ML25182A275
| ML25182A275 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 06/30/2025 |
| From: | Justin Poole Plant Licensing Branch III |
| To: | Britting J, Filbrandt A, Schultheis M Holtec Palisades |
| References | |
| EPID L-2025-LLA-0036 | |
| Download: ML25182A275 (1) | |
Text
From:
Justin Poole To:
Michael Schultheis; Johann Britting; Amy Filbrandt Cc:
Subject:
Request for Additional Information RE: Steam Generator Repair by Sleeving Amendment L-2025-LLA-0036 Date:
Monday, June 30, 2025 4:42:00 PM Attachments:
RAI-10640-R1-REDACTED.pdf Mike/Johann, By letter dated February 11, 2025, as supplemented by letters dated May 29, 2025 (Agencywide Documents Access and Management System Accession Nos.
ML25042A692 and ML25149A013), Holtec Palisades, LLC requested U.S. Nuclear Regulatory Commission (NRC) review and approval of a license amendment request (LAR) to revise the Palisades Nuclear Plant (PNP) technical specifications to allow the use of Framatome Alloy 690 sleeves to repair defective steam generator (SG) tubes as an alternative to removing the tubes from service by plugging.
On June 11, 2025, the NRC staff sent the licensee DRAFT RAIs to ensure that the questions are understandable, the regulatory basis is clear, there is no proprietary information contained in the redacted version of the RAIs, and to determine if the information was previously docketed.On June 23, an additional DRAFT RAI was included. Based on discussions with your staff, a 30-day from the date of this email to respond to the RAIs was agreed upon, though some of the documents request may go beyond that date. As stated by the PM, please identify those that may go beyond the date, the reason why, and a date when they will be submitted on the docket. Due to the proprietary information contained with the questions, the attached is the final version of the redacted RAIs. These RAIs will be put in ADAMS as a publicly available document.
Justin C. Poole Project Manager Palisades, TMI, Duane Arnold Restart NRR/DORL/LPL 3 U.S. Nuclear Regulatory Commission (301)415-2048
OFFICIAL USE ONLY - PROPRIETARY INFORMATION 1
OFFICIAL USE ONLY - PROPRIETARY INFORMATION REQUEST FOR ADDITIONAL INFORMATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION PALISADES - LAR TO SUPPORT SG REPAIR BY SLEEVING HOLTEC DECOMMISSIONING INTERNATIONAL, LLC PALISADES, UNIT 1 DOCKET NO. 05000255 ISSUE DATE: N/A
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Background===
By letter dated February 11, 2025, Holtec Palisades requested U.S. Nuclear Regulatory Commission (NRC) review and approval of a license amendment request (LAR) to revise the Palisades Nuclear Plant (PNP) technical specifications to allow the use of Framatome Alloy 690 sleeves to repair defective steam generator (SG) tubes as an alternative to removing the tubes from service by plugging. The approval of this LAR is contingent upon the prior approval of the LAR, dated December 14, 2023 (ML23348A148), that supports resumption of power operations at PNP (e.g., restores power operation technical specifications) and is currently under NRC review. Accordingly, the technical specification changes contained in both LARs must be approved and implemented to support the resumption of power operations at PNP.
The LAR to permit SG sleeve installation proposed changes to the following PNP technical specifications. Note, these proposed changes modify the PNP power operation technical specifications that are currently under NRC review in a separate LAR.
Surveillance Requirement (SR) 3.4.1.3, Verify PCS [primary coolant system] total flow rate within the limit specified in the COLR [core operating limits report],
Technical Specification (TS) 3.4.17, Steam Generator (SG) Tube Integrity, TS 5.5.8, Steam Generator (SG) Program, and TS 5.6.8, Steam Generator Tube Inspection Report.
Regulatory Basis Section 182(a) of the Atomic Energy Act requires nuclear power plant operating licenses to include TS. In 10 CFR 50.36, Technical specifications, NRC regulatory requirements related to the content of the TS are established. The TS for all current pressurized water reactor (PWR) licenses require that an SG Program be established and implemented to ensure that SG tube integrity is maintained. Programs established by the licensee, including the SG Program, are listed in the administrative controls section of the TS and contain the necessary requirements to operate the facility in a safe manner.
SG tube integrity is maintained by meeting the performance criteria specified in the TS for structural integrity and leakage integrity, consistent with the plant design and licensing basis.
