L-2025-169, U4R35 Steam Generator Tube Inspection Report
| ML25269A022 | |
| Person / Time | |
|---|---|
| Site: | Turkey Point  |
| Issue date: | 09/25/2025 |
| From: | Mack K Florida Power & Light Co |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| L-2025-169 | |
| Download: ML25269A022 (1) | |
Text
U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington DC 20555-0001 September 25, 2025 RE:
Turkey Point Nuclear Generating Station, Unit 4 Docket No. 50-251 Subsequent Renewed Facility Operating License DPR-41 U4R35 Steam Generator Tube Inspection Report L-2025-169 10 CFR 50.36 Florida Power & Light Company (FPL) hereby submits the enclosed Turkey Point Unit 4 Cycle 35 Refueling Outage (U4R35) Steam Generator Tube Inspection Report. In accordance with Turkey Point Technical Specification (TS) 5.6.5, the report is required within 180 days after the initial entry into MODE 4 following completion of the Steam Generator tube inspection required by Turkey Point TS 5.6.5.
This letter contains no new regulatory commitments.
Should you have any questions regarding this submission, please contact Ms. Maribel Valdez, Fleet Licensing Manager, at 561-904-5164.
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Director, Licensing and Regulatory Compliance Florida Power & Light Company Enclosure cc:
USNRC Regional Administrator, Region II USNRC Project Manager, Turkey Point Nuclear Generating Station USNRC Senior Resident Inspector, Turkey Point Nuclear Generating Station Mr. Clark Eldredge, Florida Department of Health Florida Power & Light Company 9760 SW 344th Street, Homestead, FL 33035
Turkey Point Unit 4 Docket No. 50-251 Enclosure TP4-35 Steam Generator Tube Inspection Report Design and Operating Parameters:
L-2025-169 Page 1 of 10 Turkey Point Unit 4 is a Westinghouse 3-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 (AV1/4, AV2/3). Rows 1-8 of tubing in each SG were stress relieved in the U-bend region after bending. A schematic of the Turkey Point Model 44F SGs is shown in Figures 4.2-4 and 4.C-1 of the Turkey Point UFSAR (Ref. proprietary version to ADAMS Accession No. ML24135A106).
The SG Tube Inspection Report for Turkey Point Unit 4 is submitted for the inspection of the SGs during refueling outage 35 (hereafter referred to as the TP4-35 inspection or outage) and is completed per section 5.6.5 of the Turkey Point Technical Specifications. The inspection in TP4-35 was performed in accordance with Technical Specification 5.5.6. Since the previous SG inspection (TP4-33), the SGs operated for approximately 17.45 EFPM and 15.52 EFPM during fuel cycles 33 and 34, respectively, leading up to the TP4-35 inspection. At unit shutdown for the TP4-35 inspection, the SGs had operated for approximately 34.02 EFPY since installation. Nominal That during the last cycle was 610 deg F. Initial entry into Mode 4 following completion of the TP4-35 inspection was made on March 30, 2025. A list of acronyms used in this report is provided in Appendix A.
A. Scope of Inspections Performed on each SG The TP4-35 inspection scope was selected to meet the requirements of plant Technical Specifications and the SG Guidelines (NEI 97-06 Rev 3), and its referenced EPRI SGMP Guidelines. The scope is characterized as 100% full-length enhanced probe exams and meets the requirements of section 5.5.6.d.2 of the Turkey Point Technical Specifications to "inspect 100% of the tubes in each SG at least every 54 effective full power months". Unless otherwise noted, the TP4-35 SG inspection scope (primary, secondary) on each SG is outlined below:
Primary-side:
- 100% full-length enhanced probe exams of all active tubes.
U-bends of rows 1 & 2 were inspected with the +Point' probe between the uppermost TSP on the HL and CL.
All other active tubes were inspected full-length with the X-probe (array/bobbin coils).
