CNL-20-078, Supplement to Application to Revise Watts Bar Nuclear Plant (Wbn), Unit 1 Technical Specifications for Steam Generator Tube Inspection Frequency and to Adopt TSTF-510, Revision to Steam Generator Program Inspection Frequencies and Tube Sa

Supplement to Application to Revise Watts Bar Nuclear Plant (Wbn), Unit 1 Technical Specifications for Steam Generator Tube Inspection Frequency and to Adopt TSTF-510, Revision to Steam Generator Program Inspection Frequencies and Tube Samp

ML20287A569
Person / Time
Site:	Watts Bar
Issue date:	10/13/2020
From:	Jim Barstow Tennessee Valley Authority
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
CNL-20-078, EPID L-2020-LLA-0161
Download: ML20287A569 (66)

Text

Tennessee Valley Authority, 1101 Market Street, Chattanooga, Tennessee 37402 CNL-20-078 October 13, 2020 10 CFR 50.90 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555-0001 Watts Bar Nuclear Plant Unit 1 Facility Operating License No. NPF-90 NRC Docket No. 50-390

Subject:

Supplement to Application to Revise Watts Bar Nuclear Plant (WBN), Unit 1 Technical Specifications for Steam Generator Tube Inspection Frequency and to Adopt TSTF-510, "Revision to Steam Generator Program Inspection Frequencies and Tube Sample Selection," (WBN-390-TS-20-012)

(EPID L-2020-LLA-0161)

References:

1. TVA letter to NRC, CNL-20-053, Application to Revise Watts Bar Nuclear Plant (WBN), Unit 1 Technical Specifications for Steam Generator Tube Inspection Frequency and to Adopt TSTF-510, "Revision to Steam Generator Program Inspection Frequencies and Tube Sample Selection,"

(WBN-390-TS-20-012), dated July 17, 2020 (ML20199M346)

2. TVA letter to NRC, CNL-20-076, Response to Request for Additional Information Regarding Application to Revise Sequoyah Nuclear Plant (SQN)

Unit 1 Technical Specifications for Steam Generator Tube Inspection Frequency (SQN-TS-20-01) (EPID L-2020-LLA-0030), dated September 23, 2020 (ML20267A525)

In Reference 1, Tennessee Valley Authority (TVA) submitted a request for an amendment to Facility Operating License No. NPF-90 for the Watts Bar Nuclear Plant (WBN), Unit 1. The proposed license amendment request (LAR) revises WBN, Unit 1 Technical Specifications (TS) 5.7.2.12, Steam Generator (SG) Program, and WBN Unit, 1 TS 5.9.9, Steam Generator Tube Inspection Report, to reflect a proposed change to the required SG tube inspection frequency from every 72 effective full power months (EFPM) to every 96 EFPM.

U.S. Nuclear Regulatory Commission CNL-20-078 Page 2 October 13, 2020 Based on information requested by the Nuclear Regulatory Commission (NRC) in Reference 2, TVA is supplementing Reference 1 as follows:

• To assist the NRC in their review of the LAR, Enclosure 1 to this submittal contains Westinghouse Document, SG-SGMP-17-9, Revision 1, "Watts Bar U1R14 Steam Generator Condition Monitoring and Operational Assessment."

• TVA is revising the proposed change to WBN Unit 1 TS 5.7.2.12.d.2 as follows: After the first refueling outage following SG installation, inspect each SG at least every 96 effective full power months. Tube inspections shall be performed using equivalent to or better than array probe technology. For regions where a tube inspection with array probe technology is not possible (such as due to dimensional constraints or tube specific conditions), the tube inspection techniques applied shall be capable of detecting all forms of existing and potential degradation in that region. Enclosure 2 to this submittal contains a revised mark-up to the proposed change to WBN Unit 1 TS 5.7.2.12.d.2 and Enclosure 3 to this submittal contains the re-typed WBN Unit 1 TS 5.7.2.12.d.2 to show the proposed change.

Enclosures 2 and 3 supersede the corresponding information provided in Enclosures 3 and 4 to Reference 1.

This letter does not change the no significant hazard considerations nor the environmental considerations contained in Reference 1. Additionally, in accordance with 10 CFR 50.91(b)(1),

TVA is sending a copy of this letter and the enclosures to the Tennessee Department of Environment and Conservation.

There are no new regulatory commitments associated with this submittal. If you have any questions about this proposed change, please contact Gordon R. Williams, Senior Manager, Fleet Licensing (Acting) at (423) 751-2687.

I declare under penalty of perjury that the foregoing is true and correct. Executed on this 13th day of October 2020.

Respectfully, James Barstow Vice President, Nuclear Regulatory Affairs & Support Services Enclosures cc: See Page 3

U.S. Nuclear Regulatory Commission CNL-20-078 Page 3 October 13, 2020

Enclosures:

1. Westinghouse Document, SG-SGMP-17-9, Revision 1

2. Revised TS Changes (Mark-Ups) for WBN Unit 1

3. Revised TS Changes (Final Typed) for WBN Unit 1 cc (Enclosures):

NRC Regional Administrator - Region II NRC Project Manager - Watts Bar Nuclear Plant NRC Senior Resident Inspector - Watts Bar Nuclear Plant Director, Division of Radiological Health - Tennessee State Department of Environment and Conservation

Enclosure 1 Westinghouse Document, SG-SGMP-17-9, Revision 1 CNL-20-078

WESTINGHOUSE NON-PROPRIETARY CLASS 3 SG-SGMP-17-9 November 2019 Revision 1 Watts Bar U1R14 Steam Generator Condition Monitoring and Operational Assessment

• • • This record was final approved on 11/21/2019 10:34:58 AM. (This statement was added by the PRIME system upon its validation)

WESTINGHOUSE NON-PROPRIETARY CLASS 3 SG-SGMP-17-9 Revision 1 Watts Bar U1R14 Steam Generator Condition Monitoring and Operational Assessment Prepared for:

Tennessee Valley Authority Author's Name: Signature I Date For Pages Thomas P. Magee *Electronical/yAyproved All Component Engineering and Chemistry Operations Verifier's Name: Signature / Date For Pages Bradley T. Carpenter *ElectronicallyApproved All Component Design and Management Programs Manager Name: Signature / Date For Pages Michael E. Bradley, Manager Electronical1y Approved All Component Design and Management Programs Reviewer's Name: Signature / Date For Pages Jeremy W. Mayo SG Program Manager Reviewer's Name: Signature / Date For Pages Tammy C. Sears Watts Bar SG Program Owner ii3/i? All This document may contain technical data subject to the export control laws of the United States. In the event that this document does contain such information, the Recipient's acceptance of this document constitutes agreement that this information in document form (or any other medium), including any attachments and exhibits hereto, shall not be exported, released or disclosed to foreign persons whether in the United States or abroad by recipient except in compliance with all U.S. export control regulations. Recipient shall include this notice with any reproduced or excerpted portion of this document or any document derived from, based on, incorporating, using or relying on the infonnation contained in this document.

Electronically Approved Records are A uthenticatedin the Electronic Document Management System Westinghouse Electric Company LLC P.O. Box 158 Madison, PA 15663

©2019 Westinghouse Electric Company LLC All Rights Reserved SGSGMP 17-9 November 2019 Revision I Page 2 of 55

• • • This record was final approved on 11/21/2019 10:34:58 AM. (This statement was added by the PRIME system upon its validation)

Record of Revisions Revision Date Description April 0a Preliminary for Tennessee Valley Authority review and comment.

2017 April 4, Incorporated review comments from TVA. Issued to the Watts Bar site in preparation 0

2017 for Mode 4 return to power.

Inspection interval investigated.

See 1 EDMS (Note: Change bars are used in the left margins where substantial or technical changes occurred. Change bars are not used for editorial changes such as formatting changes and minor non-technical corrections.)

SG-SGMP-17-9 November 2019 Revision 1 Page 3 of 55

• • • This record was final approved on 11/21/2019 10:34:58 AM. (This statement was added by the PRIME system upon its validation)

Table of Contents Executive Summary .......................................................................................................................................... 6 1.0 Introduction ................................................................................................................................... 7 2.0 Watts Bar U1R14 Primary Side Inspection Program .................................................................... 8 2.1 Base Scope Inspection Plan .......................................................................................................... 8 2.2 Inspection Expansion .................................................................................................................... 8 2.3 Inspection Results ......................................................................................................................... 8 2.4 Tube Plugging and Stabilization ................................................................................................... 9 3.0 Condition Monitoring ................................................................................................................. 10 3.1 Existing Degradation Mechanisms ............................................................................................. 10 3.1.1 Mechanical Wear at U-bend Support Structures ......................................................................... 10 3.1.2 Mechanical Wear at Horizontal ATSGs ..................................................................................... 11 3.2 Potential Degradation Mechanisms............................................................................................. 12 3.2.1 Mechanical Wear Due to Foreign Objects .................................................................................. 12 3.2.2 Tube-to-Tube Contact Wear ....................................................................................................... 12 3.3 Resolution for Classification of Indications ................................................................................ 13 3.4 SG Channel Head Primary Side Bowl and Tube Plug Visual Inspections ................................. 13 3.5 Secondary Side Activities ........................................................................................................... 14 3.5.1 Top of Tubesheet Cleaning ......................................................................................................... 14 3.5.2 Top of Tubesheet FOSAR........................................................................................................... 14 3.6 Condition Monitoring Conclusions ............................................................................................. 14 4.0 Operational Assessment .............................................................................................................. 16 4.1 Mechanical Wear at U-bend Support Structures ......................................................................... 16 4.1.1 Degradation Growth Rates .......................................................................................................... 16 4.1.2 Operational Assessment - Monte Carlo Approach ..................................................................... 17 4.1.3 Use of Volume Based Wear Approach ....................................................................................... 18 4.2 Mechanical Wear at Horizontal ATSGs ..................................................................................... 19 4.2.1 Degradation Growth Rates .......................................................................................................... 19 4.2.2 Operational Assessment - Monte Carlo Approach ..................................................................... 20 4.2.3 Use of Volume-Based Wear Approach ....................................................................................... 21 4.3 U-bend Support Structure and Horizontal ATSG Wear - Fully Probabilistic Method............... 22 4.3.1 Ahat Development ...................................................................................................................... 22 4.3.2 Site Specific Noise Measurements .............................................................................................. 22 4.3.3 Model Assisted Probability of Detection .................................................................................... 23 4.3.4 Fully Probabilistic Operational Assessment ............................................................................... 23 4.4 SG Secondary Side Foreign Objects ........................................................................................... 25 4.5 Operational Assessment Conclusions ......................................................................................... 25 5.0 References ................................................................................................................................... 26 SG-SGMP-17-9 November 2019 Revision 1 Page 4 of 55

• • • This record was final approved on 11/21/2019 10:34:58 AM. (This statement was added by the PRIME system upon its validation)

List of Tables Table 2-1: Watts Bar U1R14 SG Eddy Current Inspection - Final Indication Summary .................................... 9 Table 3-1: Watts Bar U1R14 Loose Part Indications (PLP/LPS) ....................................................................... 12 Table 3-2: Watts Bar U1R14 Resolution for Classification of Indications......................................................... 13 Table 3-3: Watts Bar U1R14 SG Tubesheet Deposit Removal .......................................................................... 14 Table 3-4: Watts Bar U1R14 SG FOSAR Summary .......................................................................................... 14 Table 4-1: Watts Bar U1R14 U-bend Support Structure Wear Growth Comparison ......................................... 16 Table 4-2: 95/50 Burst Pressures from W-VOL Cases for U-Bend Structural Support Wear ............................ 19 Table 4-3: Watts Bar U1R14 Horizontal ATSG Wear Growth Comparison ...................................................... 19 Table 4-4: Summary of Benchmark Parameters ................................................................................................. 21 Table 4-5: 95/50 Burst Pressures from W-VOL Cases for Wear at Horizontal ATSGs .................................... 22 Table 4-6: Watts Bar U1R14 Model Assisted Probability of Detection Results ................................................ 23 Table 4-7: Watts Bar U1R14 Fully Probabilistic Operational Assessment Results............................................ 24 Table A3-1: Watts Bar U1R14 U-bend Support Structure Wear Indications - All SGs .................................... 30 Table A4-1: Watts Bar U1R14 ATSG Wear Indications - SG1 ......................................................................... 33 Table A4-2: Watts Bar U1R14 ATSG Wear Indications - SG2 ......................................................................... 34 Table A4-3: Watts Bar U1R14 ATSG Wear Indications - SG3 ......................................................................... 36 Table A4-4: Watts Bar U1R14 ATSG Wear Indications - SG4 ......................................................................... 37 Table A5-1: Watts Bar U1R14 Tube Proximity Indications (PRX) - All SGs................................................... 47 List of Figures Figure 3-1: Watts Bar U1R14 U-bend Support Structure Wear Indications - All SGs ...................................... 11 Figure 3-2: Watts Bar U1R14 ATSG Wear Indication Distributions - All SGs ................................................. 12 Figure 4-1: WVOL Benchmark Calculation Regression Lines for U-bend Support Structure Wear ................. 18 Figure A3-1: Watts Bar U1R14 U-bend Support Structure Wear Indications in All SGs - Tubesheet Map ..... 30 Figure A3-2: Watts Bar U1R14 U-bend Wear Growth Cumulative Frequency Distribution - All SGs ............ 31 Figure A3-3: Watts Bar U1R14 U-bend Support Structure Wear - Monte Carlo Simulation ............................ 31 Figure A3-4: Watts Bar U1R14 U-bend Support Wear Indication - SG3 R81C56 VS4 Array Graphic 2017 .. 32 Figure A4-1: Watts Bar U1R14 Horizontal ATSG Wear Indications Map - SG1 ............................................. 40 Figure A4-2: Watts Bar U1R14 Horizontal ATSG Wear Indications Map - SG2 ............................................. 41 Figure A4-3: Watts Bar U1R14 Horizontal ATSG Wear Indications Map - SG3 ............................................. 42 Figure A4-4: Watts Bar U1R14 Horizontal ATSG Wear Indications Map - SG4 ............................................. 43 Figure A4-5: Watts Bar U1R14 Horizontal ATSG Wear Growth Cumulative Frequency Distributions........... 44 Figure A4-6: Watts Bar U1R14 Horizontal ATSG Wear Indication Growth Rates Map - All SGs .................. 45 Figure A4-7: Watts Bar U1R14 Horizontal ATSG Wear - Monte Carlo Simulation ......................................... 46 Figure A4-8: Watts Bar U1R14 Horizontal ATSG Wear Indication - SG2 R88C95 C03 Array Graphic 2017 46 Figure A5-1: Watts Bar U1R14 Tube Proximity Indications in All SGs ........................................................... 48 Figure A6-1: Watts Bar U1R14 U-bend Support and Horizontal ATSG Noise Distributions ........................... 49 Figure A6-2: Watts Bar U1R14 U-bend Support and Horizontal ATSG Noise Distributions ........................... 50 Figure A6-3: Watts Bar U1R14 U-bend Support and ATSG MAPOD Curves.................................................. 51 Figure A6-4: Watts Bar U1R14 U-bend Support and ATSG FBM Software Outputs ....................................... 52 Figure A7-1: Watts Bar U1R14 Support Structure Wear Sizing Method Comparisons..................................... 53 List of Attachments - Watts Bar U1R14 As-Implemented SG Inspection Scope .................................................. 27 - Watts Bar U1R14 SG Tube Structural and Condition Monitoring Limits ...................... 29 - Watts Bar U1R14 U-bend Support Structure Wear Indications ...................................... 30 - Watts Bar U1R14 ATSG Wear Indications......................................................................... 34 - Watts Bar U1R14 Tube Proximity Indications ................................................................... 48 - Watts Bar U1R14 MAPOD and Fully Probabilistic Operational Assessment Graphics 50 - Watts Bar U1R14 Support Structure NDE Sizing Methods .............................................. 55 SG-SGMP-10-16 November 2019 Revision 1 Page 5 of 55

