ML20290A626
| ML20290A626 | |
| Person / Time | |
|---|---|
| Issue date: | 10/30/2020 |
| From: | Ho Nieh Office of Nuclear Reactor Regulation |
| To: | Raymond Furstenau Office of Nuclear Regulatory Research |
| Bernardo B | |
| References | |
| Download: ML20290A626 (10) | |
Text
November 30, 2020 MEMORANDUM TO:
Raymond V. Furstenau, Director Office of Nuclear Regulatory Research FROM:
Ho K. Nieh, Director Office of Nuclear Reactor Regulation
SUBJECT:
CLOSURE RECOMMENDATION FOR GENERIC ISSUE 199, IMPLICATIONS OF UPDATED PROBABILISTIC SEISMIC HAZARD ESTIMATES IN CENTRAL AND EASTERN UNITED STATES ON EXISTING PLANTS The Office of Nuclear Reactor Regulation (NRR) recommends closure of Generic Issue 199 (GI-199), Implications of Updated Probabilistic Seismic Hazard Estimates in Central and Eastern United States on Existing Plants. This recommendation is based on the completion of the risk-informed reevaluation of the seismic hazards for operating power reactor plants in response to the lessons-learned from the reactor accident at the Fukushima Dai-ichi site. In addition, staff from the Office of Nuclear Material Safety and Safeguards (NMSS) and NRR completed an analysis of the applicability of these lessons-learned to facilities other than operating power reactors. The associated facilities included decommissioning reactors with spent fuel stored in spent fuel pools (SFP), and Independent Spent Fuel Storage Installations (ISFSIs). This recommendation is aligned with the U.S. Nuclear Regulatory Commissions (NRCs) Principles of Good Regulation, particularly the principles of Openness, Efficiency, Clarity, and Reliability. The associated activities have resulted in voluntary safety enhancements which improved many sites capabilities to protect and mitigate the impacts of the reevaluated seismic hazards. Moreover, the associated activities have greatly increased the NRCs level of knowledge and risk insights in the area concerning present-day seismic hazards.
As such, any additional use of NRC resources on GI-199 would only provide marginal benefits to safety.
In addition to the hazard reevaluation work completed as noted above, the NRC has implemented a process for the ongoing assessment of natural hazards information (POANHI).
The process enhancements are described in SECY-16-0144, dated December 29, 2016 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML16286A586). Guidance in NRR Office Instruction LIC-208, Process for the Ongoing Assessment of Natural Hazards Information, institutionalizes a defined structure and procedures to implement this process. Using the enhanced process, the staff can proactively seek out new hazard information and assess its potential impacts on site safety by comparing updated information to existing hazard evaluations for the fleet or individual plants, as appropriate.
CONTACT: Robert J. Bernardo, NRR/DORL 301-415-2621 Ho K. Nieh Digitally signed by Ho K.
Nieh Date: 2020.11.30 12:32:14 -05'00'
The enclosure provides a reference to the ADAMS accession numbers for the applicable staff assessments completed by the NRC staff in response to the licensees seismic hazard reevaluation activities.
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Background===
This generic issue was opened to evaluate the potential safety implications from earthquakes.
Newer data and models indicated that estimates of the potential for earthquake hazards for some nuclear power plants in the Central and Eastern United States (CEUS) could be larger than previous estimates. The newer seismic data and models warranted further study and analysis. The analysis allows the NRC to better understand margins at operating plants for earthquakes.
The issue was officially declared as GI-199 in June 2005. In accordance with Management Directive (MD) 6.4, Generic Issues Program, the NRC staff completed the safety/risk assessment on September 2, 2010 (ADAMS Package Accession No. ML100270582). The safety/risk assessment did not identify any concerns regarding adequate protection. The assessment also noted that the seismic design of operating reactors provides margin to withstand potential earthquakes exceeding the original design basis.
