ML21281A254
| ML21281A254 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 10/15/2021 |
| From: | Thomas Wengert Plant Licensing Branch IV |
| To: | Entergy Operations |
| Wengert T | |
| References | |
| EPID L-2021-LLA-0105, EPID L-2021-LLA-0106 | |
| Download: ML21281A254 (1) | |
Text
October 15, 2021 ANO Site Vice President Arkansas Nuclear One Entergy Operations, Inc.
1448 S.R. 333 Russellville, AR 72802
SUBJECT:
ARKANSAS NUCLEAR ONE, UNITS 1 AND 2 - AUDIT MEETING AGENDA AND AUDIT QUESTIONS FOR LICENSE AMENDMENT REQUEST TO ADOPT 10 CFR 50.69, RISK-INFORMED CATEGORIZATION AND TREATMENT OF STRUCTURES, SYSTEM, AND COMPONENTS FOR NUCLEAR POWER REACTORS (EPID L-2021-LLA-0105 AND EPID L-2021-LLA-0106)
Dear Sir or Madam:
By two letters dated May 26, 2021 (Agencywide Documents Access and Management System (ADAMS) Accession Nos. ML21147A234 and ML21147A264), Entergy Operations, Inc. (the licensee) submitted license amendment requests for Arkansas Nuclear One, Units 1 and 2 (ANO-1 and ANO-2), respectively. The proposed amendments would adopt Title 10 of the Code of Federal Regulations Section 50.69, Risk-informed categorization and treatment of structures, systems and components for nuclear power reactors, into the licensing basis for ANO-1 and ANO-2.
By letter dated July 19, 2021 (ADAMS Accession No. ML21200A047), the U.S. Nuclear Regulatory Commission (NRC) staff issued an audit plan that conveyed our intent to conduct a regulatory audit to support its review of the subject license amendments. In the audit plan, the NRC staff requested that an electronic portal be set up and provided a list of documents to be added to the portal. The NRC staff performed an initial review of the documents in the portal and developed a list of audit questions. The proposed dates for the audit are November 8 and November 9, 2021. The proposed agenda for the audit is provided as Enclosure 1 and the lists of audit questions are provided as Enclosures 2 and 3 to this letter, for ANO-1 and ANO-2 respectively.
If you have any questions, please contact me at (301) 415-4037 or by e-mail at Thomas.Wengert@nrc.gov.
Sincerely,
/RA/
Thomas J. Wengert, Senior Project Manager Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-313 and 50-368
Enclosures:
- 1. Audit Agenda
- 2. ANO-1 Audit Questions
- 3. ANO-2 Audit Questions cc: Listserv
AUDIT AGENDA REGARDING LICENSE AMENDMENT REQUESTS TO ADOPT 10 CFR 50.69, RISK-INFORMED CATEGORIZATION AND TREATMENT OF STRUCTURES, SYSTEMS AND COMPONENTS FOR NUCLEAR POWER REACTORS ENTERGY OPERATIONS, INC.
ARKANSAS NUCLEAR ONE, UNITS 1 AND 2 DOCKET NOS. 50-313 AND 50-368 Day 1 - Monday November 8, 2021 Morning Entrance Meeting o Opening comments by U.S. Nuclear Regulatory Commission (NRC) and Entergy Operations, Inc (Entergy, the licensee) o Introductions and logistics.
Proposed License Condition (Arkansas Nuclear One, Units 1 and 2 (ANO-1 and ANO-2)
Audit Question 1)
FLEX [Diverse and Flexible Mitigation Capability] Credit (ANO-1 and ANO-2 Audit Question 2)
Open Phase Condition (ANO-1 and ANO-2 Audit Question 3)
Afternoon Risk Categorization of Interfacing Systems Alternative Seismic Approach (ANO-1 and ANO-2 Audit Question 4)
Implementation of Section 2.3.1 of EPRI [Electric Power Research Institute]
Report 3002017583 (ANO-1 and ANO-2 Audit Question 5)
Summary of the day.
NRC staff meeting.
Day 2 - Tuesday November 9, 2021 Morning Review of outstanding items from Day 1 Other External Hazards Screening (ANO-1 and ANO-2 Audit Question 6)
Summary of audit/Exit Enclosure 1
AUDIT QUESTIONS TO SUPPORT THE REVIEW OF LICENSE AMENDMENT REQUEST TO ADOPT 10 CFR 50.69, RISK-INFORMED CATEGORIZATION AND TREATMENT OF STRUCTURES, SYSTEMS AND COMPONENTS FOR NUCLEAR POWER REACTORS ENTERGY OPERATIONS, INC.
ARKANSAS NUCLEAR ONE, UNIT 1 DOCKET NO. 50-313 By letter dated May 26, 2021 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML21147A234), Entergy Operations, Inc. (the licensee) submitted a license amendment request (LAR) for Arkansas Nuclear One, Unit 1 (ANO-1). The proposed amendment would adopt Title 10 of the Code of Federal Regulations (10 CFR) Section 50.69 (10 CFR 50.69), Risk-informed categorization and treatment of structures, systems and components for nuclear power reactors, into the licensing basis for ANO-1. The U.S. Nuclear Regulatory Commission (NRC) staff from the Division of Risk Assessment, Probabilistic Risk Assessment (PRA) Licensing Branch A (APLA) and Branch C (APLC) have reviewed the LARs and provided the following questions to discuss during the audit.
