L-2024-090, Revised Steam Generator Tube Inspection Reports

Revised Steam Generator Tube Inspection Reports

ML24156A049
Person / Time
Site:	Saint Lucie
Issue date:	06/04/2024
From:	Rasmus P Florida Power & Light Co
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
L-2024-090
Download: ML24156A049 (1)

Text

U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 Re:

St. Lucie Nuclear Plant, Units 1 and 2 Docket Nos. 50-335 and 50-389 Renewed Facility Operating Licenses DPR-67 and NPF-16 Revised Steam Generator Tube Inspection Reports

References:

L-2024-090 10 CFR 50.36 June 04, 2024

1.

St. Lucie Nuclear Plant, Units 1 and 2 - Issuance of Amendment Nos. 253 And 208 Regarding Conversion to Improved Standard Technical Specifications (EPID L-2021-LLI-OOOO), February 20, 2024 (ADAMS Accession No. M L24005A277)

2.

Florida Power & Light Company letter L-2024-075, Notification of Improved Standard Technical Specifications (ITS) Implementation, May 13, 2024 (ADAMS Accession No. ML24134A115)

3.

St. Lucie Unit 1 - Steam Generator Tube Inspection Report, November 1, 2021 (ADAMS Accession No. ML21305A868)

4.

St. Lucie Unit 2 - Steam Generator Tube Inspection Report, March 21, 2022 (ADAMS Accession No. ML22080A201)

In Reference 1, Florida Power & Light Company (FPL) received authorization to implement Improved Standard Technical Specifications (ITS) at St. Lucie Nuclear Plant Units 1 and 2 (St. Lucie). Included within were revised steam generator (SG) tube inspection and reporting requirements modeled after Technical Specification Task Force Traveler (TSTF) 577-A, Revision 1, Revised Frequencies for Steam Generator Tube Inspections (ADAMS Accession No. ML21099A086). Per the implementation notes for TSTF-577-A, Revision 1, "a SG Tube Inspection Report satisfying the TSTF-577 revised requirements must be submitted within 30 days after implementation of the license amendment." In Reference 2, FPL notified the NRC of ITS implementation at St. Lucie Units 1 and 2, effective May 6, 2024. to this letter contains the revised SG tube inspection report completed for St. Lucie Unit 1 refueling outage cycle 30 (SL 1-30). Enclosure 2 contains the revised SG tube inspection report for St.

Lucie Unit 2 refueling outage cycle SL2-26. Enclosures 1 and 2 supplement the SG tube inspection reports for St. Lucie Units 1 and 2 provided in References 3 and 4, respectively.

Should you have any questions regarding this submission, please contact Mr. Kenneth Mack, Fleet Licensing Manager, at 561-904-3635.

Sincerely,

.. /';

Pau~ Rasmus General Manager, Regulatory Affairs Florida Power & Light Company Florida Power & Light Company 6501 S. Ocean Drive, Jensen Beach, FL 34957

St. Lucie Nuclear Plant, Units 1 and 2 Docket Nos. 50-335 and 50-389 Enclosures cc:

USNRC Regional Administrator, Region II USNRC Project Manager, St. Lucie Nuclear Plant, Units 1 and 2 USNRC Senior Resident Inspector, St. Lucie Nuclear Plant, Units 1 and 2 Mr. Clark Eldredge, Florida Department of Health L-2024-090 Page 2 of 2

St. Lucie Nuclear Plant, Units 1 and 2 Docket Nos. 50-335 and 50-389 L-2024-090 St. Lucie Unit 1 Cycle SL 1-30 Revised Steam Generator Tube Inspection Report (Updated to Reflect Revised Reporting Requirements of TSTF-577-A, Revision 1)

( 5 pages follow)

St. Lucie Unit 1 Docket No. 50-335 SL 1-30 Steam Generator Tube Inspection Report Updated per revised reporting requirements of TSTF-577-A, Rev 1 Design and Operating Parameters:

L-2024-090 Page 1 of 5 St. Lucie Unit 1 is a 2-loop Combustion Engineering designed NSSS with RSGs manufactured by B&W Canada. The RSGs have Alloy 690 thermally treated tubes. Each RSG contains 8,523 U-tubes arranged in 141 rows and 167 columns. The tubes have a nominal OD of 0.75", a nominal wall thickness of 0.045",

and have a triangular pitch arrangement. The tube bundle is supported by 7 horizontal lattice grid supports (LGS) along the straight lengths of tubes; the U-bend region is also supported by 10 fan bar supports (FBS) and 2 connector bar supports (CBS), all fabricated of stainless steel. The primary-side channel head has a stay cylinder as well as divider plates which provide flow separation between the inlet and outlet plenums. Tubes in rows 2 & 3 have the smallest U-bend radii. The general arrangement of the tube bundle supports including the FBS, CBS and horizontal LGS is shown in Appendix B of the original SL 1-30 SG Tube Inspection Report (Ref 3).

