ML24117A316

"Draft Meeting" is not in the list (Request, Draft Request, Supplement, Acceptance Review, Meeting, Withholding Request, Withholding Request Acceptance, RAI, Draft RAI, Draft Response to RAI, ...) of allowed values for the "Project stage" property.

Draft Questions in Support of Robust Pre-Application Review and Meeting for EPRI Report 3002028939, Risk-informed High Energy Line Break Evaluation Requirements

ML24117A316
Person / Time
Site:	Electric Power Research Institute
Issue date:	04/22/2024
From:	Licensing Processes Branch
To:
References
EPRI TR 3002028939, EPID L-2024-LRM-0062 pre-app, Risk-Informed HELB Methodology
Download: ML24117A316 (1)

Text

DRAFT DRAFT Deterministic questions:

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?

2) Provide explanation on how the EPRI RI HELB methodology interfaces with the plants that have implemented the EPRI Topical Report TR1006937 methodology and licensees that have not implemented the EPRI Topical Report TR1006937 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, ASME Code,Section XI per MEB 3-1 or BTP 3-4 (piping near containment penetration area).

3) The EPRI RI HELB methodology allows for operator action per Section 3.3.3.2 of EPRI TR 112657 which can change the CCDP and CLERP. 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.

4) Section 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.

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.

6) Provide examples of the application of the EPRI RI HELB methodology for ASME Class 1, 2 and 3 high energy line piping.

PRA questions:

DRAFT DRAFT The NRC staff noted that the report does not appear to specifically stated that licensees 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.

7) 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 Capability Category of PRA is sufficient to support the evaluation of risk associated with the postulated high-energy line break.

8) 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.

9) 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.

10) 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.

11) 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.

12) 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.

13) 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.

14) 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 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 staff noted that (1) for RC2, RC4, and RC5 where

DRAFT DRAFT 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.