ML20230A216
| ML20230A216 | |
| Person / Time | |
|---|---|
| Issue date: | 09/16/2020 |
| From: | Ho Nieh Office of Nuclear Reactor Regulation |
| To: | Raymond Furstenau Office of Nuclear Regulatory Research |
| Bernardo R | |
| References | |
| Download: ML20230A216 (9) | |
Text
September 16, 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 204, FLOODING OF NUCLEAR SITES DUE TO UPSTREAM DAM FAILURE The Office of Nuclear Reactor Regulation (NRR) recommends closure of Generic Issue 204 (GI-204), Flooding of Nuclear Sites Due to Upstream Dam Failure. This recommendation is based on the completion of the risk-informed reevaluation of the flooding hazards, including upstream dam failures, 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 all flood hazards, including dam failure events. Moreover, the associated activities have greatly increased the NRCs level of knowledge and risk insights in the area concerning present-day flood hazards. As such, any additional use of NRC resources on GI-204 would only provide marginal benefits to safety.
Enclosure:
Flood Reevaluation Activities -
List of NRC Staff Assessments CONTACT: Robert J. Bernardo, NRR/DORL 301-415-2621 Mirela Gavrilas Digitally signed by Mirela Gavrilas Date: 2020.09.16 16:10:52 -04'00'
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.
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 flood hazard reevaluation activities.
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Background===
Generic issue GI-204 was opened to evaluate the potential safety implications for flooding of nuclear power plant sites due to upstream dam failures. The complete scope of this generic issue includes not only operating nuclear power plants sites, but also sites undergoing decommissioning with spent fuel stored in SFPs and ISFSIs. The issue was officially declared as GI-204 in February 2012. In accordance with Management Directive (MD) 6.4, the staff completed a screening analysis in July 2011 (ADAMS Accession No. ML112430114, non-public version, and ML113500495, publicly available version). The screening analysis did not identify any immediate safety concerns.
No assessment was performed, and the issue was transferred directly to the responsible program office (NRR) for resolution. By letter dated March 6, 2012 (ADAMS Accession No. ML120261155), GI-204 was transferred to NRR for Regulatory Office Implementation. The transfer occurred because of the NRCs parallel activities in response to the Near-Term Task Force1 (NTTF) recommendations to address flooding at operating reactors, including flooding from postulated upstream dam failures.
Specifically, the NTTFs work incorporated several insights from the GI-204 screening analysis, which contributed to the NTTFs recommendations regarding flooding. The NRC response to these recommendations addressed flooding issues broadly, even beyond the issues represented in the screening analysis for GI-204. As a result (and consistent with MD 6.4), it was determined that GI-204 would be addressed by the NRCs response to the NTTFs recommendations.
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 flooding issues broadly for non-operating reactors and non-reactor facilities, even beyond the issues represented in the screening analysis for GI-204. The staffs assessment can be found in Enclosure 1 of SECY-15-0081 (ADAMS Accession No. ML15050A066). Additional details are described below.
1 See Near-Term Task Force (NTTF) Review of Insights from the Fukushima Dai-ichi Accident (ADAMS Accession No. ML111861807)
With the completion of these actions, the full scope of GI-204 has been addressed by the NRCs actions in response to the accident at Fukushima Dai-ichi.
NRCs Response to Recommendation 2.1, Flooding of the NTTF Task Force 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 2 to the 50.54(f) letter requested that licensees reevaluate flood 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. Examples of dam-related guidance used by licensees include Japan Lessons-Learned Project Directorate (JLD) Interim Staff Guidance (ISG) document JLD-ISG-2013-01, Guidance for Assessments of Flooding Hazards Due to Dam Failure (ADAMS Accession No. ML13151A153), and NUREG/CR-7046, Design-Basis Flood Estimation for Site Characterization at Nuclear Power Plants in the United States of America.
A two-phase process was developed to respond to the flood hazard reevaluations requested by the 50.54(f) letter. In Phase 1 (the information gathering phase), licensees submitted flood hazard reevaluation reports (FHRR) evaluating the potential impacts of reevaluated hazards at their sites. The licensees used NRC endorsed, industry developed guidance to complete the evaluations. Each licensee also determined if interim protection measures were needed while a longer-term evaluation of the impacts of the hazard was completed. If interim protection measures were needed, the NRC inspected those actions using Temporary Instruction (TI) 2515/190, Inspection of Licensee's Proposed Interim Actions as a Result of the Near-Term Task Force Recommendation 2.1 Flooding Evaluation and documented the results in a quarterly integrated inspection report. The NRC staff reviewed the FHRR and provided an interim hazard letter to provide timely feedback on the staffs review of the flooding hazard reevaluations. The flood hazard information in the interim hazard letter was used by the licensee to complete any additional flood hazard evaluations. Separately, the NRC staff documented the technical bases for its conclusions summarized in the interim hazard letters by issuing a detailed staff assessment of the FHRR. If the reevaluated flood hazard levels were less than or equal to (i.e., bound by) the current licensing basis flood hazard levels, no further evaluations were necessary. If one or more reevaluated flood hazard levels were above the current licensing basis, additional evaluations were necessary.