• • • This record was final approved on 11/21/2019 10:34:58 AM. (This statement was added by the PRIME system upon its validation)

Executive Summary The Watts Bar U1R14 Replacement Steam Generator (RSG) inspection conducted after cumulative service equivalent to approximately 9.29 effective full power years (EFPY). The service duration from the previous U1R11 RSG eddy current inspection was 4.07 EFPY. No SG primary-to-secondary tube leakage was reported during this operating interval. At Watts Bar U1R14, approximately 100.5 effective full power months (EFPM) of the 144 EFPM in the first sequential period have been accrued and U1R14 is the last planned inspection in this sequential period. Based on the U1R14 steam generator (SG) eddy current and visual inspection data, there are two existing degradation mechanisms in the Watts Bar Unit 1 RSGs. The existing degradation mechanisms are:

Mechanical Wear at U-bend Support Structures Mechanical Wear at Horizontal Advanced Tube Support Grids (ATSGs)

No tubes have exhibited degradation exceeding the tube integrity criteria given in the Degradation Assessment (DA) for the U1R14 outage (Reference 3). No tubes required in situ pressure testing to support the Condition Monitoring (CM) assessment based on the DA and Electric Power Research Institute (EPRI) In Situ Pressure Test Guidelines (Reference 6). A summary of the number of plugged tubes in the Watts Bar Unit 1 RSGs following U1R14 is provided below.

SG # Tubes # Plugged  % Plugging 1 5,128 3 0.06%

2 5,128 5 0.10%

3 5,128 7 0.14%

4 5,128 14 0.27%

Total 20,512 29 0.14%

A final operational assessment (OA) has been performed considering the indications detected and degradation growth rates observed. Development of degradation growth rates for U-bend support structure and advanced tube support grid (ATSG) tube wear indications has been based on historical eddy current data comparisons made by the lead eddy current data analyst. These growth rates were then used to project degradation that could be encountered within the 95th percentile and 50% confidence limits.

This revision (Revision 1) of the OA report includes the results of a study to determine if the steam generators could be operated for more than the three cycles (4.5 EFPY), between inspections without violation of the performance criteria, that was determined in Revision 0. Additional calculations were performed on the growth projection of the flaws observed during U1R14 and it was determined that the SGs could be operated for 5 cycles (7.5 EFPY) before the SG performance criteria for burst was not met at 95%

probability and 50% confidence levels. Table 3-4 is a summary of results from the foreign object search and retrieval (FOSAR) inspections. An independent evaluation (Reference 7) was performed to determine how foreign objects in the steam generators would affect integrity; continued steam generator operation with the current foreign objects known to be present in the secondary side will not adversely affect steam generator tube integrity for at least five operating cycles or 7.5 EFPY. See Section 4.0 for more details. The current plant Technical Specifications do not allow for inspection intervals greater than three cycles for plants with SG tubes composed of Alloy 690 material and an approved license amendment would be required to operate longer than three cycles before inspection.

SG-SGMP-17-9 November 2019 Revision 1 Page 6 of 55

• • • This record was final approved on 11/21/2019 10:34:58 AM. (This statement was added by the PRIME system upon its validation)

1.0 Introduction This condition monitoring and operational assessment (CMOA) has been developed for the Tennessee Valley Authority (TVA) following the Watts Bar Unit 1 14th Refueling Outage (U1R14) RSG tube in-service inspection and assessment conducted in the spring of 2017. The assessments have been performed to meet the requirements and intent of NEI 97-06 Revision 3 (Reference 2). In preparation for the inspection, and to assure that the inspection adequately supports the CM and final OA evaluations required by NEI 97-06, the licensee documented the inspection scope together with the qualification of the applied nondestructive examination (NDE) techniques (References 3 and 9, and Attachment 7). This process provides assurance that the NDE techniques are appropriate for detection and measurement and to support development of degradation growth rates, repair criteria, and integrity limits for the degradation mechanisms assessed.

Based on the results obtained from the Watts Bar U1R14 inspections, a condition monitoring assessment was performed on a defect-specific basis, by demonstrating compliance with integrity criteria through comparison of reported NDE measurements with calculated structural pressure or leakage integrity limits. The indication sizing by NDE was compared to the defect-specific condition monitoring criteria specified in the degradation assessment which are repeated in Attachment 2. All indications detected in this inspection were below the integrity limits and therefore met the condition monitoring requirements provided. A final OA has been performed considering the indications detected during U1R14 and degradation growth rates. The final OA concludes that steam generator tube structural and leakage integrity will be maintained for five cycles (7.5 EFPY).

The industry has developed guidelines for SG assessment and TVA has developed a long-term strategic plan to meet or exceed the industry guidelines. The Watts Bar U1R14 SG inspections have been led by the following industry guidelines and SG integrity programs:

• EPRI Steam Generator Integrity Assessment Guidelines (Reference 5)

• EPRI PWR Steam Generator Examination Guidelines (Reference 1)

• EPRI Steam Generator In Situ Pressure Test Guidelines (Reference 6)

• 1-SI-68-907 Watts Bar Nuclear Plant Unit 1 Surveillance Instruction for Steam Generator Tubing In-service Inspection and Augmented Inspections (Reference 8)

This document was prepared in accordance with the Westinghouse Quality Management System (QMS).

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• • • This record was final approved on 11/21/2019 10:34:58 AM. (This statement was added by the PRIME system upon its validation)

2.0 Watts Bar U1R14 Primary Side Inspection Program 2.1 Base Scope Inspection Plan The inspection program, as required by the EPRI PWR SG Examination Guidelines (Reference 1), addressed the existing and potential degradation mechanisms for the Watts Bar Unit 1 RSGs. The defined scope implemented during U1R14 included the following:

• 100% combination bobbin and array probe inspection of all open tubes in all four SGs full length and tube Rows 1 through 4 to the first support from the hot leg (HL) and the cold leg (CL). The remaining portions of the tubes in Rows 1 through 4 were inspected with either a singular bobbin or array probe where necessary due to dimensional clearance restrictions.

• 100% array probe examination of dents 2 volts in the straight lengths and U-bends of all SGs. This included all dents previously identified and any additional identified during the inspections.

• +POINT'1 probe Special Interest inspections of tube locations with non-resolved bobbin and/or array probe signals and any unresolved possible loose parts (PLPs) from the base scope inspection program in both the HL and CL to characterize the underlying condition. No such examinations were necessary.

• 100% visual inspection of all installed tube plugs from the primary side on both the HL and CL.

• Visual inspection in all SGs of channel head primary side HL and CL in accordance with Westinghouse letter NSAL-12-1 (Reference 15) inclusive of the entire divider plate-to-channel head weld and all visible clad surfaces.

The Watts Bar U1R14 SG inspection plan met or exceeded the requirements of the Reference 1 EPRI Examination Guidelines and was aligned with the Reference 8 TVA Watts Bar SG Surveillance Instructions.

The Watts Bar U1R14 eddy current inspection scope as implemented during the outage is shown in .

2.2 Inspection Expansion There was no nondestructive examination (NDE) inspection scope expansion required during Watts Bar U1R14 (Reference 1).

2.3 Inspection Results Table 2-1 presents a filtered summary of the tube NDE indication results based on data relevant to evaluating tube integrity. The files listed below the table were generated by the Westinghouse STMax' eddy current results data management system and used to create the table.

1

+POINT is a trademark or registered trademark of Zetec, Inc. Other names may be trademarks of their respective owners.

2 STMax is a trademark of Westinghouse Electric Company LLC, its affiliates and/or its subsidiaries in the United States of America and may be registered in other countries throughout the world. All rights reserved. Unauthorized use is strictly prohibited. Other names may be trademarks of their respective owners.

SG-SGMP-17-9 November 2019 Revision 1 Page 8 of 55

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Table 2-1: Watts Bar U1R14 SG Eddy Current Inspection - Final Indication Summary Indications Condition SG 1 SG 2 SG 3 SG 4 ADS Absolute Drift Signal 137 158 37 117 BLG Tubesheet Bulge 2 0 0 0 DEP Deposit Signal 4 0 0 0 DFS Distorted Freespan Signal 22 56 77 74 DNG Ding at Support or Freespan 29 24 28 11 DSS Distorted Support Signal 1 0 1 0 DTS Distorted Tubesheet Signal 0 0 0 0 Possible Loose Part Signal LPS 0 0 0 1 Cleared by Visual Inspection MBM Manufacturing Burnish Mark 9 15 0 6 PCT Volumetric % Through-wall 87 150 106 135 PRX Tube Proximity Signal 6 6 8 8 WAR Wear Array Probe 87 150 106 135 SG 1: SG1_ENGINEERING_DUMP_FINAL.XLS SG 2: SG2_ENGINEERING_DUMP_FINAL.XLS SG 3: SG3_ENGINEERING_DUMP_FINAL.XLS SG 4: SG4_ENGINEERING_DUMP_FINAL.XLS 2.4 Tube Plugging and Stabilization There were no tubes required to be plugged during the Watts Bar U1R14 RSG in-service inspection.

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• • • This record was final approved on 11/21/2019 10:34:58 AM. (This statement was added by the PRIME system upon its validation)

3.0 Condition Monitoring Condition monitoring is the assessment performed on observed indications of tube degradation to confirm that the SG Integrity Performance Criteria embodied in the CM limits have not been violated. It is essentially a backward-looking evaluation. This is contrasted with the OA, which seeks to determine whether the tube integrity performance criteria will be exceeded during subsequent operation of the SGs until the next inspection. The CM limits, derived from the structural limits in accordance with the EPRI SG Integrity Assessment Guidelines (Reference 5) and the SG Degradation Specific Management Flaw Handbook (Reference 4), are provided in the outage DA (Reference 3) and echoed in Attachment 2.

Discussion of the indications in relation to CM requirements is provided in the following subsections.

3.1 Existing Degradation Mechanisms The EPRI PWR SG Examination Guidelines (Reference 1) requires that the existing degradation mechanisms identified in the DA be subject to appropriate inspection programs to comply with the plant Technical Specifications. This section addresses the existing SG degradation mechanisms for Watts Bar U1R14 and the indications identified.

3.1.1 Mechanical Wear at U-bend Support Structures Wear at U-bend support structures is an existing degradation mechanism in the Watts Bar Unit 1 RSGs. This mechanism occurs due to tube interaction with the U-bend support structures resulting from flow-induced vibration (FIV) in the upper tube bundle. The mechanical wear process is related to the tightness of the upper bundle assembly as expressed in the distribution of tube to U-bend support structure gaps. In general, at plants with similar support structures, U-bend support structure wear indications do not represent a challenge to structural or leakage integrity standards between inspections. Indications of U-bend support structure wear may require plugging should observed indication depths exceed the plant SG Technical Specification plugging criterion of 40% through-wall (TW). Plugging may also be required in order to support extended operating intervals between inspections.

Figure 3-1 is a histogram showing the distribution of %TW indications for all four RSGs combined where 59 indications were detected in total. Attachment 3 provides the full listing of tube locations and eddy current signal character for U-bend support structure wear indications detected during Watts Bar U1R14. The tables display the eddy current signal parameters for the U1R14 bobbin inspection and the corresponding percent through-wall (%TW) degradation as compared to the U1R11 or U1R8 result where available. A graphical display of the spatial distribution of the U-bend support structure wear indications is also provided in Figure A3-1. A representative depiction of the eddy current response from the Array probe for the U-bend wear indications is provided in Figure A3-4.

The bobbin probe sizing of the largest U-bend support structure wear indication observed during U1R14 was measured at 27% TW in SG3 Tube R81C56 at VS4+0.89 inch. The U1R11 OA projection was made assuming duration of 8.6 EFPY between inspection (Reference 12). Using the actual operating interval between inspections of 4.07 EFPY, the worst-case projected U-bend support structure wear indication would have been 42%TW at the U1R14 inspection. Therefore, the growth rate projection methods applied in the prior OA are validated. Further, an average change of 3.39%TW/EFPY and standard deviation of 2.04%TW/EFPY is observed in the limiting SG for growth with a normally distributed population of growth rate data points. Therefore, a reasonable and conservative growth rate projection for U-bend support structure wear can be developed in support of the OA.

Based on the inspection data for this mechanism in comparison to the limits identified in Attachment 2, structural integrity requirements have been met at the U1R14 inspection. Regarding U-bend support structure wear locations, satisfaction of structural integrity implies satisfaction of leakage integrity at accident conditions since steam line break accident condition pressure differential for pop-through is much SG-SGMP-17-9 November 2019 Revision 1 Page 10 of 55

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smaller than 3PNO for pressure-only loading of volumetric flaws. Therefore, CM has been satisfied for degradation associated with U-bend support structure wear indications at the Watts Bar U1R14 inspection.