This updated SG Tube Inspection Report for St. Lucie Unit 1 is submitted for the inspection of the SGs during refueling outage 30 (hereafter referred to as the SL 1-30 inspection or outage). In its conversion to the Improved Standard Technical Specifications under License Amendment Nos. 253 and 208 (Ref 1 ), St. Lucie has incorporated "Revised Frequencies for Steam Generator Tube Inspections" (TSTF-577-A Rev 1). The updated SL 1-30 SG Tube Inspection Report is completed per section 5.6.5 of the St. Lucie Unit 1 Technical Specifications and meets the reporting requirements for implementing TSTF-577. The inspection in SL 1-30 was performed in accordance with Technical Specification 5.5.6 and was the initial inspection (implementation outage) for TSTF-577. At unit shutdown for the SL 1-30 inspection, the SGs had operated for approximately 20.5 EFPY since installation. Nominal Thot during the cycle prior to SL 1-30 was approximately 605 °F. Initial entry into Mode 4 following completion of the SL 1-30 inspection was made on May 5, 2021. A list of acronyms used in this report is provided in Appendix A 1.

A. Scope of Inspections Performed on each SG Unless otherwise noted, the SL 1-30 SG inspection scope (primary, secondary) on each SG is outlined in Section A of the original SL 1-30 SG Tube Inspection Report (Ref 3). The scope included 100% full-length bobbin probe exams of all active tubes. In addition, enhanced probe exams were completed for the peripheral tubes at the TTS, ding/dent indications greater than 5 volts, low row U-bends and other diagnostic/special interest areas. Additional details of the inspection scope are available in Section A of Ref 3. The SL 1-30 inspection scope was selected to meet the requirements of plant Technical Specifications, NEI 97-06 Rev 3 and its referenced EPRI SGMP Guidelines. The SL 1-30 SG inspection is credited as the implementation outage for TSTF-577. The scope meets the requirements of section 5.5.6.d.2 of the St. Lucie Unit 1 Technical Specifications to "inspect 100% of the tubes in each SG at least every 96 effective full power months". Expansion of the inspection scope was not required.

B. NDE techniques utilized for tubes with increased degradation susceptibility The U-bend region of low row tubes and ding/dent indications >5 volts were examined with enhanced probes. Peripheral tube sections at the TTS were also inspected with an enhanced probe due to their susceptibility to foreign object wear. Additional details of the NOE techniques used for tubes with increased degradation susceptibility are outlined in Section A of Ref 3.

St. Lucie Unit 1 Docket No. 50-335 C. For each degradation mechanism found:

L-2024-090 Page 2 of 5 Degradation mechanisms found during the SL 1-30 inspection are provided in Section B of the original SL 1-30 SG Tube Inspection Report (Ref 3).

1. The non-destructive examination (NDE) techniques utilized NOE techniques used for detection and sizing the tube degradation mechanisms found in SL 1-30 are in Table 1 of Ref 3.

2. Location, orientation (if linear), measured size (if available), and voltage response for each indication For degradation mechanisms found in SL 1-30, this information is provided in Section D of Ref 3. All indications at tube support structures were less than 20% TW.

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 SL 1-30 inspection are described in Sections G.1 through G.3 of Ref 3 for all degradation mechanisms found. The previous inspection was conducted in SL 1-27. The margin to the tube integrity performance criteria, and comparison (benchmarking) with the margin predicted to exist at the SL 1-30 inspection by the previous forward-looking tube integrity assessment (OA) are summarized in the Table below for the wear degradation mechanisms. None of the indications were predicted to leak under limiting accident conditions. Therefore, the SL 1-30 SG inspection results met the CM structural and leakage performance criteria. Benchmarking the previous OA with the SL 1-30 results indicated that the OA methods and assumptions used at SL 1-27 were conservative.

No indications were required to be in-situ pressure tested to demonstrate that CM was satisfied.

