WBL-21-028, Cycle 3 Steam Generator Tube Inspection Report

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Cycle 3 Steam Generator Tube Inspection Report
ML21130A040
Person / Time
Site: Watts Bar Tennessee Valley Authority icon.png
Issue date: 05/10/2021
From: Anthony Williams
Tennessee Valley Authority
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
WBL-21-028
Download: ML21130A040 (18)
v • d • e


Text

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TEN.NE.SSEE VALLEY AUTHORITY Post Office Box 2000, Spring City, Tennessee 37381 WBL-21-028 May 10, 2021 10 CFR 50.4 ATTN: Document Control Desk U,S, Nuclear Regulatory Commission Washington, D.C. 20555-0001 Watts Bar Nuclear Plant, Unit 2 Facility Operating License No. NPF-96 NRC Docket No. 50-391

Subject:

Watts Bar Nuclear Plant (WBN) Unit 2 - Cycle 3 Steam Generator Tube Inspection Report In accordance with the requirements of WBN Technical Specification (TS) 5.9.9, "Steam Generator Tube Inspection Report", the Enclosure provides the 180 Day Steam Generator Inspection Report for Unit 2 Cycle 3. This report is required to be submitted within 180 days after the initial entry into MODE 4 following the completion of an inspection performed in accordance with TS 5.7.2.12, "Steam Generator (SG) Program." The report provides the complete results of the tube inspections.

There are no regulatory commitments contained in this letter. Please direct any questions concerning this matter to Tony Brown, WBN Licensing Manager, at (423) 365-7720.

Anthony L. Williams IV Site Vice President Watts Bar Nuclear Plant

U.S. Nuclear Regulatory Commission WBL-21-028 Page 2 May 10, 2021

Enclosure:

Watts Bar U2R3 180 Day Steam Generator Tube Inspection Report cc: (w/o Enclosure):

NRC Regional Administrator - Region II NRC Senior Resident Inspector - Watts Bar Nuclear Plant NRC Project Manager - Watts Bar Nuclear Plant

ENCLOSURE Tennessee Valley Authority Watts Bar Nuclear Plant Unit 2 Watts Bar U2R3 180 Day Steam Generator Tube Inspection Report

Watts Bar U2R3 180 Day Steam Generator Tube Inspection Report Author: Signature / Date For Pages 4/28/2021 Jesse S. Baron All SG Program Engineer Reviewers: Signature / Date For Pages Jeremy W. Mayo All SG Program Manager 4/30/2021 Daniel P. Folsom All NDE Eddy Current Level III Managers Name: Signature / Date For Pages Anne Robinson-Givens All Senior Programs Manager TVA EWR WO 122088253 Revision 0 April 2021 Page 1 of 15

Table of Contents 1.0 Introduction ...................................................................................................................................................... 3 2.0 180 Day Steam Generator Tube Inspection Report ......................................................................................... 4

a. The Scope of Inspections Performed on each SG .......................................................................................... 4
b. Degradation Mechanisms Found .................................................................................................................... 5
c. Nondestructive Examination (NDE) Techniques Utilized for Each Degradation Mechanism ...................... 6
d. Location, Orientation (if Linear), and Measured Sizes (if Available) of Service Induced Indications .......... 8
e. Number of Tubes Plugged or Repaired During the Inspection Outage for Each Degradation Mechanism . 13
f. The Number and Percentage of Tubes Plugged or Repaired to Date and the Effective Plugging Percentage in each SG .................................................................................................................................................... 14
g. The Results of Condition Monitoring, Including the Results of Tube Pulls and In-Situ Testing ................ 14
h. Repair Method Utilized and the Number of Tubes Repaired by Each Repair Method ................................ 15 List of Tables and Figures Figure 1-1: Tube Support Arrangement for Watts Bar Unit 2 Model D3 Steam Generators ................................. 3 Table 2-1: Watts Bar U2R3 Steam Generator Eddy Current Inspection Scope...................................................... 5 Table 2-2: Number of Indications Detected for Each Degradation Mechanism during U2R3 ............................... 6 Table 2-3: NDE Techniques for Each Degradation Mechanism ............................................................................ 7 Table 2-4: Watts Bar U2R3 Pre-Service Volumetric Indications - All SGs ........................................................... 8 Table 2-5: Watts Bar U2R3 Anti-Vibration Bar Wear Indications - All SGs ......................................................... 9 Table 2-6: Watts Bar U2R3 Tube Support Plate Wear Indications - All SGs....................................................... 10 Table 2-7: Watts Bar U2R3 Circumferential ODSCC at HTS Indications - All SGs ........................................... 11 Table 2-8: Watts Bar U2R3 Axial ODSCC at TSP Indications Excluded from GL 95 All SGs ................... 13 Table 2-9: Watts Bar U2R3 Axial ODSCC at HTS Indications - All SGs ........................................................... 13 Table 2-10: Watts Bar U2R3 Axial ODSCC at Tube Freespan Dings - All SGs.................................................. 13 Table 2-11: Watts Bar U2R3 Circumferential ODSCC at Tube Freespan Dings - All SGs ................................. 13 Table 2-12: Watts Bar U2R3 Axial PWSCC at HTS Indications - All SGs ......................................................... 13 Table 2-13: Number of Tubes Plugged for each Degradation Mechanism........................................................... 14 TVA EWR WO 122088253 Revision 0 April 2021 Watts Bar U2R3 180 Day Steam Generator Tube Inspection Report Page 2 of 15

1.0 Introduction The third in-service inspections (ISI) of the Watts Bar Unit 2 (WBN2) steam generators (SGs) were performed during the fall 2020 refueling outage designated as U2R3. The U2R3 inspection was performed after 3.354 effective full power years (EFPY) of plant operation. The inspections included eddy current testing of the SG tubing as well as primary side visual inspections, secondary side visual inspections, and secondary side cleanings.