ANO-1 AUDIT QUESTION 01 (APLA and APLC) - Proposed License Condition Paragraph (b)(2)(ii) of 10 CFR 50.69 requires, for a license amendment, a description of measures taken to assure that the level of detail of the systematic processes that evaluate the plant for internal and external events are adequate for the categorization of structures, systems, and components (SSCs). The guidance in Nuclear Energy Institute (NEI) 00-041 allows licensees to implement different approaches, depending on the scope of their PRA (e.g., the approach, where a seismic margins analysis is relied upon is different and more limiting than the approach where a seismic PRA is used). Regulatory Guide (RG) 1.2012 states, in part,
[a]s part of the NRCs review and approval of a licensees or applicants application requesting to implement § 50.69, the NRC staff intends to impose a license condition that will explicitly address the scope of the PRA and non-PRA methods used in the licensee's categorization approach.
Section 2.3, Description of the Proposed Change, of Enclosure 1, Evaluation of the Proposed Change, to the LAR proposed the following license condition:
Entergy is approved to implement 10 CFR 50.69 using the processes for categorization of Risk-Informed Safety Class (RISC)-1, RISC-2, RISC-3, and RISC-4 Structures, Systems, and Components (SSCs) using: Probabilistic Risk Assessment (PRA) models to evaluate risk associated with internal events, 1
NEI 00-04, Revision 0, 10 CFR 50.69 SSC Categorization Guideline, dated July 2005 (ADAMS Accession No. ML052910035).
2 RG 1.201, Guidelines for Categorizing Structures, Systems, and Components in Nuclear Power Plants According to their Safety Significance, dated May 2006 (ADAMS Accession No. ML061090627).
Enclosure 2
including internal flooding, and internal fire; the high wind / tornado safe shutdown equipment list to evaluate high wind / tornado missile events; the NUMARC [Nuclear Management and Resources Council] 91-06 shutdown safety assessment process to assess shutdown risk; the Arkansas Nuclear One, Unit 1 (ANO-1) passive categorization method to assess passive component risk for Class 2 and Class 3 SSCs and their associated supports; the results of the non-PRA evaluations that are based on the IPEEE [Individual Plant Examination of External Events] Screening Assessment for External Hazards updated using the external hazard screening significance process identified in ASME/ANS
[American Society of Mechanical Engineers/American Nuclear Society] PRA Standard RA-Sa-2009 for other external hazards except seismic; and the alternative seismic approach as described in the Entergy submittal letter dated Date, and all its subsequent associated supplements, as specified in License Amendment No. [XXX] dated [DATE].
Prior NRC approval, under 10 CFR 50.90, [Application for amendment of license, construction permit, or early site permit,] will be requested if ANO-1s feedback process determines that a process different from the proposed alternative seismic approach is warranted for seismic risk consideration in categorization under 10 CFR 50.69.
a) Section V.3.0 of Federal Register Volume 69, No. 224 (69 FR 68034, November 22, 2004) states, in part, that the licensee is not required to come back to the NRC for review of the categorization process provided they remain within the scope of the NRCs safety evaluation. The NRC staff notes that the above cited changes concern only the aspect of seismic risk consideration in the 10 CFR 50.69 categorization, not the remainder of the approaches proposed for the 10 CFR 50.69 categorization process itself. The proposed license condition is inconsistent with several precedents approved by the NRC staff and the NEI template for 10 CFR 50.69 LARs. Further, the LAR does not provide any justification for the proposed language (i.e., why it is appropriate to use approaches not reviewed by the NRC staff without prior NRC approval for non-seismic hazards). Justify why it is appropriate to use approaches not reviewed by the NRC staff without prior NRC approval for non-seismic hazards or propose a license condition consistent with approved precedents.
b) The NRC staff notes that the passive categorization method previously accepted by the staff is described in the approval of alternative ANO2-R&R-004.3 Provide an explanation that establishes the basis for using ANO-1s passive categorization methodology or provide an updated license condition that references ANO2-R&R-004.
3 NRC letter to Entergy Operations, Inc., Arkansas Nuclear One, Unit 2 - Approval of Request for Alternative ANO2-R&R-004, Revision 1, Request to Use Risk-Informed Safety Classification and Treatment for Repair/Replacement Activities in Class 2 and 3 Moderate and High Energy Systems, dated April 22, 2009 (ADAMS Accession No. ML090930246).
ANO-1 AUDIT Question 02 (APLA) - Credit for FLEX Equipment and Actions NRC memorandum dated May 30, 2017,4 provides the NRCs staff assessment of identified challenges and strategies for incorporating Diverse and Flexible Mitigation Capability (FLEX) equipment into a PRA model in support of risk-informed decisionmaking in accordance with the guidance of RG 1.200.5.
With regards to equipment failure probability, in the memorandum dated May 30, 2017, the NRC staff states in Conclusion 8:
The uncertainty associated with failure rates of portable equipment should be considered in the PRA models consistent with the ASME/ANS PRA Standard as endorsed by RG 1.200. Risk-informed applications should address whether and how these uncertainties are evaluated.