The TS require that a condition monitoring assessment be performed during each outage in which the SG tubes are inspected, to confirm that the performance criteria are being met. The TS include provisions regarding the scope, frequency, and methods of SG tube inspections.
These provisions require that the inspections be performed with the objective of detecting flaws of any type that may be present along the length of a tube and that may satisfy the applicable tube plugging criteria.
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OFFICIAL USE ONLY - PROPRIETARY INFORMATION The applicable tube plugging criteria, specified in the TS, are that tubes found during in service inspection to contain flaws with a depth equal to or exceeding 40 percent of the nominal wall thickness shall be plugged, unless the tubes are permitted to remain in service through application of alternate repair criteria provided in the TS. The TS also include a limit on operational primary-to-secondary leakage, beyond which the plant must be promptly shut down. Should an existing flaw that exceeds the tube integrity repair limit not be detected during the periodic tube surveillance required by the plant TS, the operational leakage limit provides added assurance of timely plant shutdown before tube structural and leakage integrity are impaired, consistent with the design and licensing bases.
The general design criteria (GDC) in Appendix A to Part 50 of Title 10 of the Code of Federal Regulations (10 CFR) provide regulatory requirements that state the reactor coolant pressure boundary (RCPB) shall have an extremely low probability of abnormal leakage and of gross rupture (GDC 14), shall be designed with sufficient margin (GDCs 15 and 31), shall be of the highest quality standards practical (GDC 30), and shall be designed to permit periodic inspection and testingto assess structural and leak tight integrity (GDC 32). For plants that were issued construction permits before the effective date of 10 CFR Part 50, Appendix A, the plant-specific principal design criteria (PDC) in the plant design basis established similar fundamental regulatory requirements pertaining to the integrity of the steam generator tubing.
Question 1, Figure 3.4-2, provides a longitudinal section of the leak limiting sleeve design. This figure, however, does not provide dimensions on the Detail of Sealing Ribs. The sealing ribs in this image appear different than the ribs shown in the slides for the closed public meeting in January 2025 (Accession No. ML25006A181). Provide a dimensioned drawing for the sleeve design, length of each hydraulic expansion, distance between adjacent expansions, and include the sealing ribs. Discuss how the sealing ribs interact with the inside diameter of the parent tube into which it is expanded.
Question 2 The final paragraph in the Enclosure 5 Executive Summary states that since most stress corrosion cracking (SCC) indications are on the hot leg, eddy current inspection from the cold leg through the tube U-bend is facilitated. Inspection from the cold leg, particularly for the low row hot leg tubes, may involve using undersized bobbin probes that will have fill factors below those currently being used for inspections. Provide the diameter of eddy current probes to be used for low row tube inspection from the cold leg. If these low row tube inspections require probes with smaller diameter than previously used, provide the fill factor for the undersized probes and discuss if site specific performance demonstration has been performed demonstrating adequate detection of outside diameter stress corrosion cracking (ODSCC). Are there any limitations on sleeving low row tubes due to inspection concerns from the cold leg?
Question 3 The existing SCC in the Palisades steam generator tubes provide an opportunity to gather additional field data on a range of SCC, before and after sleeve installation, using the same eddy current probe design and technique that would be used for inspection of a sleeve/tube
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OFFICIAL USE ONLY - PROPRIETARY INFORMATION assembly. Are there plans to gather additional field data related to detection of SCC with the recently qualified technique that will be used for sleeve assembly inspection? If so, provide a description of the additional inspections, discuss the purpose of any additional planned inspections, and provide any available results.
Question 4, states Section 3.9 States that, The sleeve design and sleeving procedure were qualified by testing for leakage in accordance with ASME B&PV Code Section XI, IWA-4725 and The relevant section in the 2007 Edition with 2008 Addenda of the Code is IWA-4725, Expansion. Confirm that the reference to -4725, Expansion should be -4720, Sleeving.
Question 5 The NRC staff notes that IWA-4721 contains multiple sub-sections that are applicable to the hydraulic sleeves addressed by this LAR. Confirm that all applicable sub-sections of IWA-4720 have been included in your qualification process.