This report documents the Watts Bar U2R3 180-Day Steam Generator Tube Inspection Report as required by the WBN2 Technical Specifications. The steam generators at WBN2 are a Westinghouse Model D3 preheater-type design where the majority of the feedwater enters the tube bundle on the cold leg side and the tubing is made from mill annealed Alloy 600 (Alloy 600MA) material. Figure 1-1 below provides the arrangement and location designation of the tube support structures for the WBN2 SGs.

Figure 1-1: Tube Support Arrangement for Watts Bar Unit 2 Model D3 Steam Generators Notes: H/C/AV = Hot Leg Support/Cold Leg Support/Anti-Vibration Bar (AVB) Location HTS/CTS = Hot Leg Top of Tubesheet/Cold Leg Top of Tubesheet HTE/CTE = Hot Leg Tube End/Cold Leg Tube End TVA EWR WO 122088253 Revision 0 April 2021 Watts Bar U2R3 180 Day Steam Generator Tube Inspection Report Page 3 of 15

2.0 180 Day Steam Generator Tube Inspection Report In accordance with WBN2 Technical Specification Section 5.7.2.12 Steam Generator Program and Technical Specification Section 5.9.9 Steam Generator Tube Inspection Report, this report documents the scope and results of the Watts Bar U2R3 SG inspections. There are eight specific reporting requirements associated with the Technical Specification. Each lettered reporting requirement listed below is followed with the associated information based on the inspections performed during U2R3.

a. The Scope of Inspections Performed on each SG The inspection program addressed the known degradation observed in the Watts Bar Unit 2 SGs during the pre-service inspection, in-service inspections, and potential SG tube degradation mechanisms relevant to the design and material of the Watts Bar Unit 2 SG tubing. The inspections were performed with qualified non-destructive examination (NDE) techniques for each existing and potential mechanism. The defined base scope and expansion scope that was implemented in all four SGs included:
  • 100% bobbin inspection of all open tubes in all four SGs full length and tube rows 1 through 4 to the top tube support plate from both the hot leg (HL) and cold leg (CL) sides.
  • 100% +POINT probe inspection of tube Rows 1 through 4 from the top tube support plate on the HL side to the top tube support plate on the CL side.
  • +POINT probe Special Interest inspections of tube locations with non-resolved bobbin and/or Array probe signals.
  • 100% +POINT probe inspection of the hot leg top of tubesheet region from HTS+2/-2 inches.
  • 50% Combination bobbin and Array probe inspection from C06 to CTS-2 inches in a checkerboard pattern. This inspection included all CL peripheral tubes two tubes deep, all tubes not inspected by the U2R2 cold leg combination bobbin and Array probe program and all possible loose part (PLP) indications detected as part of the combination bobbin and Array probe scope in the U2R2 inspections.
  • 100% +POINT or Array probe inspection of all DNTs > 2 Volts
  • 100% +POINT or Array probe inspection of all DNGs > 5 Volts in the HL straight lengths, U-bends and the top TSP on the CL side x Scope expanded to 100% +POINT or Array probe inspection of all DNGs > 2 Volts in SG2 x Scope expanded to 100% +POINT probe inspection of all DNGs > 5 Volts in SG4.

DNGs < 5 Volts were inspected with the 100% full length bobbin base scope program. The bobbin coil probe is qualified for axial ODSCC at DNGs.

  • 25% +POINT or Array probe inspection of all DNGs > 2 Volts.

x Scope was expanded to 100% +POINT or Array probe inspection of all DNGs > 2 Volts in SG2.

x Scope was expanded to 100% +POINT probe inspection of all DNGs > 5 Volts in SG4. DNGs < 5 Volts were inspected with the 100% full length bobbin base scope program. The bobbin coil is qualified for axial ODSCC at DNGs.

  • 100% +POINT probe inspection of any DNT or DNG signal located within 1.0 inch or less of a manufacturing burnish mark (MBM).
  • 100% +POINT probe inspection of TSP mix residual signals that could cause a 1.0 Volt bobbin signal to be missed or misread as required by NRC Generic Letter 95-05.
  • +POINT or Array probe inspection of tubes surrounding known locations of foreign objects from the pre-service inspections.

TVA EWR WO 122088253 Revision 0 April 2021 Watts Bar U2R3 180 Day Steam Generator Tube Inspection Report Page 4 of 15

  • +POINT or Array probe inspection of all tubes within a two-tube pitch of the region surrounding any foreign object wear or PLP locations.
  • +POINT probe inspection of SG3 tube Row 47 Column 48 at H01 and all tubes within one tube of this location at the same elevation.
  • +POINT probe inspection of bobbin tube-to-tube proximity (PRO or PRX) signals >1.25 Volts with corresponding adjacent PRO or PRX signals.
  • 100% visual inspection of all installed tube plugs from the primary side on both the HL and CL side.
  • Visual inspection in all SGs of channel head primary side HL and CL inclusive of the entire divider plate to channel head weld and all visible clad surfaces. A follow-up inspection of the channel head clad anomaly in the hot leg of SG1 was also performed to confirm that the assessment of the condition remains applicable.

The Watts Bar U2R3 inspection included all tubes with prior indications of degradation. The table below summarizes the number and type of eddy current examinations performed during U2R3.

