of Updated Probabilistic Seismic Hazard Estimates in Central and Eastern United States,’" June 9, 2005.²⁰⁸⁴
5. Regulatory Guide 1.165, "Identification and Characterization of Seismic Sources and Determination of Safe Shutdown Earthquake Ground Motion," March 1997.²⁰⁸⁵
6. Memorandum for B. Sheron from P. Hiland, "Results of Initial Screening of Generic Issue 199, ‘Implications of Updated Probabilistic Seismic Hazard Estimates in Central and Eastern United States on Existing Plants,’" February 1, 2008, ADAMS Accession No.: ML073400477 (not in pubic ADAMS)
7. Memorandum for F. Eltawila from M. Mayfield, "Identification of a Generic Seismic Issue," May 26, 2005.²⁰⁸⁶
8. EPRI Report Nos.1012044 and 1012045, "Program on Technology Innovation: Assessment of a Performance-Based Approach for Determining Seismic Ground Motions for New Plant Sites," Vol. 1 and 2, Electric Power Research Institute, 2005
9. Generic Issue 199, "Implications of Updated Probabilistic Seismic Hazard Estimates in Central and Eastern United States on Existing Plants: Safety/Risk Assessments," U.S. Nuclear Regulatory Commission, August 2010.²⁰⁸⁷
10. Kennedy, R.P., "Overview of Methods for Seismic PRA and Margins Including Recent Innovations," Proceedings of the Organization for the Economic Cooperation and Development/Nuclear Energy Agency Workshop on Seismic Risk, August 10–12, 1997, Tokyo, Japan.²⁰⁸⁸
11. Memorandum for B. Sheron from P. Hiland, ""Safety/Risk Assessment Results for Generic Issue 199, ‘Implications of Updated Probabilistic Seismic Hazard Estimates in Central and Eastern United States on Existing Plants,’" U.S. Nuclear Regulatory Commission," September 2, 2010. ²⁰⁸⁹
12. NUREG/BR-0058, "Regulatory Analysis Guidelines of the U.S. Nuclear Regulatory Commission," U.S. NRC, Revision 4, September 2004. ²⁰⁹⁰
13. Information Notice 2010-18, "Generic Issue 199, ‘Implications of Updated Probabilistic Seismic Hazard Estimates in Central and Eastern United States on Existing Plants,’" U.S. Nuclear Regulatory Commission, September 2, 2010. ²⁰⁹¹
14. Information Notice 2010-19, "Updated Probabilistic Seismic Hazard Estimates in Central and Eastern United States," U.S. NRC, September 16, 2010. ²⁰⁹²
15. Request for Information pursuant to Title 10 of the Code of Federal Regulations 50.54(f) Regarding Recommendations 2.1, 2.3, and 9.3, of the Near-Term Task Force Review of Insights from the Fukushima Dai-Ichi Accident, March 12, 2012, ADAMS Accession No. ML12056A046 (not in public adams)
16. JLD-ISG-2012-04, "Guidance on Performing a Seismic Margin Assessment in Response to the March 2012 Request for Information Letter," November 16, 2012. ²⁰⁹³
17. EPRI Report, "Seismic Evaluation Guidance, Screening, Prioritization and Implementation Details (SPID) for the Resolution of Fukushima Near-Term Task Force Recommendation 2.1: Seismic," November 2012, https://www.epri.com/research/products/000000000001025287.²⁰⁹⁴
18. NRC Endorsement of Electric Power Research Institute EPRI Report 1025287, "Screening, Prioritization and Implementation Details (SPID) for the Resolution of Fukushima Near-Term Task Force Recommendation 2.1: Seismic," November 2012.^{2244 2095}
19. EPRI Final Draft Report, "Seismic Evaluation Guidance: Augmented Approach for the Resolution of Fukushima Near Term Task Force Recommendation 2.1: Seismic," May 13, 2013. https://www.epri.com/research/products/000000003002000704. ²⁰⁹⁶
20. Letter to Enclosed List from E. Leeds, "Supplemental Information related to request for Information Pursuant to Title 10 of the Code of Federal Regulations 50.54(f) regarding Seismic Hazard Reevaluations for Recommendation 2.1 of the Near Term Task Force Review of Insights from the Fukushima Dai-ichi Accident," February 20,2014, ADAMS Accession No. ML14030A0462197