With regards to human reliability analysis (HRA), NEI 16-06,6 Section 7.5, Human Reliability Assessment, recognizes that the current HRA methods do not translate directly to human actions required for implementing mitigating strategies. Sections 7.5.4, Addressing the Actions Not Currently Addressed by Existing HRA Tools, and 7.5.5, Addressing Complex Actions in Mitigating Strategies, of NEI 16-06 describe such actions to which the current HRA methods cannot be directly applied, such as: debris removal, transportation of portable equipment, installation of equipment at a staging location, routing of cables and hoses; and those complex actions that require many steps over an extended period, multiple personnel and locations, evolving command and control, and extended time delays. In the memorandum dated May 30, 2017, the NRC staff states, in part, in Conclusion 11:
. . . Until gaps in the human reliability analysis methodologies are addressed by improved industry guidance, HEPs [Human Error Probabilities] associated with actions for which the existing approaches are not explicitly applicable, such as actions described in Sections 7.5.4 and 7.5.5 of NEI 16-06, along with assumptions and assessments, should be submitted to NRC for review. , Attachment 6, Disposition of Key Assumptions/Sources of Uncertainty, to the LAR identified FLEX equipment PRA credit. In the LAR, the licensee states that a sensitivity study was performed that removed credit of the FLEX feed pump, which resulted in less than 2 percent increase in core damage frequency risk.
a) Provide a description of all FLEX equipment and associated operator actions credited in the ANO-1 PRA including internal events, internal flooding, fire, seismic, and external events.
b) Confirm that the sensitivity study highlighted in Enclosure 1, Attachment 6 to the LAR removes all FLEX credit. If all FLEX credit is not removed, provide an assessment, such 4
NRC memorandum, Assessment of the Nuclear Energy Institute 16-06, Crediting Mitigating Strategies in Risk-Informed Decision Making, Guidance for Risk-Informed Changes to Plants Licensing Basis, dated May 30, 2017 (ADAMS Accession No. ML17031A269).
5 RG 1.200, Revision 3, Acceptability of Probabilistic Risk Assessment Results for Risk-Informed Activities, dated December 2020 (ADAMS Accession No. ML20238B871).
6 NEI 16-06, Crediting Mitigating Strategies in Risk-Informed Decision Making, Revision 0, dated August 2016 (ADAMS Accession No. ML16286A297).
as a sensitivity study, of the impact risk by FLEX equipment credited in ANO-1s PRA models. Include in this discussion the impact of FLEX on the categorization process.
c) Provide a discussion detailing the methodology used to assess the failure probabilities of any modeled equipment credited in the licensee's mitigating strategies (i.e., FLEX). The discussion should include a justification of the rationale for parameter values, and how the uncertainties associated with the parameter values are considered in the categorization process in accordance with ASME/ANS RA-Sa-20097,as endorsed by RG 1.200 (e.g., supporting requirements for HLR-DA-D).
d) Provide a discussion detailing the methodology used to assess operator actions related to FLEX equipment and the licensee personnel that perform these actions. The discussion should include:
- i. A summary of how the licensee evaluated the impact of the plant-specific HEPs and associated scenario-specific performance shaping factors listed in (a)-(j) of supporting requirement HR-G3 of ASME/ANS RA-Sa-2009, as endorsed by RG 1.200.
ii. Whether maintenance procedures for the portable equipment were reviewed for possible pre-initiator human failures that renders the equipment unavailable during an event, and whether the probabilities of the pre-initiator human failure events were assessed as described in HLR-HR-D of ASME/ANS RA-Sa-2009, as endorsed by RG 1.200.
ANO-1 AUDIT Question 03 (APLA) - Open Phase Condition In response to the January 30, 2012, Open Phase Condition (OPC) event at the Byron Station, the NRC issued Bulletin 2012-01.8 As part of the initial Voluntary Industry Initiative for mitigation of the potential for the occurrence of an OPC in electrical switchyards9,licensees have made the addition of an Open Phase Isolation System (OPIS). In accordance with Staff Requirements Memorandum (SRM)-SECY-16-0068, Interim Enforcement Policy For Open Phase Conditions In Electric Power Systems For Operating Reactors, the NRC staff was directed to ensure that licensees have appropriately implemented OPIS, and that licensing bases have been updated accordingly. From revised voluntary initiative10 and resulting industry guidance in NEI 19-0211 on estimating OPC and OPIS risk, it is understood that the risk impact of an OPC can vary widely, depending on electrical switchyard configuration and design. In light of this observation, provide the following information:
7 ASME/ANS PRA standard ASME/ANS RA-Sa-2009, Addenda to ASME/ANS RA-S-2008, Standard for Level 1/Large Early Release Frequency Probabilistic Risk Assessment for Nuclear Power Plant Applications, February 2009, New York, NY (Copyright).
8 NRC Bulletin 2012-01, Design Vulnerability in Electric Power System, dated July 27, 2012 (ADAMS Accession No. ML12074A115).
9 Anthony R. Pietrangelo to Mark A. Satorius, letter re: Industry Initiative on Open Phase Condition -
Functioning of Important-to-Safety Structures, Systems and Components (SSCs), dated October 9, 2013 (ADAMS Accession No. ML13333A147).
10 Doug True to Ho Nieh, e-mail re: Industry Initiative on Open Phase Condition, Revision 3, dated June 6, 2019 (ADAMS Accession No. ML19163A176) 11 NEI 19-02, Revision 0, Guidance for Assessing Open Phase Condition Implementation Using Risk Insights, dated April 2019 (ADAMS Accession No. ML19122A321).
a) A discussion of the risk impact of OPC and OPIS at ANO-1.
b) Discuss if the risk impact of OPC and OPIS have been, or are planned to be, incorporated as part of the plant Model of Record (MOR). If so, provide the following:
ii. The impact, if any, to key assumptions and sources of uncertainty.
iii. A discussion of the HRA methods and assumptions used for OPIS alarm manual response.
iv. The impact to external events (e.g., fire, seismic, flooding, high winds, tornado, other external events, etc.).
