ML23111A213
| ML23111A213 | |
| Person / Time | |
|---|---|
| Site: | Grand Gulf, River Bend, Waterford  |
| Issue date: | 04/21/2023 |
| From: | Couture P Entergy Operations |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| CNRO2023-00012 | |
| Download: ML23111A213 (1) | |
Text
Phil Couture Senior Manager Fleet Regulatory Assurance - Licensing 601-368-5102
Entergy Operations, Inc., 1340 Echelon Parkway, Jackson, MS 39213 CNRO2023-00012 10 CFR 50.55a April 21, 2023 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001
Subject:
Responses to Request for Additional Information concerning Relief Request Number EN-RR-22-001 - Proposed Alternative to Use ASME Code Case N-752, Risk-Informed Categorization and Treatment for Repair/
Replacement Activities in Class 2 and 3 Systems,Section XI, Division 1 Grand Gulf Nuclear Station, Unit 1 NRC Docket No. 50-416 Renewed Facility Operating License No. NPF-29 River Bend Station, Unit 1 NRC Docket No. 50-458 Renewed Facility Operating License No. NPF-47 Waterford Steam Electric Station, Unit 3 NRC Docket No. 50-382 Renewed Facility Operating License No. NPF-38 By letter dated June 30, 2022 (Reference 1), Entergy Operations, Inc. (Entergy) submitted a proposed alternative to the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code,Section XI, "Rules for Inservice Inspection of Nuclear Power Plant Components," at Grand Gulf Nuclear Station, Unit 1 (GGNS), River Bend Station, Unit 1, (RBS) and Waterford Steam Electric Station, Unit 3 (WF3). Specifically, pursuant to 10 CFR 50.55a(z)(1), Entergy requested authorization to use the alternative requirements of Code Case N-752, "Risk Informed Categorization and Treatment for Repair/Replacement Activities in Class 2 and 3 Systems,Section XI, Division 1," for determining the risk-informed categorization and for implementing alternative treatment for repair/replacement activities on moderate and high energy Class 2 and 3 items in lieu of certain ASME Boiler and Pressure Vessel Code,Section XI, IWA-1000, IWA-4000, and IWA-6000 requirements.
The NRC staff has reviewed the request and determined that additional information was required to complete their review (Reference 2).
CNRO2023-00012 Page 2 of 2 The Request for Additional Information (RAI) and the associated responses are provided in the Enclosure.
This letter contains no new regulatory commitments.
Should you have any questions or require additional information, please contact me at (601) 368-5102.
Respectfully, Phil Couture PC/gpn
Enclosure:
RESPONSES TO REQUEST FOR ADDITIONAL INFORMATION FOR RELIEF REQUEST EN-RR-22-001
References:
- 1) Entergy Operations, Inc. (Entergy) letter to the U. S. Nuclear Regulatory Commission (NRC), " Relief Request Number EN-RR-22-001 - Proposed Alternative to Use ASME Code Case N-752, Risk-Informed Categorization and Treatment for Repair/ Replacement Activities in Class 2 and 3 Systems,Section XI, Division 1," (CNRO2022-00018), ML22181B114, dated June 30, 2022.
WF-3) - FINAL RAIs for RR EN-RR-22-001, Use Code Case N-752, Risk-informed Categorization for Class 2 and 3 Systems (EPID: L-2022-LLR-0054)," dated March 24, 2023.