21. Nuclear Energy Institute - Seismic Risk Evaluations for Plants in the Central and Eastern United States, March 25, 2014, ADAMS Accession No. ML14083A596 (not in public ADAMS)²¹⁹⁸
22. Letter for those on Enclosed List from E. Leeds, "Screening and Prioritization Results Regarding Information Pursuant to Title 10 of the Code of Federal Regulations 50.54(f) Regarding Seismic Hazard Re-Evaluations for Recommendation 2.1 of the Near Term Task Force Review of Insights from the Fukushima Dai-ichi Accident," May 9, 2014, ADAMS Accession No. ML14111A147²¹⁹⁹
23. Probabilistic Seismic Hazard Analysis (PSHA): Background Information, May 20, 2014, ADAMS Accession No. ML14140A648²²⁰⁰
24. NRC Memorandum for D. Skeen from S. Flanders, "Support Document for Screening and Prioritization Results Regarding Seismic Hazard Re-Evaluations for Operating Reactors in the Central and Eastern United States," May 21, 2014, ADAMS Accession No. ML14136A126.²²⁰¹
25. NRC letter, "Supplemental Information Related to Development of Seismic Risk evaluations Regarding the Request for Information Issued Pursuant to Title 10 of the Code of Federal Regulations 50.54(f) Relating to Seismic Hazard Reevaluations for Recommendation 2.1 of the Near-term Task Force Review of Insights from the Fukushima Dai-ichi Accident'" December 10, 2014, ADAMS Accession No. ML14307B707²²¹⁰
26. Letter from W. Dean to Enclosed List, "Screening and Prioritization Results for the Western United States Sites Regarding Information Pursuant to Title 10 of the Code of Federal Regulations 50.54(f) Regarding Seismic Hazard Re-Evaluations for Recommendation 2.1 of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident," December 15, 2014, ADAMS Accession No. ML14310A033²²⁰²
27. NRC letter regarding Seismic Screening and Prioritization Results for WUS Licensees, "Screening and Prioritization Results for the Western United States Sites Regarding Information Pursuant to title 10 of The Code of Federal Regulations 50.54(f) Regarding Seismic Hazard Re-evaluations for Recommendation 2.1 of the Near Term Task Force Review of Insights from the Fukushima Dai-ichi Accident," May 13, 2015, ADAMS Accession No. ML15113B344²²⁰³
28. Nuclear Energy Institute, "Request for NRC Endorsement of High Frequency Program: Application Guidance for Functional Confirmation and Fragility Evaluation (EPRI 3002004396)," July 30, 2015, ADAMS Accession No. ML15223A095²²⁰⁴
29. Letter for A. Mauer, Nuclear Energy Institute, from J. Davis, "Endorsement of Electric Power Research Institute Final Draft Report 3002004396, "High Frequency Program: Application Guidance for Functional Confirmation and Fragility," September 17, 2015, ADAMS Accession No. ML15218A569²²⁰⁵
30. Letter from W. Dean to Enclosed List, "Final Determination of Licensee Seismic Probabilistic Risk Assessments under the Request for Information Pursuant to Title 10 of the Code of Federal Regulations 50.54(f) Regarding Recommendation 2.1 "Seismic" of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi" Accident," October 27, 2015, ADAMS Accession No. ML15194A015²²⁰⁶
31. Letter from S. Wyman to Enclosed List, "Staff Review of High Frequency Confirmation Associated with Reevaluation Seismic Hazard in Response to March 12, 2012 50.54(f) Request for Information," February 18, 2016, ADAMS Accession No. ML15364A544²²⁰⁷
32. Nuclear Energy Institute, "Request for Endorsement of Seismic Evaluation Guidance: Spent Fuel Pool Integrity Evaluation (EPRI 3002007148)," February 23, 2016, ADAMS Accession No. ML16055A017²²⁰⁸
33. Letter to J. Pollock, Nuclear Energy Institute, from J. Davis, NRC, "Endorsement of Electric Power Research Power Research Institute Report 3002007148, “Seismic Evaluation: Spent Fuel Pool Integrity Evaluation,” March 17, 2016, ADAMS Accession No. ML15350A158²²⁰⁹

REFERENCES

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