Table 2-1: Watts Bar U2R3 Steam Generator Eddy Current Inspection Scope Eddy Current Exam Type SG 1 SG 2 SG 3 SG 4 Full Length Bobbin 4198 4190 4206 4199 CL R1-R4 Low Row Bobbin 451 450 454 454 HL R1-R4 Low Row Bobbin 451 450 454 454 U-Bend +Point R1-R4 461 450 454 454 HL +Point Tubesheet 4649 4640 4660 4653 CL Straight Leg Array Probe 2701 2676 2686 2649 C06 to CTS-2 inch Ghent Probe Special Interest 4 5 3 1

+Point Straight Section Special Interest 905 930 649 353a Array Probe Special Interest 199 210 80 87 U-bend +Point Special Interest 23 10 9 7 Dent/Ding +Point Expansion 0 582 0 0 Note a: Includes SG4 scope expansion to all DNGs > 5 Volts In addition to the NDE and primary side inspections discussed, visual inspection was performed of the secondary side in all SGs in order to determine the deposit and foreign object removal effectiveness of the tubesheet cleaning process applied. This was followed by a secondary side foreign object search and retrieval (FOSAR) inspection performed at the top of the tubesheet in all four SGs. No visual inspections were performed of the SG upper internal components during U2R3 since the upper internals of all four SGs have been inspected between the U2R1 and U2R2 refueling outages.

b. Degradation Mechanisms Found The following degradation mechanisms were detected during the U2R3 inspection:

- Volumetric Indications due to Tube Fabrication and Installation (Pre-Service)

- Mechanical Wear at Anti-Vibration Bars (AVBs)

- Mechanical Wear at Tube Support Plates (TSPs)

TVA EWR WO 122088253 Revision 0 April 2021 Watts Bar U2R3 180 Day Steam Generator Tube Inspection Report Page 5 of 15

- Circumferential Outer Diameter Stress Corrosion Cracking (ODSCC) at the Hot Leg Tubesheet Expansion Transition

- Axial ODSCC at the Hot Leg TSP Intersections

- Axial ODSCC at Hot Leg Expansion Transitions/Sludge Pile - New Mechanism

- Axial ODSCC at Tube Freespan Dings - New Mechanism

- Circumferential ODSCC at Tube Freespan Dings - New Mechanism

- Axial Primary Water Stress Corrosion Cracking (PWSCC) at Hot Leg Tubesheet Expansion Transitions - New Mechanism Volumetric indications generated during tube manufacture and bundle assembly and initially detected during the pre-service inspections were also detected during U2R3. These indications are not considered an active or ongoing in-service degradation mechanism but are listed for completeness.

All of the in-service volumetric wear indications detected were located at tube intersections with either TSPs or AVBs. Axial ODSCC at Hot Leg Expansion Transitions/Sludge Pile, PWSCC at Hot Leg Expansion Transitions, and Axial and Circumferential ODSCC at Freespan Dings are new degradation mechanisms first observed during Watts Bar U2R3.

Table 2-2 below shows the number of indications reported for each degradation mechanism during the U2R3 inspections.

Table 2-2: Number of Indications Detected for Each Degradation Mechanism during U2R3 Degradation Mechanism SG1 SG2 SG3 SG4 Total Volumetric Indications (Pre-Service) 13 2 7 14 36 Wear at Anti-Vibration Bars 10 13 3 28 54 Wear at Tube Support Plates 0 0 49 3 52 Circumferential ODSCC 6 1 44 18 69 at HL TTS Expansion Transition Axial ODSCC at Tube Support Plates 200 313 390 325 1228 Axial ODSCC at Tube Support Plates 0 1 10 1 12

> Upper Voltage Repair Limit Axial ODSCC at Tube Support Plates 0 0 3 0 3 Excluded from GL 95-05 Axial ODSCC 0 0 3 1 4 at HL TTS Expansion Transition Axial ODSCC 0 1 0 1 2 at Tube Freespan Ding Circumferential ODSCC 0 2 0 0 2 at Tube Freespan Ding Axial PWSCC 0 1 0 0 1 at HL TTS Expansion Transition

c. Nondestructive Examination (NDE) Techniques Utilized for Each Degradation Mechanism Table 2-3 provides the NDE techniques that were used for the detection of each degradation mechanism considered as existing or potential for the U2R3 inspection. NDE techniques are also listed which were available for diagnostic testing, resolution, and confirmation of anomalous indications. All of the examination technique specification sheets (ETSSs) used during U2R3 are from the electric power research institute (EPRI) database. In some cases, a variable X is used in the listing of techniques in Table 2-3 which is in reference to a series of ETSSs.

TVA EWR WO 122088253 Revision 0 April 2021 Watts Bar U2R3 180 Day Steam Generator Tube Inspection Report Page 6 of 15

Table 2-3: NDE Techniques for Each Degradation Mechanism Degradation Mechanism ETSS Detection Technique Volumetric Indications due to B: 27091.1 Tube Fabrication and Installation B: 27091.2 B: 96041.1

+Pt: 10908.4 Wear at A: 17908.1 AVBs A: 17908.2 A: 17908.4 A: 17908.5 B: 96042.1 A: 11956.1 Wear at A: 11956.2 Tube Support Plates A: 11956.3 A: 11956.4 B: 27091.1 Wear due to +Pt: 21998.1 Foreign Objects A: 1790X.1 A: 1790X.3 Tube-to-Tube B: 13091.2 Contact Wear B: 96005.3 OD Pitting of the Tube Material +Pt: 21998.1 A: 24998.1

+Pt: 20511.1 Ax Axial and Circumferential +Pt: I11524 Cir PWSCC at the TTS A: 20501.1 Ax A: 20500.1 Cir