Examination of peripheral tubes at the TTS, BLG/OXP indications within the H* depth of the tubesheet, and all tubes within the tubesheet program are included in utilizing full-length enhanced probe exams.
- All "high residual stress" tubes were inspected with the +Point' probe:
in the HL tubesheet section (TSH+3" to TEH), and at all HL tube support structures, and at the uppermost CL TSP.
- 100% inspection of dings/dents >5V in the HL, U-bend and uppermost CL TSP using the
+Point' probe.
All dings/dents $.5V were screened with the bobbin coil.
Turkey Point Unit 4 Docket No. 50-251 Enclosure L-2025-169 Page 2 of 10
- Various diagnostic/special interest exams using the +Point' probe including all I-codes from the X-probe exams (bobbin/array coils), tubes in the vicinity of newly identified or prior PLPs and tubes adjacent to the locations of known foreign objects.
- Visual inspection of all mechanical and welded plugs.
- Visual inspection of all channel head bowl components and bowl scan everywhere within the channel head bowl with remote visual camera in both the HL and CL per Westinghouse NSAL 12-1 Rev 1, "Steam Generator Channel Head Degradation," October 2017.
Secondary-side:
- Visual/cleanliness inspection at the TIS (annulus, no-tube lane) after upper bundle flush and sludge lancing at the TTS.
- Foreign object search and retrieval (FOSAR) at the TIS including in-bundle exams.
- Upper-bundle visual inspection from the uppermost TSPs.
- Visual inspection of components of the Upper Internals including the feedwater ring & supports, J-tubes, and moisture separator components.
Scope Expansion: Base scope exams included a 100% full-length inspection of all tubes in each SG with an enhanced probe. Crack-like indications were not identified on any tube in TP4-35, and 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 (above) and is summarized in the Table below:
NOE Technique Susceptible Population Array probe Peripheral tubes, Bulges & Over-expansions, HL tubesheet program
+Point' probe Dings/Dents >5V, low-row U-bends, high stress tubes
Turkey Point Unit 4 Docket No. 50-251 C. For each degradation mechanism found:
Enclosure The following degradation mechanisms were identified during the TP4-35 inspection:
- Wear at A VB contact points.
- Wear at horizontal tube support structures (FDBs, TSPs).
L-2025-169 Page 3 of 10 No degradation was identified due to a corrosion damage mechanism. No new degradation mechanisms were found during the TP4-35 inspection.
- 1. The non-destructive examination (NDE) techniques utilized NDE techniques for the TP4-35 inspection utilized the array and bobbin coils the full length of the tube for detecting degradation in Rows 3 and higher. The bobbin coil was also utilized for sizing AVB wear indications. The +Point' probe was used for detecting indications in Rows 1 & 2, and for sizing of indications at the TTS, at horizontal support structures, and in the freespan. The +Point' probe was also utilized for screening tubes with increased degradation susceptibility (Ref. Section B above). NDE techniques used for the tube degradation mechanisms found in TP4-35 are summarized in Table 1.
Table 1 - NDE Techniques utilized for Sizing Probe Sizing ETSS Degradation Mechanism Applicability Bobbin 196041.1 RS AVB Wear A VB contact locations 96910.1 R12 TSP Wear (broached), TSP and FOB locations FDB Wear
+Point' 27905.1 R2 TSP Wear (edge)
Just above or below the TSP edges FOWear At TSPs 27901.1 R1 FO (VOL) wear at or just above the TTS
- 2. Location, orientation (if linear), measured size (if available), and voltage response for each indication. For tube wear at support structures less than 20 percent through-wall, only the total number of indications needs to be reported.
The location, orientation, measured size, and voltage response of the indications are provided in Appendix B and C. The Appendix B information includes tube wear indications at support structures, and at the TTS. Note: The measured size of the indication is shown in the "Util 1" field for some datasets. Appendix C provides a detailed listing of indications for tubes that were plugged based on TP4-35 ECT inspection results (Ref. section C.4 of this Report). Table 2 (below) summarizes the number of tube wear indications at support structures that are less than 20% TW.