Question 6 Figure 5-1 of Enclosure 5 illustrates locations that cannot be sleeved due to interference with a bend in the tube or due to the diagonal support. Clarify whether this diagram indicates just three locations that cannot be sleeved, or whether it illustrates that all tubes with specific characteristics, such as an upper sleeve expansion near a bend interference or adjacent to a diagonal support cannot be sleeved. How many total hot leg support plate locations would not be candidates for sleeving based on these restrictions?
Question 7, Section 6.5.2 describes Framatome Testing and Analysis. Section 6.5.2.1 discusses the Stress Indexing Test. Respond to the following questions:
a) PROPRIETARY SHOWN IN BRACKETS ((
))?
b) Was the sleeve installed using the same installation process and parameters as proposed for Palisades?
c) ((
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OFFICIAL USE ONLY - PROPRIETARY INFORMATION
)).
d) ((
)). However, the location of the cracking on the OD of the tube is different than the expected ID location, based on the industry investigations cited in Section 6.5.1 and ((
)). Please discuss why this result may have been obtained. In addition, if cracking of the parent tube were to occur, ((
)).
Question 8, Section 6.5.2.2, discusses the measurement of residual stresses from sleeve installation using an X-Ray diffraction technique that measures strain of the parent tubes crystal lattice. The second paragraph states that the PROPRIETARY SHOWN IN BRACKETS ((
............................./....................
)). Please clarify whether this is in both directions from the apex and whether each of the eight hydraulic expansions would be expected to have similar peak stresses at the expansion transition.
Question 9 Section 6.5.2.4 of Enclosure 5 states that Framatomes investigation into residual stress from hydraulic expansion agrees well with industry evaluation of hydraulic and explosive tubesheet expansions. The statement is made that expansion diameter has little effect on the residual stresses induced by hydraulic expansions. Please clarify if the expansion diameter means the diameter of the tubing being expanded (e.g., 3/4 inch as compared to 5/8 inch tubing) or the expansion amount (e.g., labeled expansion size in Table 6-2). Please provide a technical basis for this statement that expansion diameter has little effect on the residual stresses induced by hydraulic expansions.
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OFFICIAL USE ONLY - PROPRIETARY INFORMATION Question 10 Results from caustic corrosion testing are presented in Enclosure 5, Section 6.5.2.5. Table 6-2 provides results from caustic corrosion tests. Are these Alloy 690 sleeves installed in Alloy 600 tubing using the same installation process and parameters as proposed for Palisades?
Question 11 The Caustic Corrosion Testing section states that PROPRIETARY SHOWN IN BRACKETS ((
)). This appears to be a valid conclusion to draw from the laboratory test results. The applicability to the Palisades SGs is uncertain. If available, provide any primary side water chemistry measurements that would be representative of steam generator tubing primary side conditions between permanent shutdown and when the primary side chemistry was restored to within Electric Power Research Institute (EPRI) primary water chemistry guidelines. Has an assessment been made of how the primary water chemistry (prior to restoring the reactor coolant system to EPRI water chemistry guidelines) could potentially affect PWSCC in Palisades SG tubes?
Question 12 The service life of Framatomes Hydraulic Sleeve is discussed in Enclosure 5, Section 6.5.3.
The final sentence in this section states that the operating history of Palisades provides confidence that the hydraulicly expanded sleeves will last for the expected remaining life of the SGs. This statement is based on PROPRIETARY SHOWN IN BRACKETS ((
)). An alternate way of interpreting the Table 6-2 data is that some small percentage of the parent tubes with sleeves may experience relatively short times to crack initiation. Therefore, demonstrating detection of parent tube SCC in the sleeve-to-parent tube pressure boundary is a necessary part of the proposed eddy current qualification. Discuss how the eddy current qualification data demonstrates that parent tube SCC in the sleeve-to-tube assembly joints can be reliably detected before challenging tube integrity.
Question 13 Leakage is discussed in Enclosure 5, Section 8.2.5. Only the non-severed test specimens are discussed in this section, since this is the condition expected in the Palisades steam generator.
For the main steam line break (MSLB) leakage calculations, each installed sleeve is assumed to
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OFFICIAL USE ONLY - PROPRIETARY INFORMATION be leaking at the sleeve MSLB leakage rate. It is possible that over time a parent tube could experience circumferential cracking at the outermost expansion that is not detected until propagating to a larger crack size. What was the range and maximum leakage obtained from the samples PROPRIETARY SHOWN IN BRACKETS ((
)).