+Pt: I28424 Ax Axial and Circumferential

+Pt: I28425 Ax ODSCC at the TTS

+Pt: 21410.1 Cir and Sludge Pile A: 20400.1 Ax/Cir Axial ODSCC B: I28411 at Tube +Pt: I28424 Support Plates A: 20402.1 Axial and Circumferential +Pt: 96511.2 PWSCC in the or Low Row U-bends +Pt: 99997.1 ODSCC B: I28411 or B: 24013.1 B: 10013.1 ODSCC at +Pt: 22401.1 Tube Dents and Dings and Axial +Pt: 21410.1 PWSCC at Dents A: 20400.1 A: 20403.1 PWSCC B: 96012.1 A: 20500.1 ODSCC

+Pt: I28424 Ax

+Pt: I28425 Ax

+Pt: 21410.1 Cir ODSCC and PWSCC at Tube A: 20400.1 Ax/Cir Bulges and Overexpansions PWSCC

+Pt: 20511.1 Ax

+Pt: I11524 Cir TVA EWR WO 122088253 Revision 0 April 2021 Watts Bar U2R3 180 Day Steam Generator Tube Inspection Report Page 7 of 15

Degradation Mechanism ETSS Detection Technique A: 20501.1 Ax A: 20500.1 Cir B: I28412 Axial ODSCC in the Freespan B: I28413 A: 20403.1 ODSCC at Dents and Dings +Pt: 22401.1 Coincident with an MBM +Pt: 21410.1 Diagnostic ETSS Technique Gh: 20406.1 Gh: 20407.1 Anomalous Gh: 20507.1 Indications Gh: 20508.1 Gh: 20509.1 Acronym Definitions for Table 2-3

+Pt: +POINT Probe Gh: Ghent Probe A: Array Probe MBM: Manufacturing Burnish Mark AVB: Anti-Vibration Bar OD: Outer Diameter Ax: Axial ODSCC: Outer Diameter Stress Corrosion Cracking B: Bobbin Probe PWSCC: Primary Water Stress Corrosion Cracking Cir: Circumferential SCC: Stress Corrosion Cracking ETSS: Eddy current Technique Specification Sheet TTS: Top of the Tubesheet

d. Location, Orientation (if Linear), and Measured Sizes (if Available) of Service Induced Indications Table 2-4 through Table 2-12 provide a listing of all pre-service and service-induced indications reported during the U2R3 inspection. The tables also provide the estimated depths from the associated NDE technique and an indication of whether the tube has been plugged.

Implementation of GL 95-05 voltage-based alternate repair criteria for axial ODSCC degradation at TSP intersections excludes certain tubes and locations from application of the criteria.

Indications of axial ODSCC at TSPs in excluded tube locations are identified in Table 2-8. The remaining indications of axial ODSCC at TSPs which have been addressed by GL 95-05 requirements are provided in NRC Accession Number ML21042B342.

Table 2-4: Watts Bar U2R3 Pre-Service Volumetric Indications - All SGs SG Row Col Location Inch1 Indication %TW Plugged?

1 6 74 HTS -0.19 VOL 30 Yes - U2R2 1 3 99 C14 0.08 VOL 17 No 1 10 38 C12 -2.5 VOL 23 No 1 10 55 C13 32.84 VOL 11 No 1 14 18 AV1 3.8 VOL 14 No 1 14 98 C14 1.69 VOL 18 No 1 28 83 C14 0.49 VOL 46 Yes - Pre-Service 1 30 73 C13 28.64 VOL 5 No 1 31 80 C14 1.84 VOL 24 No 1 32 65 C01 2.4 VOL 8 No 1 32 96 C14 0.52 VOL 27 No 1 34 77 C14 1.52 VOL 6 No 1 34 87 C14 0.2 VOL 41 Yes - Pre-Service 1 35 48 H08 25.26 VOL 18 No 1 38 72 AV4 29.55 VOL 39 Yes - Pre-Service 1 39 72 C14 -2.74 VOL 17 No 1 41 73 C14 0.58 VOL 30 No 2 5 103 H01 0.62 VOL 14 No 2 5 110 H01 0.44 SVI 46 Yes - U2R1 2 21 16 H03 33.19 VOL 11 No 2 25 28 C10 13.37 VOL 48 Yes - Pre-Service 2 27 31 C01 12.32 VOL 57 Yes - Pre-Service 3 19 37 C13 2.74 VOL 14 No 3 21 41 C01 3.88 VOL 20 No TVA EWR WO 122088253 Revision 0 April 2021 Watts Bar U2R3 180 Day Steam Generator Tube Inspection Report Page 8 of 15

SG Row Col Location Inch1 Indication %TW Plugged?

3 22 43 C01 1.46 VOL 15 No 3 32 46 H01 4.89 VOL 32 No 3 38 42 H01 1.75 VOL 21 No 3 38 42 H01 1.12 VOL 11 No 3 38 58 H06 40.09 VOL 21 No 3 40 42 H01 1.97 VOL 38 Yes - Pre-Service 4 1 87 H01 2.96 VOL 21 No 4 3 106 C11 12.01 VOL 10 No 4 8 84 H04 21.84 VOL 20 No 4 9 44 H07 30.94 VOL 10 No 4 20 46 H07 22.43 VOL 10 No 4 21 31 H06 9.99 VOL 18 No 4 21 31 H06 2.03 VOL 14 No 4 21 31 H06 17.06 VOL 7 No 4 23 77 C09 7.31 VOL 13 No 4 27 46 H04 22.89 VOL 20 No 4 28 95 H04 25.6 VOL 16 No 4 29 100 C13 36.1 VOL 30 No 4 30 14 C10 9.02 VOL 20 No 4 30 35 C10 8.8 VOL 23 No 4 38 84 H04 3.39 VOL 15 No Table 2-5: Watts Bar U2R3 Anti-Vibration Bar Wear Indications - All SGs SG Row Col Location Inch1 Ind %TW Plugged?