cc:
NRC Region IV-Regional Administrator NRC Senior Resident Inspector-Grand Gulf Nuclear Station NRC Senior Resident Inspector-River Bend Station NRC Senior Resident Inspector-Waterford Steam Electric Station NRC Project Manager-Grand Gulf Nuclear Station NRC Project Manager-River Bend Station NRC Project Manager-Waterford Steam Electric Station NRC Project Manager-Entergy Fleet Philip Couture Digitally signed by Philip Couture Date: 2023.04.21 09:56:27 -05'00'
ENCLOSURE CNRO2023-00012 RESPONSES TO REQUEST FOR ADDITIONAL INFORMATION FOR RELIEF REQUEST EN-RR-22-001
CNRO2023-00012 Enclosure Page 1 of 7 RESPONSES TO REQUEST FOR ADDITIONAL INFORMATION FOR RELIEF REQUEST EN-RR-22-001 Background to RAIs No. 1 - 5:
In its letter dated June 30, 2022 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML22181B114), the licensee states that Code Case N-752 is based on the Arkansas Nuclear One, Unit 2 (ANO 2) Relief Request (ANO2-R&R-004, Revision 1), and authorized in NRC safety evaluation dated April 22, 2009 (ML090930246). The licensee further states that the ANO-2 Relief Request was developed to serve as an industry pilot for developing a risk-informed repair/replacement. In Section 5.2.B. of its submittal, the licensee states that:
"The categorization process of Code Case N-752 is delineated in Appendix I of the Code Case. This categorization process is technically identical to the process approved by the NRC under Relief Request ANO2-R&R-004, Revision 1 (Reference 1), which, in turn, is based on founding principles in [Electric Power Research Institute] EPRI Report TR-112657, Revision B-A, "Revised Risk-Informed Inservice Inspection Evaluation Procedure," and the categorization process of Code Case N-660, but with improvements and lessons learned from trial applications. The attachment to this enclosure provides a comparison of the categorization processes of Code Case N-752 and Relief Request ANO2-R&R-004, Revision 1, as approved by the NRC (Reference 1). Note that attached comparison does not address editorial differences or clarifications. However, it does demonstrate that the two categorization processes are technically identical."
RAI No. 1:
Section 3.5.1 of the EPRI report contains the definition of piping segment consisting of four criteria. The EPRI report is referenced in Code Case N-752 without a clear reference to whether the definition of piping segment is used.
- a. Explain how the piping segments are defined in the licensees proposed alternative, that is in accordance with Code Case N-752.
- b. If the definition is different from that which is described in EPRI TR-112657, provide an evaluation and justification for any deviations in the definition of piping segments for Code Case N-752 from N-660, or from ANO-2-R&R-004.
- c. For deviations in the definition of piping segments, discuss the risk impact of these differences in terms of 10 CFR 50.69 risk-informed safety class (RISC) categorization.
Entergys Response to RAI No. 1:
- a. Entergy is requesting to use ASME Code Case N-752 with no exceptions or deviations.
ASME Code Case N-752 provides a definition of piping segment in -9000 Glossary (shown below), which Entergy will utilize to define a pipe segment for categorization.
"piping segment: a portion of piping, components, or a combination thereof, and their supports, in which a failure (i.e. loss of its pressure-retaining function) at any location results in the same consequence (e.g., loss of a system, loss of a pump train, indirect effects)"
CNRO2023-00012 Enclosure Page 2 of 7
- b. The ASME Code Case N-752 definition of a piping segment is the same as the ASME Code Case N-660 and ANO2-R&R-004 definition of a piping segment. Note: The ANO2-R&R-004 definition of piping segment is determined from Reference 1 (February 2008 document) where the glossary of the ANO2-R&R-004 method was provided in a submittal November 15, 2006 (Reference 4). Additionally, N-660 was conditionally approved by the NRC in RG 1.147 Revision 15 for Class 2, 3 and non-Class pressure retaining components and their associated supports.
The ASME Code Case N-752 definition of a piping segment is very similar to that contained in EPRI TR-112657 Revision B-A with the exception that failure likelihood is not included in the ASME Code Case N-752 definition of a piping segment. That is because ASME Code Case N-752 conservatively assumes a failure probability of 1.0 which is more conservative than evaluating the likelihood of failure as is required in EPRI TR-112657 Revision B-A Rl-lSl methodology.
To provide some additional background EPRI TR-112657 Revision B-A is also codified in ASME Code Case N-578 and Appendix R, Supplement 2. And a streamlined version of the RI-ISI methodology is contained in NRC endorsed ASME Code Case N-716.
While slightly different in wording, each of these approaches to "piping segments" have the same purpose. That is, to group pressure retaining items (e.g., welds, valve bodies, pipe runs, etc.) by common consequence.
- c. As discussed in RAI No. 1 a. and b. above, while there may be slightly different wording, there is no deviation in the definition of piping segments in Code Case N-752, N-660, or ANO-2-R&R-004. While EPRI TR-112657 Revision B-A considers likelihood of failure in its definition of a piping segment, the definition in N-752, N-660, and ANO-2-R&R-004 is more conservative in that it assumes failure with a probability of 1.0. As such, there is no risk impact of these differences in terms of 10 CFR 50.69 risk-informed safety class (RISC) categorization. See also response to RAI No. 3 for additional information.