Table 2 - No. of Indications <20% TW (at support structures)
Degradation Mechanism SG-A SG-B SG-C AVBWear 23 20 25 TSP Wear (broached, edge) 4 10 4
FOB Wear 9
10 2
Screening of tubes with high residual stress, BLGs/OXPs and locations with DNG/DNT>5V (per Section A of this report) revealed no indications of corrosion degradation.
Turkey Point Unit 4 Docket No. 50-251 L-2025-169 Page4of10 Enclosure
- 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 Each degradation mechanism identified in TP4-35 (Ref. section C above) were evaluated against the respective CM screening charts, which define the CM structural limits. The maximum observed wear indication was less than the respective CM limit lines. Wear indications at tube support structures were relatively shallow in depth and within the calculated structural limits. All existing degradation mechanisms met industry requirements for structural and leakage integrity. No tubes required in-situ pressure testing (ISPT) to demonstrate CM margins.
The previous inspection/tube integrity assessment (OA) was conducted in TP4-33. A simple deterministic analysis approach was used in the OA for TP4-33 based on worst-case projections for each degradation mechanism. A comparison with the TP4-35 results confirmed that the previous OA's worst-case projected depths were bounding for all wear degradation. In addition, the number of newly detected indications at TP4-35 is less than the ones at the previous (TP4-33) inspection; therefore, the OA methods and input assumptions for tube wear were confirmed to remain acceptable. The margin to the tube integrity performance criteria, and comparison with the margin predicted to exist at the TP4-35 inspection by the previous forward-looking tube integrity assessment (OA) are summarized in the Table below for the TP4-35 degradation mechanisms.
Degradation TP4-35 Max NDE Previous OA max proj'd EOC structural Mechanism depth (%TW) 95/50 depth (% TW) limit (%TW)
AVB wear 26 47.1 64.9 TSP wear (broached) 17 43.9 66.6 TSP wear (edge) 20 39.4 66.6 FDB wear 17 45.6 71.4 FO wear at TTS 25 N/A Note 1 N/A Note 1: There were no FOs reported at TTS locations with FO wear. Therefore, no growth is projected since there is no source of future wear on the tubes.
- 4. The number of tubes plugged during the inspection outage Seven (7) tubes were plugged during the TP4-35 inspection outage; all were in SG-4B. No tube reported degradation during the TP4-35 inspection that reached the plugging criteria (2:40% TW) per plant Technical Specifications. Additional details of the ECT indication results for these tubes are provided in Appendix C. Tubes plugged for each degradation mechanism are summarized below in Table 3:
Table 3 - TP4-35 Tubes Plugged SG Tube Degradation Mechanism Location Notes B
R30 C73 Preventive plugging AV4-0.25" Higher than typical AVB wear growth AV3-0.17" rate (7% TW) when compared to TP4-33 at multiple AVB locations.
Tube preventively plugged, stabilized to add margin to the OA.
Turkey Point Unit 4 Docket No. 50-251 SG B
B B
B B
B Tube R43 C37 R43 C38 R43 C39 R44 C38 R44 C39 R9 C5 Enclosure Degradation Mechanism Location FO Wear (part present) 04C+0.53" 04C+0.45" 04C+0.53" FO Wear (PLPs on 04C+0.48" nearby tubes) 04C+0.53" Discretionary plugging for N/A potential risk of fatigue failure.
(No degradation reported that required plugging.)
Notes L-2025-169 Page 5 of 10 PLPs signals were reported for these tubes, with wear on each tube.
Tubes preventively plugged and stabilized to add margin to the OA.
PLP signals reported on nearby tubes. Tubes preventively plugged, stabilized to add margin to the OA.
Potential risk is based on results of an independent engineering evaluation for operation above 10%
tube plugging under SLR. Tube preventively plugged and stabilized.
