L-2025-081, Revised Steam Generator Tube Inspection Reports
| ML25120A015 | |
| Person / Time | |
|---|---|
| Site: | Point Beach  |
| Issue date: | 04/30/2025 |
| From: | Mack K Point Beach |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| L-2025-081 | |
| Download: ML25120A015 (1) | |
Text
NEXTera ENERGYS POINT BEACH U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington DC 20555-0001 RE: Point Beach Nuclear Plant, Units 1 and 2 Docket Nos. 50-266 and 50-301 Renewed Facility Operating Licenses DPR-24 and DPR-27 Revised Steam Generator Tube Inspection Reports
References:
April 30, 2025 L-2025-081 10 CFR 50.36
- 1. NextEra Energy Letter L-2022-161, Point Beach Nuclear Plant, Unit 1 (U1 R40) Steam Generator Tube Inspection Report, October 13, 2022 (ADAMS Accession No.
M L22286A079)
- 2. Point Beach Nuclear Plant Letter NRG 2022-0015, Fall 2021 Unit 2 (U2R38) Steam Generator Tube Inspection Report, April 27, 2022 (ADAMS Accession No. ML22117A172)
- 3. Point Beach Nuclear Plant, Units 1 and 2 - Issuance of Amendment Nos. 277 and 279 Regarding Adoption of TSTF-577, "Revised Frequencies for Steam Generator Tube Inspections" (EPID L-2024-LLA-0104) (ADAMS Accession No. ML25016A209)
In Reference 3, NextEra Energy received authorization to adopt TSTF-577, which includes revised steam generator (SG) tube inspection and reporting requirements. Per the implementation notes for TSTF-577, a SG Tube Inspection Report satisfying the TSTF-577 revised requirements must be submitted after implementation of the license amendment. to this letter contains the revised SG tube inspection report for Point Beach Unit 1 (U1 R40). Enclosure 2 contains the revised SG tube inspection report for Point Beach Unit 2 (U2R38). Enclosures 1 and 2 supplement the SG tube inspection reports for Point Beach Units 1 and 2 dated October 13, 2022, and April 27, 2022, respectively (Reference 1 and Reference 2).
Should you have any questions regarding this submittal, please contact Ms. Maribel Valdez, Fleet Licensing Manager, at 561-904-5164.
Sincerely,
~~
KnnethAack Director, Licensing and Regulatory Compliance NextEra Energy Point Beach, LLC 6610 Nuclear Road, Two Rivers, WI 54241
Point Beach Nuclear Plant, Units 1 and 2 Docket Nos. 50-266 and 50-301 Enclosures cc:
USNRC Regional Administrator, Region Ill USNRC, Project Manager, Point Beach Nuclear Plant USNRC, Senior Resident Inspector, Point Beach Nuclear Plant Public Service Commission of Wisconsin L-2025-081 Page 2 of 2
Point Beach Nuclear Plant, Units 1 and 2 Docket Nos. 50-266 and 50-301 Point Beach Units 1 and 2 Point Beach Unit 1 (U1 R40), Steam Generator Tube Inspection Report (Updated to Reflect Revised Reporting Requirements of TSTF-577)
(5 pages follow)
Point Beach Unit 1 Docket No. 50-266 Point Beach Unit 1: U1 R40 Steam Generator Tube Inspection Report Updated per revised reporting requirements of TSTF-577-A, Rev 1 Design and Operating Parameters:
L-2025-081 Page 1 of 5 Point Beach Unit 1 is a Westinghouse 2-loop PWR with Model 44F steam generators (SGs). The SGs are U-tube heat exchangers with tube bundles fabricated using thermally treated Alloy 600 tubing. Each SG contains 3,214 tubes arranged in 45 rows and 92 columns, in a square-pitch configuration. Nominal tube OD is 0.875" with a 0.050" nominal wall thickness. Each SG tube bundle is supported by one drilled-hole flow distribution baffle (FOB) and 6 quatrefoil, broached-hole tube support plates {TSPs), all fabricated from stainless steel. Two (2) sets of anti-vibration bars (AVBs) in the U-bends also provide tube bundle support (AV1 / AV4, AV2 / AV3). Rows 1-8 of tubing in each SG were stress relieved in the U-bend region after bending. A schematic of a typical Model 44F SG is shown in Figure 1 of ADAMS Accession No. ML23095A171.
