W3F1-2024-0019, (Waterford 3) - Steam Generator Tube Inspection Report for the 25th Rf Inspection Performed During Operating Cycle 25 / Refuel 25

(Waterford 3) - Steam Generator Tube Inspection Report for the 25th Rf Inspection Performed During Operating Cycle 25 / Refuel 25

ML24204A270
Person / Time
Site:	Waterford
Issue date:	07/22/2024
From:	Twarog J Entergy Operations
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
W3F1-2024-0019
Download: ML24204A270 (1)

Text

) entergy W3F1-2024-0019 July 22, 2024 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555

Subject:

Steam Generator Tube Inspection Report for the 25th RF Inspection Performed During Operating Cycle 25 / Refuel 25 Waterford Steam Electric Station, Unit 3 (Waterford 3)

Docket No. 50-382 Renewed Facility Operating License No. NPF-38 John Twarog Manager Regulatory Assurance 504-739-67 4 7 Entergy Operations, Inc. (EOI) Waterford Steam Electric Station, Unit 3 (Waterford 3) hereby submits the Steam Generator Tube Inspection Report for the 25th Refueling Outage.

This report is being submitted in accordance with Technical Specification 6.9.1.5 and provides the complete results of the Steam Generator Tube Inspection conducted during the 25th Refueling outage.

There are no new commitments contained in this submittal.

Please contact me at (504) 739-6747 should you have any questions regarding this submittal.

Respectfully, JRT/llb

Enclosure:

1.

Waterford 3 Steam Electric Station Steam Generator Tube Inspection Report for the 25th Refueling Outage Entergy Operations, Inc., 17265 River Road Killona, LA 70057-3093

W3F1-2024-0019 Page 2 of 2 cc:

NRC Region IV Regional Administrator NRC Senior Resident Inspector-Waterford 3 NRC Project Manager - Waterford 3 Louisiana Department of Environmental Quality Brad.Schnexnayder@LA.gov Jessica.Walker@LA.gov American Nuclear Insurers (ANI)

Dfreiermuth@amnucins.com

Enclosure to W3F1-2024-0019 Waterford Steam Electric Station Unit 3 (Waterford 3)

Steam Generator Tube Inspection Report for the 25th Refueling Outage

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WATERFORD 3 STEAM GENERATOR TUBE INSPECTION REPORT 1

INTRODUCTION Waterford 3 (WF3) Technical Specification (TS) 6.9.1.5, Steam Generator Tube Inspection Reports, requires Entergy Operations to submit a Tube Inspection Report to the NRC within 180 days after entry into MODE 4 following a steam generator inspection performed in accordance with TS 6.5.9, Steam Generator (SG) Program. The EPRI Steam Generator Integrity Analysis Guidelines, Revision 5 includes additional requirements for plants implementing TSTF-577.

The report shall include:

a. Design and operating parameters;

b. The scope of inspections performed on each SG and if applicable, a discussion of the reason for scope expansion;

c. The nondestructive examination techniques utilized for tubes with increased degradation susceptibility;

d. For each degradation mechanism found:

1. The nondestructive examination techniques utilized;

2. The 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;

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. (Discuss any degradation that was not bounded by the prior operational assessment in terms of projected maximum flaw dimensions, minimum burst strength, and/or accident induced leak rate. Provide details of any in situ pressure test.); and

4. The number of tubes plugged during the inspection outage. Also, provide the tube location and reason for plugging.

e. 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.

The effective full power months of operation permitted for the current operational assessment;

f.

The number and percentage of tubes plugged to date, and the effective plugging percentage in each SG; and

g. The results of any SG secondary side inspections. The number, type, and location (if available) of loose parts that could damage tubes removed or left in service in each SG;

h. The scope, method, and results of secondary-side cleaning performed in each SG;

i.

The results of primary side component visual inspections performed in each SG;

j.

Any plant-specific reporting requirements, if applicable.

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2 DESIGN The replacement steam generators for Waterford 3 are a Westinghouse Delta 110 design. The tube bundle consists of 8968 U-tubes fabricated from thermally treated Alloy 690. The tubing material complies with the requirements of ASME Section II SB-163, ASME Section III, NB-2000.

The nominal outside diameter (OD) of each U-tube is 0.75 in. The nominal tube wall is 0.044 inches thick for tube rows 1 and 2 and 0.043 inches thick for all other tube rows (rows 3 through 138). The ends of the tubes are expanded the full depth of the tubesheet and welded to the cladding on the tubesheet primary side.

The tubes are supported on the secondary side by eight (8) tube support plates (TSP). The TSP material is stainless steel (ASME SA-240, Type 405). All TSPs have trefoil-shaped holes arranged on a triangular pitch, produced by broaching, to reduce the potential for tube dry out and chemical concentration in the regions where the tubes pass through the support plates.

Five (5) sets of anti-vibration bars (AVBs) are installed to provide support for the U-bend region of the tube bundle. The anti-vibration bar assemblies stiffen the U-bend region of the tube bundle and facilitate proper tube spacing and tube alignment while mitigating tube vibration. Each AVB assembly consists of a V shaped, rectangular bar of stainless steel (ASME SA-479, Type 405) and two (2) end caps of thermally treated Alloy 690. Each end of each AVB assembly is secured to the U-bend peripheral retaining rings by welding the corresponding end cap. Twenty (20) U-shaped retainer bars of chrome plated, thermally treated Alloy 690 are installed between several U-tubes. These retainer bars provide support to the AVB assemblies during seismic and postulated steam line break loading conditions.