Figure 3-1: Watts Bar U1R14 U-bend Support Structure Wear Indications - All SGs 3.1.2 Mechanical Wear at Horizontal ATSGs Wear at horizontal advanced tube support grids (ATSGs) is an existing degradation mechanism in the Watts Bar Unit 1 RSGs. Flow-induced vibration leading to wear at the ATSGs is governed primarily by thermal hydraulic characteristics and the sizes of the tube-to-support gaps. This suggests that wear rates are subject to steam generator specific conditions and will vary between plants and between steam generators at a specific plant. This has been the primary source of tube degradation leading up to the Watts Bar U1R14 inspection. Industry operating experience reviews indicate that plants with similar horizontal tube support designs have also identified ongoing wear at relatively low levels.

Figure 3-2 contains histograms showing the distribution of %TW indications between all four RSGs. Table A4-1 through Table A4-4 provides the full listing tube locations and eddy current signal character for advanced tube support grid (ATSG) wear indications detected during Watts Bar U1R14. The tables also display the eddy current signal parameters for the U1R14 bobbin inspection and the corresponding %TW degradation as compared to the U1R11 or U1R8 result where available. A graphical display of the distribution of the ATSG wear indications is also provided for each of the RSGs in Figure A4-1 through Figure A4-4. A representative depiction of the eddy current response from the Array probe for the ATSG wear indications is provided in Figure A4-8.

The bobbin probe sizing of the largest ATSG wear indication observed during U1R14 was measured at 37%TW which occurred in SG2 Tube R88C95 at C03-1.04 inches. The U1R11 OA projection was made assuming duration of 8.6 EFPY between inspection (Reference 12). Using the actual operating interval between inspections of 4.07 EFPY the worst-case projected U-bend support structure wear indication would have been 42%TW at the U1R14 inspection. Therefore, the growth rate projection methods applied in the prior OA are validated. An average change of 2.58%TW/EFPY and standard deviation of 1.86%TW/EFPY is observed for the indications across all four RSGs. Therefore, a reasonable and conservative growth rate projection for ATSG wear can be developed in support of the OA.

Based on the inspection data for this mechanism in comparison to the limits identified in Attachment 2, structural integrity requirements have been met at the U1R14 inspection. Regarding ATSG wear locations, satisfaction of structural integrity implies satisfaction of leakage integrity at accident conditions since steam line break accident condition pressure differential for pop-through is much smaller than 3PNO for pressure-only loading of volumetric flaws. Therefore, CM has been satisfied for degradation associated with horizontal ATSG wear indications at the Watts Bar U1R14 inspection.

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Figure 3-2: Watts Bar U1R14 ATSG Wear Indication Distributions - All SGs 3.2 Potential Degradation Mechanisms The EPRI Pressurized Water Reactor (PWR) SG Examination Guidelines (Reference 1) require that the potential degradation mechanisms identified in the DA be subject to appropriate inspection programs to comply with the plant Technical Specifications. This section addresses the potential degradation mechanisms listed in the Reference 3 degradation assessment for Watts Bar U1R14.

3.2.1 Mechanical Wear Due to Foreign Objects Although foreign objects have been observed in the Watts Bar Unit 1 RSGs at previous inspections, no tube degradation associated with the presence of these objects has been identified to date. The Array probe was utilized to supplement the detection of foreign objects and foreign object wear during U1R14. During the entirety of the Watts Bar U1R14 eddy current inspections there was only one signal corresponding to a new possible loose part (PLP) which is listed in Table 3-1. There was no tube wall degradation detected by eddy current coincident with this PLP indication. The location was visually inspected from the secondary side and no foreign object or contributing deposit condition was observed. Therefore, the indication was subsequently changed to a resolved loose part indication (LPS) based on the visual examination.

Table 3-1: Watts Bar U1R14 Loose Part Indications (PLP/LPS)

SG Row Col Volts Deg Ind Chn Locn Inch1 BegT EndT PDia PType Cal 4 3 12 2.95 97 PLP/LPS 152 CTS 0.02 VS3 CTE 0.61 ZYAXH 58 Visual inspections performed from the SG secondary side did identify a variety of small foreign objects, some of which were removed from the SGs. Those that remain have been evaluated for continued operation in Reference 7. During the FOSAR, there were no visible signs that any of the objects had caused tube wear due to interaction with adjacent tubes. The tube wear potential of the objects known to remain resident on the SG secondary side is evaluated as part of the OA.

3.2.2 Tube-to-Tube Contact Wear Tube-to-tube wear can occur due to the interaction that occurs when two or more tubes come in contact with each other. This form of tube degradation would occur in the tube bundle straight sections generally near the mid-span between two subsequent tube support structures. However, it can also occur in the U-bend region SG-SGMP-17-9 November 2019 Revision 1 Page 12 of 55

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where unanticipated secondary side fluid flow characteristics create the conditions that would lead to tube reciprocating motions and interaction.

Indications of tube-to-tube proximity can be traced back to the baseline eddy current inspection of the Watts Bar Unit 1 RSGs. Low level indications of proximity (PRX), all measuring less than 1.0 volt, were detected during the U1R14 inspections. The listing and a mapping of these indications is shown in , Table A5-1. As tube-to-tube proximity alone is not a degradation mechanism, it is a condition which could potentially lead to tube interaction with one another. As such, each PRX indication was reviewed through the eddy current data analysis process for an associated volumetric wear indication. The eddy current results database was also reviewed for adjacent signals which may be indicative of tube-to-tube wear such that they are flagged for further diagnostic testing. No indications of tube-to-tube contact wear were detected through eddy current data analysis or review of the results database during the Watts Bar U1R14 inspections.

3.3 Resolution for Classification of Indications Indications reported with flaw-like characteristics in the Watts Bar Unit 1 RSGs may include those initially reported as distortions of preexisting signals such as absolute drift indications (ADI/ADS), tube support indications (DSI/DSS), distorted tubesheet signals (DTI/DTS) and manufacturing burnish marks (MBI, MBM). The character of I-code signals is further determined by data history review, lead analyst review, or by follow-up examination with alternate NDE techniques. Those indications with a three letter code ending with an I are compared to historical data and are changed to an S if they have not changed within normal technique variations. The resolution of indications from Watts Bar U1R14 is summarized in Table 3-2 below.

Table 3-2: Watts Bar U1R14 Resolution for Classification of Indications Distorted Distorted Absolute Mfg. Burnish Support Tubesheet SG Drift Signals Marks Signals Signals (ADI/ADS) (MBI/MBM)

(DSI/DSS) (DFI/DFS) 1 0 / 137 0/1 0 / 22 0/9 2 0 / 158 0/0 0/0 0 / 15 3 0 / 37 0/1 0 / 77 0/0 4 0 / 117 0/0 0 / 74 0/6 A number of the ADS indications in the Watts Bar RSGs are residual effects from the RSG tube thermal treatment process. The distorted support and tubesheet bobbin signals from the U1R14 inspection have all been cleared by either review of the corresponding Array probe data or data history review. Finally, an MBM is most typically a burnishing relic created by the tube manufacturer to buff out surface blemishes. All of these eddy current indications have been cleared through the NDE analysis process as being free from tube degradation.

3.4 SG Channel Head Primary Side Bowl and Tube Plug Visual Inspections Visual inspections have been performed of the SG channel head bowl in the vicinity of the drain line in all SGs during Watts Bar U1R14. These inspections are performed based on industry operating experience and guideline requirements discussed in the Reference 3 degradation assessment. Visual inspections of the SG hot leg and cold leg divider plate, inclusive of the entire divider plate-to-channel head weld and all visible clad surfaces, were performed in accordance with Westinghouse NSAL-12-1 (Reference 15). This inspection was performed using the SG manway channel head bowl cameras. Satisfactory inspection results were observed in all SGs with no indications of cladding surface degradation (Reference 11).

All previously installed tube plugs were also inspected from the primary side in all four of the Watts Bar Unit 1 RSGs using the cameras mounted to the eddy current robots. The inspection results were satisfactory SG-SGMP-17-9 November 2019 Revision 1 Page 13 of 55

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and showed no indication of tube plug leakage or failure. Inspection of the channel head bowl and all installed tube plugs is planned to be performed again during Watts Bar U1R17 in all RSGs at the subsequent inspection.

3.5 Secondary Side Activities 3.5.1 Top of Tubesheet Cleaning A top of tubesheet deposit cleaning process was performed in all four SGs during Watts Bar U1R14. There are two main purposes of the cleaning process. The first is to remove hardened deposits that preferentially form at the top of the tubesheet and the second is to force and filter out any loose parts or foreign objects that have migrated to the SG secondary side during operation. The mass of deposit material and debris removed by the top of tubesheet cleaning process is summarized in Table 3-3 below.

Table 3-3: Watts Bar U1R14 SG Tubesheet Deposit Removal SG 1 8.5 lbs SG 2 7.5 lbs SG 3 9.5 lbs SG 4 7.0 lbs All SGs 32.5 lbs Periodic views of the in-line grit tank screen were also performed throughout the tubesheet cleaning process.

These confirmed that the process was successful at removing foreign objects and material from the RSG secondary side in addition to the hardened sludge deposits.

3.5.2 Top of Tubesheet FOSAR A secondary side tubesheet FOSAR has been performed in all four SGs during Watts Bar U1R14 following a top of tubesheet cleaning. Sludge, scale, foreign objects, and other deposit accumulations at the top of the tubesheet may have been removed as part of the tubesheet sludge lancing process prior to FOSAR inspection of each SG. The FOSAR inspections included visual examination of tube bundle periphery tubes from both the annulus and tubelane on both the hot and cold legs and through the no tube lane. A limited top of tubesheet in-bundle visual inspection was also performed in each SG for the purpose of assessing the level of hardened deposit buildup in the kidney region. Table 3-4 is a summary of the final results from the FOSAR inspections.

Table 3-4: Watts Bar U1R14 SG FOSAR Summary SG Identified Retrieved Remaining 1 2 0 2 2 1 0 1 3 1 0 1 4 8 6 2 All SGs 12 6 6 During Watts Bar U1R14, a total of six foreign objects were removed from the top of the tubesheet. The majority of the foreign objects retrieved were small pieces of metal, wires and bristles. There were no indications of a significant or ongoing breakdown of foreign material exclusion processes. Any foreign objects not able to be retrieved were mapped and an engineering evaluation performed in Reference 7 to justify continued operation with the objects present on the SG secondary side.

3.6 Condition Monitoring Conclusions Based on the inspection data, no tubes exhibited degradation that required in situ pressure testing to demonstrate structural and leakage integrity. There was no reported primary-to-secondary leakage prior to the end of the Watts Bar Unit 1 RSG inspection interval. No secondary side tube degradation attributable to SG-SGMP-17-9 November 2019 Revision 1 Page 14 of 55

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foreign objects has been identified from the FOSAR and visual inspections. No indications of U-bend support structure or horizontal ATSG wear were found to be in excess of the CM limits. The SG performance criteria for operating leakage and structural integrity were satisfied for the preceding Watts Bar Unit 1 RSG inspection interval.

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4.0 Operational Assessment NEI 97-06 (Reference 2) requires that an operational assessment be performed to determine if existing degradation mechanisms observed in a steam generator will continue to meet tube structural and leakage integrity performance criteria until the next inspection. An operational assessment of each existing tube degradation mechanism identified during Watts Bar U1R14 along with the foreign objects that remain on the secondary side is provided in the following sections.

4.1 Mechanical Wear at U-bend Support Structures The two approaches that are used to project future wear depths are based on a constant progression of either the maximum depth of the wear or the volume of material worn away. Revision 0 of this report (Reference

17) utilized the depth-based approach. This approach is retained in this revision for comparison, and is described in Sections 4.1.1, 4.1.2 and 4.3. The volume based wear approach, new to Revision 1, is described in Section 4.1.4.

4.1.1 Degradation Growth Rates Based on application of conservative U-bend support structure wear growth rates, the condition of the Watts Bar Unit 1 RSG tubes has been analyzed with respect to continued operability until the end of Cycle 19 without exceeding the limits for structural and leakage integrity. Upon completion of the combination bobbin and Array probe data program, the growth rates have been determined by comparative analysis of the U-bend support structure wear sites.

In order to determine growth rates, a data history review was performed by the lead eddy current analyst for all U-bend support structure wear indications measuring 20%TW or greater and a sampling of indications below this threshold. The purpose was to determine whether a measurable precursor signal was present but unreported in the prior inspection and the associated growth rate for use on the OA projections. The growth rates are determined given an operating duration of 4.07 EFPY from U1R11 to U1R14 and normalizing to a

%TW/EFPY basis. The results of the comparative analysis with the purpose of developing a representative growth rate are shown in Attachment 3 Table A3-1. The cumulative frequency distribution (CDF) of growth rates for all SGs combined using the Benards median rank fraction method (Reference 5) is shown in Figure A3-2 and is confirmed to be slightly conservative in comparison to the fit of a normal distribution. A summary of growth rates for the U-bend support structure wear indications in all four SGs is summarized in Table 4-1 below.

Table 4-1: Watts Bar U1R14 U-bend Support Structure Wear Growth Comparison Max Standard Upper 95th Number of Average Growth Outage SG Indication Deviation Percentile Indications (%TW/EFPY)1

(%TW) (%TW/EFPY) 1 (%TW/EFPY) 2 1 13 21 4.52 0.54 5.41 2 11 24 1.97 2.11 5.44 U1R14 3 23 27 3.86 1.98 7.11 4 12 23 2.87 2.24 6.56 All 59 27 3.39 2.04 6.74 Note 1: Considering growth rates based on history review for indications 20%TW and greater and a sampling of those less than 20%TW.

Note 2: Based on a normally distributed growth rate population.

As an evaluation of conservatism in the approach to determining growth rates, all U-bend support wear indications <20%TW where no history review was performed were set to a non-degraded condition (0%TW) at the U1R11 inspection and assumed to grow to the measured depth at U1R14. The resulting 95th percentile growth rates were reduced from the approach where only growth rates associated with indications greater than 20%TW and those where a history review was performed were considered. A review was also performed of growth rates on a SG-specific basis and no single SG showed U-bend wear indication growth rates uncharacteristic of the others. Therefore, application of the growth rate data points associated with SG-SGMP-17-9 November 2019 Revision 1 Page 16 of 55

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wear indications of greater than 20%TW and only a sampling of those less for all SGs is an appropriate and conservative measure.