This updated SG Tube Inspection Report for Point Beach Unit 1 is submitted for the inspection of the SGs during refueling outage 40 (hereafter referred to as the U 1 R40 inspection or outage). The original SG Tube Inspection Report is docketed under ML22286A079 (Ref 1 ). Point Beach has implemented License Amendments 277 and 279 (Ref 3) to adopt "Revised Frequencies for Steam Generator Tube Inspections" (TSTF-577 Rev 1 ). This updated U1 R40 SG Tube Inspection Report is completed per section 5.6.8 of the Point Beach Technical Specifications. The inspection in U1 R40 was performed in accordance with Technical Specification 5.5.8 and is credited as the initial inspection (implementation outage) for transitioning to TSTF-577. At unit shutdown for the U 1 R40 inspection, the SGs had operated for approximately 32.8 EFPY since installation. Nominal That during full-power operation is approximately 607 deg F. Initial entry into Mode 4 following completion of the U1 R40 inspection was made on 4/19/22. A list of acronyms used in this report is provided in Appendix A.
A. Scope of Inspections Performed on each SG Unless otherwise noted, the U1 R40 SG inspection scope (primary, secondary) on each SG is outlined in Section A of the original SG Tube Inspection Report (Ref 1 ). The primary side scope is characterized as 100% full-length enhanced probe exams. The U1 R40 inspection scope was selected to meet the requirements of section 5.5.8.d of plant Technical Specifications, NEI 97-06 Rev 3 and its referenced EPRI SGMP Guidelines.
Scope Expansion: Since the base scope exams included a 100% full-length inspection of all tubes in each SG with enhanced probes, expansion of the inspection scope was not required.
B. NOE techniques utilized for tubes with increased degradation susceptibility This information is outlined in Section A of the original U 1 R40 SG Tube Inspection Report (Ref 1) and is summarized in the Table below:
Susceptible population NOE Techniques High stress tubes, Low row U-bends, Dings/Dents >5V +Point' Dings/Dents ~ 5V Bobbin Peripheral tubes, Bulges/Over-expansions Array
Point Beach Unit 1 Docket No. 50-266 C. For each degradation mechanism found:
L-2025-081 Page 2 of 5 Degradation mechanisms found during the U1 R40 inspection are provided in Section B of the original SG Tube Inspection Report (Ref 1 ).
- 1. The non-destructive examination (NDE) techniques utilized NOE techniques used for sizing the tube degradation mechanisms found in U1 R40 are in Table 1b of Ref 1. NOE techniques used for detecting tube degradation are found in Table 1a of Ref 1.
- 2. Location, orientation (if linear), measured size (if available), and voltage response for each indication For tube degradation mechanisms found in U1 R40, this information is presented in Section D of Ref 1 and listed explicitly in Appendix B of Ref 1 for each indication. The total number of tube wear indications at support structures that are less than 20% TW is summarized below:
Degradation Mechanism SG-A SG-B AVB Wear 91 81 TSP Wear 10 6
- 3. A description of the condition monitoring assessment and results, including the margin to the tube integrity performance criteria and comparison with the margin predicted to exist at the inspection by the previous forward-looking tube integrity assessment Condition monitoring (CM) assessment and results for the U1 R40 inspection are described in Sections G.1 through G.4 of Ref 1 for all degradation mechanisms found. The previous inspection was conducted in U1 R38. The margin to the tube integrity performance criteria, and comparison with the margin predicted to exist at the inspection by the previous forward-looking tube integrity assessment (OA) are summarized in the Table below for the degradation mechanisms found. All detected tube indications were smaller than the critical sizes for burst and therefore posed no challenges to tube structural integrity. No indications were required to be in-situ pressure tested to demonstrate that CM was satisfied.