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 A deterministic forward-looking tube integrity assessment (OA) was completed for each volumetric wear degradation at tube support intersections and due to foreign objects. The assessment methodology was based on predicted burst pressures and accident-induced leakage, site-specific structural limits, and degradation growth rates. The inspection interval used in the assessment is 2 cycles. Since Turkey Point Unit 4 transitioned from 18-month to 24-month fuel cycles during the TP4-35 outage 1, the 2-cycle inspection interval used was 48 EFPM (4.0 EFPYs) to remain within the 54 EFPM limit under TSTF-577 for SGs having A600TT tubes with sec history. The tube integrity conditions predicted to exist at the next scheduled inspection (TP4-37) is summarized in the Table below.
Degradation TP4-35 NOE max depth OA projections at EOC structural Mechanism returned to svc (% TW)
TP4-37 (% TW) limit(%TW)
AVB wear 26 48.6 64.9 TSP wear (broached) 17 49.5 66.6 TSP wear (edge) 19 46.8 66.6 FOB wear 17 55.3 71.4 FO wear at TTS 25 N/A Note 1 N/A Note 1: There were no FOs reported at TTS locations with FO wear. Therefore, no growth is projected since there is no source of future wear on the tubes.
Although no corrosion degradation was observed on tubes during the TP4-35 inspection, axial ODSCC in the U-bend region is still an existing degradation mechanism. Therefore, an OA was also performed to demonstrate that margin requirements will be satisfied for this mechanism. A forward-looking tube integrity assessment (OA) was developed for axial ODSCC U-bend cracking (assuming all U-bend tubes can be susceptible) and used fully probabilistic analyses per Section 8.3 of the EPRI SGMP Integrity Assessment Guidelines (IAGLs). The model input variables were adjusted by modifying the inspection interval to 24-month fuel cycles, revising the POD and growth 1 Turkey Point Units 3 & 4 - Issuance of Amendment Nos. 301 regarding incorporation of advanced fuel products and extension of surveillance intervals to facilitate transition to a 24-month fuel cycle; NRC ADAMS Accession No. ML25021A189
Turkey Point Unit 4 Docket No. 50-251 Enclosure L-2025-169 Page 6 of 10 rate functions, and choosing an axial length distribution appropriate to PTN Unit 4. The key input parameters for each OA input distribution (POD, growth rate, structural length and Weibull initiation function) were modified for PTN Unit 4. The "typical" default SCC growth rates in the IAGLs were used in the analyses, and model benchmarking was performed to the observed NOE results of the current and prior inspections.
Assessment results after a 2-cycle (48 EFPM) inspection interval predicts 1 to 2 axial ODSCC detections, and a POB of 1.31 % at TP4-37 inspection. The calculated 95/50 leak rate is negligible.
Therefore, the margin requirements for both burst and leakage integrity satisfy the NEI 97-06 acceptance criteria for the next 2-cycle inspection interval.
E. The number and percentage of tubes plugged to date, and the effective plugging percentage in each SG The number and percentage of SG tubes plugged to-date, and the effective plugging percentage in each SG are summarized in Table 4.
Table 4 - Tubes plugged to-date and effective plugging percentage SG-4A SG-48 SG-4C Total Tubes Plugged 37 36 13 86 Percent Plugged 1.15%
1.12%
0.40%
0.89%
F. The results of any SG secondary side inspections A total of 26 lbs. of sludge was removed from the three SGs based on sludge lancing after upper bundle flush (UBF) activities in TP4-35 (7.5, 8 and 10.5 lbs. in SGs A, Band C, respectively). One newly identified, irregular-shaped FO (11/16" x 3/8") was found during peripheral tube exams during TTS FOSAR in SG-A. The object was magnetic in nature and was removed. No PLPs or FOs were reported in the vicinity of the tubes with FO wear at the TTS (Ref. Appendix B). An evaluation is in place for all irretrievable, legacy FOs that have the potential to cause tube damage; no wear was associated with legacy objects. Tubes with FO wear and with a coincident PLP signal were plugged/stabilized in TP4-35 (Ref. Appendix C).