- v. A discussion of the risk impact of inadvertent OPIS actuation and justification for its exclusion.
c) If OPC and OPIS are not planned to be included in the MOR, provide justification why the risk impact is not included by performing either a qualitative or sensitivity analysis.
ANO-1 AUDIT Question 04 (APLC) - Alternative Seismic Approach Paragraph (b)(2)(ii) of 10 CFR 50.69 requires that the quality and level of detail of the systematic processes that evaluate the plant for external events during operation are adequate for the categorization of SSCs.
In the LAR, the licensee proposes to address seismic hazard risk using the alternative seismic approach for seismic Tier-2 plants described in Electric Power Research Institute (EPRI)
Report 3002017583 and that takes into account the plant-specific seismic risk insights. The NRC staff understands that EPRI Report 3002017583 is an updated version of EPRI Report 3002012988 and both reports were reviewed by the staff in conjunction with its safety evaluation for the adoption of 10 CFR 50.69 in Amendment Nos. 249 and 235 for LaSalle County Station, Units 1 and 2 (LaSalle), respectively (ADAMS Accession No. ML21082A422).
The NRC staff has not endorsed EPRI Report 3002012988 or EPRI Report 3002017583 as a topical report for generic use. As such, each licensee needs to perform a plant-specific evaluation of the applicability of the information in the EPRI report to its proposed alternative seismic approach.
The NRC staff reviewed and approved LaSalles alternative seismic approach based on the information in the LaSalle LAR dated January 31, 2020 (ADAMS Accession No. ML20031E699),
EPRI Report 3002012988, EPRI Report 3002017583, and supplements to the LaSalle LAR dated October 1, 2020; October 16, 2020; and January 22, 2021 (ADAMS Accession Nos. ML20275A292, ML20290A791, and ML21022A130, respectively). The NRC staff notes that the licensees proposed alternative seismic approach is similar to that approved in the staffs LaSalle safety evaluation. Since the information submitted in the LaSalle LAR supplements was requested and reviewed by the NRC staff for the LaSalle LAR for adoption of 10 CFR 50.69, the staff is unable to use it for the ANO-1 licensees docket unless it is incorporated in the licensees LAR. This information is necessary for the NRC staff to make its regulatory finding on the licensees proposed alternative seismic approach and has not been submitted by the licensee. Thus, the licensee is requested to address the following:
a) Identify and justify any differences between the licensees proposed alternative seismic approach and that approved in the NRC staffs safety evaluation of the LaSalle 10 CFR 50.69 LAR, including any ANO-1 specific considerations.
b) If the licensees proposed alternative seismic approach is the same as that approved for LaSalle, provide similar information for ANO-1 as that provided in the above-mentioned information in the LaSalle LAR supplements dated October 1, 2020; October 16, 2020; and January 22, 2021, to support the NRC staffs regulatory finding on the licensees proposed alternative seismic approach. This information can be provided either by incorporating by reference the identified supplements as part of the licensees LAR or by responding to the requests for additional information in the LaSalle LAR supplements identified above.
c) The licensee cited EPRI Report 3002017583 as applicable to its submittal. The NRC staff notes that EPRI has recently submitted a copy of the report on the NRC docket (ADAMS Accession No. ML21082A170). Include the citation for the docketed EPRI Report 3002017583 as part of the proposed alternative seismic approach or provide the report on the docket as part of this application.
d) In Enclosure 1 to the LAR (pages 7, 10, and 12 of 34), the licensee refers to EPRI Markups provided in Attachment 2 of References [4] and [5]. The NRC staff notes that Reference [5] is the safety evaluation that approved the Vogtle Electric Generating Plant, Units 1 and 2, use of its seismic PRA model for categorization and has no Attachment 2.
It is unclear to the NRC staff the relevance of this reference for the proposed alternative seismic approach. Clarify if Attachment 2 of References [4] and [5] should read Attachment 2 of References [4] and [61].
ANO-1 AUDIT Question 05 (APLC) - Implementation of Section 2.3.1 of EPRI Report 3002017583 In Section 3.2.3, Seismic Hazards, of Enclosure 1 to the LAR, the licensee indicated that the categorization team will evaluate correlated seismic failures and seismic interactions between SSCs for each system categorized, and that this process is detailed in Section 2.3.1 of EPRI Report 3002017583. The licensee also indicated that determination of seismic insights will make use of the full power internal events PRA model supplemented by focused seismic walkdowns. However, the NRC staff noted that the LAR did not include any site-specific information on how the guidance in Section 2.3.1 of EPRI Report 3002017583 and its revision markups included in the 10 CFR 50.69 LAR supplements for LaSalle will be applied to seismic evaluation for 10 CFR 50.69 categorization at ANO-1. Such information is important for evaluating seismic risk insights for seismic Tier 2 plants such as ANO-1 and, therefore, should be included in the LAR.
Describe how ANO-1 will implement the guidance in Section 2.3.1 of EPRI report 3002017583 and its revision markups included in the LaSalle 10 CFR 50.69 LAR supplements, taking into account ANO-1 plant conditions.
ANO-1 AUDIT Question 06 (APLC) - Other External Hazards Screening NEI 00-04, Revision 0, Section 5.4, Assessment of Other External Hazards, provides guidance on assessment of other external hazards (excluding fire and seismic) in 10 CFR 50.69 categorization of SSCs. Specifically, Figure 5-6, Other External Hazards, of NEI 00-04
illustrates a process that begins with an SSC selected for categorization and proceeds through a flow chart for each external hazard. Figure 5-6 indicates that if a component participates in a screened scenario then, in order for that component to be considered as a low safety significant item, it has to be further shown that if the component was removed the screened scenario would not become unscreened.