3 REPORT REQUIREMENTS 3.1 Design and Operating Parameters SG Model / Tube Material / # SGs Westinghouse D110 / Alloy 690TT / 2

1. of Tubes per SG / Nominal Tube Diameter / Tube Thickness 8968 / 0.75 in. / 0.044 rows 1-2, 0.043 rows 3-138 Support Plate Style / Material / # of Support Plates Broached Trefoil / Stainless Steel / 8 Last Inspection Date April 2017 during RF21 EFPM Since Last Inspection 67.5 EFPM Total Cumulative SG EFPY 9.53 EFPY Mode 4 Entry 1/23/24 Observed Primary-to-Secondary Leak Rate No observed leakage Nominal Thot at Full Power Operation 105°F Loose Parts Strainer The WF3 SGs have forty-two (42) feedwater spray nozzles which are perforated with flow holes on one side and help prevent the introduction of foreign objects into the SGs Degradation Mechanism Sub Population During RF25, a sub-population was identified for TSP wear in rows 1-2 of SG1 Deviations from SGMP Guidelines Since Last Inspection None Steam Generator Schematic See Figures 3.1.1 and 3.1.2

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Figure 3.1.1 WF3 SG Schematic

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Figure 3.1.2 WF3 SG Tube Support Arrangement Notes: A# - Anti-Vibration Bar

1. 1. H/##C - Hot/Cold Leg Tube Support Plate TSH/TSC - Hot/Cold Tubesheet (designates top of tubesheet)

TEH/TEC - Hot/Cold Tube End 3.2 Scope of Inspections Performed on Each SG The RF25 inspection scope included:

Bobbin Probe Examination (both SGs) o 100% full length tube-end to tube-end o Post-test examinations of tubes following in situ pressure testing o All bobbin probes were run through a deposit standard Array Probe Examination (both SGs) o Examinations with.610 array probe (610XP) on the periphery tubes where the secondary-side velocity exceeds 6 ft/sec and additional tubes selected by the Tube Integrity Engineer in the Degradation assessment (DA). The inspection was performed by pulling the probe from the 1st support to the tube end (01H-THE, 01C-TEC) o Samples of AVB and TSP wear o Bobbin BLG indications >18V o The one bobbin PLP indication (later changed per guidelines) and one tube bounding exams for all Array confirmed PLP indications 06H --------- 06C 05HIII---------- 05C 04H111---------- 04C 03HIII---------- 03C 02H111---------- 02C 01H I----------I 01C TSH TSC

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o Freespan Dings >5V o Tube Support Dents >2V o 25% of all existing and new proximity (PRX) bobbin indications >1V o Post-test examinations of tubes following in situ pressure testing o All array probes were run through a deposit standard Rotating Pancake Coil (RPC) ((+Point)) Probe (both SGs) o Select AVB and TSP wear flaws for in situ pressure test screening and flaw characterization o Post-test examinations of tubes following in situ pressure testing Primary Side Visual Inspections (both SGs) o All tube plugs installed in the SGs o SG channel head bowl cladding and internal surfaces to address NSAL 12-1 concerns Secondary Side Inspections (both SGs) o Visual inspections and, as needed, Foreign Object Search and Retrieval (FOSAR) o Top of Tubesheet (TTS) visual inspections to assess material condition, structural integrity, deposit accumulation and foreign objects including the no-tube lane and annulus region o Visual Inspections of steam drum including Feedwater spray nozzles and primary separators Sludge collectors Overall inspections of secondary moisture separators, feedring and supports, steam venturis, upper tube supports, and general area conditions 3.3 Nondestructive Examination Techniques Utilized for Tubes with Increased Degradation Susceptibility An array probe inspection was performed in both steam generators of the periphery tubes where the secondary-side velocity exceeds 6 ft/sec. The inspection was performed by pulling the probe from the 1st support to the tube end (01H-TEH, 01C-TEC). A +Point inspection was performed on select AVB and TSP wear flaws for in situ pressure test screening and flaw characterization.

See Table 3.4.1.1 for a list of examination techniques utilized for each degradation mechanism.

3.4 Degradation Mechanisms Found At RF19 the first service induced degradation was identified as wear at the AVBs in both SG31 and SG32. There were four tubes preventatively plugged (PTP) in SG32 which enabled the Cycle 20 and 21 Operational Assessment to successfully analyze a two (2) cycle operating interval.

At RF21, wear at the TSPs was detected as the second service induced degradation mechanism, in addition to wear at the AVBs, in both SG31 and SG32. There were three (3) tubes plugged in SG31 and twenty-four (24) tubes plugged in SG32 which enabled the Operational Assessment to successfully analyze a three (3) cycle operating interval.

At RF25, wear at AVBs and TSPs was detected. Indications greater than or equal to 20% are provided in Appendices 1-4. All AVB wear flaws in both SGs satisfied CM for structural integrity.

In situ pressure testing was required for 4 tubes in SG31 which failed to meet condition monitoring criteria analytically for TSP wear. Two (2) tubes passed and two (2) tubes failed in situ pressure

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testing. All other TSP wear flaws in SG31 and all wear flaws in SG32 satisfied CM analytically for structural integrity.

3.4.1 Nondestructive Examination (NDE) Techniques Utilized Table 3.4.1.1 below provides the NDE techniques utilized for the detection and sizing of each degradation mechanism identified during the RF25 inspection including the Examination Technique Specification Sheet (ETSS) used.