The safety/risk assessment panel recommended that lead responsibility for subsequent GI-199 actions be transferred to NRR for regulatory office implementation and that 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 NRR staff issued two information notices (IN) to inform stakeholders of the GI-199 safety/risk assessment report and results. On September 2, 2010, the NRC issued IN 2010-18, Generic Issue 199, Implications of Updated Probabilistic Seismic Hazard Estimates in Central and Eastern United States on Existing Plants (ADAMS Accession No. ML101970221) to operating nuclear power plants and ISFSIs. On September 16, 2010, the NRC issued IN 2010-19, Updated Probabilistic Seismic Hazard Estimates in Central and Eastern United States (ADAMS Accession No. ML102160735) to fuel cycle facilities.
On March 11, 2011, the Great East Japan Earthquake occurred off the coast of Japan. The earthquake and subsequent tsunami caused wide-spread devastation across northeastern Japan. The tsunami inundated the Fukushima Dai-ichi Nuclear Power Plant, resulting in extensive damage and a complete loss of all alternating current power. In response to the accident, the NRC established a Near-Term Task Force (NTTF) to conduct a systematic and methodical review of NRC processes and regulations to determine if the NRC should make additional improvements to its regulatory system. The NTTF provided a set of 12 recommendations1 to the Commission for its consideration. The NRC incorporated GI-199 into the work being done by the staff in response to the Fukushima Dai-ichi accident and the NTTF recommendations.
Specifically, the NTTFs work incorporated several insights from the GI-199 safety/risk assessment, which contributed to the NTTFs recommendations regarding seismic reevaluations. The NRC response to these recommendations addressed seismic issues broadly. As a result (and consistent with MD 6.4), it was determined that GI-199 would be addressed by the NRCs response to the NTTFs recommendations. The NTTF seismic 1 See Near-Term Task Force (NTTF) Review of Insights from the Fukushima Dai-ichi Accident (ADAMS Accession No. ML111861807).
recommendations expand the scope of the seismic activities to include operating power reactor sites in the Western United States.
The NTTF recommendations were applicable to operating power reactor sites. However, tasking Memorandum COMGBJ-11-0002 (ADAMS Accession No. ML110820875) also directed the staff to assess the applicability of the lessons-learned from the accident to non-operating reactors, non-power reactors, and non-reactor facilities. Staff actions in response to this tasking memorandum addressed seismic issues broadly for non-operating reactors and non-reactor facilities. The staffs assessment can be found in Enclosure 1 of SECY-15-0081, Staff Evaluation of Applicability of Lessons Learned from the Fukushima Dai-Ichi Accident to Facilities Other Than Operating Power Reactors (ADAMS Accession No. ML15050A066).
Additional details are described below.
With the completion of these actions, the full scope of GI-199 has been addressed by the NRCs actions in response to the accident at Fukushima Dai-ichi.
NRCs Response to Recommendation 2.1, Seismic of the NTTF Report 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 10 of the Code of Federal Regulations (10 CFR),
Section 50.54(f) (hereafter referred to as the 50.54(f) letter). Enclosure 1 to the 50.54(f) 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.
A two-phase process was developed to respond to the seismic hazard reevaluations requested by the 50.54(f) letter. In Phase 1 (the information gathering phase), licensees were requested to complete a reevaluation of the seismic hazard that could affect their sites using updated seismic hazard information and present-day regulatory guidance and methodologies to develop a ground motion response spectrum (GMRS). Licensees were then asked to compare the new GMRS to the safe shutdown earthquake (SSE) ground motion and then report to the NRC in a seismic hazard screening report (SHSR). To provide a uniform and acceptable industry response, the Electric Power Research Institute (EPRI) developed a technical report, EPRI 1025287, Screening, Prioritization and Implementation Details (SPID) for the Resolution of Fukushima Near-Term Task Force Recommendation 2.1: Seismic (ADAMS Accession No. ML12333A170). The NRC endorsed the SPID guidance in a letter dated February 15, 2013 (ADAMS Accession No. ML12319A074).