Degradation SL 1-30 Max NOE Previous OA max proj'd EOC structural Mechanism depth (%TW) 95/50 depth (% TW) limit (%TW)

FBS wear 17 50.6 60.6 LGS wear 17 60.4 67.6 PLP wear at TTS Note 1 18 N/A N/A Note 1: No FOs were reported at locations with PLP wear. No growth of PLP wear indications since first reported; therefore, no source of future wear on the tubes.

4. The number of tubes plugged during the inspection outage Ten (10) tubes were plugged during the SL 1-30 inspection outage. Table 3 of Ref 3 provides the degradation mechanism attributed to each plugged tube.

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 inspection at SL 1-30, a bounding, deterministic forward-looking tube integrity assessment (OA) was initially used to conservatively evaluate the condition of tubes with detected wear.

Assessment results determined that the SIPC margin requirements of 3xNOPD, and the AILPC under postulated accident conditions, were satisfied in accordance with NEI 97-06 for all detected wear indications (including the ones left in-service), for a 3-cycle inspection interval (until SL 1-33).

St. Lucie Unit 1 Docket No. 50-335 L-2024-090 Page 3 of 5 Since the SL 1-30 inspection was also credited as the implementation outage for "Revised Frequencies for SG Tube Inspections" (TSTF-577), the original OA was reviewed to extend the operating interval as allowed by TSTF-577-A Rev 1 through conversion of plant Technical Specifications to NUREG-1432 (Ref 1).

The deterministic OA was completed based on predicted burst pressures and accident-induced leakage, site-specific structural limits, and degradation growth rates, based on guidance in the SGMP Integrity Assessment Guidelines. Each degradation mechanism was evaluated for a run-time plan for future cycles of operation, and the next inspection interval. For LGS wear, although growth rates of repeat indications in SL 1-30 had consistently attenuated to approximately

0. 75% TW/EFPY (max), as a conservative measure, the wear rate for LGS wear was assumed to be 4% TW/EFPY. The projected worst-case depth of known wear indications (including total measurement error at the upper 95% bound) for a 5-cycle inspection interval, was calculated to be less than the EOC structural limit for LGS wear. For FBS wear, the wear rate (6.0% TW/EFPY) used in the deterministic approach, was based on the 95% bound wear rate for the prior inspection (SL 1-27), following significant attenuation post-EPU. Although continuous reduction in wear rates have been observed over the 20.5-EFPY in-service period of the RSGs (except for post-EPU results of SL 1-25), growth rate attenuation in future operation is conservatively ignored in the SL 1-30 OA to give additional margin on the projection of FBS wear. Results of the deterministic OA calculations (including measurement error) showed that the SIPC margin requirement will be met for degraded tubes with FBS wear for a 4-cycle inspection interval.

To further assess FBS wear, a probabilistic full-bundle, multi-cycle OA analysis was performed (based on guidance in the SGMP Integrity Assessment Guidelines) to support the planned 5-cycle inspection interval. The probabilistic analyses were performed using the WearMulti program and consist of a Monte Carlo simulation of the processes of flaw initiation and degradation growth, ECT inspection, and the removal of degraded tubes. For the OA, the wear rates are conservatively estimated from past data. To obtain the most accurate predictions of the EOC flaw population, benchmarking was performed for the predicted vs. actual/observed for the following parameters:

number of indications detected, depths of the simulated indications and extreme depth of the indications. The limiting SG for FBS wear was conservatively assumed to be a composite of both SG-1A and SG-1 B, as supported by the nearly identical inspection results from the SL 1-30 ECT examination. The wear rate distribution was based on the repeat and newly detected wear indications at SL 1-30; random sampling from the wear rate distribution was used. In addition, no credit was taken for wear rate attenuation over future operating cycles. The statistical distributions representing the uncertainties in the input variables to determine structural and leakage integrity include the mechanical strength, flaw characterization (sizes, shapes), the POD functions and degradation (wear) growth rates. The benchmarks on the number of detected flaws and maximum observed depths were comparable with the model predictions when using the inputs to the WearMulti program; the comparison shows very good agreement between the inspection data and the calculated results.