1 24 108 AV4 0.13 PCT 14 No 1 35 14 AV2 0.16 PCT 10 No 1 36 91 AV3 0.12 PCT 21 No 1 40 79 AV2 0.19 PCT 13 No 1 42 90 AV3 0.05 PCT 17 No 1 43 54 AV3 0 PCT 12 No 1 47 64 AV2 0 PCT 12 No 1 48 73 AV2 0 PCT 10 No 1 48 79 AV2 0 PCT 10 No 1 48 81 AV3 0 PCT 11 No 2 20 6 AV1 -0.17 PCT 13 No 2 22 8 AV3 0.16 PCT 12 No 2 23 6 AV4 0.2 PCT 16 No 2 24 8 AV2 0.19 PCT 15 No 2 25 9 AV2 0.26 PCT 17 No 2 27 21 AV4 -0.05 PCT 10 No 2 30 23 AV4 0.13 PCT 11 No 2 32 15 AV2 0.15 PCT 10 No 2 35 85 AV3 0.19 PCT 18 No 2 35 93 AV2 0.1 PCT 11 No 2 36 79 AV3 -0.19 PCT 13 No 2 37 38 AV3 0.17 PCT 11 No 2 47 41 AV1 0.12 PCT 10 No 3 30 105 AV3 -0.1 PCT 9 No 3 42 93 AV4 0.04 PCT 10 No 3 43 73 AV2 0.16 PCT 16 No 4 28 79 AV3 0 PCT 8 No 4 29 79 AV3 0.14 PCT 9 No 4 29 90 AV1 0.34 PCT 12 No 4 33 14 AV3 0.09 PCT 10 No 4 34 13 AV2 0.17 PCT 10 No 4 35 68 AV2 0.16 PCT 11 No 4 38 21 AV3 0.14 PCT 15 No 4 41 24 AV2 0.16 PCT 10 No 4 41 24 AV3 0.23 PCT 14 No 4 41 74 AV3 0.17 PCT 14 No TVA EWR WO 122088253 Revision 0 April 2021 Watts Bar U2R3 180 Day Steam Generator Tube Inspection Report Page 9 of 15

SG Row Col Location Inch1 Ind %TW Plugged?

4 41 88 AV3 -0.07 PCT 10 No 4 41 90 AV4 -0.02 PCT 7 No 4 41 94 AV3 0.24 PCT 12 No 4 42 29 AV2 0.25 PCT 19 No 4 42 29 AV3 0.16 PCT 12 No 4 42 36 AV3 0 PCT 21 No 4 42 40 AV2 0.21 PCT 13 No 4 42 40 AV3 0.32 PCT 18 No 4 42 64 AV1 0 PCT 11 No 4 42 65 AV3 0.14 PCT 14 No 4 42 78 AV3 -0.02 PCT 11 No 4 44 28 AV3 0.14 PCT 13 No 4 44 40 AV3 0 PCT 10 No 4 44 78 AV3 -0.02 PCT 10 No 4 46 75 AV3 0.07 PCT 10 No 4 49 59 AV1 0.12 PCT 15 No 4 49 60 AV3 0 PCT 14 No 4 49 60 AV4 0 PCT 14 No Table 2-6: Watts Bar U2R3 Tube Support Plate Wear Indications - All SGs SG Row Col Location Inch1 Ind %TW Plugged?

3 45 63 C06 -0.24 PCT 4 No 3 46 56 C05 0.02 PCT 5 No 3 46 56 C06 -0.28 PCT 9 No 3 46 57 C06 0 PCT 6 No 3 46 58 C06 -0.24 PCT 7 No 3 46 59 C05 0 PCT 6 No 3 46 60 C06 -0.24 PCT 4 No 3 46 61 C05 -0.02 PCT 13 No 3 46 61 C06 -0.03 PCT 4 No 3 46 65 C06 -0.21 PCT 8 No 3 47 56 C06 -0.28 PCT 8 No 3 47 57 C06 -0.16 PCT 6 No 3 47 58 C05 0.36 PCT 3 No 3 47 59 C02 0 PCT 7 No 3 47 59 C05 0.3 PCT 11 No 3 47 59 C06 -0.23 PCT 3 No 3 47 60 C03 0.3 PCT 4 No 3 47 60 C06 -0.16 PCT 26 No 3 47 62 C06 -0.21 PCT 7 No 3 47 63 C05 0 PCT 17 No 3 47 63 C06 -0.19 PCT 5 No 3 47 64 C05 -0.02 PCT 5 No 3 47 64 C06 -0.19 PCT 10 No 3 47 65 C05 0 PCT 9 No 3 48 51 C06 0.44 PCT 5 No 3 48 53 C05 -0.26 PCT 5 No 3 48 55 C05 -0.09 PCT 4 No 3 48 55 C06 -0.2 PCT 3 No 3 48 56 C05 0 PCT 5 No 3 48 56 C06 0 PCT 6 No 3 48 58 C03 0.14 PCT 5 No 3 48 58 C05 -0.02 PCT 6 No 3 48 60 C05 0.33 PCT 7 No 3 48 60 C06 -0.14 PCT 26 No TVA EWR WO 122088253 Revision 0 April 2021 Watts Bar U2R3 180 Day Steam Generator Tube Inspection Report Page 10 of 15

SG Row Col Location Inch1 Ind %TW Plugged?