4.1.2 Operational Assessment - Deterministic (Depth-Based) Approach An Operational Assessment for U-bend support structure wear using a deterministic, depth-based approach is first considered for a period of three cycles.

The Examination Technique Specification Sheet (ETSS) 96004.1, Revision 13, is the bobbin technique used to size U-bend support structure wear. As a result, the associated sizing equation (y = 0.98x + 2.89 and Syx =

4.19%) is appropriate for the character of U-bend support structure wear indications that have been detected.

This technique is part of the Appendix H ETSS library in the Reference 1 guidelines and, therefore, the standard error of the regression (Syx) for the ETSS 96004.1 sizing equation to be applied for tube integrity must be multiplied by 1.645 to represent the 95% probability/50% confidence allowance and then multiplied by 1.12 to include analyst uncertainty. Thus, the projected wear depth of the largest indication at U1R17, using the largest indication and growth rate from Table 4-1, is calculated as follows:

Projected U1R17 U-bend Support Structure Wear Measured with ETSS 96004.1 Revision 13

%TW at U1R17 = [Corrected U1R14 Measurement]+[Growth]+[Total NDE Error]

%TW at U1R17 = [(0.98 x 27%) + 2.89%]+[7.11%/EFPY x 4.5 EFPY]+[1.12(1.645 x 4.19%)] = 69.06%TW The table in Attachment 2 notes that the CM limit is 51%TW for a 2.5 inch long flaw. A deterministic, depth-based projection does not meet the CM criterion after three cycles of operation. Therefore, a Monte Carlo OA approach is considered.

4.1.3 Operational Assessment - Monte Carlo (Depth-Based) Approach The Westinghouse configured software Single Flaw Model (SFM) Version 2.2 has been used for the OA projection using the inputs discussed previously and material properties from the Reference 3 DA. The associated software runs are attached to this document in the Westinghouse Electronic Document Management System (EDMS) and the configuration control is documented in Reference 10. With this software, the burst pressure of projected flaws is determined through the Monte Carlo simulation method described in Reference 5 and compared against the structural and leakage integrity performance criteria. The OA projection considers 95th percentile and 50% confidence level contributions from depth, relation, material and growth in the reduction in tube burst pressure due to degradation.

The largest indication returning to service following Watts Bar U1R14 measures 27% TW and 0.4 inch long in SG 3 R81C56 which will remain in service for an assumed 4.5 EFPY between inspections. This projection uses a Normal distribution with a mean of 3.86 and standard deviation of 1.98 to represent the growth rate function in the simulation and a bounding length growth rate of 0.1 inch/EFPY (or 0.4 inch/4.07 EFPY). The resulting projected flaw has a burst pressure of 4,028 psi (58% TW and 0.85 inch long) which is in excess of the 3,798 psi structural integrity performance criterion. A capture of the SFM software inputs and output is provided in Figure A3-3. Since the largest indication returning to service is greater than the 95th percentile detection threshold for bobbin inspection (see Figure A6-3), this conclusion also applies to the assumed undetected indications of U-bend support structure wear.

Using SFM, it was determined that this same, largest indication could remain in service for as long as 4.9 EFPY between inspections without the resulting projected flaw burst pressure falling below the 3,798 psi structural integrity performance criterion.

For pressure-only loading of volumetric flaws, satisfaction of the structural integrity implies satisfaction of leakage integrity at accident conditions since steam line break accident condition pressure differential for pop-through is much smaller than 3PNO.

The maximum inspection interval that can be established using the depth-based Monte Carlo approach in SFM is three cycles. Therefore, the volume-based wear approach as discussed in the next section, is applied SG-SGMP-17-9 November 2019 Revision 1 Page 17 of 55

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4.1.4 Use of Volume Based Wear Approach The Westinghouse software W-VOL (Reference 16) was utilized to further evaluate an inspection interval that can be considered by TVA should a Technical Specification amendment permit extension of the inspection intervals beyond the current licensing basis limits for Alloy 690 plants. The W-VOL code applies a volume-based approach towards calculating wear over time. This method can project a flaw growth that is based on the applicable work function that actually occurs with the mechanical wear experienced in the SGs, and thus removes excess conservativism when calculated using wear depth methods. Ultimately, this method can demonstrate an increased operational assessment interval in which the SG performance criteria is maintained for a flaw distribution set.

Benchmarking is performed to define the plant-specific performance parameters for application of the volume predictive model. Benchmarking allows the program to assess flaws that do not have prior history without having to make the excessively conservative assumption that they initiated from 0%TW at a prior inspection. For the U-bend support structures at Watts Bar Unit 1, the amount of wear depth data that was available from U1R8 and U1R11 was insufficient to perform benchmarking for individual SGs; however, when the data from all four SGs was combined benchmarking parameters could be derived. The benchmark calculation regression lines for U-bend support structure wear are shown below in Figure 4-1. Figure 4-1 presents plots of reported versus predicted depths for each SG. The figure shows a regression line (green line) with a slope of 0.22; a slope less than unity (red line) indicates a conservative condition for application of the benchmark parameters. Table 4-4 summarizes the regression parameters that were determined by benchmarking.

Figure 4-1: WVOL Benchmark Calculation Regression Lines for U-bend Support Structure Wear The data used as input to W-VOL are the measured wear depths from the U1R14 inspection, and the eddy current lookup depths for these flaws from the U1R8 and U1R11 inspections. The program is able to establish flaw growth for the flaws based on the growth experienced between U1R11 and U1R14 in terms of the volume-removed method. The results are summarized in Table 4-2.

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Table 4-2: 95/50 Burst Pressures from W-VOL Cases for U-Bend Structural Support Wear Largest Projected Max R14 Flaw Beginning Indication (including 95/50 of End of Remaining NDE Burst Growth Growth Growth In-Service Projection Uncertainty) Pressure SG Period Period EFPY (%TW) EFPY (%TW) (psi) 1 R11 R14 4.07 21 7.5 48.4 4833 2 R11 R14 4.07 24 7.5 50.5 4682 3 R11 R14 4.07 27 7.5 60.6 3807 4 R11 R14 4.07 23 7.5 50.5 4602 The flaw population in all SGs meets the performance criteria of 3798 psi at 95% probability and 50%

confidence levels for 5 cycles (7.5 EFPY) of operation for mechanical wear at U-bend support structures.

4.2 Mechanical Wear at Horizontal ATSGs The two approaches that are used to project future wear depths are based on a constant progression of either the maximum depth of the wear or the volume of material worn away. Revision 0 of this report (Reference

17) utilized the depth-based approach. This approach is retained in this revision for comparison, and is described in Sections 4.2.1, 4.2.2 and 4.3. The volume based wear approach, new to Revision 1, is described in Section 4.2.4.

4.2.1 Degradation Growth Rates Based on application of conservative horizontal ATSG wear growth rates, the condition of the Watts Bar Unit 1 RSG tubes has been analyzed with respect to continued operability without exceeding the limits for structural and leakage integrity. Upon completion of the bobbin and Array probe data program, the growth rates have been determined by comparative analysis of the ATSG wear sites.

In order to determine growth rates, a data history review was performed by the lead eddy current analyst for each new horizontal ATSG wear indication measuring 20%TW or greater and a sampling of indications below this threshold. The purpose was to determine whether a measurable precursor signal was present but unreported in the prior inspection and the associated growth rate for use on the OA projections. The growth rates are determined given an operating duration of 4.07 EFPY from U1R11 to U1R14 and normalizing to a

%TW/EFPY basis. The results of the comparative analysis for the purpose of developing a representative growth rate are shown in Attachment 4, Tables A4-1 through A4-4. The cumulative frequency distribution (CDF) of growth rates for each individual SG using the Benards median rank fraction method (Reference 5) is shown in Figure A4-5 and is confirmed to be slightly conservative in comparison to the fit of a normal distribution. A mapped depiction of horizontal ATSG growth rates is provided in Figure A4-6. A summary of growth rates for the horizontal ATSG support structure wear indications in all four SGs is summarized below in Table 4-3.

Table 4-3: Watts Bar U1R14 Horizontal ATSG Wear Growth Comparison Max Standard Upper 95th Number of Average Growth Outage SG Indication Deviation Percentile Indications (%TW/EFPY)1

(%TW) (%TW/EFPY) 1 (%TW/EFPY) 2 1 74 33 2.08 1.52 4.58 2 139 37 1.93 1.46 4.33 U1R14 3 83 26 2.42 1.83 5.43 4 123 34 2.58 1.86 5.64 All 419 37 1.97 1.85 5.09 Note 1: Considering growth rates based on history review for indications 20%TW and greater and a sampling of those less than 20%TW.

Note 2: Assuming a normally distributed growth rate population.

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As an evaluation of conservatism in the approach to determining growth rates, all horizontal ATSG support wear indications <20%TW where no history review was performed were set to a non-degraded condition (0%TW) at the U1R11 inspection and assumed to grow to the measured depth at U1R14. The resulting 95th percentile growth rates for all four SGs were reduced from the approach where only growth rates associated with indications greater than 20%TW and those where a history review was performed were considered. A review was also performed of growth rates on an SG-specific basis and no single SG showed horizontal ATSG wear indication growth rates uncharacteristic of the others. Therefore, application of the growth rate data points associated with wear indications of greater than 20%TW and only a sampling of those less for all SGs is an appropriate and conservative measure.

4.2.2 Operational Assessment - Deterministic (Depth-Based) Approach An Operational Assessment for horizontal ATSG wear using a deterministic, depth-based approach is first considered for a period of three cycles.

The Examination Technique Specification Sheet (ETSS) 96004.1, Revision 13, is the bobbin technique used to size horizontal ATSG wear. As a result, the associated sizing equation (y = 0.98x + 2.89 and Syx = 4.19%)

is appropriate for the character of horizontal ATSG wear indications that have been detected. This technique is part of the Appendix H ETSS library in the Reference 1 guidelines and, therefore, the standard error of the regression (Syx) for the ETSS 96004.1 sizing equation to be applied for tube integrity must be multiplied by 1.645 to represent the 95% probability/50% confidence allowance and then multiplied by 1.12 to include analyst uncertainty. Thus, the projected wear depth of the largest indication at U1R17, using the largest indication and growth rate from Table 4-3, is calculated as follows:

Projected U1R17 Horizontal ATSG Wear Measured with ETSS 96004.1 Revision 13

%TW at U1R17 = [Corrected U1R14 Measurement]+[Growth]+[Total NDE Error]

%TW at U1R17 = [(0.98 x 37%) + 2.89%]+[5.64%/EFPY x 4.5 EFPY]+[1.12(1.645 x 4.19%)] = 72.25%TW The table in Attachment 2 notes that the CM limit is 52%TW for a 2.0 inch long flaw. A deterministic, depth-based projection does not meet the CM criterion after three cycles of operation. Therefore, a Monte Carlo OA approach is considered.

4.2.3 Operational Assessment - Monte Carlo (Depth-Based) Approach The Westinghouse configured software Single Flaw Model (SFM) Version 2.2 has been used for the OA projection using the inputs discussed previously and material properties from the Reference 3 DA. The associated software runs are attached to this document in the Westinghouse EDMS and the configuration control is documented in Reference 10. With this software, the burst pressure of projected flaws is determined through the Monte Carlo simulation method described in Reference 5 and compared against the structural and leakage integrity performance criteria. The OA projection considers 95th percentile and 50%

confidence level contributions from depth, relation, material and growth in the reduction in tube burst pressure due to degradation.

The largest indication returning to service following Watts Bar U1R14 measures 37% TW and 0.39 inch long in SG2 Tube R88C95 at C03 and will be in service for an assumed 4.5 EFPY. This projection uses a normal distribution with a mean of 1.97 and standard deviation of 1.85 to represent the growth rate function in the simulation and a bounding length growth rate of 0.1 inch/EFPY (or 0.39 inch/4.07 EFPY). The resulting projected flaw has a burst pressure of 3,988 psi (59% TW and 0.85 inch long) which is in excess of the 3,798 psi structural integrity performance criterion. A capture of the SFM software inputs and output is provided in Figure A4-7. Since the largest indication returning to service is much greater than the 95th percentile detection threshold for bobbin inspection (see Figure A6-3), this conclusion also applies to the assumed undetected indications of horizontal ATSG wear.

Using SFM, it was determined that this same, largest indication could remain in service for as long as 4.93 EFPY between inspections without the resulting projected flaw burst pressure falling below the 3,798 psi structural integrity performance criterion.

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For pressure-only loading of volumetric flaws, satisfaction of the structural integrity implies satisfaction of leakage integrity at accident conditions since steam line break accident condition pressure differential for pop-through is much smaller than 3PNO.

The maximum inspection interval that can be established using the depth-based Monte Carlo approach in SFM is three cycles. Therefore, the volume-based wear approach as discussed in the next section, is applied 4.2.4 Use of Volume-Based Wear Approach The Westinghouse software W-VOL (Reference 16) was utilized to gain additional margin in terms of inspection interval that can be considered by TVA should a Technical Specification amendment permit extension of the inspection intervals beyond the current licensing basis limits for Alloy 690 plants. The W-VOL code applies a volume-based approach towards calculating wear over time. The method models a reduced volume removal rate over time due to less surface contact duration between the wear-initiating support structure and the tube. Therefore, this method can project a flaw growth that is based on the applicable work function that actually occurs with the mechanical wear experienced in the SGs, and thus removes excess conservativism when calculated using wear depth methods. Ultimately, this method can demonstrate an increased operational assessment interval in which the SG performance criteria is maintained for a flaw distribution set.

Benchmarking is performed to define the plant-specific performance parameters for application of the volume predictive model. Benchmarking allows the program to assess flaws that do not have prior history without having to make the excessively conservative assumption that they initiated from 0%TW at a prior inspection. Table 4-4 provides a summary of the benchmark parameters that were calculated by the W-VOL program. All slopes are less than unity; a slope less than unity indicates a conservative condition for application of the benchmark parameters.