Table 3.4.1.1 Nondestructive Examination Techniques Utilized at RF25 Degradation Mechanism Detection Technique EPRI ETSS Sizing Technique EPRI ETSS AVB Wear Bobbin 96041.1 R8 Bobbin

+Point 96041.1 R8 10908.5 R0 TSP Wear Bobbin 96004.1 R14 Bobbin

+Point 96004.1 R14 27902.1 R2 3.4.2 Location, Orientation (if linear), Measured Size (if available), and Voltage Response for each Indication Due to the large number of indications, the NDE results for bobbin indications greater than or equal to 20% are contained in the following attachments: : SG31 RF25 Wear at AVBs 20% : SG31 RF25 Wear at TSPs 20% : SG32 RF25 Wear at AVBs 20% : SG32 RF25 Wear at TSPs 20%

3.4.3 Description of the Condition Monitoring (CM) Assessment and Results for AVB Wear The Bobbin probe ETSS 96041.1 Rev. 8 was used for detection and depth sizing of AVB wear. The +Point probe was used for detailed depth and length sizing and collecting measurements to calculate structural equivalence as necessary.

Since the AVBs intersect the SG tubing at varying angles, the axial length of the AVB wear flaw can be larger than the actual AVB width of 0.48, approaching double that dimension, from review of +Point ECT sizing data for longer flaws. Of the AVB wear flaws profiled from all WF3 inspections, using line-by-line sizing, the largest structural equivalent axial length was determined to be 0.80 with an NDE length of 0.9. The CM curve for bobbin technique 96041.1 Rev 8 along with the RF25 AVB wear flaw bobbin depths from SGs 31 and 32 were respectively plotted at a conservative assumed bounding length of 1.0. This length is chosen to bound any potential contact width between the tube and AVBs and is greater than the maximum measured AVB NDE flaw length of 0.9 (based on +Point) observed in RF25.

In SG 31, the deepest measured AVB wear flaw by bobbin was 58%TW (SG31 R123 C88 at A06). In SG 32, the deepest measured AVB wear flaw by bobbin was 59%TW (SG32 R128 C87 at A06). Both wear flaws exceeded the bobbin CM limit curve.

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To further evaluate AVB wear for structural integrity, a population of the largest AVB wear flaws identified by bobbin (including flaws below the bobbin CM limit) was selected for examination with the +Point probe. Maximum depth and total lengths were measured with the corresponding +Point technique (ETSS 10908.5 Rev 0). The maximum depth and total length for each flaw (i.e., assumed flat profiles) were compared to the CM limit.

One flaw, SG31 R123-C88 at A06 required further evaluation to account for the flaw profile (i.e., tapered flaw shape) by determining the structural equivalence in accordance with EPRI Guidelines.

When including the additional length and depth characterization using +Point, all AVB wear flaws in both SGs satisfied CM for structural integrity.

3.4.4 Description of the Condition Monitoring (CM) Assessment and Results for TSP Wear The Bobbin probe ETSS 96004.1 Rev.14 was used for detection and depth sizing of TSP wear. The +Point probe was used for detailed depth and length sizing and collecting measurements to calculate structural equivalence, as necessary. The CM curve for bobbin technique 96004.1 Rev.14 along with all RF25 TSP wear flaws from both SGs were plotted at an assumed length of 1.42, bounding both the length (thickness) of the TSPs of 1.125 as well as the maximum TSP NDE flaw length of 1.41 (based on +Point) observed in RF25. The deepest measured TSP wear flaws by bobbin were 77%TW in SG31 (R1 C4 at 05C) and 51% in SG 32 (R1 C120 at 05C). There were fourteen (14)

Bobbin wear flaws in seven (7) tubes in SG31 and one (1) Bobbin wear flaw in SG32 that exceeded the bobbin CM limit curve.

To further evaluate TSP wear for structural integrity, a population of the largest TSP wear flaws identified by bobbin (including flaws that were under the bobbin CM limit) was selected for examination with the +Point probe. Maximum depth and total lengths were measured with the corresponding +Point technique (ETSS 27902.1 Rev 2). The maximum depth and total length for each flaw (i.e., assumed flat profiles) were compared to the CM limit. Twelve (12) flaws, all in SG31 at cold leg supports, required further evaluation to account for the flaw profile (i.e., tapered flaw shape) by determining the structural equivalence in accordance with EPRI Guidelines.

Nine (9) flaws, which were distributed among four (4) separate tubes in SG31, failed to satisfy condition monitoring by analysis. SG31 tubes R1-C4, R1-C112, R1-C138 and R2-C35 contained flaws that failed to satisfy CM analytically. In accordance with EPRI Guidelines, the tubes required in situ pressure testing with further discussion provided in Section 3.4.5. All other locations in SG31 and all locations in SG32 satisfied CM analytically for structural integrity.

3.4.5 In Situ Pressure Testing In situ pressure testing the full length of the four (4) tubes containing flaws which exceeded the CM criteria, including selection of hold pressures and evaluation of uncertainties, was conducted in accordance with the EPRI In Situ Pressure Test Guidelines (ISPTGL),

Revision 5.

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The bounding normal operating pressure differential (NOPD) for WF3 was calculated to be 1414 psi, resulting in a 3xNOPD of 4242 psi for in situ pressure testing. Note that the test pressures are higher than actual MSLB or 3xNOPD due to the correction factors for pressure gauge error and material properties at elevated temperature, as required by the ISPTGL. This resulted in a final hold point of 5500 psi.