Question 14 Section 9 of Enclosure 5 discusses sleeve installation. Figure 9-3 provides the typical installation process expansion curve. Discuss the actions taken if there is a deviation from the typical curve during sleeve installation. In addition, describe what steps would be taken if a system leak is detected during installation of a sleeve to ensure the sleeve is properly installed and that the most recent sleeve installations before the leak was detected were properly installed.
Question 15 Eddy current inspection following the installation of a tube sleeve is described in Enclosure 5, Section 9.3. Provide a detailed discussion of the information obtained in the baseline eddy current examination performed after sleeve installation, including whether bobbin coil profiling is used to verify that the sleeve expansion was in the expected range.
Question 16, Section 10.1 - Eddy Current Requirements for Tubing with Sleeves, states that in tubing with multiple hot leg sleeves, the parent tubing between the sleeves is inspected full length with the +PointTM probe. Please confirm that the +Point will be used for the entire parent tube inspection even when sleeve elevations are far apart (e.g., Tube Support Plate (TSP)-1 and TSP-5). In addition, if the highest sleeve elevation in a given tube is at TSP-4, discuss which inspection technique will be used from the TSP-4 sleeve elevation to the TSP-5 elevation.
Question 17 From the drawings included in LAR Enclosure 5, Figure 5-4, there appears to be an OD taper at both ends of each sleeve, which creates a small air gap between the sleeve and parent tube.
Please discuss how this air gap affects eddy current inspection capability in this region and how the transition from the end of a sleeve to the parent tube affects eddy current data, including noise.
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OFFICIAL USE ONLY - PROPRIETARY INFORMATION Question 18, Section 10.3.4 Eddy Current Sleeve Experience Conclusion Section, states that OE in the industry also demonstrated the successful detection of axial ODSCC (groove intergranular attack (IGA)) below the sleeve in the parent tubing with the +PointTM probe at a Once-Through Steam Generator (OTSG) plant. Please discuss these inspection results in more detail, such as the groove IGA location relative to the sleeve, and the depth and length of groove IGA that was detected, if available.
Question 19 Confirm that all in-service tube/sleeve assemblies will be inspected each outage that SG tube inspections are performed.
Question 20 Reference 3 to Enclosure 5 of the LAR is Framatome Document 08-9384357-001, Hydraulically Expanded Sleeves for 3/4 Inch Steam Generator Tubes at Palisades Nuclear Power Plant, January 2025. Table 9-6 in this document provides Sleeve Freespan Expansion Dimensions.
Define what portion of the sleeve is considered the sleeve Freespan. There is a typographical error for the maximum Tube OD dimension. Also, clarify if the listed values for maximum and minimum tube wall, sleeve ID, and sleeve OD that dont seem consistent with the column headings of maximum and minimum are correct.
Question 21 Provide a sample of eddy current test results (e.g., range of flaw amplitudes and flaw lengths) that compare Palisades stress corrosion cracking signals before and after sleeving that demonstrate the ability to detect cracking in the parent tube behind the sleeve with eddy current testing.
Question 22 Please provide the following reference documents on the docket:
Framatome Document 08-9384357-001, Design Specification - Hydraulically Expanded Sleeves for 3/4 Inch Steam Generator Tubes at Palisades Nuclear Power Plant, January 2025.
Framatome Document 32-9386352 Calculation Summary Sheet, 3/4 Mechanical TSP Sleeve Leak Rate Analysis for Palisades, January 2025.
Framatome Document 32-9387171-000, Palisades SG Sleeve Primary Stress and Fatigue Evaluation, January 2025.
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OFFICIAL USE ONLY - PROPRIETARY INFORMATION Framatome Document 43-10202-P-00, Mechanical TSP Sleeve Qualification for 3/4 OD Tubes, December 1994.
Framatome Document 51-9391941, Palisades Eddy Current Sleeve Site Qualification, May 2025.
Framatome Document 51-9321652-000, "Palisades Steam Generator Condition Monitoring for 1R27.
Framatome Condition Monitoring and Operational Assessment (CMOA) for Restart Inspection 1D28.
Framatome Document 51-9385821, Tube Support Plate (TSP) Sleeving Procedure Specification (SPS) for Palisades Steam Generator 3/4 Tubes, May 2025.