Table 4-4: Summary of Benchmark Parameters Standard Location SG Slope Intercept Error ATSG 1 0.095 19.496 2.557 ATSG 2 0.179 17.412 3.777 ATSG 3 0.096 18.096 2.565 ATSG 4 0.07 20.348 2.687 U-bend All 0.022 20.386 2.024 The data used as input to W-VOL are the measured wear depths from the U1R14 inspection, and the eddy current look-up depths for these flaws from the U1R8 and U1R11 inspections. The program is able to establish flaw growth for the flaws based on the growth experienced between U1R11 and U1R14 in terms of the volume-removed method.

The Watts Bar ATSG wear flaws have been observed to be primarily tapered wear, as opposed to flat (or uniform depth) wear. To distinguish flat wear from tapered wear it is necessary to review terrain map graphics from rotating probe inspections, such as that shown in Figure A4-8. In the volume-based approach the type of wear is important because at a given maximum depth flat wear will result in a greater volume of material that has worn away than tapered wear with the same maximum depth. It is conservative to assume that ATSG wear is flat wear.

If it is assumed that all ATSG wear is flat wear, the W-VOL model only projects 5.4 EFPY of operation before burst pressure and probability of burst criteria are exceeded. A review of the data showed that two wear indications that were left in service are the cause of the limitation in the projection:

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SG2-R88C95-C03 was 37%TW at U1R14 and 21%TW at U1R11 SG4-R94C37-C03 was 34%TW at U1R14 and 16%TW at U1R11 These indications are relatively deep and have relatively large growth rates for extended projections of operation. Graphics for both of these indications were reviewed and it was shown that both indications are tapered wear. When it is modelled that these two indications are tapered wear, and it is assumed that all other ATSG wear is flat wear, the W-VOL model projects 7.5 EFPY (5 cycles) of operation before tube integrity criteria are exceeded. The SG2-R88C95-C03 indication is the controlling indication, even as tapered wear, and prevents a projection of six cycles.

The results are summarized in Table 4-5.

Table 4-5: 95/50 Burst Pressures from W-VOL Cases for Wear at Horizontal ATSGs Largest Projected Max R14 Flaw Beginning Indication (including 95/50 of End of Remaining NDE Burst Growth Growth Growth In-Service Projection Uncertainty) Pressure SG Period Period EFPY (%TW) EFPY (%TW) (psi) 1 R11 R14 4.07 33 7.5 59.9 3918 2 R11 R14 4.07 37 7.5 59.8 4070 3 R11 R14 4.07 26 7.5 51.1 4523 4 R11 R14 4.07 34 7.5 56.6 4064 The flaw population in all SGs meets the performance criteria of 3798 psi at 95% probability and 50%

confidence levels for five cycles (7.5 EFPY) of operation for mechanical wear at horizontal ATSGs.

4.3 U-bend Support Structure and Horizontal ATSG Wear - Fully Probabilistic Method A fully probabilistic model has been developed for the Watts Bar Unit 1 U-bend support structure and horizontal ATSG degradation mechanisms as a confirmation of the conservatism involved with the Monte Carlo OA methods. This modeling entails the development of four different aspects including an Ahat function to represent analysis detection, site-specific eddy current data noise measurements in the regions of interest, a model assisted probability of detection (MAPOD) regression, and associated inputs to the full bundle model software. These three aspects are discussed below along with the results.

4.3.1 Ahat Development The process of Ahat modeling is a form of regression analysis in which a structural variable such as length or depth is used as the independent variable while signal amplitude (voltage) is used as the dependent variable.

With Ahat modeling, a continuous probability of detection (POD) function is directly calculated avoiding the need for fitting a model to binary hit and miss data which has been conventional with ETSS development until recently. In preparation for accurately sizing wear during the Watts Bar U1R14 inspection, TVA developed an eddy current wear calibration curve based on the tapered wear flaws standards of EPRI ETSS 27091. Data was collected on the actual EPRI wear standards, which has the same tube material and size as the Watts Bar Unit 1 RSGs, using the same collection process to be used during the inspection. Through this process, sufficient data points were generated to create an Ahat function relating maximum vertical voltage (Vvm) versus depth to the tapered wear flaw geometry which closely matches the degradation observed at Watts Bar Unit 1 (see Attachment 6 Figure A6-1).

4.3.2 Site Specific Noise Measurements The second required input is the noise in terms of voltage amplitude within the region of interest. The Westinghouse auto analysis software program Real Time Auto Analysis (RTAA) collected Vvm noise SG-SGMP-17-9 November 2019 Revision 1 Page 22 of 55

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measurements at the U-bend support structures and horizontal ATSGs in every tube tested in all four RSGs.

As this is an incredibly large volume of noise data, only one calibration group was selected in each of the four RSGs to represent the remainder of the tube bundle. The noise measurements were taken from the calibration group with the majority of the indications of tube degradation for each RSG. These were Cal 22 for SG1, Cal 36 for SG2, Cal 26 for SG3, and Cal 14 for SG4. The combined noise distributions for the diagonal bars, vertical straps and ATSGs are provided in Figure A6-2. Although noise measurements were taken at the center, leading edge and trailing edge of each support structure, only the edge noise measurements were used as this is where the degradation has been found to initiate at Watts Bar Unit 1.

4.3.3 Model Assisted Probability of Detection A POD model is a functional measure of the ability of a Non-Destructive Examination (NDE) system to detect degradation and is one of the essential inputs to an OA. The POD is used to estimate degradation remaining in service after an eddy current program scope is performed. The POD associated with each eddy current detection technique is a standard part of the EPRI ETSS development process. However, industry experience has shown that eddy current noise can affect POD. The United States Nuclear Regulatory Commission (USNRC) has also requested that future POD developments consider the potential effects of noise on the detection of degradation. As a result, EPRI and the industry have adopted a model assisted probability of detection (MAPOD) method that incorporates both the ETSS data set with the site-specific noise data in order to develop a site-specific POD for a particular type of degradation. The EPRI software MAPOD has been developed for this purpose (Reference 14). Recent EPRI guideline updates have also incorporated considerations for noise measurements and POD development.

The MAPOD simulation software developed for industry wide application by EPRI was used to generate the site-specific POD for Watts Bar Unit 1. Three different MAPOD runs were made corresponding to the edges of the diagonal bars, vertical straps and the ATSGs. An analyst reporting threshold of 1.5 to 2.0 Signal to Noise (S/N) was applied as discussed in the MAPOD Users Manual (Reference 14). The POD regressions determined from the four MAPOD software runs are summarized in Table 4-6 below:

Table 4-6: Watts Bar U1R14 Model Assisted Probability of Detection Results Noise Measurement No. of Noise Function Slope Intercept POD(95)

Data Set Measurements Fit Type Diagonal Bars 1,791 4.633 -3.34 22%TW Vertical Straps 2,755 Log-Logistic 3.991 -0.101 6%TW Horizontal ATSGs 8,387 -2.086 -4.467 13%TW Figure A6-3 provides the graphical representations of the POD regressions for each support type. Although these regressions show 95th percentile detection at degradation levels that are quite low, it is notable that the POD (95) associated with the diagonal bar noise measurements is not quite as good as those for the vertical strap and the ATSG intersections.

4.3.4 Fully Probabilistic Operational Assessment The fully probabilistic or full bundle operational assessment method entails accounting for non-detected flaws resulting from limitations of the applied NDE technique such as the POD and projecting the degradation forward in SG operating time. The full bundle method considers all relevant sources of error and uncertainty to evaluate whether the structural and leakage integrity requirements will be met with a probability of 95% at 50% confidence levels. The Westinghouse configured software Full Bundle Model (FBM) Version 2.0 has been used to evaluate these requirements. The FBM configuration control software release letter is documented in Reference 13 and the program input/output files are attached to this report in EDMS. The initial inputs to the fully probabilistic model, including tube geometry, material properties, normal operating, accident pressures and leakage limits are from the Reference 3 degradation assessment.

The fully probabilistic models of U-bend support structure and horizontal ATSG wear developed for Watts Bar Unit 1 is discussed below.

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The return to service depth distribution of U-bend support flaws was established by fitting a LogNormal distribution with a mean of 2.88, standard deviation of 0.135, upper and lower truncations of 12%TW and 27%TW to the population of 59 total flaws returned to service. Growth of U-bend flaws was modeled by a Beta distribution with an alpha of 0.746, a beta of 0.790, upper and lower bounds of 0%TW/EFPY and 7%TW/EFPY. All flaws returned to service were set assumed to be 2.5 inches in length with no potential for growth. The postulated undetected population of flaws was estimated by processing a uniform flaw distribution through the POD function using the uniform and forward feature of the FBM software. This process simulates a non-detected flaw distribution based on the input POD curve and maximum assumed non-detected flaw depth. The maximum assumed non-detected flaw was very conservatively selected to be 30%TW and all non-detected flaws were again assumed to be 2.5 inches in length. A total of 35 undetected flaws were used in the simulation.

The return to service depth distribution of horizontal ATSG flaws was established by fitting a LogNormal distribution with a mean of 2.92, standard deviation of 0.136, upper and lower truncations of 8%TW and 37%TW to the limiting population of 139 total flaws returned to service in SG2. Growth of horizontal ATSG flaws was assumed to be a constant of 5.9%TW/EFPY which was the largest single growth rate observed. All flaws returned to service were set assumed to be 2.0 inches in length with no potential for growth. The postulated undetected population of flaws was estimated by processing a uniform flaw distribution through the POD function using the uniform and forward feature of the FBM software. This process simulates a non-detected flaw distribution based on the input POD curve and maximum assumed non-detected flaw depth. The maximum assumed non-detected flaw was very conservatively selected to be 25%TW and all undetected flaws were again assumed to be 2.0 inches in length. A total of 40 undetected flaws were used in the simulation.

Although the Watts Bar flaws have been observed to be primarily tapered, flat wear was assumed in the model and no flaw geometry factor was applied. No flaw initiates were modeled as experience has shown the burst probability of wear mechanisms to be dominated by the flaws returned to service.

The Westinghouse FBM software ran a total of 500,000 Monte Carlo simulations in each case to develop the cumulative probability distribution (CPD) for structural burst and leakage. The industry wide SG tube integrity performance criteria are less than 5% cumulative probability of burst and leakage greater than that assumed in the limiting accident analysis. The results of the depth-based fully probabilistic model for 4.5 EFPY and 4.74 EFPY of operation between inspections are shown in Table 4-7 below and screen captures of the outputs are provided in Figure A6-4. The FBM software runs are attached to this letter in EDMS.

Table 4-7: Watts Bar U1R14 Fully Probabilistic Operational Assessment Results Tube Integrity Leak Rate at Probability Probability Criteria 5% Probability Case EFPY Description of Burst of Leakage Satisfied? (gpm) 1 U-bend Support Structure 0.04% 0% Yes 0.0 4.5 2 Horizontal ATSG 1.66% 0% Yes 0.0 3 U-bend Support Structure 0.14% 0% Yes 0.0 4.74 4 Horizontal ATSG 4.82% 0% Yes 0.0 The cumulative probability of structural burst and leakage is determined after 4.5 EFPY and 4.74 EFPY of operation for each of the depth-based scenarios described. The results of each of these depth-based cases show that structural and leakage integrity is projected to be maintained for 4.74 EFPY. In comparison, the volume-based approaches discussed in Sections 4.1.4 and 4.2.4 demonstrated acceptable operation for 7.5 EFPY.

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4.4 SG Secondary Side Foreign Objects During Watts Bar U1R14 there was one signal corresponding to a new PLP in SG4 R3C12 at the top of the tubesheet on the cold leg side. The location was visually inspected from the secondary side and no foreign object or contributing deposit condition was observed. There was no tube degradation detected by eddy current or visual inspection coincident with this PLP indication. As a result, no degradation is anticipated as a result of the PLP indication in the upcoming 7.5 EFPY estimated operating interval.

For the objects known to be remaining in the SG secondary side following Watts Bar U1R14, the analysis performed in Reference 7 establishes that at least five cycles or 7.5 EFPY of operating time would accrue before the object with the greatest potential to cause tube wear degradation could potentially exceed the tube structural limit. Furthermore, for tube wear to approach 3P burst dimensions, the depth must exceed the structural limit for the degraded tube length. The actual axial flaw lengths for the remaining foreign objects are expected to be much less than those applied in the Reference 7 foreign object wear evaluation.

For pressure-only loading of volumetric flaws, satisfaction of the structural integrity implies satisfaction of leakage integrity at accident conditions since steam line break accident condition pressure differential for pop-through is much smaller than 3PNO. Therefore, it is projected that there will be no challenge to the Watts Bar Unit 1 SG structural and leakage integrity performance criteria relative to this degradation mechanism before the Watts Bar U1R19 eddy current inspections.

4.5 Operational Assessment Conclusions An operational assessment is performed to assess whether degradation mechanisms observed in a plant will continue to meet the SG tube structural and leakage integrity performance criteria at the end of the upcoming inspection interval. Based on application of conservative U-bend support structure and horizontal ATSG wear growth rates, the condition of the Watts Bar Unit 1 RSG tubes has been analyzed with respect to continued operability of the SGs until the end of Cycle 19 without exceeding the SG tube integrity performance criteria. The growth rates were determined by comparative analysis of U-bend support structure and horizontal ATSG wear sites for all SGs. Based on conservative wear rate analysis applied to the retained foreign objects observed, there is no challenge to tube integrity in the upcoming five operating cycles until eddy current is performed again in U1R19. The operational assessment projections show that conditions exceeding the SG integrity performance criteria will not occur in any of the four SGs at Watts Bar Unit 1 during the five-cycle inspection interval from U1R14 to U1R19.

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5.0 References

1. Steam Generator Management Program: Pressurized Water Reactor Steam Generator Examination Guidelines: Revision 8, EPRI, Palo Alto, CA: 2016. 3002007572.

2. Steam Generator Program Guidelines, NEI 97-06, Revision 3, January 2011.

3. Westinghouse Document SG-SGMP-16-17, Revision 1, Watts Bar U1R14 Steam Generator Degradation Assessment, April 2017.

4. Steam Generator Degradation Specific Management: Steam Generator Degradation Specific Management Flaw Handbook, Revision 2. EPRI, Palo Alto, CA: 2015. 3002005426.