Light-to-moderate deposits was noted on the tubes of the upper bundle. Minor erosion of the magnetite layer and discoloration were noted on the inside wall of some riser barrels due to steam discharging from the primary moisture separator swirl vanes. This condition has been noted in prior exams but does not appear to be progressing. No fouling was noted on the openings of the secondary separators. Components of the Upper Internals including the feedring and supports, appear to be structurally sound, and all welds were intact. Upper tube-bundle visual exams in all 3 SGs in the upper bundle reported the broached openings on the TSPs to be open/free of deposits. No other anomalies or degradation were noted during secondary side inspections.
Channelhead Visual Inspections: During the inspection of tube plugs in TP4-35, all installed plugs were confirmed to be in their correct location. All plugs were found to be dry; no dripping plugs were identified. No degradation or visible signs of leakage were noted on the plugs during the visual inspection. Inspections performed per Westinghouse NSAL 12-1 Rev 1 revealed no degradation; the observed condition was consistent with the manufacturing process.
Turkey Point Unit 4 Docket No. 50-251 Enclosure L-2025-169 Page7of10 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 No primary-to-secondary leakage was observed during the previous 2 cycles (Cycles 33, 34).
H. The calculated accident induced leakage rate from the portion of the tubes below 18.11 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 1.82 times the maximum operational primary to secondary leakage rate, the report should describe how it was determined As described in the H* alternate repair criteria (ARC) for the Turkey Point Plant2, the accident induced leakage rate from the portion of the tubes below 18.11 inches from the TTS is calculated from any observed normal operating leakage that cannot be attributed to a source other than the tubesheet expansion region. For Turkey Point Unit 4, the maximum operational primary-to-secondary leakage rate from the portion of the tubes below 18.11 inches from the top of the tubesheet is determined by multiplying any normal operating leakage by a factor of 1.82 to determine the accident induced leakage rate. Since no operational primary-to-secondary leakage has been observed (per section G of this report), the calculated accident induced leakage rate is zero.
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 A condition for licensing H* was to monitor for tube slippage within the tubesheet region.
Monitoring for tube slippage was completed during the TP4-35 inspections. No tube slippage was reported.
2 Turkey Point Nuclear Generating Station Unit Nos. 3 and 4 - Issuance of Amendments Regarding Permanent Alternate Repair Criteria for SG Tubes (TAC Nos. ME8515 and ME8516); ADAMS Accession No. ML12292A342
Turkey Point Unit 4 Docket No. 50-251 Enclosure L-2025-169 Page 8 of 10 APPENDIX A - Additional Information Abbreviations and Acron~ms:
ARC Alternate Repair Criteria OA Operational Assessment (forward-AVB Anti Vibration Bar looking tube integrity assessment)