If the new GMRS was not bound by the SSE, Enclosure 1 of the 50.54(f) letter requested more detailed evaluations of the impact from the hazard. Those licensees were asked to evaluate whether interim protection measures were needed while the more detailed evaluations were completed. This evaluation was called the expedited seismic evaluation process (ESEP). The ESEP is a screening, evaluation, and equipment modification process performed by licensees to provide additional seismic margin and expedite plant safety enhancements for certain core cooling and containment components while the more detailed and comprehensive plant seismic risk evaluations are being performed. The licensees for 34 sites were screened in by this process and requested to submit an ESEP evaluation report to the NRC.
The NRC and nuclear industry provided the guidance documents listed in Table 1 for the performance of the reevaluated seismic hazard reviews.
Table 1 - NRC and Industry Guidance Documents Guidance Document ADAMS Accession No.
NRC guidance for performing a Seismic Margin Assessment -
JLD-ISG-2012-04 ML12286A029 Industry Letter - Proposed path forward for NTTF Recommendation 2.1: Seismic ML13101A345 Industry Guidance Document - ESEP - EPRI 3002000704 ML13102A142 NRC letter endorsing the ESEP approach ML13106A331 Industry letter on relay chatter review ML13281A308 NRC letter with guidance on the content of seismic reevaluation submittals (includes operability and reportability discussions)
ML14030A046 Industry letter on seismic risk evaluations for CEUS plants ML14083A596 NRC background paper - Probabilistic seismic hazard analysis ML14140A648 By letters dated May 9, 2014, and May 13, 2015 (ADAMS Accession Nos. ML14111A147 and ML15113B344, respectively), the NRC informed licensees of the initial screening and prioritization results based on a review of the licensees SHSR. The NRC updated the screening and prioritization results in a letter dated October 3, 2014 (ADAMS Accession No. ML14258A043). The NRC provided the final determination of required seismic evaluations in a letter dated October 27, 20152 (ADAMS Accession No. ML15194A015). These evaluations could consist of a seismic probabilistic risk assessment (SPRA),3 a high frequency evaluation, a low-frequency evaluation,4 and/or an SFP evaluation. Table 2 is a listing of the guidance documents to perform the various additional assessments.
Table 2 - NRC and Industry Guidance Documents for Additional Seismic Evaluations Guidance Document ADAMS Accession No.
Industry High Frequency Application Guidance - EPRI 3002004396 ML15223A095 NRC letter endorsing High Frequency Application Guidance ML15218A569 Industry SFP evaluation guidance - EPRI 3002007148 ML16055A017 NRC letter endorsing SFP evaluation guidance ML15350A158 SPRA Guidance - Section 6.1.1 of SPID - EPRI 1025287 ML12333A170 NRC letter endorsing SPID ML12319A074 If the reevaluated GMRS did not exceed the SSE (or the exceedance was considered de minimis5), a licensee was screened out from any further evaluations. Those not screened out were required to perform an SPRA and/or the limited scope evaluations (a high-frequency evaluation, a low-frequency evaluation, and/or a spent fuel pool evaluation). If a licensee was screened in to provide one or more of the limited scope evaluations without the need to complete an SPRA, the NRC staff reviewed the submittal and provided a staff assessment to document the staffs review. If the staff concluded that the limited scope evaluation met the 2 The licensees for the four sites noted in Table 1b of the October 15, 2015, letter, all choose Option 2 and submitted a high frequency evaluation and SFP evaluation.
3 Catawba Nuclear Station, Units 1 and 2, and McGuire Nuclear Station, Units 1 and 2, subsequently were screened out from the need to perform an SPRA (ADAMS Accession No. ML16344A313) and submitted high frequency and SFP evaluations.