5. Steam Generator Management Program: Steam Generator Integrity Assessment Guidelines, Revision 4. EPRI, Palo Alto, CA: 2016. 3002007571.

6. Steam Generator Management Program: Steam Generator In Situ Pressure Test Guidelines, Revision 5, EPRI, Palo Alto, CA: 2016. 3002007856.

7. Westinghouse Letter LTR-SGMP-17-33, Revision 1, Evaluation of Foreign Objects in the Secondary Side of the Watts Bar Unit 1 Steam Generators - Spring 2017 U1R14 Outage, October 2019.

8. Watts Bar Nuclear Plant Document 1-SI-68-907, Revision 32, Steam Generator Tubing Inservice Inspection and Augmented Inspections, April 2017.

9. Tennessee Valley Authority Document EDMS # L18 170222802, Latest Revision, Watts Bar Nuclear Power Plant Unit 1 Use of Appendix H and Appendix I Qualified Techniques U1R14 Outage, March 2017.

10. Westinghouse Letter No. LTR-CDMP-19-38, Revision 0, Software Release Letter for Single Flaw Model, Version 2.4, September 2019.

11. Watts Bar Unit 1 SG Channel Head Primary Examination Reports, April 2017. (Attached to this document in EDMS)

12. Tennessee Valley Authority Document, Degradation Assessment and Technical Review and Justification for not Performing Primary or Secondary Inspections of the Steam Generators Watts Bar Nuclear Plant Unit 1 Cycle 13, October 2015. (Attached to this document in EDMS)

13. Westinghouse Letter LTR-SGMP-14-67, Revision 0, Software Release Letter for Full Bundle Model, Version 2.0, October 2014.

14. MAPOD-R Software Manual: A Monte Carlo POD Simulator in R - Version 2. EPRI, Palo Alto, CA:

2016. 3002007857.

15. Westinghouse Nuclear Safety Advisory Letter NSAL-12-1, Revision 1, Steam Generator Channel Head Degradation, October 2017.

16. Westinghouse Letter RT-LTR-18-45, Revision 0, Software Release Letter for W-VOL Version 1.0, February 2018.

17. Westinghouse Report SG-SGMP-17-9, Revision 0, Watts Bar U1R14 Steam Generator Condition Monitoring and Operational Assessment, April 2017.

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Attachment 1 - Watts Bar U1R14 As-Implemented SG Inspection Scope SG-SGMP-17-9 November 2019 Revision 1 Page 27 of 55

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Attachment 2 - Watts Bar U1R14 SG Tube Structural and Condition Monitoring Limits Degradation Condition Plugging Structural Limit Mechanism Monitoring Limit Existing Wear at 62% TW 51% TW for 2.5 U-bend Support 40% TW for 2.5 inch 96004.1 Revision 13 Structures Wear at 63% TW 52% TW for 2.0 Horizontal 40% TW for 2.0 inch 96004.1 Revision 13 ATSGs Potential Wear due to 64% TW 44% TW for 1.5 40% TW Foreign Objects for 1.5 inch 21998.1 Revision 4 Tube-to-Tube 63% TW 55% TW for 2.0 40% TW Contact Wear for 2.0 inch 27905.2 Revision 2 Diagnostic Pitting in the 78% TW 57% TW for 0.3 Plug on Detection Sludge Pile Region for 0.3 inch 21998.1 Revision 4 Note: The structural and condition monitoring limits identified in this table are from the Reference 3 Degradation Assessment.

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Attachment 3 - Watts Bar U1R14 U-bend Support Structure Wear Indications Table A3-1: Watts Bar U1R14 U-bend Support Structure Wear Indications - All SGs Per 20171 Per 20121 Delta SG Row Col Locn Inch1 Ind

(%TW) (%TW) (%TW/EFPY) 1 53 74 VS4 -1.15 PCT 15 1 58 47 VS3 1.29 PCT 16 1 58 47 VS3 -0.96 PCT 16 1 66 65 VS4 0.86 PCT 19 0 4.7 1 77 56 VS3 -0.91 PCT 18 1 77 82 VS3 -1.12 PCT 17 1 82 83 VS4 -1.01 PCT 18 1 95 58 VS2 -0.61 PCT 15 1 105 68 DS2 0.62 PCT 21 0 5.2 1 105 68 VS2 -0.03 PCT 19 0 4.7 1 105 68 VS2 -0.72 PCT 18 0 4.4 1 105 68 VS4 -1.03 PCT 17 1 105 68 DS2 -0.23 PCT 15 0 3.7 2 65 98 VS2 1.24 PCT 17 2 67 96 VS2 1.05 PCT 14 2 75 54 VS4 0.86 PCT 22 13 2.2 2 90 67 VS4 -0.76 PCT 18 2 90 67 VS2 -0.85 PCT 12 2 91 58 VS2 0.8 PCT 20 15 1.2 2 96 63 VS3 -0.64 PCT 22 0 5.4 2 99 58 VS4 0.8 PCT 18 2 100 63 VS2 -0.75 PCT 24 19 1.2 2 100 63 VS2 0.55 PCT 18 19 -0.2 2 101 52 VS1 -0.93 PCT 13 3 24 69 DS4 -0.03 PCT 23 0 5.7 3 43 78 VS3 -1.2 PCT 16 3 50 85 VS3 -0.38 PCT 20 0 4.9 3 53 82 VS3 -0.12 PCT 19 0 4.7 3 63 82 VS3 1.35 PCT 17 3 64 81 VS3 1.82 PCT 17 3 81 56 VS4 0.89 PCT 27 0 6.6 3 82 43 VS2 -0.95 PCT 18 3 96 67 VS2 -0.78 PCT 16 3 97 56 VS3 0.74 PCT 20 0 4.9 3 97 56 VS3 1.21 PCT 19 0 4.7 3 97 64 DS3 -0.83 PCT 19 14 1.2 3 98 71 VS4 0.73 PCT 20 16 1.0 3 99 50 DS3 0.82 PCT 18 3 99 58 VS4 0.96 PCT 21 0 5.2 3 99 58 VS4 0.03 PCT 17 0 4.2 3 100 55 VS2 -0.75 PCT 20 16 1.0 3 100 63 DS3 0.8 PCT 17 3 100 67 DS3 0.75 PCT 18 3 101 58 DS2 -0.8 PCT 21 18 0.7 3 101 58 VS4 0.84 PCT 19 0 4.7 3 101 58 VS3 -0.31 PCT 17 3 102 73 VS1 -0.91 PCT 19 0 4.7 4 92 81 VS2 0.9 PCT 23 17 1.5 4 93 70 VS2 0.92 PCT 19 16 0.7 4 93 70 VS2 0.06 PCT 18 16 0.5 4 93 70 VS2 -0.82 PCT 18 16 0.5 4 93 80 VS2 0.96 PCT 21 0 5.2 4 93 80 VS2 0.2 PCT 17 0 4.2 4 96 83 DS2 -0.83 PCT 20 0 4.9 4 97 72 VS3 -0.24 PCT 18 4 98 47 VS2 0.82 PCT 15 4 101 70 VS3 0.61 PCT 19 16 0.7 4 102 57 VS3 -1.14 PCT 22 0 5.4 4 102 57 DS2 -0.76 PCT 21 0 5.2 Note 1: Determined either from production data results or lead analyst review of raw eddy current data history.

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Figure A3-5: Watts Bar U1R14 U-bend Support Structure Wear Indications in All SGs - Tubesheet Map 100 SG1 SG2 SG3 SG4 80 60 Tube Row 40 20 0

0 20 40 60 80 100 120 Tube Column Note: A small number of tube locations have multiple wear indications. Therefore, some data points are plotted on top of each other on this map.

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Figure A3-6: Watts Bar U1R14 U-bend Wear Growth Cumulative Frequency Distribution - All SGs 1

0.95 0.9 0.85 0.8 0.75 CUMULATIVE FREQUENCY DISTRIBUTION (CDF) 0.7 0.65 0.6 0.55 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 GROWTH (%TW/EFPY)

Figure A3-7: Watts Bar U1R14 U-bend Support Structure Wear - Monte Carlo Simulation SG-SGMP-17-9 November 2019 Revision 1 Page 32 of 55

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Figure A3-8: Watts Bar U1R14 U-bend Support Wear Indication - SG3 R81C56 VS4 Array Graphic 2017 SG-SGMP-17-9 November 2019 Revision 1 Page 33 of 55

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Attachment 4 - Watts Bar U1R14 ATSG Wear Indications Table A4-1: Watts Bar U1R14 ATSG Wear Indications - SG1 Per 20171 Per 20121 Delta SG Row Col Locn Inch1 Ind

(%TW) (%TW) (%TW/EFPY) 1 1 48 H04 -1.06 PCT 18 1 1 48 H07 0.19 PCT 17 1 1 116 C04 -0.88 PCT 18 1 7 64 H09 0.66 PCT 19 1 7 88 H06 -0.97 PCT 22 0 5.4 1 7 102 H08 0.63 PCT 18 1 8 99 H09 -1.06 PCT 19 1 8 127 C05 -0.67 PCT 17 1 9 100 C10 -0.87 PCT 19 1 9 100 C11 0.76 PCT 18 1 9 104 H07 -0.92 PCT 22 18 1.0 1 18 103 H07 -0.92 PCT 20 0 4.9 1 23 84 C11 0.78 PCT 19 1 26 123 C06 -0.7 PCT 19 1 27 124 C06 -0.84 PCT 20 0 4.9 1 28 45 C11 0.67 PCT 19 1 29 124 C06 0.77 PCT 20 20 0.0 1 29 124 C05 -0.9 PCT 17 1 34 123 C05 -0.87 PCT 19 1 59 112 C06 -0.67 PCT 17 1 60 115 C05 -0.67 PCT 18 1 67 112 C06 0.83 PCT 19 1 68 111 C06 0.75 PCT 18 1 71 110 C06 0.81 PCT 19 1 76 107 C06 0.62 PCT 22 17 1.2 1 77 106 C06 0.72 PCT 18 1 79 104 C03 -0.84 PCT 17 1 82 103 C04 -0.74 PCT 15 1 83 26 C03 0.73 PCT 19 16 0.7 1 83 102 C03 -0.76 PCT 19 1 83 102 C06 0.67 PCT 17 1 84 99 C04 0.75 PCT 22 16 1.5 1 84 99 C03 -0.76 PCT 19 1 84 99 C07 1 PCT 18 1 85 30 C03 0.73 PCT 21 17 1.0 1 85 94 C03 -1 PCT 18 1 85 98 C04 0.81 PCT 18 1 85 100 C03 -0.79 PCT 27 19 2.0 1 86 97 C04 0.56 PCT 17 1 86 99 C03 -0.9 PCT 18 1 87 30 C02 0.73 PCT 21 17 1.0 1 87 96 C04 -0.87 PCT 19 1 87 98 C03 0.76 PCT 21 16 1.2 1 88 31 C03 0.78 PCT 17 0 4.2 1 88 95 C03 -0.87 PCT 22 16 1.5 1 88 97 C03 0.78 PCT 21 15 1.5 1 89 94 C04 0.73 PCT 18 1 89 96 C03 -0.79 PCT 33 18 3.7 1 90 93 C03 -0.75 PCT 20 14 1.5 1 90 95 C04 0.59 PCT 22 15 1.7 1 90 95 C03 -0.78 PCT 21 0 5.2 1 91 90 C04 -0.98 PCT 19 1 91 92 C03 -0.9 PCT 19 1 91 94 C06 0.64 PCT 20 0 4.9 1 92 91 C03 -0.9 PCT 18 1 92 93 C03 -0.79 PCT 24 16 2.0 1 95 88 C03 0.75 PCT 22 15 1.7 1 96 89 C03 -0.93 PCT 18 1 97 84 C07 0.78 PCT 21 18 0.7 1 97 84 C03 -0.79 PCT 20 15 1.2 1 98 85 C05 -0.92 PCT 22 16 1.5 1 98 85 C03 0.73 PCT 20 15 1.2 SG-SGMP-17-9 November 2019 Revision 1 Page 34 of 55

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Per 20171 Per 20121 Delta SG Row Col Locn Inch1 Ind

(%TW) (%TW) (%TW/EFPY) 1 100 83 C05 -0.95 PCT 23 15 2.0 1 100 83 C03 0.75 PCT 22 13 2.2 1 101 66 C03 0.78 PCT 17 1 101 78 C03 -0.95 PCT 20 15 1.2 1 102 71 C03 -0.81 PCT 17 1 102 71 C04 -1 PCT 16 1 102 79 C03 0.73 PCT 23 15 2.0 1 103 54 C03 0.95 PCT 18 1 103 74 C03 0.95 PCT 18 1 104 63 C03 0.78 PCT 18 1 105 64 C05 -0.92 PCT 22 18 1.0 1 105 64 C03 0.75 PCT 20 16 1.0 Note 1: Determined either from production data results or lead analyst review of raw eddy current data history.