Results of the probabilistic OA determined that the projected limiting indication sizes at SL 1-35 met the SIPC margin requirement of 3xNOPD, where the POB was calculated to be 0.04% which is less than the 5% acceptance standard. In addition, cumulative leakage at limiting accident conditions was determined to be negligible as contrasted to the acceptance criterion of less than 0.25 gpm per SG. Therefore, based on the results of the revised forward-looking tube integrity assessment, the PSL Unit 1 SGs will satisfy the NEI 97-06 performance goals in maintaining tube integrity for the updated scheduled inspection interval of 5 operating cycles until the next tube examination.

The tube integrity conditions predicted to exist at the next scheduled inspection (SL 1-35) relative to the applicable performance criteria are summarized in the Table below for each degradation mechanism.

St. Lucie Unit 1 Docket No. 50-335 Degradation Mechanism FBS wear LGS wear PLP wear at TTS SL 1-30 max NOE depth SL 1-30 OA projections returned to svc (% TW) at SL 1-35 (% TW) Note 1 17 27.9 17 56.9 18 N/A Note2 EOC structural limit (%TW) 60.6 67.6 N/A L-2024-090 Page 4 of 5 Note 1: OA projections for FBS and LGS wear are based on probabilistic and deterministic analyses, respectively.

Note 2: No growth of PLP wear indications since first reported; therefore, no source of future wear on the tubes.

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 SL 1-30 SG Tube Inspection Report (Ref 3).

F. The results of any SG secondary side inspections The results of secondary side inspections are described in Sections G.4 and G.6 of Ref 3. The inspection results for channel head components are described in Section G.5 of Ref 3.

St. Lucie Unit 1 Docket No. 50-335 L-2024-090 Page 5 of 5 APPENDIX A 1 - Additional Information Abbreviations and Acronyms:

AILPC Accident-induced leakage perf crit.

NEI Nuclear Energy Institute BAC Baffle plate cold NOPD Normal operating press. differential BAH Baffle plate hot NSSS Nuclear steam supply system BLG Bulge OA Operational Assessment (forward-CBS Connector bar support looking tube integrity assessment)

CL Cold Leg OD Outside Diameter CM Condition Monitoring ODSCC OD Stress Corrosion cracking ONG Ding OXP Over-expansion ONT Dent POB Probability of burst ECT Eddy Current Testing POD Probability of detection EFPY Effective Full Power Years RSG Replacement steam generator EOC End of cycle SG Steam Generator EPRI Electric Power Research Institute SGMP SG Management Program FBS Fan bar support SIPC Structural integrity perf. criteria FOB Flow Distribution Baffle TS Tubesheet FO Foreign Object TSP Tube Support Plate HL Hot Leg TSTF Tech Spec Task Force ISPT In-Situ Pressure Test TTS Top of Tube Sheet LGS Lattice grid support TW Through Wall

St. Lucie Nuclear Plant, Units 1 and 2 Docket Nos. 50-335 and 50-389 L-2024-090 St. Lucie Unit 2 Cycle SL2-26 Revised Steam Generator Tube Inspection Report (Updated to Reflect Revised Reporting Requirements of TSTF-577-A, Revision 1)

( 5 pages follow)

St. Lucie Unit 2 Docket No. 50-389 SL2-26 Steam Generator Tube Inspection Report Updated per revised reporting requirements of TSTF-577-A, Rev 1 Design and Operating Parameters:

L-2024-090 Page 1 of 5 St. Lucie Unit 2 is a 2-loop Combustion Engineering designed NSSS with Model 86/19TI RSGs manufactured by AREVA. The RSGs were fabricated using thermally treated lnconel 690 tubing. Each RSG contains 8,999 U-tubes; each tube has a nominal OD of 0.75" and a nominal wall thickness of 0.0429". The tubes have a tri-pitch arrangement and are supported by 7 broached-hole tube support plates (TSPs) and 4 sets of anti-vibration bars (AVBs), all fabricated of stainless steel. The upper internals section is equipped with a fine-mesh loose part trapping screen to prevent foreign objects in the feedwater train from reaching the tube bundle entrance region. The general arrangement of the St.

Lucie Unit 2 SG tube bundle is shown in Figures 1-4 of past SG Tube Inspection Reports (Ref.

ADAMS Accession No. ML14279A237).