Using the reevaluated hazard information and a graded approach, the NRC identified the need for, and prioritization and scope of, any needed additional plant specific assessments. On July 18, 2016, the staff issued JLD-ISG-2016-01, Guidance for Activities Related to Near-Term Task Force Recommendation 2.1, Flooding Hazard Reevaluation, Focused Evaluation and Integrated Assessment (ADAMS Accession No. ML16162A301). The ISG provided the guidance to complete the Phase 1 flooding assessments and endorsed, with appropriate exceptions and clarifications, industry guidance provided in the Nuclear Energy Institute (NEI) guidance document NEI 16-05, External Flooding Integrated Assessment Guidelines (ADAMS Accession No. ML16165A178). The NRC staffs graded approach enabled a site with hazard exceedance above its current licensing basis to demonstrate the sites ability, through a Focused Evaluation (FE), to cope with the reevaluated hazard through appropriate protection or mitigation measures which are timely, effective, and reasonable. An Integrated Assessment (IA) would be needed by those sites with the greatest potential for additional safety
enhancements. The IAs are intended for the NRC to assess the sites capability to cope with the reevaluated hazard and to determine if additional regulatory actions are necessary under the backfit regulation.
If a licensee submitted an FE, the NRC staff reviewed the submittal and provided a staff assessment to document the staffs review. If the staff concluded that the FE is the appropriate evaluation mechanism, the site was screened out from any further regulatory actions and no further evaluations were required. Only those plants that met the criteria to perform a flooding IA needed to proceed to Phase 2 (the regulatory decisionmaking phase). 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 IA. 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 flooding IA plant into one of three groups:
Group 1 will include plants for which available information indicates that further regulatory action is not warranted. For flooding hazards, Group 1 will include plants that have demonstrated (1) effective protection for severe flood hazards, and (2) that consequential flooding is expected to occur only for hazards with a sufficiently small mean annual frequency of exceedance.
Group 2 will include plants for which further regulatory action should be considered under the NRC's backfit provisions. This group may include plants that are unable to protect against relatively frequent flood hazards 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 will include 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 evaluation process that was performed to provide the basis for the staff's grouping recommendation to the SMRP for each site is described in the staff assessment issued for each IA. Six operating reactor sites met the criteria for the performance of an IA. Based on its evaluation, the staff recommended to the SMRP that each site be classified as a Group 1 plant and therefore, no further regulatory action was warranted. As documented in the staff assessments, the SMRP approved the staffs recommendations that the applicable hazard(s) for each site should be classified as Group 1, meaning that no further response or regulatory action is required.
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 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 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-204, the staff assessed the risk of external events for the decommissioned power reactors that have fuel stored in their spent fuel pools, including five recently shutdown sites. Previous studies and analyses (e.g., 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 the SECY paper. 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 flood hazards applicable to their sites, including the effects of postulated upstream dam failure. These reevaluations used present-day, modern techniques and information to determine the flood hazards 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 flood 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 flood hazards at operating power reactor sites. This includes flood hazards associated with upstream dam failures.
In addition to flood 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, the NRC staff has determined that 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-204, POANHI has enhanced the existing NRC processes such that the staff proactively and systematically reviews new natural hazard information and assess 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-204 would be assessed by this new, improved, and enhanced process.
The full scope of GI-204 has been addressed through the NRC response to the Fukushima Lessons-Learned. All agency actions associated with GI-204 are complete, including implementation and verification activities by the regulatory office. No additional evaluations or regulatory activities are necessary. Therefore, NRR recommends that GI-204 be closed.
Flood Reevaluation Activities - List of NRC Staff Assessments
- via email NRR-106 OFFICE NRR/DORL/PBMB/PM NRR/DANU/UARL/LA*
NRR/DORL/PBMB/BC(A)*
NAME RBernardo SLent KMorgan-Butler DATE 08/17/2020 8/18/2020 8/24/2020 OFFICE NRR/DORL/D*
NRR/D*
NAME CErlanger (DWrona for)
HNieh (MGavrilas for)
DATE 8/27/2020 9/16/2020