Section 3.2.4, Other External Hazards, of Enclosure 1 to the LAR states, in part, that all other external hazards were screened with Attachment 4, External Hazards Screening, of the LAR providing the results. The NRC staff notes that LAR Attachment 4 screens all other external events besides tornado missiles and seismic events. Based on this description, it appears to the NRC staff that at the time an SSC is categorized, it will not be evaluated using the guidance in NEI 00-04, Figure 5-6, to confirm that the SSC is not credited in screening an external hazard because that evaluation has already been made. The NRC staff notes that plant changes, plant or industry operational experience, or identified errors or limitations in the PRA models could potentially impact the conclusion that an SSC is not needed to screen an external hazard.
Therefore, address the following:
a) Clarify whether an SSC will be evaluated during categorization of the SSC using the guidance in NEI 00-04, Figure 5-6, to confirm that the SSC is not credited in screening an external hazard.
b) If an SSC will not be evaluated using the guidance in NEI 00-04, Figure 5-6, to confirm that the SSC is not credited in screening an external hazard at the time of categorization because that evaluation has already been made, explain how plant changes, plant or industry operational experience, or identified errors or limitations in the PRA models that could change that decision are addressed.
c) Attachment 4 to the Enclosure of the LAR indicates that for the ANO-1 and ANO-2 Focused Evaluation (ADAMS Accession No. ML17214A029), the NRC staff concluded that the station demonstrated effective flood protection from the reevaluated flood hazards. However, the licensee did not provide any detailed information about whether any SSCs are credited for the flood protection, and how the SSCs are categorized.
Identify any active and passive SSCs that are credited for screening the external flooding hazard and discuss how those SSCs will be included and considered in the proposed categorization process.
AUDIT QUESTIONS TO SUPPORT THE REVIEW OF LICENSE AMENDMENT REQUEST TO ADOPT 10 CFR 50.69, RISK-INFORMED CATEGORIZATION AND TREATMENT OF STRUCTURES, SYSTEMS AND COMPONENTS FOR NUCLEAR POWER REACTORS ENTERGY OPERATIONS, INC.
ARKANSAS NUCLEAR ONE, UNIT 2 DOCKET NO. 50-368 By letter dated May 26, 2021 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML21147A264), Entergy Operations, Inc. (the licensee) submitted a license amendment request (LAR) for Arkansas Nuclear One, Unit 2 (ANO-2). The proposed amendment would adopt Title 10 of the Code of Federal Regulations (10 CFR) Section 50.69 (10 CFR 50.69), Risk-informed categorization and treatment of structures, systems and components for nuclear power reactors, into the licensing basis for ANO-2. The U.S. Nuclear Regulatory Commission (NRC) staff from the Division of Risk Assessment, Probabilistic Risk Assessment (PRA) Licensing Branch A (APLA) and Branch C (APLC) have reviewed the LAR and provided the following questions to discuss during the audit.
ANO-2 AUDIT QUESTION 01 (APLA & APLC) - Proposed License Condition Paragraph (b)(2)(ii) of 10 CFR 50.69 requires, for a license amendment, a description of measures taken to assure that the level of detail of the systematic processes that evaluate the plant for internal and external events are adequate for the categorization of structures, systems, and components (SSCs). The guidance in Nuclear Energy Institute (NEI) 00-041 allows licensees to implement different approaches, depending on the scope of their PRA (e.g., the approach where a seismic margins analysis is relied upon that is different and more limiting than an approach where a seismic PRA is used). Regulatory Guide (RG) 1.2012 states, in part,
[a]s part of the NRCs review and approval of a licensees or applicants application requesting to implement § 50.69, the NRC staff intends to impose a license condition that will explicitly address the scope of the PRA and non-PRA methods used in the licensee's categorization approach.
Section 2.3, Description of the Proposed Change, of Enclosure 1, Evaluation of the Proposed Change, to the LAR proposed the following license condition:
Entergy is approved to implement 10 CFR 50.69 using the processes for categorization of Risk-Informed Safety Class (RISC)-1, RISC-2, RISC-3, and RISC-4 Structures, Systems, and Components (SSCs) using: Probabilistic Risk Assessment (PRA) models to evaluate risk associated with internal events, 1
NEI 00-04, Revision 0, 10 CFR 50.69 SSC Categorization Guideline, dated July 2005 (ADAMS Accession No. ML052910035).
2 RG 1.201, Guidelines for Categorizing Structures, Systems, and Components in Nuclear Power Plants According to their Safety Significance, dated May 2006 (ADAMS Accession No. ML061090627).
Enclosure 3
including internal flooding, and internal fire; the high wind / tornado safe shutdown equipment list to evaluate high wind / tornado missile events; the NUMARC [Nuclear Management and Resources Council] 91-06 shutdown safety assessment process to assess shutdown risk; the Arkansas Nuclear One, Unit 2 (ANO-2) passive categorization method to assess passive component risk for Class 2 and Class 3 SSCs and their associated supports; the results of the non-PRA evaluations that are based on the IPEEE [Individual Plant Examination of External Events] Screening Assessment for External Hazards updated using the external hazard screening significance process identified in ASME/ANS
[American Society of Mechanical Engineers/American Nuclear Society] PRA Standard RA-Sa-2009 for other external hazards except seismic; and the alternative seismic approach as described in the Entergy submittal letter dated Date, and all its subsequent associated supplements, as specified in License Amendment No. [XXX] dated [DATE].