This updated SG Tube Inspection Report for St. Lucie Unit 2 is submitted for the inspection of the SGs during refueling outage 26 (hereafter referred to as the SL2-26 inspection or outage). In its conversion to the Improved Standard Technical Specifications under License Amendment Nos. 253 and 208 (Ref 1 ), St. Lucie has incorporated "Revised Frequencies for Steam Generator Tube Inspections" (TSTF-577-A Rev 1). The updated SL2-26 SG Tube Inspection Report is completed per section 5.6.5 of the St. Lucie Unit 2 Technical Specifications and meets the reporting requirements for implementing TSTF-577. The inspection in SL2-26 was performed in accordance with Technical Specification 5.5.6 and was the initial inspection (implementation outage) for TSTF-577. At unit shutdown for the SL2-26 inspection, the SGs had operated for approximately 11.85 EFPY since installation. Nominal Thot during the cycle prior to SL2-26 was approximately 605 °F. Initial entry into Mode 4 following completion of the SL2-26 inspection was made on September 25, 2021. A list of acronyms used in this report is provided in Appendix A2.

A. Scope of Inspections Performed on each SG Unless otherwise noted, the SL2-26 SG inspection scope (primary, secondary) on each SG is outlined in Section A of the original SL2-26 SG Tube Inspection Report (Ref 4). The scope included 100% full-length bobbin probe exams of all active tubes. In addition, enhanced probe exams were completed for the peripheral tubes at the TTS, low row U-bends and other diagnostic/special interest areas.

Additional details of the inspection scope are available in Section A of Ref 4. The SL2-26 inspection scope was selected to meet the requirements of plant Technical Specifications, NEI 97-06 Rev 3 and its referenced EPRI SGMP Guidelines. The SL2-26 SG inspection is credited as the implementation outage for TSTF-577. The scope meets the requirements of section 5.5.6.d.2 of the St. Lucie Unit 2 Technical Specifications to "inspect 100% of the tubes in each SG at least every 96 effective full power months". Expansion of the inspection scope was not required.

B. NDE techniques utilized for tubes with increased degradation susceptibility Peripheral tube sections at the TTS were inspected with an enhanced probe due to their susceptibility to foreign object wear. The U-bend region of low row tubes were also examined with enhanced probes. Additional details of the NOE techniques used for tubes with increased degradation susceptibility are outlined in Section A of Ref 4.

St. Lucie Unit 2 Docket No. 50-389 C. For each degradation mechanism found:

L-2024-090 Page 2 of 5 Degradation mechanisms found during the SL2-26 inspection are provided in Section B of the original SL2-26 SG Tube Inspection Report (Ref 4).

1. The non-destructive examination (NDE) techniques utilized NOE techniques used for detection and sizing the tube degradation mechanisms found in SL2-26 are in Table 1 of Ref 4.

2. Location, orientation (if linear), measured size (if available), and voltage response for each indication For degradation mechanisms found in SL2-26, this information is summarized in Section D of Ref 4. The location, orientation, measured size, and voltage response for each indication is provided in Appendix B through F of Ref 4.

There were 12,489 indications of tube wear at support structures that were less than 20% TW (included in Appendix B, C and F of Ref 4). The locations of these indications are outlined in the Table below.

Wear at No. of indications <20% TW SG-2A SG-28 Total TSPs 191 199 390 V-SSPs 2

1 3

AVBs Note 1 6,443 5,653 12,096 Total=

6,636 5,853 12,489 Note 1: Indications at AVB U-bend Apex locations are included in the count of AVB wear indications.

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 SL2-26 inspection is described in Sections G.1 through G.5 of Ref 4 for all degradation mechanisms found. The previous inspection was conducted in SL2-24. The margin to the tube integrity performance criteria, and comparison (benchmarking) with the margin predicted to exist at the SL2-26 inspection by the previous forward-looking tube integrity assessment (OA) are summarized in the Table below for the wear degradation mechanisms. The CM calculations were performed to maintain at least a 95/50 lower bound tube integrity. Based on the ECT inspection results, it was determined for CM that the structural limits and leakage rates assumed under postulated accident conditions were both maintained since the previous inspection. In-situ pressure testing was not required.

Therefore, the detected wear degradation met the structural and leakage integrity performance criteria of NEI 97-06.

Degradation SL2-26 Max NOE Previous OA max proj'd EOC structural Mechanism depth (%TW) 95/50 depth (% TW) limit (%TW)

AVB wear 45 52 Note 1 54.9 TSP wear 29 46.4 65.1 V-SSP ('appui) wear 26 49.6 64.8 Note 1: Based on a conservative estimate of wear rates, following the SGMP Integrity Assessment Guidelines.