Degradation Mechanism Max depth at Previous OA max CM limit U1 R40 (%TW) proj'd depth (% TW)
(%TW)
AVB wear 37 48.3 58.3 TSP wear (broached) 16 34.8 48.3 Foreign Object wear 36 Note 1 50.5 Maintenance Anomalies Note 2 Note 1: The deepest indication was caused by a transient foreign object with no history.
Note 2: This mechanism, caused by use of legacy sludge lance equipment, was redefined as historical maintenance anomalies for tracking purposes.
- 4. The number of tubes plugged during the inspection outage Fifteen (15) tubes were plugged during the U1 R40 inspection outage. This information is provided in Section E of Ref 1 for each degradation mechanism.
Point Beach Unit 1 Docket No. 50-266 L-2025-081 Page 3 of 5 D. An analysis summary of the tube integrity conditions predicted to exist at the next scheduled inspection (the forward-looking tube integrity assessment) relative to the applicable performance criteria, including the analysis methodology, inputs, and results For the wear-related degradation mechanisms reported in U1 R40, the mixed arithmetic/simplified statistical analysis technique (using a mixed strategy of projecting the worst-case degraded tube and combining uncertainties), is used for the OA calculations and its associated structural integrity. The operational assessment (OA) calculations were performed for both 2-cycle and 4-cycle inspection intervals in anticipation of transitioning from TSTF-510 to TSTF-577 prior to the next SG inspection. The worst-case BOC physical depth is chosen as the largest indication left in service. A Monte Carlo simulation was used to generate the EOC allowable depth limit while accounting for material property and burst relation uncertainties at the 0.95 probability and 50% confidence. To calculate the EOC projection, the 95th percentile NOE sizing uncertainties were deterministically applied to the largest flaw left in service.
For AVB wear, a growth rate of 2.5% TW/EFPY was used for the projection calculations, which was more conservative than the U1 R40 and U1 R38 growth rates of 1.41 % TW/EFPY and 1.51 % TW/EFPY, respectively. Due to the low number of TSP wear flaws with an associated growth, a growth rate of 3.5% TW/EFPY was used for the projection calculations for TSP wear, which was more conservative than the 1.0% TW/EFPY growth rate of the prior OA. An engineering evaluation completed for the remaining foreign objects in each SG (performed with respect to the worst flow conditions and tube vibration) showed that the limiting/largest objects had a wear time greater 6 EFPYs. For the maintenance anomalies from the use of historical sludge lance equipment, since the CM criteria are met and no continued degradation is anticipated, the structural and leakage criteria are expected to be met throughout the next 4 cycles.
The tube integrity conditions predicted to exist at the next scheduled SG inspection (U1 R44) relative to the applicable performance criteria are summarized in the Table below for each degradation mechanism. In all cases, the structural and leakage criteria are projected to be met at U1R44.
Degradation Mechanism U1 R40 max depth Max proj'd depth EOC structural returned to svc (% TW) at U1R44 (%TW) limit(%TW)
AVB wear 37 58.8 61.4 TSP wear (broached) 16 52.8 58.0 Foreign Object wear 24 Note 1 64.0 Maintenance Anomalies Note 2 Note 1: No continuing degradation expected from this historical FO wear with the part no longer present.
Note 2: No projected change in existing flaws caused by use of legacy sludge lance equipment.
E. The number and percentage of tubes plugged to date, and the effective plugging percentage in each SG See response provided in Section F of the original SG Tube Inspection Report (Ref 1 ).
F. The results of any SG secondary side inspections The results of secondary side inspections are described in Section G.6 of Ref 1. The inspection results for channel head components are described in Section G.5 of Ref 1.