Table A4-2: Watts Bar U1R14 ATSG Wear Indications - SG2 Per 20171 Per 20121 Per 20081 Delta SG Row Col Locn Inch1 Ind

(%TW) (%TW) (%TW) (%TW/EFPY) 2 1 42 H04 -0.8 PCT 16 2 1 44 H08 -0.91 PCT 16 2 1 44 H04 -0.86 PCT 13 2 1 48 H04 0.91 PCT 17 2 1 70 H05 -0.95 PCT 16 2 1 74 H04 -0.6 PCT 18 2 2 31 H06 -0.99 PCT 19 2 2 41 H07 -0.94 PCT 17 2 2 53 H05 -0.72 PCT 16 2 2 69 H04 -0.94 PCT 17 2 2 73 H04 -0.88 PCT 16 2 2 101 H06 0.86 PCT 17 2 6 1 C03 0.81 PCT 17 2 8 1 C03 0.56 PCT 18 2 8 77 H08 -0.98 PCT 25 9 1.9 2 8 77 H07 -1.01 PCT 21 6 1.8 2 8 127 C04 0.82 PCT 22 17 1.2 2 8 127 C03 0.76 PCT 21 0 5.2 2 10 127 C03 0.75 PCT 21 12 2.2 2 14 123 C03 0.92 PCT 17 2 18 73 H07 -1.04 PCT 19 2 19 124 C05 -0.93 PCT 18 2 19 124 C03 0.76 PCT 17 2 19 126 C03 0.79 PCT 17 2 20 123 C03 0.86 PCT 18 2 21 122 C09 -1.04 PCT 20 15 1.2 2 22 123 C03 0.73 PCT 30 16 3.4 2 22 123 C07 0.76 PCT 23 15 2.0 2 22 123 C07 -0.92 PCT 23 15 2.0 2 22 123 C05 0.64 PCT 18 2 22 123 C06 -1.07 PCT 18 2 22 125 C03 0.7 PCT 18 2 22 125 C06 0.73 PCT 18 2 23 44 C12 0.67 PCT 20 0 4.9 2 23 48 C12 -0.84 PCT 17 2 23 122 C03 0.76 PCT 22 16 1.5 2 25 28 C12 -0.79 PCT 13 0 3.2 2 25 122 C03 0.76 PCT 23 12 2.7 2 26 123 C03 0.65 PCT 21 16 1.2 2 26 123 C04 0.64 PCT 19 2 26 123 C03 -0.95 PCT 18 16 0.5 2 26 125 C03 0.7 PCT 18 2 27 4 C06 -1.04 PCT 15 10 1.2 2 27 124 C03 0.81 PCT 21 0 5.2 2 27 124 C05 -0.98 PCT 19 2 28 119 C06 -0.82 PCT 21 17 1.0 SG-SGMP-17-9 November 2019 Revision 1 Page 35 of 55

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Per 20171 Per 20121 Per 20081 Delta SG Row Col Locn Inch1 Ind

(%TW) (%TW) (%TW) (%TW/EFPY) 2 28 123 C03 0.78 PCT 26 16 2.5 2 30 7 C06 0.76 PCT 16 14 0.5 2 30 123 C06 0.84 PCT 27 22 1.2 2 30 123 C07 -0.86 PCT 27 20 1.7 2 30 123 C03 0.73 PCT 26 10 3.9 2 30 123 C05 -0.89 PCT 23 19 1.0 2 30 123 C06 -0.84 PCT 20 22 -0.5 2 30 123 C04 0.65 PCT 18 2 31 54 C12 -1.03 PCT 22 15 1.7 2 32 121 C03 0.73 PCT 19 2 32 121 C05 -0.93 PCT 18 2 33 122 C03 -0.9 PCT 19 2 33 122 C04 0.73 PCT 18 2 33 122 C07 0.53 PCT 18 2 36 7 C06 -0.84 PCT 18 15 0.7 2 36 121 C03 -0.92 PCT 20 15 1.2 2 37 8 C03 0.75 PCT 18 12 1.5 2 38 7 C03 0.94 PCT 16 2 39 8 C07 -1.07 PCT 15 15 0.0 2 47 10 C03 0.88 PCT 19 11 2.0 2 50 9 C04 -0.9 PCT 19 14 1.2 2 51 118 C03 -0.98 PCT 18 2 53 118 C03 -0.89 PCT 21 15 1.5 2 59 114 C04 0.62 PCT 15 2 60 115 C03 -0.96 PCT 19 2 60 115 C06 -1.12 PCT 19 2 60 115 C07 -1.01 PCT 17 2 62 15 C05 0.67 PCT 19 9 2.5 2 62 15 C04 -1.03 PCT 17 10 1.7 2 62 113 C07 -0.98 PCT 25 18 1.7 2 62 113 C03 -0.95 PCT 18 2 62 113 C04 0.62 PCT 18 2 63 114 C03 -1.04 PCT 17 2 63 114 C06 0.64 PCT 15 2 64 113 C03 -0.87 PCT 17 2 71 110 C05 0.65 PCT 16 2 72 109 C03 -1.2 PCT 20 0 4.9 2 76 107 C03 0.65 PCT 16 2 77 104 C03 -0.76 PCT 19 2 77 104 C04 -1.01 PCT 18 2 78 105 C03 -0.82 PCT 18 2 79 104 C03 -1.04 PCT 18 2 79 104 C04 -0.96 PCT 17 2 80 103 C06 -0.95 PCT 19 2 83 100 C04 0.54 PCT 20 0 4.9 2 85 100 C06 -0.99 PCT 21 16 1.2 2 85 100 C04 0.65 PCT 19 2 85 100 C07 -1.22 PCT 18 2 86 97 C04 0.89 PCT 18 2 86 97 C03 0.68 PCT 17 2 86 99 C04 0.7 PCT 22 0 5.4 2 87 30 C03 0.74 PCT 18 14 1.0 2 87 32 C06 -1.72 PCT 19 13 1.5 2 87 94 C04 0.73 PCT 20 12 2.0 2 87 98 C06 -0.95 PCT 30 19 2.7 2 87 98 C03 -0.95 PCT 23 16 1.7 2 87 98 C04 0.67 PCT 19 2 88 95 C03 -1.04 PCT 37 21 3.9 2 88 95 C03 0.53 PCT 16 21 -1.2 2 88 95 C06 0.78 PCT 16 2 89 32 C03 -0.94 PCT 19 16 0.7 2 89 32 C03 0.82 PCT 16 16 0.0 2 89 94 C03 -0.98 PCT 25 15 2.5 2 89 96 C06 -1.04 PCT 17 2 90 95 C04 0.73 PCT 23 13 2.5 SG-SGMP-17-9 November 2019 Revision 1 Page 36 of 55

• • • This record was final approved on 11/21/2019 10:34:58 AM. (This statement was added by the PRIME system upon its validation)

Per 20171 Per 20121 Per 20081 Delta SG Row Col Locn Inch1 Ind

(%TW) (%TW) (%TW) (%TW/EFPY) 2 90 95 C07 -0.95 PCT 18 2 91 94 C03 -0.92 PCT 25 15 2.5 2 92 35 C04 -0.86 PCT 17 15 0.5 2 92 35 C03 -0.92 PCT 16 15 0.2 2 92 93 C07 -0.87 PCT 19 2 92 93 C04 0.73 PCT 18 2 92 93 C06 -0.88 PCT 18 2 95 82 C03 -1.15 PCT 17 2 96 85 C06 0.89 PCT 19 2 96 85 C07 -1.06 PCT 17 2 96 87 C03 -0.82 PCT 18 2 97 86 C03 -1.12 PCT 19 2 97 88 C03 -0.96 PCT 20 13 1.7 2 98 43 C05 0.71 PCT 20 18 0.5 2 98 79 C03 -1.12 PCT 19 2 98 83 C03 -1.18 PCT 18 2 99 84 C02 0.62 PCT 16 2 100 81 C04 0.78 PCT 23 18 1.2 2 101 78 C03 -1.15 PCT 20 15 1.2 2 101 80 C03 -1.2 PCT 20 15 1.2 2 103 62 C03 0.92 PCT 17 2 103 66 C05 0.67 PCT 22 14 2.0 2 103 74 C03 -1.15 PCT 19 2 104 61 C06 -0.9 PCT 16 2 104 69 C05 0.7 PCT 19 2 105 66 C03 0.72 PCT 23 16 1.7 2 105 66 C05 0.67 PCT 17 2 105 68 C03 0.75 PCT 20 0 4.9 Note 1: Determined either from production data results or lead analyst review of raw eddy current data history.

Table A4-3: Watts Bar U1R14 ATSG Wear Indications - SG3 Per 20171 Per 20121 Delta SG Row Col Locn Inch1 Ind

(%TW) (%TW) (%TW/EFPY) 3 1 72 H04 -0.88 PCT 15 3 1 72 H05 -0.96 PCT 14 3 1 72 H04 0.91 PCT 13 3 1 78 H04 -0.91 PCT 20 15 1.2 3 1 86 H04 -0.85 PCT 15 3 7 2 C03 0.83 PCT 16 3 9 106 C06 -0.78 PCT 18 3 10 1 C03 0.72 PCT 23 16 1.7 3 10 1 C05 -0.92 PCT 17 3 13 4 C03 0.75 PCT 18 3 14 51 H10 0.68 PCT 18 3 14 51 C11 -1.06 PCT 17 3 14 81 H06 -0.9 PCT 18 3 15 2 C04 -0.97 PCT 20 0 4.9 3 15 2 C03 0.83 PCT 17 3 15 4 C06 -0.91 PCT 19 15 1.0 3 17 102 C12 -1.06 PCT 20 19 0.2 3 17 102 C12 0.66 PCT 18 19 -0.2 3 18 53 C12 -0.89 PCT 17 3 19 2 C04 -0.98 PCT 23 18 1.2 3 20 61 C10 -0.98 PCT 19 0 4.7 3 23 124 C06 0.69 PCT 23 21 0.5 3 24 3 C05 0.8 PCT 18 3 26 5 C03 -0.8 PCT 18 3 28 119 C12 -0.86 PCT 18 3 32 5 C03 -0.89 PCT 18 3 34 5 C03 -1 PCT 20 0 4.9 3 53 118 C06 0.69 PCT 16 0 3.9 3 59 14 C03 -1.03 PCT 21 16 1.2 3 61 114 C06 0.83 PCT 26 15 2.7 3 61 114 C06 -0.75 PCT 17 15 0.5 SG-SGMP-17-9 November 2019 Revision 1 Page 37 of 55

• • • This record was final approved on 11/21/2019 10:34:58 AM. (This statement was added by the PRIME system upon its validation)

Per 20171 Per 20121 Delta SG Row Col Locn Inch1 Ind

(%TW) (%TW) (%TW/EFPY) 3 64 17 C03 -0.89 PCT 16 3 64 111 C04 -0.77 PCT 18 12 1.5 3 64 111 C07 -1 PCT 14 12 0.5 3 65 18 C03 -0.98 PCT 18 3 67 112 C06 -1.11 PCT 16 16 0.0 3 68 19 C03 0.63 PCT 18 3 71 104 C03 0.87 PCT 17 0 4.2 3 76 107 C04 0.75 PCT 21 16 1.2 3 76 107 C06 0.8 PCT 20 16 1.0 3 77 22 C03 0.72 PCT 16 3 79 24 C03 0.75 PCT 18 3 82 25 C03 0.69 PCT 16 3 82 27 C03 0.67 PCT 16 3 83 26 C03 0.95 PCT 15 3 84 29 C03 0.72 PCT 20 0 4.9 3 84 95 C05 0.91 PCT 16 0 3.9 3 84 99 C03 -0.92 PCT 17 0 4.2 3 85 28 C03 0.75 PCT 21 14 1.7 3 85 96 C03 0.8 PCT 18 0 4.4 3 85 98 C02 -0.94 PCT 22 17 1.2 3 86 31 C03 0.66 PCT 17 3 86 95 C03 0.71 PCT 20 0 4.9 3 86 97 C02 -0.82 PCT 22 20 0.5 3 86 99 C05 0.74 PCT 22 0 5.4 3 86 99 C02 -0.85 PCT 21 16 1.2 3 86 99 C04 0.62 PCT 18 17 0.2 3 86 99 C03 -0.89 PCT 17 0 4.2 3 89 32 C03 0.69 PCT 18 3 89 96 C03 -0.92 PCT 22 16 1.5 3 90 33 C03 0.66 PCT 21 0 5.2 3 90 93 C04 -0.97 PCT 15 12 0.7 3 90 95 C04 -0.85 PCT 18 0 4.4 3 90 95 C03 -0.8 PCT 17 16 0.2 3 91 34 C03 -0.92 PCT 25 19 1.5 3 92 35 C03 -0.98 PCT 25 17 2.0 3 92 91 C03 -0.83 PCT 19 0 4.7 3 92 91 C05 -0.95 PCT 16 14 0.5 3 92 93 C04 -0.98 PCT 17 0 4.2 3 93 36 C03 -0.89 PCT 18 3 93 36 C04 0.69 PCT 18 3 93 90 C03 0.8 PCT 19 0 4.7 3 94 37 C06 -0.92 PCT 19 14 1.2 3 94 41 C07 -1.12 PCT 21 19 0.5 3 94 89 C03 -0.92 PCT 18 0 4.4 3 95 38 C02 -0.77 PCT 19 9 2.5 3 95 38 C04 0.69 PCT 17 3 96 85 C06 0.79 PCT 19 10 2.2 3 97 40 C04 0.72 PCT 16 3 97 42 C04 0.69 PCT 26 18 2.0 3 97 42 C06 0.86 PCT 16 3 100 75 C03 0.72 PCT 18 3 101 68 C03 0.8 PCT 21 0 5.2 Note 1: Determined either from production data results or lead analyst review of raw eddy current data history.