RAI No. 2:
Code Case N-752 specifies corrective actions for those structures, systems, and components (SSCs) which have been categorized low safety significance (LSS). Describe how corrective actions will be programmatically addressed, including deviations from these program requirements.
Entergys Response to RAI No. 2:
Entergy is requesting to use ASME Code Case N-752 with no exceptions or deviations.
As described in section -1420 of ASME Code Case N-752, Entergy shall define the requirements to confirm reasonable confidence that each LSS item remains capable of performing its safety-related function(s) under design basis conditions, including the considerations (a through j) noted in the code case and the Entergy request.
LSS item requirements will be determined and documented per Entergy procedures. Deviations from these requirements are considered undesired conditions and will be reported through the Entergy corrective action process. The Entergy corrective action process takes appropriate
CNRO2023-00012 Enclosure Page 3 of 7 actions to monitor, investigate, and/or correct undesired conditions with the level of emphasis and effort commensurate with the risk and significance of the issue.
Section 5.2.E.12 from the Entergy Relief Request also provides additional details and notes:
"Corrective action of adverse conditions associated with LSS items will be identified and addressed in accordance with Entergy's existing corrective action program."
RAI No. 3:
In Section 5.2.F of the proposed alternative, the licensee states that " categorization and treatment requirements of Code Case N-752 applicable to repair/replacement activities are consistent with NRC requirements specified in 10 CFR 50.69."
Discuss all deviations in categorization of SSCs from the 10 CFR 50.69 risk-informed categorization program and the licensees proposed alternative that is in accordance with Code Case N-752. Discuss why any deviations are acceptable in accordance with 10 CFR 50.55a(z).
Entergys Response to RAI No. 3:
Entergy is requesting to use ASME Code Case N-752 with no exceptions or deviations.
Arkansas Nuclear One, Unit 1 & 2 as well as Waterford Steam Electric Station, Unit 3 are currently approved to use 10 CFR 50.69, while Grand Gulf Nuclear Station, Unit 1 and River Bend Station, Unit 1 are not.
As specified in Entergy Relief Request Section 5.2.F, the categorization methodology of ASME Code Case N-752 is consistent with that used in 10 CFR 50.69. Many licensees, [including Entergys Arkansas Nuclear One, Unit 1 & 2 as well as Waterford Steam Electric Station, Unit 3], have adopted 10 CFR 50.69 citing the ANO2-R&R-004 methodology (References 1 and 2) for the categorization of passive components and the passive function of active components. A comparison of the ANO2-R&R-004 methodology to ASME Code Case N-752 is provided in Reference 3, Enclosure Attachment 1 and is incorporated by reference. This comparison demonstrates that the categorization methodology of ASME Code Case N-752 is technically identical to that used in Relief Request ANO2-R&R-004 and many 10 CFR 50.69 applications.
One specific difference between implementation of ANO2-R&R-004 methodology for 10 CFR 50.69 and ASME Code Case N-752 is the code case allows implementation on a system basis or on individual items as noted in the Code Case Section -1100 "Scope" (included in response to RAI No. 4.a below).
As noted in Reference 2, the ASME Code Case N-752 categorization methodology will satisfactorily classify the affected Class 2 and 3 components as HSS or LSS.
Licensees that have implemented 10 CFR 50.69, "Risk-informed categorization and treatment of structures, systems and components for nuclear power reactors," may specify alternative treatment for Risk-Informed Safety Class (RISC)-3 and RISC-4 SSCs to the Inservice Inspection (ISI) Program and the Repair/Replacement Program (with the exception of fracture toughness) requirements for ASME Class 2 and Class 3 SSCs in 10 CFR 50.55a(g). Entergy has not yet implemented 10 CFR 50.69 at Grand Gulf Nuclear Station, Unit 1 and River Bend Station,
CNRO2023-00012 Enclosure Page 4 of 7 Unit 1; however, Code Case N-752 also permits exemptions from ASME Code,Section XI, Subsection IWA requirements for Repair/Replacement Activities. The specified exemptions in Code Case N-752 are consistent with scope of the requirements for RISC-3 and RISC-4 SSCs listed in 10 CFR 50.69(b)(1) that licensees can voluntarily exempt after implementation of 10 CFR 50.69.
Code Case N-752 requires the licensee to define alternative treatment requirements that confirm with reasonable confidence that each LSS item remains capable of performing its safety-related functions under design-basis conditions. Code Case N-752, paragraph -1420, "LSS Items," describes the characteristics that must be addressed by the licensee's alternate treatment for these activities on LSS components, including the specific elements delineated in the code case and in the Relief Request Section 5.2.E.
