ML24117A330
| ML24117A330 | |
| Person / Time | |
|---|---|
| Site: | Electric Power Research Institute |
| Issue date: | 05/21/2024 |
| From: | Lois James Licensing Processes Branch |
| To: | Gerond George Licensing Processes Branch |
| James L, NRR/DORL/LLPB | |
| References | |
| EPRI TR 3002028939, EPID L-2024-LRM-0062 pre-app, Risk-Informed HELB Methodolog | |
| Download: ML24117A330 (1) | |
Text
May 21, 2024 MEMORANDUM TO:
Gerond A. George, Chief Licensing Projects Branch Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation FROM:
Lois M. James, Senior Project Manager
/RA/
Licensing Projects Branch Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation
SUBJECT:
SUMMARY
OF ROBUST PRE-APPLICATION REVIEW AND MEETING FOR EPRI REPORT 3002028939, RISK-INFORMED HIGH-ENERGY LINE BREAK EVALUATION REQUIREMENTS (EPID NO. L-2024-LRM-0062)
On April 25, 2024, the U.S. Nuclear Regulatory Commission (NRC) staff met with Electric Power Research Institute (EPRI) representatives to discuss a robust pre-application review of EPRI Report 3002028939, Risk-informed High-Energy Line Break Evaluation Requirements. The meeting summary is Enclosure 1, and the list of attendees is Enclosure 2.
If you have any questions or comments, please contact me via email at Lois.James@nrc.gov.
Docket No. 99902021
Enclosures:
- 1. Meeting Summary
- 2. List of Attendees CONTACT: Lois M. James, NRR/DORL 301-415-3306
U.S. Nuclear Regulatory Commission Public Meeting Summary
Title:
Robust Pre-Application Review and Meeting for Electric Power Research Institute Report 3002028939, Risk-informed High-Energy Line Break Evaluation Requirements Date of Meeting: April 25, 2024, 1:00 pm - 3:00 pm Location:
Hybrid Type of Meeting: This was an Observation meeting in which attendees had an opportunity to observe the U.S. Nuclear Regulatory Commission (NRC) performing its regulatory function or discussing regulatory issues. Attendees had an opportunity to ask questions of the NRC staff or make comments about the issues discussed following the business portion of the meeting; however, the NRC was not actively soliciting comments towards regulatory decisions at this meeting.
Purpose of the Meeting: To provide NRC staffs comments on the draft Electric Power Research Institute (EPRI) Report 3002028939, Risk-informed High-Energy Line Break Evaluation Requirements (RI-HELB), to help EPRI produce a high-quality, complete report.
General Details: The NRC staff held a public, observational meeting with EPRI to provide NRC staffs comments on the draft EPRI Report 3002028939, Risk-informed High-Energy Line Break Evaluation Requirements, to help EPRI produce a high-quality, complete report. The meeting began at 1:00 pm and ended at 3:00 pm. There were fourteen NRC staff members, seven EPRI representatives, sixteen industry members, and four members of the public or individuals who did not identify an affiliation. The meeting began with introductions of the NRC staff and EPRI representatives.
By email dated April 8, 2024, EPRI requested a robust pre-application meeting to discuss the NRC staffs initial comments and questions on EPRI Report 3002028939 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML24117A319). In order to prepare for this meeting, EPRI provided access to the draft EPRI Report 3002028939 via the EPRI Reading Library.
Summary of Meeting: After introductions, the NRC staff began the discussion with the comments and questions previously provided to EPRI by e-mail dated April 22, 2024 (ADAMS Accession No. ML24117A312).
Question #1: Is the intent of the EPRI RI-HELB methodology to be used for licensees to address high-energy line break nonconformances and degraded conditions (operability) in addition to changing the HELB design and licensing basis?
The NRC staff and EPRI representatives had a detailed discussion about the scope and applicability of the EPRI RI-HELB methodology.