Two tubes from SG 31 (R1-C112 and R1-C138) were tested over the range of prescribed test pressures and successfully reached and maintained the structural limit pressure test of 5500 psi. No tube leakage was measured at any test pressure for these two tubes.

Two tubes from SG 31 (R1-C4 and R2-C35) were tested over the range of prescribed test pressures. Tube R1-C4 was unable to reach the structural limit test pressure as it experienced pop-through at 5243 psi. No leakage was measured in this tube at lower test pressures prior to the pop-through. Tube location R2-C35 was able to temporarily achieve the structural limit test pressure point at 5500 psi, but lost leak tight integrity via pop-through after a combined 131 seconds above the target pressure of 5500 psi. The combined 131 seconds at pressure was achieved by a period of 41 seconds above the test target, then briefly dropping below 5500 psi before being re-established above 5500 psi for 90 seconds prior to the pop through. No tube leakage was observed at any test pressure below the structural limit test.

Examination of pre-and post-test +Point and Array probe data confirmed that flaws in tube R1-C4 at 05C and in tube R2-C35 at 07C burst.

3.4.6 Number of Tubes Plugged During the Inspection Outage Table 3.3.4.1 lists all tubes plugged during RF25 including location and reason for plugging. For the location column, A## indicates the Anti-Vibration Bar and ##H/##C indicates the Tube Support Plate on the Hot/Cold Leg. For the reason column, TS indicates a wear indication greater than or equal to the technical specification 40%

plugging limit and P indicates a tube that was preventatively plugged to support the operational assessment.

Table 3.3.4.1 Tubes Plugged During RF25 SG Row Col Mechanism Location Stabilized Reason 31 1

60 TSP Wear 06C N

TS 41%

31 2

31 TSP Wear 06C N

TS 43%

31 3

114 TSP Wear 07C N

TS 40%

31 7

90 TSP Wear 06C N

TS 46%

31 1

30 TSP Wear 06C N

P 33%

31 1

62 TSP Wear 05C N

P 38%

31 1

164 TSP Wear 06C N

P 34%

31 2

49 TSP Wear 03C N

P 32%

31 3

62 TSP Wear 07C N

P 36%

31 4

51 TSP Wear 05C N

P 36%

31 5

68 TSP Wear 04C N

P 39%

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31 5

72 TSP Wear 04C N

P 36%

31 5

74 TSP Wear 04C N

P 30%

31 5

90 TSP Wear 04C N

P 33%

31 5

94 TSP Wear 07C N

P 35%

31 6

75 TSP Wear 07C N

P 37%

31 7

34 TSP Wear 06C N

P 34%

31 7

46 TSP Wear 05C N

P 34%

31 7

54 TSP Wear 04C N

P 35%

31 12 75 TSP Wear 07C N

P 38%

31 1

4 TSP Wear 05C Y

TS 77%

31 1

112 TSP Wear 04C Y

TS 67%

31 1

134 TSP Wear 06C Y

TS 52%

31 1

138 TSP Wear 06C Y

TS 73%

31 2

35 TSP Wear 06C Y

TS 68%

31 2

113 TSP Wear 04C Y

TS 51%

31 123 88 AVB Wear A06 Y

TS 58%

32 1

6 TSP Wear 04C N

P 31%

32 1

30 TSP Wear 06C N

P 32%

32 1

40 TSP Wear 05C N

TS 40%

32 2

1 TSP Wear 06C N

P 35%

32 2

133 TSP Wear 05C N

P 31%

32 3

138 TSP Wear 07C N

P 32%

32 7

104 TSP Wear 06C N

P 34%

32 85 84 AVB Wear A05 N

TS 42%

32 97 90 AVB Wear A07 N

TS 44%

32 114 85 AVB Wear A08 N

TS 45%

32 122 83 AVB Wear A06 N

TS 47%

32 123 86 AVB Wear A06 N

P 39%

32 125 86 AVB Wear A08 N

P 37%

32 126 75 AVB Wear A08 N

TS 41%

32 127 82 AVB Wear A07 N

P 46%

32 128 111 AVB Wear A07 N

P 37%

32 130 75 AVB Wear A06 N

TS 47%

32 130 79 AVB Wear A06 N

P 39%

32 131 78 AVB Wear A07 N

TS 43%

32 1

120 TSP Wear 05C Y

TS 51%

32 128 87 AVB Wear A06 Y

TS 59%

Notes:

TWD: through-wall depth (wear indications exceeding 40% plugging limit)

PTP: preventative tube plug

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3.5 Analysis Summary of the Tube Integrity Conditions Predicted to Exist at the Next Scheduled Inspection The observed forms of tube degradation in the Waterford 3 steam generators at the RF25 inspection were AVB wear and TSP wear. Operational assessment (OA) calculations for each degradation mechanism are presented below and demonstrate reasonable assurance that the performance criteria will be met for operating cycles 26 through 27. The OA was evaluated for a bounding inspection interval of 2.6 EFPY.

The RF25 OA for AVB and TSP wear used a probabilistic full-bundle approach that sampled from conservative distributions for wear growth rates and wear flaw structural parameters. The probabilistic approach is more responsive to extreme value growth rates because it explicitly captures the fact that if more deep wear flaws are returned to service, there is an increasing probability that large growth rates will be matched with large BOC depths, making deep end of cycle (EOC) indications more likely.