Entergy's adherence to the above elements covered in Code Case N-752 for Repair/Replacement Activities provides reasonable confidence that each LSS item will remain capable of performing its safety-related function.
The list of treatment requirements in Code Case N-752, paragraph -1420 is consistent with 10 CFR 50.69(d)(2), "RISC-3 SSCs." The regulation 10 CFR 50.69(d)(2) states, in part, that "inspection and testing, and corrective action shall be provided for RISC-3 SSCs." The Entergy Relief Request stated that the Inservice Inspection (ISI), Inservice Testing (IST), Snubber IST, and other inspection programs of LSS components were not affected by this Relief Request (Section 5.2.E.11). In addition, Section 5.2.E.12 of the application defines corrective actions for LSS items. Therefore, the Entergy alternative treatment requirements are consistent with the requirements in 10 CFR 50.69(d)(2)(ii), "Corrective Action."
Entergy intends to review and assess the existing PRAs to verify that they support the evaluations required by Code Case N-752, and will also maintain a feedback and adjustment process as defined in 10 CFR 50.69(e), which will require updates to the PRA and categorization and treatment process based on review of changes to the plant, operational practices, and applicable plant and industry operational experiences. In the Relief Request, Entergy states that these reviews and process adjustments will be done in a timely manner and at a period not to exceed every two refueling outages (Section 5.2.D).
RAI No. 4:
NRC Safety Evaluation for Relief Request ANO2-R&R-004 states, in part, that:
"Entergyhas requested to categorize passive SSCs (e.g., piping) and implement alternative special treatment activities limited to the repair/replacement activities for Class 2 and 3 pressure retaining items or their associated supports"
- a. Describe how the licensees application of Code Case N-752 in the proposed alternative aligns or deviates from the intent of the statement above.
- b. If the licensees use of Code Case N-752 allows categorization of components with active functions, describe how those components are evaluated for categorization and provide justification that active components are not categorized solely based on their pressure retaining function.
CNRO2023-00012 Enclosure Page 5 of 7 Entergys Response to RAI No. 4:
- a. Entergy is requesting to use ASME Code Case N-752 with no exceptions or deviations.
The Entergy request aligns with the statement above from the NRC Safety Evaluation for Relief Request ANO2-R&R-004 (Reference 2). Entergy is requesting to categorize passive SSCs (e.g., piping) and implement alternative special treatment activities limited to the Repair/Replacement Activities for Class 2 and 3 pressure retaining items or their associated supports with exceptions noted in ASME Code Case N-752 Section -1100 "Scope." The exceptions noted in the Code Case are also reflected in the Entergy request.
Specifically, ASME Code Case N-752 Section -1100 "Scope" states:
"This Case provides a process for determining the risk-informed categorization and treatment for repair/replacement activities on Class 2 and 3 items, except (a) that portion of the Class 2 feedwater system [>NPS 4 (>DN 100)] of pressurized water reactors (PWRs) from the steam generator, including the steam generator, to the outer containment isolation valve.
(b) piping within the break exclusion region [>NPS 4 (>DN 100)] for high energy piping systems as defined by the Owner.
This Case may be applied on a system basis, including all pressure-retaining items and their associated supports, or on individual items categorized as low-safety significant (LSS) within the selected systems."
The Entergy Relief Request Section 1.0 states:
"All ASME Class 2 and 3 items or components except the following:
(a)
Class CC and MC items.
(b)
Piping within the break exclusion region [> Nominal Pipe Size (NPS) 4 (DN 100)] for high energy piping systems1 as defined by the Owner.
(c)
That portion of the Class 2 feedwater system [> NPS 4 (DN 100)] of pressurized water reactors (PWRs) from the steam generator (SG), including the SG, to the outer containment isolation valve."
- b. Many pressure retaining components only have a pressure boundary (passive) function (e.g., a run of piping, an elbow). However, there are a number of pressure retaining components that have a passive function as well as an active function (e.g., valve opens/closes). The ASME Code Case N-752 categorization process as well as the alternate treatment process of ASME Code Case N-752 only applies to the pressure boundary function of these components. That is, the active function of these components will be "uncategorized" by the ASME Code Case N-752 application and there will be no changes to treatment applied to the active function of these components due to the ASME Code Case N-752 application.