St. Lucie Unit 2 Docket No. 50-389

4. The number of tubes plugged during the inspection outage L-2024-090 Page 3 of 5 Sixty-five (65) tubes were plugged during the SL2-26 inspection outage. Table 3 of Ref 4 provides the degradation mechanism attributed to each plugged tube.

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 fully probabilistic assessment was used to evaluate tube wear at AVB support locations due to the large number of wear indications. The assessment was applied to the full bundle using a Monte Carlo simulation method for the worst-case (limiting) SG, SG-2A, regarding this mechanism, for defining the operating interval. As stated in section G.5 of Ref 4, preventive tube plugging for AVB wear was completed in SL2-26, beyond the ones required by Technical Specifications, to provide added margin on wear rates and to limit the likelihood that the CM screening limits would be exceeded during the next scheduled inspection (SL2-29).

The model used in the analysis projects the growth of both the detected and undetected flaw populations returned to service based on the POD metrics for the ETSS' used in SL2-26. In addition, new flaws that may initiate during the operating interval are included via a Weibull initiation model. The input distributions for the Monte Carlo analysis included wear rate distribution, exam technique POD, length distribution (for detected wear indications) and distribution of wear shape characteristics. For analysis purposes, wear at AVB U-bend Apex locations is included in the OA results for AVB wear. With growth rates included, the projected flaw populations are established, from which structural and leakage integrity assessments are made by comparing projected tube burst pressures and flaw depth sizes with SIPC and AILPC margin requirements. OA results determined that the POB for the worst-case tube was calculated to be 3.12% for the SIPC margin requirement of 3xNOPD, using even the conservative AVB wear rate analysis (assuming no wear rate attenuation during the period). Accident-induced leakage is projected to be zero.

For TSP and V-SSP wear indications, a bounding deterministic, forward-looking tube integrity assessment (OA) was performed (per guidance in the SGMP Integrity Assessment Guidelines) based on the predicted worst-case wear depths and conservatively assumed input parameters at the 95/50 probability level. The input parameters include material strengths, wear rates, probability of detection, and sizing uncertainties. The next SG inspection is planned after 3 fuel cycles in SL2-

29. Tube integrity assessment results for TSP and V-SSP wear show that the margins to the structural integrity performance criteria (SIPC) will be met for these mechanisms at SL2-29; accident-induced leakage is projected to be zero.

The tube integrity conditions predicted to exist at the next scheduled inspection (SL2-29) relative to the applicable performance criteria are summarized in the Table below for each degradation mechanism.

Degradation SL2-26 NOE max depth SL2-26 OA projections EOC structural Mechanism returned to svc (% TW) at SL2-29 (% TW) limit (%TW)

AVB wear Note 2 39 53 Note 1 54.9 TSP wear 29 57.8 65.1 V-SSP ('appui') wear 26 47.9 64.8 Note 1: Projection is based on using a fully-probabilistic OA model for wear at AVB locations.

Note 2: For analysis purposes, wear at AVB U-bend Apex locations is included in the OA results for AVB wear.

St. Lucie Unit 2 Docket No. 50-389 L-2024-090 Page 4 of 5 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 SL2-26 SG Tube Inspection Report (Ref 4).

F. The results of any SG secondary side inspections The results of secondary side inspections are described in Sections G. 7 and G.8 of Ref 4. The inspection results for channel head components are described in Section G.6 of Ref 4.

St. Lucie Unit 2 Docket No. 50-389 L-2024-090 Page 5 of 5 APPENDIX A2 - Additional Information Abbreviations and Acronyms:

AILPC Accident-induced leakage Perf. Grit.

OA Operational Assessment (forward-AVB Anti Vibration Bar looking tube integrity assessment)

CL Cold Leg OD Outside Diameter CM Condition Monitoring POB Probability of burst ECT Eddy Current Testing POD Probability of detection EFPY Effective Full Power Years RSG Replacement steam generator EOC End of cycle SG Steam Generator EPRI Electric Power Research Institute SGMP SG Management Program ETSS Exam Technique Specification Sheet SIPC Structural integrity performance crit.

FO Foreign Object TS Tubesheet HL Hot Leg TSP Tube Support Plate ISPT In-Situ Pressure Test TSTF Tech Spec Task Force NEI Nuclear Energy Institute TTS Top of Tube Sheet NOPD Normal operating press. differential TW Through Wall NSSS Nuclear steam supply system V-SSP V-shaped support pad