EPRI representatives stated that EPRI is currently weighing a near-term, narrow scope need versus long-term broad applicability scope and acknowledged that the near-term, narrow scope need was of higher importance. As a result of the discussion, EPRI representatives stated that EPRI will ensure that the scope of EPRI Report 3002028939 will be well defined and communicated.
Question #2: Provide explanation on how the EPRI RI-HELB methodology interfaces with the plants that have implemented the EPRI Topical Report TR-1006937 methodology and licensees that have not implemented the EPRI Topical Report TR-1006937 methodology. For example the requirement for 100% volumetric inservice examination of all pipe welds should be conducted during each inspection interval as defined in IWA-2400, American Society of Mechanical Engineers (ASME) Code,Section XI per MEB [Mechanical Engineering Branch] 3-1 or BTP
[Branch Technical Position] 3-4 (piping near containment penetration area).
The NRC staff explained that the question is whether a licensee which implements the RI-HELB methodology can change the licensing basis for plants that use EPRI Topical Report TR-1006937 risk-informed break exclusion region (RI-BER) or plants that are licensed to the MEB 3-1 or BTP 3-4 requirement for 100% volumetric inservice examination of all pipe welds (piping near containment penetration area) should be conducted during each inspection interval as defined in IWA-2400, ASME Code,Section XI?
EPRI representatives stated that was not the intent of EPRI Report 3002028939 and the scope of EPRI Report 3002028939 will be revised to be very clear on the intent and use of EPRI Report 3002028939.
Question #3: The EPRI RI-HELB methodology allows for operator action per Section 3.3.3.2 of EPRI TR 112657 which can change the conditional core damage probability and conditional large early release probability. For example, a high-energy line piping segment potentially being reclassified from a higher safety significance to a lower safety significance.
Operator recovery actions (isolation of the break) can only be credited if:
There is an alarm and/or clear indication, to which the operator will respond, The response is directed by procedure, The isolation equipment (e.g. valves) is not affected by the break, There is enough time to perform isolation and reduce consequences.
Provide explanation how operator (including manual) recovery actions can be used for ASME Class 1, 2, and 3 high-energy piping segments while plant is operating and not shutdown.
Note NCV 05000277,05000278/2023012-01 documents an example where operator action per Section 3.3.3.2 of EPRI TR 112657 was inadequately used for a non-high-energy line piping segment.
EPRI representatives stated that it is unlikely that manual actions to isolate high-energy lines would pass the criteria stated above due to time limitations, location of the break, personnel safety, etc.
The NRC staff recommended to EPRI that additional explanation of where and how this TR could be applied should be added to the scope.
Question #4: Sections 2.2.1 and 2.2.3 of the EPRI RI-HELB approach documents all the degradation mechanisms that will used to implement this methodology. ASME Section III Appendix W contains degradation mechanisms which are not included in the EPRI RI-HELB document. Has EPRI performed an analysis/evaluation to rule out certain ASME Section III Appendix W degradation mechanisms for example but not limited to ASME Class 1, 2, and 3 high-energy lines.
EPRI representatives stated that the degradation mechanisms mentioned in EPRI Report 3002028939 are based on RI-ISI. EPRI could add a reference to ASME Section III Appendix W, but ultimately it is the plant-specific analysis that needs to justify that no new or different degradation mechanisms are applicable.
The NRC staff explained that ASME Section III, Appendix W, is a good repository of degradation mechanisms and it is important to remind users of EPRI Report 3002028939 that new or different degradation mechanisms need to be considered in light of the plant, conditions, and locations. It was noted that NUREG-1801, Rev. 2, Generic Aging Lessons Learned (GALL)
Report (ADAMS Accession No. ML103490041) also has a useful list of degradation mechanisms.
Question #5: Provide examples of how a plant modification will reduce the consequence from high to medium and high to low as described in Section 2.4 of EPRI RI-HELB document.
The NRC staff recommended that EPRI Report 3002028939 clarify what is meant by plant modification so the NRC staff understands the potential applications of the report and can then provide better documentation in the safety evaluation.