4 A low-frequency review was only required at Edwin I. Hatch Nuclear Plant, Units 1 and 2. The SPID provides guidance for the licensee to evaluate any low-frequency exceedances.
5 Too trivial or minor to merit consideration.
applicable guidance and was an appropriate response to Enclosure 1 of the 50.54(f) letter, the site was screened out from any further regulatory actions and no further evaluations were required. Only those sites with a significant exceedance were screened in to perform an SPRA (with or without one or more of the limited scope evaluations). If a site was required to perform an SPRA, additional regulatory decisionmaking per Phase 2 of the process was needed. This Phase 2 decisionmaking is detailed in letters dated September 21, 2016 and March 2, 2020 (ADAMS Accession Nos. ML16237A103 and ML20043D958, respectively), and describes how the NRC will make any regulatory decisions using existing guidance for risk-informed decisionmaking and for evaluating plant-specific backfits.
These memoranda describe the formation of a Senior Management Review Panel (SMRP) consisting of three division directors from NRR. The SMRP is expected to reach a decision for each plant submitting an SPRA. The SMRP is supported by NRC technical staff who are responsible for consolidating relevant information and developing recommendations for the consideration of the panel. In presenting recommendations to the SMRP, the supporting technical staff recommended placement of each SPRA plant into one of three groups:
Group 1 includes plants for which available information indicates that further regulatory action is not warranted. For seismic hazards, Group 1 will include plants for which the mean seismic core damage frequency and mean seismic early release frequency clearly demonstrate that a plant-specific backfit would not be warranted. For plants in Group 1, the SMRP will ensure that conclusions based primarily on numerical factors are supported by available qualitative risk insights before deciding that no further regulatory action is required.
Group 2 includes plants for which further regulatory action should be considered under the NRC's backfit provisions. This group may include plants with relatively large seismic core damage frequency or seismic large early release frequency such that the event frequency in combination with other factors result in a risk to public health and safety for which a regulatory action is expected to provide a substantial safety enhancement.
Group 3 includes plants for which further regulatory action may be needed, but for which more thorough consideration of both qualitative and quantitative risk insights is needed before determining whether a formal backfit analysis is warranted.
The basis for the staff's grouping recommendation to the SMRP for each site is described in the staff assessment issued for each SPRA. Fifteen6 operating reactor sites met the criteria for the performance of an SPRA. Based on its evaluation, which included consideration of voluntary enhancements to improve the sites ability to cope with a seismic event, the staff recommended to the SMRP that no further regulatory action was warranted for any of the sites. As documented in the staff assessments, the SMRP approved the staffs recommendations for each site to be classified as Group 1, meaning that no further response or regulatory action is required.
6 Two additional operating power reactor sites which met the criteria for performance of an SPRA have approved deferrals to a date beyond the anticipated early shutdown date and are not expected to complete an SPRA.
NRCs Response to Tasking Memorandum COMGBJ-11-0002 The NTTF recommendations were applicable to operating power reactor sites. As one of the longer-term activities, COMGBJ-11-0002 also directed the staff, in part, to assess the applicability of the lessons-learned from the accident to non-operating reactors, including those with spent fuel in the SFPs, and ISFSIs. Very shortly after the accident, NRC staff from NMSS and NRR performed limited assessments to ensure that no immediate safety concerns existed at these facilities.
In calendar year 2015, with insights gained from NRC activities related to operating power reactors and from the results of inspections at fuel cycle facilities, NRC staff more fully evaluated issues and possible actions related to non-operating reactors and other NRC-licensed materials, devices, and non-reactor facilities. The NRC staffs detailed evaluation can be found in Enclosure 1 of SECY-15-0081. The assessments specific to ISFSIs is included in Section 1 of the enclosure. The assessments specific to decommissioning reactors is included as Section 7 of the enclosure.