To account for potential decrease in SG pressure during cycles 26 and 27, a bounding NOPD of 1430 psi is used as identified in the Degradation Assessment. The EOC27 probability of meeting the structural integrity requirement of a minimum burst pressure of 3xNOPD (4290 psi) was calculated for each return to service and each new wear flaw depth. As part of the full bundle analysis, a postulated population of new wear flaws was introduced into the model.

The projected quantity of new wear flaws was based on a Weibull fit per SG to the number of new indications detected during the RF19 through RF25 inspections. The postulated new flaw depths were determined using a Monte Carlo simulation that sampled from a Kunin distribution fit of the RF25 population of new wear indications from each SG. This is a conservative approach as the new flaw population in RF25 had been allowed to develop over 4-cycles (5.62 EFPY) compared to a 2-cycle OA interval of 2.6 EFPY.

Accident Induced Leakage Performance Criteria was satisfied by passing structural integrity or by passing the leakage hold points during in situ pressure testing. Operational leakage integrity was demonstrated by the absence of any detected primary-to-secondary leakage during the prior operating cycles since RF21.

In addition to the OA performed by the inspection vendor and accepted by Entergy, an independent third-party OA was obtained to confirm the allowable inspection interval. This OA, utilizing a fully probabilistic method, confirmed there is reasonable assurance that the performance criteria will be met for operating cycles 26 through 27.

3.5.1 OA for Wear at AVBs The growth rate distributions used to model AVB wear for upcoming cycles 26 and 27 conservatively bounded the average, upper 95th, and maximum growth rates measured in each SG during the RF25 inspection. The AVB wear OA projections were performed, and plugging limits were established separately for each SG. A comparison of cumulative distribution function (CDF) plots of AVB wear growth rates through RF25 shows that overall, the AVB wear growth rate is attenuating.

The probability of survival (POS), that is the probability that the tube bundle will meet a minimum burst pressure of 3xNOPD is the product of all the probabilities of each wear

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indication within the tube bundle meeting 3xNOPD. For each SG, ten runs were made with 100,000 trials per run. The result of the ten runs were averaged for a calculated POS of 0.99 in both SG31 and SG32. The projected structural integrity probabilities exceed the required 0.95 per-bundle probability demonstrating with reasonable assurance that the structural performance criteria will not be exceeded during the next two operating cycles (26 and 27).

The use of an operating period of 2.6 EFPY, bounding RF25 growth rate distribution, bounding distributions for structural length and structural depth ratio (structural depth to maximum depth ratio), an EOC flaw population taken from an interval more than twice as long as the one projected, and a bounding 3xNOPD value all act to make the probability estimates conservative for operating cycles 26 and 27.

3.5.2 OA for Wear at TSPs When considering both steam generators, SG31 had the bounding upper 95th growth rate (9.318 %TW/EFPY), and the bounding maximum growth rate (10.14 %TW/EFPY). The TSP wear OA projections were performed, and plugging limits were selected separately for each SG and used SG-specific growth rates to avoid unduly penalizing SG 32. Since TSP wear was not detected in RF19, the only growth rate data is from RF21 to RF25.

Similar to the AVB model, the POS is the product of all the probabilities of each wear indication within the tube bundle meeting 3X NOPD. For each SG, ten runs were made with 100,000 trials per run. The result of the ten runs were averaged for a calculated POS of 0.97 for SG31 and 0.99 for SG32. The projected structural integrity probabilities exceed the required 0.95 per-bundle probability demonstrating with reasonable assurance that the structural performance criteria will not be exceeded during the next two operating cycles (26 and 27).

The use of an operating period of 2.6 EFPY, bounding RF25 growth rate distribution, bounding distributions for structural length and structural depths (structural depth to maximum depth ratios), and a bounding 3X NOPD value all act to make the probability estimates conservative for operating cycles 26 and 27.

3.5.3 OA for TSP Wear in SG1 Considering Sub-Populations During review of the preliminary OA and causal investigation into the TSP wear that resulted in exceedance of CM limits, it was observed that there is a sub-population of TSP wear in SG1 Rows 1-2 that needed to be treated separately. To re-evaluate SG 31 TSP wear, a zoned OA approach was used, dividing the SG 31 TSP wear into sub-populations.

The first population consisted of row 1-2 flaws. The second population consisted of row 3 and higher. Probabilistic models were created for each sub-population. The growth rates for each sub-population were individually derived. In this zoned evaluation, the structural depth to max depth ratio of all flaws in all rows was set to a fixed value of 1.0 conservatively modeling all flaws as completely flat. It should be noted that when the entire SG population was evaluated for the OA in Section 3.5.2, a tube wall thickness of 0.043 was used for all tubes. This was conservative, as the row 1 and 2 tubes are fabricated from 0.044 wall material and as such will have a higher burst pressure. For the new zoned evaluations that separated rows 1-2 vs row 3 and higher, a wall thickness

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of 0.044 was used for rows 1 and 2. In conjunction, the population of row 3 and higher tubes was re-evaluated separately since the probability of survival (POS) of the SG is the product of the POS of each of the zoned populations.

The probabilistic models were run with the remaining parameters the same as those detailed in section 3.5.2. Models for Rows 1-2 and Row 3+ were run ten times each, each run comprising 100,000 Monte Carlo simulations, resulting in an average POS for row 1-2 of 0.9774 and average POS for row 3 and higher of 0.9966. The combined POS of 0.9740 meets the acceptance criterion of >0.95.