Question #6: Provide examples of the application of the EPRI RI-HELB methodology for ASME Class 1, 2, and 3 high-energy line piping.
The NRC staff noted that all options provided by EPRI Report 3002028939 are not exercised in the non-safety example provided. Further, the NRC staff explained that it would be beneficial to the industry user and the NRC staff to see additional examples, including a safety-related example, that exercise most, if not all of the options provided by EPRI Report 3002028939.
EPRI representatives acknowledged additional examples would be beneficial, but the development of additional examples takes time. EPRI asked if the development and inclusion of additional examples would be an acceptance issue or could it be addressed as a request for additional information.
The NRC staff indicated that the development and inclusion of additional examples could be addressed as a request for additional information.
Question #7: The NRC staff noted that the report does not appear to specifically state that licensees probabilistic risk assessment (PRA) model used to support the RI-HELB program should be assessed against Regulatory Guide (RG) 1.200, An Approach for Determining the Technical Adequacy of Probabilistic Risk Assessment Results for Risk-Informed Activities.
EPRI representatives stated that EPRI understood the comment and will ensure that EPRI Report 3002028939 is clear with regards to PRA acceptability.
Question #8: The report also does not identify the Capability Category (CC) that the PRA model should be evaluated against. Upon identifying the CC, provide the justification that the selected CC of PRA is sufficient to support the evaluation of risk associated with the postulated high-energy line break.
EPRI representatives stated that they understood the comment and will ensure that EPRI Report 3002028939 is clear with regards to PRA acceptability.
Question #9: Internal Flooding is an integral part of the consequence evaluation. Clarify whether the internal flooding risk must be evaluated quantitatively. Clarify how the licensee would evaluate the consequence if the target equipment (or associated failure mode due to internal flooding) is not modeled in the PRA.
EPRI representatives stated that EPRI Report 3002028939 is based on RI-ISI, but EPRI understood the question and will consider best how to address.
Question #10: It is not clear whether the risk calculation included contribution from fire and external hazards. Clarify the treatments for the impact of fire risk and impact of other external events risks.
EPRI representatives stated that they understood the question and will consider language to remind users to consider how changes made under implementation of EPRI Report 3002028939 may impact other PRA hazards.
Question #11: Understanding the spatial impacts due to indirect effects is an essential element of the consequence evaluation. Section 3.2.3 of the report provided many important walkdown observations. However, the report does not indicate whether a walkdown is required. Clarify whether a walkdown is required.
EPRI representatives stated that a walkdown would likely be required and will consider adding language similar to walkdown language for the RI-ISI walkdown requirements.
Question #12: Confirm that the licensee will provide a discussion of how the key assumptions and sources of uncertainty were identified, and how their impact on the RI-HELB was assessed and dispositioned.
EPRI representatives stated that they understood the comment and will ensure that EPRI Report 3002028939 is clear with regards to PRA acceptability.
Question #13: Confirm that the licensee will provide personnel with expertise in PRA, plant operation, system design, safety or accident analysis to perform the risk-informed evaluation, review, and documentation.
EPRI representatives stated that they understood the question and will consider how best to address personnel expertise requirements.
Question #14: Risk-informed changes to the licensing basis should not resulted in any substantial change in the effectiveness of the barriers that prevent or mitigate radioactivity release. Release of radioactive materials from the reactor to the environment is prevented by a succession of passive barriers, including the fuel cladding, reactor coolant pressure boundary, and containment structure. RG 1.174, Rev. 3, Section 2.1.1.2 identifies seven considerations to evaluate how the proposed licensing basis change impacts defense-in-depth. It is not clear in the report how those considerations have been considered such that the licensing basis change is consistent with the defense-in-depth philosophy.
EPRI representatives stated that they understood the question and will consider where and how to address considering all aspects of risk-informed decisionmaking.