3 48 61 C02 0.02 PCT 10 No 3 48 61 C05 0.07 PCT 16 No 3 48 61 C06 -0.14 PCT 7 No 3 48 63 C05 -0.26 PCT 4 No 3 48 63 C06 -0.21 PCT 4 No 3 48 64 C05 0 PCT 20 No 3 48 64 C06 -0.21 PCT 8 No 3 48 65 C05 0 PCT 27 No 3 48 66 C05 -0.2 PCT 3 No 3 48 66 C06 0.02 PCT 22 No 3 49 59 C05 -0.23 PCT 7 No 3 49 59 C06 -0.14 PCT 8 No 3 49 60 C02 0 PCT 5 No 3 49 60 C06 -0.19 PCT 21 No 3 49 61 C06 -0.14 PCT 16 No 4 48 46 C06 -0.28 PCT 10 No 4 48 77 C05 0.15 PCT 7 No 4 49 74 C06 -0.26 PCT 5 No Table 2-7: Watts Bar U2R3 Circumferential ODSCC at HTS Indications - All SGs Indication Summary Resolution Sizing Depth Profiling Sizing Plugged?

+POINT Maximum Segment Quick Maximum Segment Depth Depth SG Row Col Ind Locn Inch1 300kHz Depth, Arc, Screen Depth, Arc, Profile Profiled?

Vpp %TW Deg. PDA %TW Deg. PDA 1 3 70 SCI HTS -0.04 0.09 79 55.4 7.2 Yes 79 65 13.81 Yes 1 4 57 SCI HTS -0.05 0.09 44 32.3 2.3 No - - - Yes 1 4 65 SCI HTS -0.03 0.1 61 115.4 11.5 Yes 44 114 9.54 Yes 1 30 77 SCI HTS -0.16 0.27 90 163.1 24.1 Yes 86 172 35.42 Yes 1 41 39 SCI HTS -0.17 0.15 15 56.9 1.9 No - - - Yes 1 44 30 SCI HTS -0.02 0.19 90 67.7 10.0 Yes 96 81 19.91 Yes 2 45 65 SCI HTS -0.06 0.11 50 84.6 6.9 No - - - Yes 3 5 96 SCI HTS -0.12 0.18 NQI1 66.2 2.2 No - - - Yes 3 6 21 SCI HTS -0.02 0.28 9 116.9 3.8 No - - - Yes 3 9 70 SCI HTS -0.03 0.22 63 61.5 6.3 No - - - Yes 3 9 98 SCI HTS -0.11 0.19 45 86.2 6.4 No - - - Yes 1

3 10 78 SCI HTS -0.15 0.2 NQI 81.5 2.7 No - - - Yes 3 12 67 MCI HTS -0.08 0.17 53 83.1 7.2 No - - - Yes 3 12 100 SCI HTS -0.07 0.33 30 166.2 8.2 No - - - Yes 3 12 105 SCI HTS -0.11 0.16 36 90.8 5.4 No - - - Yes 3 13 88 SCI HTS -0.09 0.16 26 52.3 2.2 No - - - Yes 3 14 55 SCI HTS -0.15 0.25 NQI1 109.2 3.6 No - - - Yes 3 14 57 SCI HTS -0.17 0.13 53 49.2 4.3 No - - - Yes 3 14 91 MCI HTS -0.05 0.21 31 123.1 6.3 No - - - Yes 3 14 98 SCI HTS -0.08 0.18 67 66.2 7.3 No - - - Yes 3 14 99 SCI HTS -0.1 0.29 73 87.7 10.5 Yes 45 101 8.91 Yes 3 14 101 SCI HTS -0.05 0.29 48 116.9 9.2 No - - - Yes 3 15 82 SCI HTS -0.04 0.17 31 116 5.9 No - - - Yes 3 16 71 SCI HTS -0.15 0.14 12 43.1 1.4 No - - - Yes 3 17 44 SCI HTS -0.04 0.41 0 198.5 6.5 Yes 20 194 11.3 Yes 3 19 57 SCI HTS -0.09 0.19 35 160 9.2 No - - - Yes 3 21 56 SCI HTS -0.04 0.29 45 113.8 8.4 No - - - Yes 3 22 62 SCI HTS -0.05 0.31 35 184.6 10.6 No - - - Yes TVA EWR WO 122088253 Revision 0 April 2021 Watts Bar U2R3 180 Day Steam Generator Tube Inspection Report Page 11 of 15

Indication Summary Resolution Sizing Depth Profiling Sizing Plugged?

+POINT Maximum Segment Quick Maximum Segment Depth Depth SG Row Col Ind Locn Inch1 300kHz Depth, Arc, Screen Depth, Arc, Profile Profiled?