Prior NRC approval, under 10 CFR 50.90, [Application for amendment of license, construction permit, or early site permit,] will be requested if ANO-2s feedback process determines that a process different from the proposed alternative seismic approach is warranted for seismic risk consideration in categorization under 10 CFR 50.69.
a) Section V.3.0 of the Federal Register Volume 69, No. 224 notes (69 FR 68034, November 22, 2004) states, in part, that the licensee is not required to come back to the NRC for review of the categorization process provided they remain within the scope of the NRCs safety evaluation. The NRC staff notes that the above cited changes concern only the aspect of seismic risk consideration in the 10 CFR 50.69 categorization, not the remainder of the approaches proposed for the 10 CFR 50.69 categorization process itself. The proposed license condition is inconsistent with several precedents approved by the NRC staff and the NEI template for 10 CFR 50.69 LARs.
Further, the LAR does not provide any justification for the proposed language (i.e., why it is appropriate to use approaches not reviewed by the staff without prior NRC approval for non-seismic hazards). Justify why it is appropriate to use approaches not reviewed by the NRC staff without prior NRC approval for non-seismic hazards or propose a license condition consistent with approved precedents.
b) Provide a description of the ANO-2 feedback method for determining whether a different process for seismic categorization, other than the proposed alternative seismic approach, is warranted for seismic risk categorization. If this feedback method is significantly different from the feedback methods for determining the suitability of other categorization processes applicable to 10 CFR 50.69, provide a description of these additional feedback methods.
ANO-2 AUDIT QUESTION 02 (APLA) - Credit for FLEX Equipment and Actions NRC memorandum dated May 30, 2017,3 provides the NRCs staff assessment of identified challenges and strategies for incorporating Diverse and Flexible Mitigation Capability (FLEX) 3 NRC memorandum, Assessment of the Nuclear Energy Institute 16-06, Crediting Mitigating Strategies in Risk-Informed Decision Making, Guidance for Risk-Informed Changes to Plants Licensing Basis, dated May 30, 2017 (ADAMS Accession No. ML17031A269).
equipment into a PRA model in support of risk-informed decisionmaking in accordance with the guidance of RG 1.200.4 With regards to equipment failure probability, in the memorandum dated May 30, 2017, the NRC staff states in Conclusion 8:
The uncertainty associated with failure rates of portable equipment should be considered in the PRA models consistent with the ASME/ANS PRA Standard as endorsed by RG 1.200. Risk-informed applications should address whether and how these uncertainties are evaluated.
With regards to human reliability analysis (HRA), NEI 16-06,5 Section 7.5, Human Reliability Assessment, recognizes that the current HRA methods do not translate directly to human actions required for implementing mitigating strategies. Sections 7.5.4, Addressing the Actions Not Currently Addressed by Existing HRA Tools, and 7.5.5, Addressing Complex Actions in Mitigating Strategies, of NEI 16-06 describe such actions to which the current HRA methods cannot be directly applied, such as: debris removal, transportation of portable equipment, installation of equipment at a staging location, routing of cables and hoses; and those complex actions that require many steps over an extended period, multiple personnel and locations, evolving command and control, and extended time delays. In the memorandum dated May 30, 2017, the NRC staff states, in part, in Conclusion 11:
. . . Until gaps in the human reliability analysis methodologies are addressed by improved industry guidance, HEPs [Human Error Probabilities] associated with actions for which the existing approaches are not explicitly applicable, such as actions described in Sections 7.5.4 and 7.5.5 of NEI 16-06, along with assumptions and assessments should be submitted to NRC for review. , Attachment 6, Disposition of Key Assumptions/Sources of Uncertainty, to the LAR describes how assigning credit to the FLEX portable diesel generator is a source of uncertainty in the Fire PRA. In Attachment 6, the licensee states, in part, that:
The model of record is being updated (scheduled to be complete in one quarter 2021) that will include additional refinement to remove FPRA [fire PRA] modeling conservatisms associated with the station emergency diesel generators.
a) Confirm that the model of record (MOR) was updated as scheduled. Provide an assessment, such as a sensitivity study, of the impact risk by FLEX equipment credited in ANO-2s PRA models. Include in this discussion the impact of FLEX on the categorization process.
b) Provide a discussion detailing the methodology and sources of data used to assess the failure probabilities of any modeled equipment credited in the licensees mitigating strategies (i.e., FLEX). The discussion should include a justification of the rationale for parameter values, and how the uncertainties associated with the parameter values are 4
RG 1.200, Revision 3, Acceptability of Probabilistic Risk Assessment Results for Risk-Informed Activities, dated December 2020 (ADAMS Accession No. ML20238B871).
5 NEI 16-06, Crediting Mitigating Strategies in Risk-Informed Decision Making, Revision 0, dated August 2016 (ADAMS Accession No. ML16286A297).
considered in the categorization process in accordance with ASME/ANS RA-Sa-2009,6,as endorsed by RG 1.200 (e.g., supporting requirements for HLR-DA-D).
c) Provide a discussion detailing the methodology used to assess operator actions related to FLEX equipment and the licensee personnel that perform these actions. The discussion should include:
- i. A summary of how the licensee evaluated the impact of the plant-specific HEPs and associated scenario-specific performance shaping factors listed in (a)-(j) of supporting requirement HR-G3 of ASME/ANS RA-Sa-2009, as endorsed by RG 1.200.
ii. Whether maintenance procedures for the portable equipment were reviewed for possible pre-initiator human failures that renders the equipment unavailable during an event, and whether the probabilities of the pre-initiator human failure events were assessed as described in HLR-HR-D of ASME/ANS RA-Sa-2009, as endorsed by RG 1.200.