3.6 Number and Percentage of Tubes Plugged to Date, and the Effective Plugging Percentage in Each SG Table 3.6.1 below summarizes the total tubes plugged at RF25, cumulative total tubes plugged and percent of tubes plugged in each SG.

Table 3.6.1 Tubes Plugged to Date SG-31 SG-32 Total Total Tubes in Replacement Steam Generators 8968 8968 17936 Total Tubes Plugged Prior to RF25 3

28 31 RF25 Tubes Plugged due to AVB Wear 1

13 14 RF25 Tubes Plugged due to TSP Wear 26 8

34 RF25 Total Tubes Plugged 27 21 48 Total Tubes Plugged - Post RF25 30 49 79 Total % Tubes Plugged - Post RF25 0.33%

0.55%

0.44%

3.7 SG Secondary Side Inspection Results The intent of the TTS visual inspections was to assess material condition, structural condition, deposit accumulation and foreign objects. Areas reviewed included the no-tube lane and annulus region. No degradation was identified during these inspections, and overall, the SGs were very clean with few light sludge piles identified on the TTS.

ECT inspection did not detect any evidence of foreign object wear in either SG. All confirmed foreign objects from visual inspections and ECT identified Possible Loose Part (PLP) indications which required FOSAR are summarized in Table 3.7.1 below.

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Table 3.7.1 PLP Indications and Foreign Objects identified in RF25 SG Item #

Description Location Detect Method Removed?

Comments 31 2

Sludge rock with PLP R13 C10 TSC-0.27 Array No Broke up when touched, no further action needed 31 3

Cylindrical metallic object with PLP R21 C164 TSC+0.22 R20 C165 TSC+0.14 Array Yes Item Removed 31 4

Sludge rock with PLP R133 C84 TSH+0.40 R134 C85 TSH+0.33 Array No Broke up when touched, no further action needed 32 1

Flat metallic object with PLP R19 C12 TSC+1.45 R18 C13 TSC+1.31 R20 C13 TSC+1.38 Array Yes Item removed 32 2

Small piece of shredded plastic Annulus/ drain hole Visual Yes Item removed Visual inspections of the steam drum included the feedwater spray nozzles, primary moisture separators, secondary moisture separators, feedring and supports, steam venturis, sludge collectors, and general area conditions. All components were inspected visually for structural integrity, presence of related components, as well as surface conditions. No degradation or abnormalities were noted.

While inspecting the feed ring area of SG 31, objects were identified protruding from the flow holes in the feedwater spray nozzles. The associated feed ring was opened, and the inside was inspected for accumulation of foreign material. A total of eight objects (which included the objects seen lodged in the flow holes) were retrieved. Based on the minimal amount of material retrieved from the SG 31 feed ring, the SG 32 feed ring was not opened for inspection.

3.8 SG Secondary Side Cleaning No sludge lancing was completed during the WF3 RF25 SG inspection outage.

3.9 Primary Side Component Visual Inspection Results The hot leg and cold leg primary side channel heads in each SG were visually inspected during the RF25 outage. The visual inspection results performed during RF25 did not identify any anomalies or degradation of the channel head cladding or associated welds. Visual examinations of tube plugs showed no evidence of leakage or other notable conditions.