Point Beach Unit 1 Docket No. 50-266 L-2025-081 Page 4 of 5 G. The primary to secondary leakage rate observed in each SG {if it is not practical to assign the leakage to an individual SG, the entire primary to secondary leakage should be conservatively assumed to be from one SG) during the cycle preceding the inspection which is the subject of the report See response provided in Section H of Ref 1.
H. The calculated accident induced leakage rate from the portion of the tubes below 20.6 inches from the top of the tubesheet for the most limiting accident in the most limiting SG. In addition, if the calculated accident induced leakage rate from the most limiting accident is less than 5.22 times the maximum operational primary to secondary leakage rate, the report should describe how it was determined See response provided in Section I of Ref 1.
I.
The results of monitoring for tube axial displacement {slippage). If slippage is discovered, the implications of the discovery and corrective action shall be provided See response provided in Section J of Ref 1
Point Beach Unit 1 Docket No. 50-266 L-2025-081 Page 5 of 5 APPPENDIX A - Additional Information Abbreviations and Acronyms:
ARC Alternate Repair Criteria NOD No Degradation Detected AVB Anti Vibration Bar NOE Non-destructive Examination BLG Bulge NEI Nuclear Energy Institute BOC Beginning of Cycle NSAL Nuclear Safety Advisory Letter CL Cold Leg OD Outside Diameter CM Condition Monitoring ODSCC Outside Diameter sec ONG Ding OXP Over-expansion ONT Dent PLP Possible Loose Part ECT Eddy Current Testing PWSCC Primary Water sec EFPM Effective Full Power Months SG Steam Generator EFPY Effective Full Power Years SGMP SG Management Program EOC End of Cycle TEC Tube End Cold EPRI Electric Power Research Institute TEH Tube End Hot ETSS Exam Technique Spec Sheet TS Tubesheet FOB Flow Distribution Baffle TSC Tube Sheet Cold FO Foreign Object TSH Tube Sheet Hot FOSAR Foreign Object Search and Retrieval TSP Tube Support Plate FSH Freespan Signal in History TTS Top ofTube Sheet HL Hot Leg TW Through Wall INR Indication Not Reportable VOL Volumetric ISPT In-Situ Pressure Test
Point Beach Nuclear Plant, Units 1 and 2 Docket Nos. 50-266 and 50-301 Point Beach Units 1 and 2 Point Beach Unit 2 (U2R38), Steam Generator Tube Inspection Report (Updated to Reflect Revised Reporting Requirements of TSTF-577)
(4 pages follow)
Point Beach Unit 2 Docket No. 50-301 Point Beach Unit 2: U2R38 Steam Generator Tube Inspection Report Updated per revised reporting requirements of TSTF-577-A, Rev 1 Design and Operating Parameters:
L-2025-081 Page 1 of 4 Point Beach Unit 2 is a Westinghouse 2-loop PWR with Model Delta 47F steam generators (SGs). The SGs are U-tube heat exchangers with tube bundles fabricated using thermally treated Alloy 690 tubing.
Each SG contains 3,499 tubes arranged in 86 rows and 105 columns, in a triangular pitch configuration.
Nominal tube OD is 0.875" with a 0.050" nominal wall thickness. Each SG tube bundle is supported by a flow distribution baffle (FOB) and 7 trefoil-shaped, broached-hole tube support plates (TSPs), all fabricated from stainless steel. Three (3) sets of stainless-steel anti-vibration bars (AVBs) in the U-bends also provide tube bundle support. Rows 1-14 of tubing in each SG were stress relieved in the U-bend region after bending. A schematic of a typical Model Delta 47F SG is shown in Figure 4.2-5 of the Point Beach UFSAR (Ref. ML24116A050).