Question #15: The licensee should propose monitoring programs that adequately track the performance of equipment that, when degraded, can affect the conclusions of the licensees engineering evaluation and integrated decisionmaking that support the change to the licensing basis. The NRC staff noted that in Section 4 of the report indicates that there are no unique aspects of the RI-HELB methodology insofar as monitoring requirements are concerned. The NRC staff noted that (1) for RC2, RC4, and RC5 where plant modifications are used to lower the consequences, and (2) RC5 involves 10% inspection based on Degradation Mechanism. It is not clear to staff if current inspection programs are sufficient to monitor the performance of equipment consistent with RG 1.174, Revision 3, Section 3. Confirm that the licensee would include a description of the implementation and monitoring program as described in RG 1.174, Revision 3, Section 3.
EPRI representatives stated that they understood the question and the intent to follow the NRC policy on applying risk-informed principles in regulatory decisionmaking. EPRI representatives further stated that, while EPRI Report 3002028939 is not an RG 1.174 submittal, additional language could be included in EPRI Report 3002028939 to highlight the principles and make a link to updating corresponding PRA models when changes are made under RI-HELB.
The NRC staff highlighted the importance of both PRA configuration control and a feedback mechanism, like that required by 50.69 to Title 10 of the Code of Federal Regulations, because other plant changes could affect the risk significance of high-energy lines and thus their treatment under RI-HELB.
Public Participation Themes:
No member of the public spoke on the webinar.
Action Items/Next Steps:
The NRC staff will prepare and issue a meeting summary.
Attachments:
Meeting description and agenda - ADAMS Accession No. ML24106A211 NRC slide presentation - ADAMS Accession No. ML24117A327
U.S. Nuclear Regulatory Commission Public Meeting - Attendees List April 25, 2024
Title:
Robust Pre-Application Review and Meeting for Electric Power Research Institute Report 3002028939, Risk-informed High-Energy Line Break Evaluation Requirements U.S. Nuclear Regulatory Commission (NRC) Participants Name Affiliation Chakrapani Basavaraju NRC John Bozga NRC Adrienne Brown NRC James Delosreyes NRC David Gennardo NRC Gerond George NRC Lois James NRC Kamal Manoly NRC Demetrius Murray NRC Ching Ng NRC Jeff Poehler NRC David Rudland NRC Robert Tregoning NRC Ian Tseng NRC Electric Power Research Institute (EPRI) Participants Name Affiliation Ferrante, Fernando EPRI Richard Fougerousse EPRI Doug Kull EPRI Ashley Lindeman EPRI Patrick ORegan EPRI Michael Ruszkowski EPRI Jim Moody EPRI Industry Participants Name Affiliation Thomas Basso Nuclear Energy Institute Roy Linthicum Constellation Nuclear Brian Madderom Constellation Nuclear James Orr Constellation Nuclear Jeffrey Stone Constellation Nuclear Deann Raleigh Curtis-Wright Bob Post Enercon Services Industry Participants Name Affiliation John L. Wright Enercon Services Kerry Gaston Entergy James Laborde Entergy Bradley Tyers GE Vernova Bryan Daiber Entergy Jason Douglass Southern Nuclear Company Emily Ciobota Jensen Hughes Kenneth L. Fossum Idaho National Laboratory Tom Gazda Nexus Technical Services Corporation Public Participants Name Affiliation Phone number Public Suyash Deshpande Public Denis Gomes Public Daniel Laudien Public
ML24117A330 (NRC slides are listed in summary) ^via eConcurrence NRR-106 OFFICE NRR/DORL/LLPB/PM^
NRR/DORL/LLPB/LA^
NRR/DEX/EMIB/BC^
NRR/DRA/APLA/BC^
NAME LJames DHarrison SBailey BPascarelli DATE 05/02/2024 05/03/2024 05/16/2024 05/21/2024 OFFICE NRR/DORL/LLPB/BC^
NRR/DORL/LLPB/PM^
NAME GGeorge LJames DATE 05/21/2024 05/21/2024