The types of events that NRC staff assessed for these facilities included postulated external events, seismic hazards, external flooding hazards, internal flooding hazards, wind and tornado loading, extended loss of alternating current or emergency power, and fires, to determine if existing regulatory requirements appropriately address such hazards. In addition to the evaluation of initiating events and external hazards, NRC staff assessed these licensees qualitatively in terms of (1) policy issues related to Fukushima, (2) the NTTFs findings and recommendations, and (3) other domestic and international studies and evaluations. The NRC staffs review was broad in scope and was not limited to specific recommendations and considerations provided by the NTTF, which tend to be discussed in the context of operating power reactors.
In each case, the NRC staffs analysis determined that no further study or regulatory action is recommended for decommissioning power reactor sites nor ISFSIs. Specifically concerning GI-199, the staff assessed the risk of external events for the decommissioned power reactors that have fuel stored in their SFPs, including five recently shutdown sites. Previous studies and analyses such as NUREG-1738, Technical Study of Spent Fuel Pool Accident Risk at Decommissioning Nuclear Power Plants and NUREG-2161, Consequence Study of a Beyond-Design-Basis Earthquake Affecting the Spent Fuel Pool for a U.S. Mark I Boiling Water Reactor (ADAMS Accession Nos. ML010430066 and ML14255A365, respectively) have shown that the spent fuel pool structure is extremely robust and capable of withstanding the external events addressed in SECY-15-0081. In addition, based on the decay heat levels of recently permanently shutdown reactors and the time available to take mitigating actions, there are no identified safety concerns that need further analysis.
Conclusions Since March 2012, all operating power reactor licensees have reevaluated the seismic hazard applicable to their sites. These reevaluations used modern techniques and information to determine the seismic hazard applicable to each site. The NRC staff reviewed each licensees submittals and evaluations. Using a graded, risk-informed approach, the NRC staff used that information to determine if any further regulatory actions would be warranted under the NRCs backfit rule. Based on the completion of seismic reevaluation activities related to the lessons-learned from the Fukushima Dai-ichi accident, the staff has determined that there are no
additional regulatory actions that are needed to address seismic hazards at operating power reactor sites.
In addition to seismic hazards applicable to operating power reactor sites, the NRC staff performed a detailed evaluation of the need to apply any of the NTTF recommendations to non-operating power reactors, non-power reactors, and non-reactor facilities. The NRC staff concluded that, except for some additional follow-up activities for fuel cycle facilities and higher-power research reactors, further assessments are not needed based on Fukushima lessons-learned and that the existing regulatory requirements and processes ensure adequate protection of public health and safety. The limited follow-up actions have been completed.
Therefore, no additional regulatory actions were needed to address non-operating power reactors (i.e., decommissioning facilities and ISFSIs).
Although not directly related to the resolution of GI-199, POANHI has enhanced the existing NRC processes such that the staff proactively and systematically reviews new natural hazard information and assesses its impact on site safety by comparing updated information to existing hazard evaluations for the fleet or individual plants, as appropriate. Any future issues that may be similar in nature to GI-199 would be assessed by this improved and enhanced process.
The full scope of GI-199 has been addressed through the NRC response to the Fukushima lessons-learned. All agency actions associated with GI-199 are complete, including implementation and verification activities by the regulatory office. No additional evaluations or regulatory activities are necessary. Therefore, NRR recommends that GI-199 be closed.
Enclosure:
Seismic Reevaluation Activities -
List of NRC Staff Assessments
- via email NRR-106 OFFICE NRR/DORL/PBMB/PM*
NRR/DRA/APLC/PM*
NRR/DANU/UARL/LA*
NAME RBernardo MValentin SLent DATE 10/16/2020 10/19/2020 10/19/2020 OFFICE NRR/DORL/PBMB/BC(A)*
NRR/DORL/D*
NRR/D*
NAME KMorgan-Butler CErlanger (DWrona for)
HNieh DATE 10/21/2020 10/29/2020 11/30/2020
Seismic Reevaluation Activities - List of NRC Staff Assessments Enclosure