ANO-2 AUDIT QUESTION 03 (APLA) - Open Phase Condition In response to the January 30, 2012, Open Phase Condition (OPC) event at the Byron Station, the NRC issued Bulletin 2012-01.7 As part of the initial Voluntary Industry Initiative (VII) for mitigation of the potential for the occurrence of an OPC in electrical switchyards,8,licensees have made the addition of an Open Phase Isolation System (OPIS). In accordance with Staff Requirements Memorandum (SRM)-SECY-16-0068, Interim Enforcement Policy For Open Phase Conditions In Electric Power Systems For Operating Reactors, the NRC staff was directed to ensure that licensees have appropriately implemented OPIS, and that licensing bases have been updated accordingly. From the revised voluntary initiative9 and the resulting industry guidance in NEI 19-0210 on estimating OPC and OPIS risk, it is understood that the risk impact of an OPC can vary widely, depending on electrical switchyard configuration and design.
In light of this observation, provide the following information:
a) A discussion of the risk impact of OPC and OPIS at ANO-2.
b) Discuss if the risk impact of OPC and OPIS have been, or are planned to be, incorporated as part of the plant MOR. If so, provide the following:
6 ASME/ANS PRA standard ASME/ANS RA-Sa-2009, Addenda to ASME/ANS RA-S-2008, Standard for Level 1/Large Early Release Frequency Probabilistic Risk Assessment for Nuclear Power Plant Applications, February 2009, New York, NY (Copyright).
7 NRC Bulletin 2012-01, Design Vulnerability in Electric Power System, dated July 27, 2012 (ADAMS Accession No. ML12074A115).
8 Anthony R. Pietrangelo to Mark A. Satorius, letter re: Industry Initiative on Open Phase Condition -
Functioning of Important-to-Safety Structures, Systems and Components (SSCs), dated October 9, 2013 (ADAMS Accession No. ML13333A147).
9 Doug True to Ho Nieh, e-mail re: Industry Initiative on Open Phase Condition, Revision 3, dated June 6, 2019 (ADAMS Accession No. ML19163A176).
10 NEI 19-02, Revision 0, Guidance for Assessing Open Phase Condition Implementation Using Risk Insights, dated April 2019 (ADAMS Accession No. ML19122A321).
ii. The impact, if any, to key assumptions and sources of uncertainty.
iii. A discussion of the HRA methods and assumptions used for OPIS alarm manual response.
iv. The impact to external events (e.g., fire, seismic, flooding, high winds, tornado, other external events, etc.).
- v. A discussion of the risk impact of inadvertent OPIS actuation and justification for its exclusion.
c) If OPC and OPIS are not planned to be included in the MOR, provide justification why the risk impact is not included by performing either a qualitative or sensitivity analysis.
ANO-2 AUDIT Question 04 (APLC) - Alternative Seismic Approach Paragraph (b)(2)(ii) of 10 CFR 50.69 requires that the quality and level of detail of the systematic processes that evaluate the plant for external events during operation are adequate for the categorization of SSCs.
In the LAR, the licensee proposes to address seismic hazard risk using the alternative seismic approach for seismic Tier-2 plants described in Electric Power Research Institute (EPRI)
Report 3002017583 and that takes into account the plant-specific seismic risk insights. The NRC staff understands that EPRI Report 3002017583 is an updated version of EPRI Report 3002012988 and both reports were reviewed by the staff in conjunction with its safety evaluation for the adoption of 10 CFR 50.69 in Amendment Nos. 249 and 235 for LaSalle County Station, Units 1 and 2 (LaSalle), respectively (ADAMS Accession No. ML21082A422).
The NRC staff has not endorsed EPRI Report 3002012988 or EPRI Report 3002017583 as a topical report for generic use. As such, each licensee needs to perform a plant-specific evaluation of the applicability of the information in the EPRI report to its proposed alternative seismic approach.
The NRC staff reviewed and approved LaSalles alternative seismic approach based on the information in the LaSalle LAR dated January 31, 2020 (ADAMS Accession No. ML20031E699),
EPRI Report 3002012988, EPRI Report 3002017583, and supplements to the LaSalle LAR dated October 1, 2020; October 16, 2020; and January 22, 2021 (ADAMS Accession Nos. ML20275A292, ML20290A791, and ML21022A130, respectively). The NRC staff notes that the licensees proposed alternative seismic approach is similar to that approved in the staffs LaSalle safety evaluation. Since the information submitted in the LaSalle LAR supplements was requested and reviewed by the NRC staff for the LaSalle LAR for adoption of 10 CFR 50.69, the staff is unable to use it for the ANO-2 licensees docket unless it is incorporated in the licensees LAR. This information is necessary for the NRC staff to make its regulatory finding on the licensees proposed alternative seismic approach and has not been submitted by the licensee. Thus, the licensee is requested to address the following:
a) Identify and justify any differences between the licensees proposed alternative seismic approach and that approved in the NRC staffs safety evaluation of the LaSalle 10 CFR 50.69 LAR, including any ANO-2 specific considerations.