Attachment to W3F1-2024-0019 Page 14 of 23 SG31 RF25 Wear at AVBs 20%

ROW COL VOLTS PER LOCN INCH 83 78 0.65 21 A07

-0.07 99 82 0.94 26 A06

-0.08 123 88 1.2 29 A09

-0.02 123 88 1.42 31 A08

-0.11 123 88 7.4 58 A06 0

123 88 2.57 40 A05

-0.07 134 79 1.49 32 A07

-0.09 134 79 1.57 33 A06

-0.08

Attachment to W3F1-2024-0019 Page 15 of 23 SG31 RF25 Wear at TSPs 20%

ROW COL VOLTS PER LOCN INCH 1

2 0.98 31 07C 0

1 2

0.68 25 05C

-0.23 1

4 4.13 60 06C

-0.05 1

4 8.97 77 05C

-0.05 1

4 3.71 58 04C 0.39 1

12 0.63 24 06C 0.34 1

16 0.66 25 06C 0.36 1

30 1.12 33 06C

-0.64 1

60 0.75 21 07C

-0.18 1

60 1.63 41 06C

-0.14 1

62 1.42 38 05C

-0.36 1

110 0.98 25 06C 0

1 110 1.1 27 03C 0

1 112 6.25 67 04C 0

1 112 3.09 49 07C 0

1 112 4.66 59 03C

-0.02 1

132 1.14 28 07C

-0.16 1

134 3.54 52 06C

-0.16 1

138 7.13 73 06C 0

1 138 4.05 60 07C

-0.21 1

140 0.61 23 06C

-0.14 1

144 1.03 26 06H

-0.25 1

164 1.16 34 06C 0.27 1

168 0.6 23 07C 0.3 2

1 0.75 21 07C

-0.23 2

17 0.87 29 07C

-0.57 2

17 0.81 22 06C

-0.16 2

17 0.62 24 05C

-0.68 2

31 1.82 43 06C

-0.18 2

35 5.79 65 07C 0

2 35 5.82 68 06C 0.25 2

45 1.24 29 06C

-0.18 2

49 1.06 32 03C

-0.09 2

107 0.68 25 06C 0.25 2

109 0.72 26 03C

-0.09 2

113 1.51 33 07C 0

2 113 2.72 46 06C

-0.16

Attachment to W3F1-2024-0019 Page 16 of 23

2 113 3.35 51 04C 0

2 113 1.61 34 03C 0

2 117 0.76 21 06C

-0.14 3

14 0.6 23 06C 0

3 62 1.27 36 07C

-0.2 3

114 2.08 40 07C 0

3 114 1.52 39 06C

-0.14 4

25 0.62 24 06C 0.3 4

45 0.72 26 05C 0

4 51 1.79 36 05C

-0.18 4

133 0.48 20 04C 0.34 4

143 0.57 22 06C 0.36 5

68 2

39 04C 0

5 68 0.73 26 03C 0.32 5

72 1.3 36 04C 0

5 72 0.82 22 03C

-0.11 5

74 1.34 30 04C 0

5 90 1.56 33 04C

-0.16 5

90 1.15 28 03C 0

5 94 1.21 35 07C 0.23 6

1 0.48 20 05C

-0.57 6

39 0.87 23 05C

-0.16 6

53 0.72 26 04C 0.3 6

69 0.49 20 07C 0

6 75 1.34 37 07C

-0.18 6

139 0.49 20 06C

-0.07 7

34 0.83 22 07C

-0.21 7

34 1.16 34 06C

-0.14 7

42 0.96 25 04C

-0.14 7

46 1.13 34 05C

-0.05 7

54 1.2 35 04C

-0.11 7

90 2.74 46 06C

-0.25 7

98 0.75 27 03C 0

8 45 0.74 21 04C

-0.11 12 75 1.44 38 07C

-0.23 12 75 0.91 24 05C

-0.16 13 70 0.55 22 06C

-0.14 13 70 0.63 24 05C 0.39 13 100 0.69 25 05C 0.05 15 64 0.58 23 06C

-0.69

Attachment to W3F1-2024-0019 Page 17 of 23

18 95 0.47 20 05C 0.43 80 17 0.5 21 05C

-0.44 138 99 0.56 22 05H

-0.7

Attachment to W3F1-2024-0019 Page 18 of 23 SG32 RF25 Wear at AVBs 20%

ROW COL VOLTS PER LOCN INCH 74 95 0.69 22 A07 0.12 76 91 0.64 21 A07

-0.24 78 79 0.64 21 A07

-0.07 82 95 0.61 21 A08 0.04 82 95 0.59 20 A07 0.12 84 75 0.94 26 A05 0

84 83 0.75 23 A06

-0.13 85 84 0.72 23 A08 0

85 84 3

42 A05

-0.09 85 86 1

27 A05 0.03 86 75 0.63 21 A05

-0.15 86 87 0.8 24 A07 0.11 87 84 1.03 27 A05

-0.02 87 86 1.56 33 A05 0.06 88 83 1.2 29 A06 0.02 89 86 1.24 29 A05 0.06 91 86 1.19 29 A06

-0.16 91 90 1.54 32 A06

-0.11 91 90 1.17 29 A05

-0.04 92 77 1.08 28 A05

-0.2 92 77 1.69 34 A06

-0.13 92 79 1.77 34 A07

-0.02 92 91 0.84 24 A05

-0.04 93 88 0.67 22 A06

-0.03 93 96 1.93 36 A06

-0.05 93 96 1.49 32 A05

-0.02 94 91 1.11 28 A07

-0.02 95 74 0.9 25 A06 0.05 96 93 1.53 32 A07

-0.02 97 76 0.79 24 A07

-0.07 97 86 1.05 27 A07

-0.19 97 88 0.71 22 A06

-0.02 97 90 3.35 44 A07 0

98 73 0.73 23 A06

-0.15 98 81 1.74 34 A08 0.07 98 81 1.18 29 A07 0.12 98 87 0.79 24 A06 0

Attachment to W3F1-2024-0019 Page 19 of 23

98 91 0.71 22 A08

-0.04 99 78 0.68 22 A05

-0.02 99 86 1.06 27 A09

-0.04 99 86 0.87 25 A06

-0.2 100 83 0.61 21 A06 0.05 103 84 0.81 24 A07 0.06 103 90 1.67 34 A07

-0.02 103 90 1.78 34 A06

-0.05 104 81 1.17 29 A07

-0.12 104 91 0.78 24 A06

-0.05 105 90 0.61 21 A06

-0.07 107 80 0.61 21 A05 0.05 107 88 0.68 22 A06