Vpp %TW Deg. PDA %TW Deg. PDA 3 22 66 SCI HTS -0.1 0.62 39 186.2 11.9 Yes 52 212 26.61 Yes 3 22 84 SCI HTS -0.11 0.11 22 72.3 2.6 No - - - Yes 3 23 56 MCI HTS -0.06 0.27 27 197 8.7 Yes 75 319 28.29 Yes 3 23 85 SCI HTS -0.04 0.14 68 166.2 18.5 Yes 86 177 29.66 Yes 3 25 60 SCI HTS -0.23 0.32 36 135.4 8.0 No - - - Yes 3 26 45 SCI HTS -0.1 0.28 18 95.4 3.1 No - - - Yes 3 26 71 SCI HTS -0.09 0.2 21 90.8 3.1 No - - - Yes 3 29 21 SCI HTS -0.1 0.19 NQI1 118.5 3.9 No - - - Yes 3 32 57 SCI HTS -0.05 0.15 70 83.1 9.5 No - - - Yes 3 38 59 MCI HTS -0.04 0.15 78 144.6 18.5 Yes 48 161 21.79 Yes 3 39 28 SCI HTS -0.05 0.11 14 80 2.6 No - - - Yes 3 40 64 MCI HTS -0.05 0.27 33 150.8 8.2 No - - - Yes 3 41 71 SCI HTS -0.1 0.15 39 60 3.8 No - - - Yes 3 43 25 SCI HTS -0.08 0.26 52 67.7 5.8 No - - - Yes 26A SCI HTS -0.05 0.16 51 73.8 6.2 Yes 51.0 89 8.41 Yes 3 44 26B SCI HTS -0.05 0.26 52 100 8.5 Yes 76 110 16.9 Yes 3 45 28 SCI HTS -0.08 0.22 55 76.9 6.9 No - - - Yes 3 45 38 SCI HTS -0.03 0.13 34 143.1 8.0 No - - - Yes 3 46 74 MCI HTS -0.14 0.18 50 84.6 6.9 No - - - Yes 3 46 83 SCI HTS -0.05 0.17 16 55.4 1.8 No - - - Yes 3 47 73 SCI HTS -0.07 0.18 28 100 4.6 No - - - Yes 3 49 31 SCI HTS -0.04 0.26 NQI1 146.2 4.8 No - - - Yes 3 49 79 SCI HTS -0.04 0.17 NQI1 61.5 2.0 No - - - Yes 38A MCI HTS -0.05 0.21 44 116.9 8.4 Yes 40.0 114 8.23 Yes 3 49 38B MCI HTS -0.06 0.18 81 60 8.0 Yes 84 63 11.32 Yes 4 5 76 SCI HTS 0.07 0.17 21 163.1 5.6 No - - - Yes 4 6 82 SCI HTS 0.04 0.24 21 166.2 5.7 No - - - Yes 4 6 84 SCI HTS 0 0.2 32 232.3 12.2 Yes 60 251 20.41 Yes 4 10 82 SCI HTS -0.15 0.19 35 58.5 3.4 No - - - Yes 4 11 56 SCI HTS -0.1 0.17 27 95.4 4.7 No - - - Yes 4 15 104 SCI HTS -0.06 0.24 26 144.6 6.2 No - - - Yes 4 15 105 SCI HTS -0.06 0.2 11 107.7 3.5 No - - - Yes 4 16 55 SCI HTS -0.13 0.25 21 110.8 3.8 No - - - Yes 4 16 79 SCI HTS -0.03 0.26 42 95.4 6.6 No - - - Yes 4 17 67 SCI HTS -0.71 0.21 39 133.8 8.6 No - - - Yes 4 18 66 SCI HTS -0.21 0.27 50 190.8 15.6 Yes 62 192 13.51 Yes 4 19 68 SCI HTS -0.1 0.24 58 67.7 6.4 No - - - Yes 4 19 77 SCI HTS -0.1 0.24 24 56.9 2.2 No - - - Yes 4 20 68 SCI HTS -0.01 0.3 26 196.9 8.4 Yes 64 190 20.15 Yes 4 21 57 SCI HTS -0.01 0.36 43 180 12.7 Yes 65 204 27.38 Yes 4 21 67 SCI HTS -0.03 0.21 28 136.9 6.3 No - - - Yes 4 21 74 SCI HTS -0.19 0.18 39 67.7 4.3 No - - - Yes 4 22 57 SCI HTS -0.34 0.41 28 116.9 5.4 Yes 39 147 11.71 Yes Note 1: An NQI is a non-quantifiable indication where the eddy current data analysts believe the indication is flaw-like although the associated depth is not measurable.

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Table 2-8: Watts Bar U2R3 Axial ODSCC at TSP Indications Excluded from GL 95 All SGs Axial SG Row Col Location Inch1 Ind %TW Plugged?

Ext. (in.)

3 21 37 H01 0.13 SAI 58.2 0.26 Yes 3 27 47 H01 0.11 MAI 48.6 0.24 Yes 3 47 87 H04 -0.01 SAI 51.7 0.39 Yes Note: The remaining indications of axial ODSCC at TSPs which have been addressed by GL 95-05 requirements are provided in ML21042B342.

Table 2-9: Watts Bar U2R3 Axial ODSCC at HTS Indications - All SGs Axial SG Row Col Location Inch1 Ind %TW Plugged?

Ext. (in.)

3 23 56 HTS 0.5 SAI 47.6 0.45 Yes 3 23 66 HTS 0.2 SAI 52.8 0.23 Yes 3 24 65 HTS 0.6 SAI 48.1 0.20 Yes 4 22 69 HTS -0.11 SAI 60.0 0.10 Yes Table 2-10: Watts Bar U2R3 Axial ODSCC at Tube Freespan Dings - All SGs Flaw Ding Ding Axial Axial Bobbin SG Row Col Location Inch1 Ind %TW Plugged?

Ext. Ext. Vpp (in.) (in.) (Volts) 2 9 86 H02 1.27 SAI 65 0.29 0.96 13 Yes 4 49 84 AV2 1.32 SAI 70 0.19 0.79 16 Yes Table 2-11: Watts Bar U2R3 Circumferential ODSCC at Tube Freespan Dings - All SGs Flaw Ding Ding Circ Circ Bobbin SG Row Col Location Inch1 Ind %TW Plugged?

Ext. Ext. Vpp (Deg.) (Deg.) (Volts) 2 17 109 C14 -2.02 SCI 66 57 168 26 Yes 2 7 58 H02 -1.95 SCI 67 25 101 27 Yes Table 2-12: Watts Bar U2R3 Axial PWSCC at HTS Indications - All SGs Axial SG Row Col Location Inch1 Ind %TW Plugged?