b) If the licensees proposed alternative seismic approach is the same as that approved for LaSalle, provide similar information for ANO-2 as that provided in the above-mentioned information in the LaSalle LAR supplements dated October 1, 2020; October 16, 2020; and January 22, 2021, to support the NRC staffs regulatory finding on the licensees proposed alternate seismic approach. This information can be provided either by incorporating by reference the identified supplements as part of the licensee's LAR or by responding to the requests for additional information in the identified supplements.
c) The licensee cited EPRI Report 3002017583 as applicable to its submittal. The NRC staff notes that the EPRI has recently submitted a copy of the report on the NRC docket (ADAMS Accession No. ML21082A170). Include the citation for the docketed EPRI Report 3002017583 as part of the proposed alternative seismic approach or provide the report on the docket as part of this application.
d) In Enclosure 1 to the LAR (pages 7, 10, and 12 of 35), the licensee refers to EPRI Markups provided in Attachment 2 of References [4] and [5]. The NRC staff notes that Reference [5] is the safety evaluation that approved the Vogtle Electric Generating Plant, Units 1 and 2, use of its seismic PRA model for categorization and has no Attachment 2.
It is unclear to the NRC staff the relevance of this reference for the proposed alternative seismic approach. Clarify if Attachment 2 of References [4] and [5] should read Attachment 2 of References [4] and [61]. The NRC staff also notes that Reference
[61], included in the ANO-1 LAR, is missing in ANO-2 LAR.
ANO-2 AUDIT Question 05 (APLC) - Implementation of Section 2.3.1 of EPRI Report 3002017583 In Section 3.2.3, Seismic Hazards, of Enclosure 1 to the LAR, the licensee indicated that the categorization team will evaluate correlated seismic failures and seismic interactions between SSCs for each system categorized and that this process is detailed in Section 2.3.1 of EPRI Report 3002017583. The licensee also indicated that determination of seismic insights will make use of the full power internal events PRA model supplemented by focused seismic walkdowns. However, the NRC staff noted that the LAR did not include any site-specific information on how the guidance in Section 2.3.1 of EPRI Report 3002017583 and its revision markups included in the 10 CFR 50.69 LAR supplements for LaSalle will be applied to seismic evaluation for 10 CFR 50.69 categorization at ANO-2. Such information is important for evaluating seismic risk insights for seismic Tier 2 plants such as ANO-2 and, therefore, should be included in the LAR.
Describe how ANO-2 will implement the guidance in Section 2.3.1 of EPRI Report 3002017583 and its revision markups included in the LaSalle 10 CFR 50.69 LAR supplements, taking into account ANO-2 plant conditions.
ANO-2 AUDIT Question 06 (APLC) - Other External Hazards Screening NEI 00-04, Revision 0, Section 5.4, Assessment of Other External Hazards, provides guidance on assessment of other external hazards (excluding fire and seismic) in 10 CFR 50.69 categorization of SSCs. Specifically, Figure 5-6, Other External Hazards, of NEI 00-04 illustrates a process that begins with an SSC selected for categorization and proceeds through a flow chart for each external hazard. Figure 5-6 indicates that if a component participates in a screened scenario then, in order for that component to be considered as a low safety significant
item, it has to be further shown that if the component was removed the screened scenario would not become unscreened.
Section 3.2.4, Other External Hazards, of Enclosure 1 to the LAR states, in part, that all other external hazards were screened with Attachment 4, External Hazards Screening, of the LAR providing the results. The NRC staff notes that LAR Attachment 4 screens all other external events besides tornado missiles and seismic events. Based on this description, it appears to NRC staff that at the time an SSC is categorized it will not be evaluated using the guidance in NEI 00-04, Figure 5-6 to confirm that the SSC is not credited in screening an external hazard because that evaluation has already been made. The NRC staff notes that plant changes, plant or industry operational experience, or identified errors or limitations in the PRA models could potentially impact the conclusion that an SSC is not needed to screen an external hazard.
Therefore, address the following:
a) Clarify whether an SSC will be evaluated during categorization of the SSC using the guidance in NEI 00-04, Figure 5-6 to confirm that the SSC is not credited in screening an external hazard.
b) If an SSC will not be evaluated using the guidance in NEI 00-04, Figure 5-6, to confirm that the SSC is not credited in screening an external hazard at the time of categorization because that evaluation has already been made, then explain how plant changes, plant or industry operational experience, or identified errors or limitations in the PRA models that could change that decision are addressed.
c) Attachment 4 to the LAR Enclosure indicates that for the ANO-1 and ANO-2 Focused Evaluation (ADAMS Accession No. ML17214A029), the NRC staff concluded that the station demonstrated effective flood protection from the reevaluated flood hazards.
However, the licensee did not provide any detailed information about whether any SSCs are credited for the flood protection, and how the SSCs are categorized. Identify any active and passive SSCs that are credited for screening the external flooding hazard and discuss how those SSCs will be included and considered in the proposed categorization process.
ML21281A254 *by e-mail **by memorandum OFFICE NRR/DORL/LPL4/PM NRR/DORL/LPL4/LA* NRR/DRA/APLA/BC**
NAME TWengert PBlechman RPascarelli DATE 10/8/2021 10/14/2021 9/21/2021 OFFICE NRR/DRA/APLC* NRR/DORL/LPL4/BC* NRR/DORL/LPL4/PM*
NAME SRosenberg JDixon-Herrity TWengert DATE 9/21/2021 10/15/2021 10/15/2021