-0.02 107 90 1.07 28 A06

-0.07 108 85 1.29 30 A05

-0.02 108 89 1.68 34 A05

-0.12 109 78 0.6 20 A07 0

109 78 1.35 31 A06 0.05 109 78 0.69 22 A05

-0.05 109 86 0.7 22 A04 0.02 109 90 0.65 21 A07

-0.09 110 75 0.55 20 A07

-0.12 111 88 0.62 21 A05

-0.05 112 79 0.59 20 A07

-0.05 113 84 0.9 25 A08

-0.24 113 84 1.12 28 A05 0

114 81 0.94 26 A06 0

114 81 0.89 25 A05 0

114 85 3.62 45 A08 0

114 85 0.91 25 A09 0

114 87 0.64 21 A06

-0.05 114 89 0.93 26 A09 0.03 114 89 1.61 33 A08

-0.09 114 89 0.84 24 A07

-0.05 114 93 1.93 36 A07

-0.12 114 93 1.08 28 A06

-0.05 116 87 1.52 32 A07

-0.07 116 87 0.9 25 A05

-0.02 117 84 0.72 23 A05

-0.07 117 84 0.56 20 A08 0

Attachment to W3F1-2024-0019 Page 20 of 23

118 85 0.61 21 A05

-0.02 120 79 0.68 22 A06

-0.11 120 83 0.64 21 A07

-0.02 120 87 1.17 29 A05

-0.07 120 89 0.92 26 A07

-0.07 120 91 0.72 23 A05

-0.02 120 95 0.91 25 A07

-0.07 120 95 1.01 27 A06

-0.07 121 76 0.63 21 A07

-0.17 121 90 1.14 28 A08

-0.06 121 90 1.11 28 A06

-0.02 122 81 0.79 24 A06 0

122 83 1.67 34 A07

-0.16 122 83 4.13 47 A06

-0.13 122 83 0.56 20 A05

-0.12 123 80 1

27 A06 0

123 80 0.57 20 A05

-0.02 123 84 1.95 36 A06 0

123 84 0.79 24 A07 0

123 86 0.77 23 A07

-0.07 123 86 2.43 39 A06

-0.02 124 89 0.58 20 A05

-0.1 124 91 1.84 35 A07

-0.09 124 91 1.17 29 A06

-0.07 124 99 1.16 29 A08

-0.04 124 99 1.38 31 A07

-0.1 124 99 0.72 23 A06 0.02 124 99 0.87 25 A05

-0.07 125 84 1.52 32 A07

-0.05 125 84 0.9 25 A06

-0.15 125 84 0.74 23 A09

-0.04 125 84 1.9 35 A08

-0.04 125 86 0.62 21 A09

-0.07 125 86 2.18 37 A08

-0.08 125 86 0.65 21 A05

-0.07 125 86 0.86 25 A07

-0.07 126 75 0.92 26 A06 0

126 75 2.88 41 A08 0

126 75 2.52 39 A07 0

127 82 0.73 23 A09 0

Attachment to W3F1-2024-0019 Page 21 of 23

127 82 3.82 46 A07 0

127 82 2.94 42 A06 0

127 82 1.58 33 A05 0

127 88 0.84 24 A05

-0.07 127 88 1.24 29 A07

-0.16 127 94 1.42 31 A07

-0.09 127 94 1.29 30 A06 0

128 87 1.1 28 A08

-0.12 128 87 2.05 36 A07

-0.05 128 87 3.49 44 A05

-0.02 128 87 8.21 59 A06

-0.24 128 91 1.19 29 A07

-0.07 128 91 1.66 33 A06

-0.13 128 111 1.48 32 A08

-0.02 128 111 2.19 37 A07

-0.1 128 111 1.77 34 A06

-0.02 130 75 1.55 33 A07

-0.09 130 75 4.29 47 A06

-0.04 130 75 3.54 44 A05 0.1 130 79 1.36 31 A07

-0.19 130 79 0.93 26 A08

-0.08 130 79 2.44 39 A06

-0.11 130 79 0.73 23 A05

-0.09 131 78 1.18 29 A09

-0.11 131 78 2.25 38 A08

-0.14 131 78 3.32 43 A07

-0.39 131 78 2.42 39 A06

-0.4 131 80 0.9 25 A06

-0.17 131 84 0.89 25 A06

-0.13

Attachment to W3F1-2024-0019 Page 22 of 23 SG32 RF25 Wear at TSPs 20%

ROW COL VOLTS PER LOCN INCH 1

6 1.26 29 06C

-0.07 1

6 1

31 04C

-0.14 1

16 0.68 25 05C 0.3 1

16 0.64 24 03C

-0.16 1

24 1.06 32 05C

-0.09 1

24 1.87 37 03C

-0.09 1

26 0.84 28 04C

-0.14 1

30 1.15 28 07C

-0.09 1

30 1.47 32 06C

-0.16 1

30 0.89 23 05C

-0.16 1

36 1.06 26 03C 0

1 36 1.2 28 05C 0

1 40 1.55 40 05C 0.43 1

62 0.8 28 06C

-0.18 1

120 2.08 45 06C

-0.14 1

120 3.33 51 05C

-0.18 1

134 1.54 39 05C

-0.11 1

154 0.5 21 06C 0.27 1

156 0.73 26 05C 0

2 1

1.11 27 05C

-0.18 2

1 1.21 35 06C

-0.21 2

17 0.95 24 06C

-0.18 2

17 0.63 24 05C 0.39 2

107 1.03 32 05C

-0.07 2

115 0.77 27 06C

-0.18 2

117 0.65 24 06C

-0.18 2

133 0.99 31 05C

-0.11 2

133 0.64 24 06C

-0.18 2

137 0.89 29 05C 0.34 2

161 0.58 23 06C

-0.43 3

10 0.7 26 07C

-0.16 3

116 0.54 22 06C

-0.16 3

138 1.04 32 07C

-0.16 3

168 1.39 38 05C

-0.16 6

1 0.51 21 06C

-0.64 6

39 0.52 21 05C 0.25 6

67 0.56 22 07C 0.32

Attachment to W3F1-2024-0019 Page 23 of 23

7 104 1.14 34 06C

-0.18 7

116 0.82 28 05C

-0.16 7

136 0.48 20 05C

-0.16 7

138 0.7 26 05C

-0.16 8

123 0.72 26 05C

-0.18 12 69 0.61 24 07C 0.33 15 2

0.5 21 06C 0.32