1 NUREG-0800, section 3.6.2 provides a method for defining this scope of piping.
CNRO2023-00012 Enclosure Page 6 of 7 RAI No. 5:
The ANO2-R&R-004 LAR (ML071150108) states the following:
"This process shall be applied on a system basis, including pressure-retaining items and their associated supports within the selected system."
"Entergy will define the boundaries included in the scope of the RISC evaluation process consistent with the previously approved [risk-informed inservice inspection] (RI-ISI) application."
- a. Describe how the licensees application of Code Case N-752 in the proposed alternative aligns or deviates from the intent of the statements above.
- b. If the licensees use of Code Case N-752 deviates from the scope as defined above, provide justification for how the evaluation process sufficiently captures impacts from unanalyzed components within a system.
Entergys Response to RAI No. 5:
- a. Entergy is requesting to use ASME Code Case N-752 with no exceptions or deviations.
As discussed in the Entergy Relief Request, Paragraph -1100 of Code Case N-752 states:
"This Case may be applied on a system basis, including all pressure retaining items and their associated supports, or on individual items categorized LSS within the selected systems."
The risk-informed methodology contained in Code Case N-752 requires that the component's pressure boundary function be assumed to fail with a probability of 1.0, and all impacts caused by the loss of the pressure boundary function be identified. This would include identifying impacts of the pressure boundary failure on the component under evaluation, identifying impacts of the pressure boundary failure of the component on the system in which the component resides, as well as identifying impacts of the pressure boundary failure of the component on any other plant SSC. This includes direct effects (e.g., loss of the flow path) of the component failure and indirect effects of the component failure (e.g., flooding, spray, pipe whip, loss of inventory). This comprehensive assessment of total plant impact caused by a postulated individual component failure is then used to determine the final consequence ranking. As such, the final consequence rank of the individual component would be the same regardless of whether the entire system or only the individual component is subject to the risk informed methodology.
The boundaries of the evaluation are determined by the owner and documented as part of the categorization.
- b. Code Case N-752 is limited to Class 2 and 3 items. All unanalyzed Class 2 and 3 components will continue to meet their applicable nuclear special treatment requirements (e.g., Repair/Replacement per ASME Section XI requirements, Quality Assurance Program Manual per Appendix B, etc.).
CNRO2023-00012 Enclosure Page 7 of 7 Request for Confirmation of Information (RCI) No. 1 In Section 5.2.E.12 of the proposed alternative, the licensee states that "Conditions that would prevent a LSS item from performing its safety-related function(s) under design basis conditions will be corrected in a timely manner."
Confirm that for those SSCs under 10 CFR 50.36, "Technical Specifications," they will be addressed within the timeline of the limiting conditions of operability or the necessary action statements will be performed.
Entergys Response to RCI No. 1 For the proposed alternative to adopt ASME Code Case N-752, Entergy hereby confirms that the Technical Specifications required by 10 CFR 50.36 will continue to be complied with in every aspect. Specifically, in accordance with Limiting Condition for Operation (LCO) 3.0.1, LCOs will be met during the Modes or other specified conditions in the Applicability. This includes LCOs containing SSCs that have been categorized as LSS. If a LCO is not met during the Modes or other specified conditions in the Applicability, the Required Actions of the associated Conditions will be met in accordance with LCO 3.0.2. The Required Actions would be taken within the associated Completion Times. Required Actions must be completed prior to the expiration of the specified Completion Time.
References:
- 1. Entergy Letter to NRC dated April 17, 2007, "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 Energy Systems,"
(ML071150108) as supplemented by letters (ML072220160) dated August 6, 2007, (ML080520186) February 20, 2008, and (ML090120620) January 12, 2009.
- 2. Safety Evaluation Report (SER) by the Office of Nuclear Reactor Regulation "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," (ML090930246), dated April 22, 2009.
- 3. Entergy letter to NRC, "Relief Request Number EN-20-RR-001 - Proposed Alternative to Use ASME Code Case N-752, Risk-Informed Categorization and Treatment for Repair/Replacement Activities in Class 2 and 3 Systems,Section XI, Division 1,"
(ML20148M343), dated May 27, 2020.
- 4. Entergy letter to NRC, "Request for Alternative ANO2-R&R-004 Request to Use ASME Code Case N-752, Risk-Informed Safety Classification and Treatment for Repair /
Replacement Activities in Class 2 and 3 Moderate Energy Systems," (ML063250351),
dated November 15, 2006.