This updated SG Tube Inspection Report for Point Beach Unit 2 is submitted for the inspection of the SGs during refueling outage 38 (hereafter referred to as the U2R38 inspection or outage). The original SG Tube Inspection Report is docketed under ML22117A172 (Ref 2). Point Beach has implemented License Amendments 277 and 279 (Ref 3) to adopt "Revised Frequencies for Steam Generator Tube Inspections" (TSTF-577 Rev 1 ). This updated U2R38 SG Tube Inspection Report is completed per section 5.6.8 of the Point Beach Technical Specifications. The inspection in U2R38 was performed in accordance with Technical Specification 5.5.8 and is credited as the initial inspection (implementation outage) for transitioning to TSTF-577. At unit shutdown for the U2R38 inspection, the SGs had operated for approximately 21.4 EFPY since installation. Nominal Thot during full-power operation is approximately 607 deg F. Initial entry into Mode 4 following completion of the U2R38 inspection was made on 10/30/21. A list of acronyms used in this report is provided in Appendix A.
A. Scope of Inspections Performed on each SG Unless otherwise noted, the U2R38 SG inspection scope (primary, secondary) on each SG is outlined in Section A of the original SG Tube Inspection Report (Ref 2). The primary side scope is characterized as 100% full-length bobbin probe exams (except for low row U-bends). In addition, diagnostic/special interest exams were performed using the +Point' probe for tubes in areas of interest with increased degradation susceptibility. The U2R38 inspection scope was selected to meet the requirements of section 5.5.8.d of plant Technical Specifications, NEI 97-06 Rev 3 and its referenced EPRI SGMP Guidelines.
Scope Expansion: Expansion of the inspection scope was not required.
B. NDE techniques utilized for tubes with increased degradation susceptibility This information is outlined in Section A of the original U2R38 SG Tube Inspection Report (Ref 2) and is summarized in the Table below:
Susceptible population NOE Techniques Low row U-bends, Peripheral tubes, Bulges/Over-expansions +Point'
Point Beach Unit 2 Docket No. 50-301 C. For each degradation mechanism found:
L-2025-081 Page 2 of 4 Degradation mechanisms found during the U2R38 inspection are provided in Section B of the original SG Tube Inspection Report (Ref 2).
- 1. The non-destructive examination (NDE) techniques utilized NOE techniques used for sizing the tube degradation mechanisms found in U2R38 are in Table 1 b of Ref 2. NOE techniques used for detecting tube degradation are found in Table 1a of Ref 2.
- 2. Location, orientation (if linear), measured size (if available), and voltage response for each indication For tube degradation mechanisms found in U2R38, this information is presented in Section D of Ref 2 for each indication. All tube wear indications were at support structures, less than 20% TW, and are summarized below:
Degradation Mechanism SG-A SG-B AVB Wear 8
0 TSP Wear 20 6
- 3. A description of the condition monitoring assessment and results, including the margin to the tube integrity performance criteria and comparison with the margin predicted to exist at the inspection by the previous forward-looking tube integrity assessment Condition monitoring (CM) assessment and results for the U2R38 inspection are described in Section G.1 of Ref 2 for all degradation mechanisms found. The previous inspection was conducted in U2R35. The margin to the tube integrity performance criteria, and comparison with the margin predicted to exist at the inspection by the previous forward-looking tube integrity assessment (OA) are summarized in the Table below for the degradation mechanisms found. All detected tube indications were smaller than the critical sizes for burst and therefore posed no challenges to tube structural integrity. No indications were required to be in-situ pressure tested to demonstrate that CM was satisfied.
Degradation Mechanism Max depth at Previous OA max U2R38 (%TW) proj'd depth (% TW)
AVB wear 9
19 TSP wear (broached) 10 16
- 4. The number of tubes plugged during the inspection outage No tubes were plugged during the U2R38 inspection outage.