BAC Baffle plate cold OD Outside Diameter BAH Baffle plate hot ODSCC OD Stress Corrosion cracking BLG Bulge OXP Over-expansion CL Cold Leg PLP Potential Loose Part CM Condition Monitoring POB Probability of burst DNG Ding POD Probability of Detection DNT Dent PTN Turkey Point ECT Eddy Current Testing SAi Single Axial Indication EFPM Effective Full Power Months sec Stress Corrosion Cracking EFPY Effective Full Power Years SG Steam Generator EOC End Of Cycle SGMP SG Management Program EPRI Electric Power Research Institute SLR Subsequent License Renewal FDB Flow Distribution Baffle TEH Tube-end Hot FO Foreign Object TS Tubesheet FOSAR Foriegn Object Search & Retrieval TSH Tubesheet Hot HL Hot Leg TSP Tube Support Plate IAGL Integrity Assessment Guidelines TTS Top of Tube Sheet ISPT In-Situ Pressure Test TW Through Wall LAR Lead Analyst Review TWD Through wall depth NDE Non Destructive Evaluation UBF Upper Bundle Flush NEI Nuclear Energy Institute UFSAR Updated Final Safety Analysis Rpt NSAL Nuclear Safety Advisory Letter VOL Volumetric WAR Tube Wear
Turkey Point Unit 4 Docket No. 50-251 Enclosure L-2025-169 Page9of10 APPENDIX B - Indication Listing Tube Wear Indications at Support Structures Customer: FPL Plant: Turkey Point Unit: 4 Component: S/G 4A ROW COL VOLTS IND %TW LOCATION
--- ---====== --- --- --------------------
29 25 0.95 TWD 21 AV4 -0.16 37 71 0.73 TWD 20 AV3 +0.34 1.13 TWD 2 6 AV2 +0.47 Customer: FPL Plant: Turkey Point Unit: 4 Component: S/G 4B ROW COL VOLTS IND %TW LOCATION 2 6 64 0.77 TWD 24 AV3 +0.79 0.67 TWD 22 AV2 +0. 29 27 72 0.80 TWD 23 AVl -0.25 30 73 0.79 TWD 24 AV4 -0.25 Customer: FPL Plant: Turkey Point Unit: 4 Component: S/G 4C ROW COL VOLTS IND %TW LOCATION
--- ---====== --- --- --------------------
32 16 0.49 35 31 0.88 Customer: FPL ROW COL VOLTS 8
3 0.38 0.44 TWD 20 AV2 +0.1 8 TWD 23 AV2 +0.47 Plant: Turkey Point IND %TW LOCATION
==
WAR WAR 02H -0.67 02H -0.67 Tube Wear Indications near the TTS Customer: FPL Plant: Turkey Point ROW COL VOLTS IND %TW LOCATION
==
34 73 0.13 WAR TSH +0.05 Customer: FPL Plant: Turkey Point ROW COL VOLTS IND %TW LOCATION 27 22 0.23 WAR TSH +0.08 Unit: 4 UTIL 1 14 19 Component: S/G 4B UTIL 2
=
96910.1 27905.1 Unit: 4 Component: S/G 4A UTIL 1 UTIL 2 PROBE
==
17 27901.1 680PP Unit: 4 Component: S/G 4B UTIL 1 UTIL 2 PROBE
==
25 27901.1 680PP
Turkey Point Unit 4 Docket No. 50-251 Enclosure L-2025-169 Page 10 of 10 Appendix C - Indication Listing (for tubes plugged based on TP4-35 ECT inspection results)**
==
30 73 0.79 0.55 0.30 43 37 0.62 0.22 0.26 43 38 0.12 0.16 0.91 Plant: Turkey Point Unit: 4 Component:
DEG CHAN 87 M2 108 M2 99 M2 77 7
108 P5 73 2
52 P5 268 2 91 7
IND %TW LOCATION UTIL 1 PROBE TWO 24 TWD 19 TWO 12 PLP WAR 9 WAR 14 WAR 6 WAR 10 PLP
======
AV4-0.25 720XB AV3-0.17 720XB AV2+0.11 720XB 04C +0. 56 LAR 680PP 04C +O. 53 96910.1 680PP 04C +O. 53 27905.1 680PP 04C+0.53 96910.1 680PP 04C+0.45 27905.1 680PP 04C+0.49 LAR 680PP 43 39 0.14 0.18 0.57 44 38 0.39 0.51 44 39 0.14 0.14 89 P5 113 2 83 7
102 P5 111 2 WAR 6 04C +0.53 WAR 11 04C +0.53 PLP 04C +0.64 WAR 15 04C+0.48 WAR 20 04C+0.48 96910.1 680PP 27905.1 680PP LAR 680PP 96910.1 680PP 27905.1 680PP 90 P5 WAR 6 04C+0.53 96910.1 680PP 95 2
WAR 11 04C+0.53 27905.1 680PP l
S/G 4B
- Per Table 3, Tube R9C5 was plugged for reasons other than ECT results; thus, it is not included in Appendix C.