Ext. (in.)

2 17 100 HTS 0.04 SAI 68 0.11 Yes

e. Number of Tubes Plugged or Repaired During the Inspection Outage for Each Degradation Mechanism There were 189 tubes plugged during the Watts Bar U2R3 SG in-service inspection. Table 2-13 below provides the numbers and percentages of tubes plugged following U2R3.

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Table 2-13: Number of Tubes Plugged for each Degradation Mechanism SG1 SG2 SG3 SG4 Total Plugged Tubes prior to U2R3 25 34 14 21 94 Plugging Reason Tubes Plugged during U2R3 Volumetric Indication from Pre-Service 0 0 0 0 0 Wear at AVBs 0 0 0 0 0 Wear at TSPs 0 0 0 0 0 Circumferential ODSCC at HTS 6 1 44 18 69*

Axial ODSCC at HL TSPs 3* 17 75 17* 112*

Axial ODSCC at HTS 0 0 3 1 4 Axial ODSCC at Tube Freespan Dings 0 1 0 1 2*

Circumferential ODSCC at Tube 0 2 0 0 2 Freespan Dings Axial PWSCC at HTS 0 1 0 0 1 Preventive 1 0 0 0 1 Total Plugged Following U2R3 34* 56 136 57* 283*

Effective Tube Percentage 0.73% 1.20% 2.91% 1.22% 1.51%

Plugged Following U2R3

  • Two tubes had pluggable indications by two different degradation mechanisms. The Total Plugged Following U2R3 line item total has been adjusted to reflect this distinction.

One of the tubes plugged in SG1 was preventively plugged due to tube material pilgering chatter along the inner diameter observable by the bobbin probe inspection. The remaining tubes were plugged due to indications of cracking degradation in accordance with the requirements of the Watts Bar Unit 2 Technical Specification. There were no tubes repaired during the Watts Bar U2R3 refueling outage inspections.

f. The Number and Percentage of Tubes Plugged or Repaired to Date and the Effective Plugging Percentage in each SG Table 2-13 provides the number and percentage of tubes plugged to date along with the effective tube plugging percentage in each SG and overall. No tubes have been repaired at Watts Bar Unit 2 to date.
g. The Results of Condition Monitoring, Including the Results of Tube Pulls and In-Situ Testing Condition Monitoring, Tube Pulls and In-Situ Testing A condition monitoring (CM) assessment was performed as required by the Watts Bar Unit 2 steam generator program. Based on the Watts Bar U2R3 SG inspection data, all tubes with observed degradation satisfied the condition monitoring criteria for structural and leakage integrity with the exception of axial ODSCC at tube support intersections evaluated in accordance with NRC GL 95-05 voltage-based alternate repair criteria. Evaluation of axial ODSCC at tube support intersections against GL 95-05 is provided separately in ML21042B342.

In situ pressure testing was not required to demonstrate structural and leakage integrity. There was no detectable primary-to-secondary leakage during the operating interval prior to the Watts Bar U2R3 SG inspections. No indications of degradation addressed by this report were found to be in excess of the CM limits. The SG performance criteria for operating leakage and structural integrity TVA EWR WO 122088253 Revision 0 April 2021 Watts Bar U2R3 180 Day Steam Generator Tube Inspection Report Page 14 of 15

were satisfied for the preceding Watts Bar Unit 2 SG inspection interval. No tube pulls were planned or performed during U2R3.

Primary and Secondary Side Visual Inspection Results Visual inspections were performed on both the primary and secondary sides during U2R3 in all four SGs. Primary side inspections performed in accordance with Westinghouse Nuclear Safety Advisory Letter NSAL-12-1 included the hot leg and cold leg divider plate, inclusive of the divider plate-to-channel head weld, and all visible clad surfaces of the SG channel head. The NSAL-12-1 examinations performed during U2R1 showed visually apparent evidence of minor indications of degradation of the cladding in SG1 located on the hot leg side just above the primary manway opening. This indication was re-inspected during U2R3. The conclusion of the engineering evaluation performed after U2R1 was that acceptable margin exists for maintenance of structural integrity of the SG channel head base metal for at least six cycles of operation. This conclusion was considered to remain applicable following the U2R3 inspection. No new indications were reported from the visual examinations of the channel head cladding.

All previously installed tube plugs were visually inspected from the primary side in all four SGs.

The inspection results were satisfactory and showed no indication of tube plug leakage or failure.

Prior to the secondary side FOSAR inspections, sludge, scale, foreign objects, and other deposit accumulations at the top of the tubesheet were removed as part of the top of tubesheet sludge lancing process. A total of 55.2 pounds of deposit was removed as a result of sludge lancing from all four SGs in total.

The secondary side FOSAR inspections performed in all four SGs included visual examination of tube bundle periphery tubes from the hot leg and cold leg annulus and center no-tube lane inclusive of the blowdown pipe connections with the tubesheet. A total of nineteen foreign objects were identified, six of which were removed from the top of the tubesheet region. The foreign objects retrieved consist of wire bristles, sludge rocks, and hardened scale. Of the thirteen objects remaining in the SG secondary side, only two of them are believed to be metallic. These include a 0.5 inch long 0.015 inch diameter metal bristle and a small metal object measuring 0.75 x 0.3 x 0.2 inch. Foreign objects remaining in the SGs were characterized and an analysis performed to demonstrate acceptability of continued operation without exceeding the tube integrity performance criteria.

Visual inspections of the steam drum upper internal components were not performed during U2R3.

h. Repair Method Utilized and the Number of Tubes Repaired by Each Repair Method No tubes have been repaired at Watts Bar Unit 2 to date.

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