CM limit
(%TW) 46 42 D. An analysis summary of the tube integrity conditions predicted to exist at the next scheduled inspection (the forward-looking tube integrity assessment) relative to the applicable performance criteria, including the analysis methodology, inputs, and results For the wear-related degradation mechanisms reported in U2R38, the simplified analysis technique (using a mixed strategy of projecting the worst-case degraded tube and combining uncertainties), is used for the OA calculations and its associated structural integrity. The operational assessment (OA) calculations were performed for both 3-cycle and 5-cycle inspection intervals in antfcipation of transitioning from TSTF-510 to TSTF-577 prior to the next
Point Beach Unit 2 Docket No. 50-301 L-2025-081 Page 3 of 4 SG inspection. The worst-case BOC physical depth is chosen as the largest indication left in service. A Monte Carlo simulation was used to generate the EOG allowable depth while accounting for uncertainties at the 0.95 probability and 50% confidence. To calculate the EOG projection, the 95th percentile NOE sizing uncertainties were applied to the largest flaw left in service.
For AVB wear, the growth rates were determined by a comparative analysis of paired data for SG-A, since no AVB wear was reported in SG-B. The U2R38 growth rates using paired data (with U2R35 were) all zero or negative except for one indication which had a measured growth rate point of 0.23% TW/EFPY, which was also the largest NOE measured growth rate.
Therefore, as a conservative measure, a growth rate of 2.14% TW/EFPY was used for OA projection calculations. This growth rate is based on 2 times the highest observed growth rate (for both AVB, TSP wear) during the prior (U2R35) inspection.
For TSP wear, the median rank fraction using Benard's approximation was used to calculate a 95th percentile growth rate. This growth rate (1. 72% TW/EFPY) was bounded by the conservatively calculated U2R35 growth rate of 2.14% TW/EFPY. Therefore, the more conservative 2.14%TW/EFPY was used for OA projection calculations.
The tube integrity conditions predicted to exist at the next scheduled SG inspection (U2R43) relative to the applicable performance criteria are summarized in the Table below for each degradation mechanism. In all cases, the structural and leakage criteria are projected to be met at U2R43.
Degradation Mechanism U2R38 max depth Max proj'd depth EOG structural returned to svc (% TW) at U2R43 (% TW) limit(%TW)
AVB wear 9
38.1 54 TSP wear (broached) 10 42.1 52 E. The number and percentage of tubes plugged to date, and the effective plugging percentage in each SG See response provided in Section F of the original SG Tube Inspection Report (Ref 2).
F. The results of any SG secondary side inspections The results of secondary side inspections are described in Section G.3 of Ref 2. The inspection results for channel head components are described in Section G.2 of Ref 2.
Point Beach Unit 2 Docket No. 50-301 L-2025-081 Page 4 of 4 APPPENDIX A - Additional Information Abbreviations and Acronyms:
ARC Alternate Repair Criteria NOD No Degradation Detected AVB Anti Vibration Bar NOE Non Destructive Examination BLG Bulge NEI Nuclear Energy Institute BOC Beginning of Cycle NSAL Nuclear Safety Advisory Letter CL Cold Leg OD Outside Diameter CM Condition Monitoring ODSCC Outside Diameter sec ONG Ding OXP Over-expansion ONT Dent PLP Possible Loose Part ECT Eddy Current Testing PWSCC Primary Water sec EFPM Effective Full Power Months SG Steam Generator EFPY Effective Full Power Years SGMP SG Management Program EOC End of Cycle TEC Tube End Cold EPRI Electric Power Research Institute TEH Tube End Hot ETSS Exam Technique Spec Sheet TS Tubesheet FOB Flow Distribution Baffle TSC Tube Sheet Cold FO Foreign Object TSH Tube Sheet Hot FOSAR Foreign Object Search and Retrieval TSP Tube Support Plate FSH Freespan Signal in History TTS Top ofTube Sheet HL Hot Leg TW Through Wall INR Indication Not Reportable VOL Volumetric ISPT In-Situ Pressure Test