Table A4-4: Watts Bar U1R14 ATSG Wear Indications - SG4 Per 20171 Per 20121 Delta SG Row Col Locn Inch1 Ind

(%TW) (%TW) (%TW/EFPY) 4 3 42 C11 -0.96 PCT 23 0 5.7 4 3 42 C12 -1.09 PCT 19 4 6 37 C11 -1.01 PCT 17 4 6 73 H07 -0.87 PCT 21 0 5.2 4 6 127 C03 0.76 PCT 23 15 2.0 4 9 40 C11 -0.96 PCT 17 SG-SGMP-17-9 November 2019 Revision 1 Page 38 of 55

• • • This record was final approved on 11/21/2019 10:34:58 AM. (This statement was added by the PRIME system upon its validation)

Per 20171 Per 20121 Delta SG Row Col Locn Inch1 Ind

(%TW) (%TW) (%TW/EFPY) 4 9 42 H06 0.62 PCT 24 0 5.9 4 9 42 H07 0.72 PCT 17 4 10 41 C09 -0.87 PCT 19 4 10 61 H07 -1.12 PCT 18 4 12 71 H06 -0.86 PCT 22 0 5.4 4 12 71 H07 -1.23 PCT 22 0 5.4 4 13 78 C10 0.64 PCT 31 17 3.4 4 14 3 C04 0.69 PCT 20 15 1.2 4 18 63 C12 0.61 PCT 23 0 5.7 4 18 63 C11 0.64 PCT 21 0 5.2 4 22 123 C03 -1.1 PCT 18 4 23 124 C03 -0.88 PCT 21 19 0.5 4 23 124 C06 -0.84 PCT 21 21 0.0 4 24 91 H06 -0.22 PCT 19 4 24 125 C03 0.87 PCT 24 13 2.7 4 24 125 C06 0.75 PCT 18 4 25 62 C11 0.67 PCT 20 16 1.0 4 26 35 C12 -0.92 PCT 17 4 26 123 C04 0.76 PCT 21 17 1.0 4 26 123 C08 -0.93 PCT 19 4 26 123 C03 -0.9 PCT 18 4 27 124 C03 -0.93 PCT 23 21 0.5 4 28 123 C04 -0.87 PCT 20 13 1.7 4 30 5 C05 -0.78 PCT 18 4 31 124 C03 -0.93 PCT 20 19 0.2 4 32 5 C02 0.76 PCT 17 4 32 7 C02 0.82 PCT 20 0 4.9 4 32 7 C03 0.73 PCT 18 4 33 8 C03 0.94 PCT 18 4 35 122 C03 0.97 PCT 20 17 0.7 4 43 8 C04 0.98 PCT 19 4 44 9 C06 -0.7 PCT 18 4 44 121 C03 1 PCT 22 16 1.5 4 45 8 C03 -0.82 PCT 18 4 49 110 C12 -0.48 PCT 18 4 50 87 H01 -1.22 PCT 19 4 53 118 C02 -0.87 PCT 21 19 0.5 4 60 115 C07 0.9 PCT 18 4 63 114 C06 -1.11 PCT 21 22 -0.2 4 65 112 C05 -0.84 PCT 19 4 71 108 C06 0.73 PCT 16 4 77 104 C03 0.71 PCT 26 16 2.5 4 78 103 C03 0.8 PCT 18 4 83 98 C03 0.71 PCT 18 4 83 98 C04 -0.9 PCT 16 4 83 100 C03 0.72 PCT 20 0 4.9 4 84 97 C04 -0.94 PCT 20 18 0.5 4 84 97 C03 0.74 PCT 19 4 84 101 C04 -0.94 PCT 22 16 1.5 4 84 101 C03 0.71 PCT 21 16 1.2 4 84 101 C02 0.68 PCT 20 12 2.0 4 84 101 C06 -0.91 PCT 18 4 85 28 C03 -0.86 PCT 22 0 5.4 4 85 94 C03 -0.84 PCT 20 15 1.2 4 85 96 C04 -0.95 PCT 18 4 85 100 C04 -0.86 PCT 20 15 1.2 4 87 92 C04 0.78 PCT 19 4 87 96 C03 -0.89 PCT 24 16 2.0 4 87 96 C05 -0.72 PCT 19 4 87 98 C04 -0.89 PCT 20 18 0.5 4 88 31 C03 -0.95 PCT 22 13 2.2 4 88 95 C03 -0.75 PCT 17 4 89 94 C05 0.66 PCT 17 4 89 96 C03 -0.89 PCT 23 17 1.5 4 89 96 C05 0.71 PCT 18 SG-SGMP-17-9 November 2019 Revision 1 Page 39 of 55

• • • This record was final approved on 11/21/2019 10:34:58 AM. (This statement was added by the PRIME system upon its validation)

Per 20171 Per 20121 Delta SG Row Col Locn Inch1 Ind

(%TW) (%TW) (%TW/EFPY) 4 90 35 C03 -1.18 PCT 19 0 4.7 4 90 39 C04 0.88 PCT 17 4 90 91 C04 -0.92 PCT 18 4 91 34 C03 -0.89 PCT 24 17 1.7 4 91 34 C05 0.74 PCT 20 0 4.9 4 91 36 C04 0.71 PCT 22 14 2.0 4 91 36 C03 -1.2 PCT 21 11 2.5 4 91 38 C03 -0.92 PCT 22 0 5.4 4 91 92 C04 -0.8 PCT 20 16 1.0 4 91 94 C03 0.71 PCT 23 19 1.0 4 92 37 C03 -0.86 PCT 25 14 2.7 4 92 91 C03 0.65 PCT 17 4 92 93 C03 0.74 PCT 20 0 4.9 4 93 36 C03 -0.74 PCT 22 13 2.2 4 93 36 C05 0.68 PCT 21 19 0.5 4 94 37 C03 -1.17 PCT 34 16 4.4 4 94 39 C03 -0.86 PCT 22 10 2.9 4 94 39 C07 -0.92 PCT 18 11 1.7 4 94 41 C03 -0.92 PCT 23 15 2.0 4 95 40 C05 0.71 PCT 19 0 4.7 4 95 40 C06 -1.03 PCT 18 17 0.2 4 95 42 C03 -0.83 PCT 26 17 2.2 4 95 86 C03 0.68 PCT 24 16 2.0 4 96 41 C03 0.71 PCT 22 0 5.4 4 96 41 C05 -0.98 PCT 19 17 0.5 4 96 43 C03 -0.95 PCT 19 4 96 45 C03 -0.92 PCT 21 16 1.2 4 96 81 C03 0.92 PCT 18 4 97 42 C05 -0.97 PCT 22 17 1.2 4 97 78 C03 0.81 PCT 21 0 5.2 4 97 86 C03 0.74 PCT 25 19 1.5 4 97 88 C03 0.8 PCT 21 17 1.0 4 97 88 C03 -0.74 PCT 18 17 0.2 4 97 88 C07 -0.86 PCT 18 4 98 43 C07 0.77 PCT 19 14 1.2 4 98 43 C03 -0.95 PCT 18 0 4.4 4 98 45 C03 -0.94 PCT 30 17 3.2 4 98 81 C03 0.59 PCT 18 4 98 85 C03 0.71 PCT 23 16 1.7 4 99 44 C03 0.88 PCT 19 0 4.7 4 99 44 C06 0.79 PCT 17 0 4.2 4 99 44 C08 0.71 PCT 17 0 4.2 4 99 46 C03 -0.89 PCT 22 17 1.2 4 100 81 C03 0.7 PCT 18 4 100 83 C03 -0.86 PCT 21 0 5.2 4 100 83 C07 -1.17 PCT 18 4 101 80 C03 0.7 PCT 20 0 4.9 4 102 49 C03 0.8 PCT 21 0 5.2 4 102 51 C04 0.78 PCT 19 4 102 79 C03 0.73 PCT 19 4 103 76 C03 0.67 PCT 21 16 1.2 4 104 71 C03 -0.9 PCT 23 18 1.2 Note 1: Determined either from production data results or lead analyst review of raw eddy current data history.

SG-SGMP-17-9 November 2019 Revision 1 Page 40 of 55

• • • This record was final approved on 11/21/2019 10:34:58 AM. (This statement was added by the PRIME system upon its validation)

Figure A4-9: Watts Bar U1R14 Horizontal ATSG Wear Indications Map - SG1 100 Cold Leg Hot Leg Plugs 80 60 Tube Row 40 20 0

0 20 40 60 80 100 120 Tube Column SG-SGMP-17-9 November 2019 Revision 1 Page 41 of 55

• • • This record was final approved on 11/21/2019 10:34:58 AM. (This statement was added by the PRIME system upon its validation)

Figure A4-10: Watts Bar U1R14 Horizontal ATSG Wear Indications Map - SG2 100 Cold Leg Hot Leg Plugs 80 60 Tube Row 40 20 0

0 20 40 60 80 100 120 Tube Column SG-SGMP-17-9 November 2019 Revision 1 Page 42 of 55

• • • This record was final approved on 11/21/2019 10:34:58 AM. (This statement was added by the PRIME system upon its validation)

Figure A4-11: Watts Bar U1R14 Horizontal ATSG Wear Indications Map - SG3 100 Cold Leg Hot Leg Plugs 80 60 Tube Row 40 20 0

0 20 40 60 80 100 120 Tube Column SG-SGMP-17-9 November 2019 Revision 1 Page 43 of 55

• • • This record was final approved on 11/21/2019 10:34:58 AM. (This statement was added by the PRIME system upon its validation)

Figure A4-12: Watts Bar U1R14 Horizontal ATSG Wear Indications Map - SG4 100 Cold Leg Hot Leg Plugs 80 60 Tube Row 40 20 0

0 20 40 60 80 100 120 Tube Column SG-SGMP-17-9 November 2019 Revision 1 Page 44 of 55

• • • This record was final approved on 11/21/2019 10:34:58 AM. (This statement was added by the PRIME system upon its validation)

Figure A4-13: Watts Bar U1R14 Horizontal ATSG Wear Growth Cumulative Frequency Distributions SG 1 WEAR GROWTH RATE DISTRUBTION SG 2 WEAR GROWTH RATE DISTRUBTION 1 1 0.95 0.95 0.9 0.9 0.85 0.85 0.8 0.8 0.75 0.75 CUMULATIVE FREQUENCY DISTRIBUTION (CDF) CUMULATIVE FREQUENCY DISTRIBUTION (CDF) 0.7 0.7 0.65 0.65 0.6 0.6 0.55 0.55 0.5 0.5 0.45 0.45 0.4 0.4 0.35 0.35 0.3 0.3 0.25 0.25 0.2 0.2 0.15 0.15 0.1 0.1 0.05 0.05 0 0 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 GROWTH (%TW/EFPY) GROWTH (%TW/EFPY)

SG 3 WEAR GROWTH RATE DISTRUBTION SG 4 WEAR GROWTH RATE DISTRUBTION 1 1 0.95 0.95 0.9 0.9 0.85 0.85 0.8 0.8 0.75 0.75 CUMULATIVE FREQUENCY DISTRIBUTION (CDF) CUMULATIVE FREQUENCY DISTRIBUTION (CDF) 0.7 0.7 0.65 0.65 0.6 0.6 0.55 0.55 0.5 0.5 0.45 0.45 0.4 0.4 0.35 0.35 0.3 0.3 0.25 0.25 0.2 0.2 0.15 0.15 0.1 0.1 0.05 0.05 0 0 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 GROWTH (%TW/EFPY) GROWTH (%TW/EFPY)

SG-SGMP-17-9 November 2019 Revision 1 Page 45 of 55

• • • This record was final approved on 11/21/2019 10:34:58 AM. (This statement was added by the PRIME system upon its validation)

Figure A4-14: Watts Bar U1R14 Horizontal ATSG Wear Indication Growth Rates Map - All SGs Note: The plotted locations include both HL and CL wear indications in all four (4) RSGs and only those indications where a history review was performed are shown. The largest growth rate is indicated for tube locations with indications in multiple RSGs. Refer to the listing in Table A4-1 through Table A4-4 SG-SGMP-17-9 November 2019 Revision 1 Page 46 of 55

• • • This record was final approved on 11/21/2019 10:34:58 AM. (This statement was added by the PRIME system upon its validation)

Figure A4-15: Watts Bar U1R14 Horizontal ATSG Wear - Monte Carlo Simulation Figure A4-16: Watts Bar U1R14 Horizontal ATSG Wear Indication - SG2 R88C95 C03 Array Graphic 2017 SG-SGMP-17-9 November 2019 Revision 1 Page 47 of 55

• • • This record was final approved on 11/21/2019 10:34:58 AM. (This statement was added by the PRIME system upon its validation)

Attachment 5 - Watts Bar U1R14 Tube Proximity Indications Table A5-1: Watts Bar U1R14 Tube Proximity Indications (PRX) - All SGs SG Row Col Volts Deg Ind Chn Locn Inch1 Inch2 PDia PType Cal 1 80 101 0.49 86 PRX P52 DS1 4 41.66 0.61 ZYAXH 3 1 95 62 0.44 87 PRX P52 DS1 16.74 57.29 0.61 ZYAXH 25 1 95 62 0.66 103 PRX P52 DS3 4.43 33.05 0.61 ZYAXH 28 1 94 85 0.42 77 PRX P52 DS4 6.01 58.15 0.61 ZYAXH 24 1 92 85 0.49 263 PRX P52 DS4 7.08 58.84 0.61 ZYAXH 22 1 96 75 0.48 262 PRX P52 VS5 2.25 28.68 0.61 ZYAXH 28 2 101 64 0.77 110 PRX P52 DS1 18.52 59.45 0.61 ZYAXH 37 2 99 64 0.55 239 PRX P52 DS1 16.71 60.5 0.61 ZYAXH 37 2 103 74 0.48 92 PRX P52 DS3 0.34 17.56 0.61 ZYAXH 50 2 103 64 0.27 0 PRX P52 DS4 8.03 60.25 0.61 ZYAXH 64 2 97 50 0.72 97 PRX P52 DS4 2.13 22.13 0.61 ZYAXH 22 2 103 72 0.89 267 PRX P52 VS2 2.69 25.11 0.61 ZYAXH 33 3 81 100 0.68 109 PRX P52 DS1 5.85 41.43 0.61 ZYAXH 25 3 97 68 0.43 86 PRX P52 DS1 3.71 - 0.61 ZYAXH 65 3 99 60 0.73 110 PRX P52 DS2 2.11 33.43 0.61 ZYAXH 9 3 97 60 0.55 104 PRX P52 DS2 2.87 32.75 0.61 ZYAXH 9 3 93 46 0.41 328 PRX P52 DS4 2.32 23.5 0.61 ZYAXH 28 3 77 38 0.33 236 PRX P52 DS4 2.77 43.13 0.61 ZYAXH 28 3 101 68 0.44 101 PRX P52 VS2 4.41 - 0.61 ZYAXH 65 3 103 58 0.63 90 PRX P52 VS4 4.33 22.88 0.61 ZYAXH 64 4 95 86 0.95 355 PRX P52 DS1 7.94 56.39 0.61 ZYAXH 1 4 96 67 0.69 85 PRX P52 DS1 24.71 57.81 0.61 ZYAXH 49 4 94 65 0.8 94 PRX P52 DS1 6.27 53.61 0.61 ZYAXH 51 4 96 51 0.68 104 PRX P52 DS1 24.5 56.57 0.61 ZYAXH 23 4 91 90 0.42 122 PRX P52 DS4 5.93 50.6 0.61 ZYAXH 16 4 87 56 0.61 266 PRX P52 DS4 1.8 24.07 0.61 ZYAXH 30 4 99 52 0.36 115 PRX P52 DS4 4.64 39.15 0.61 ZYAXH 12 4 92 45 0.59 79 PRX P52 DS4 3.02 24.12 0.61 ZYAXH 10 SG-SGMP-17-9 November 2019 Revision 1 Page 48 of 55

• • • This record was final approved on 11/21/2019 10:34:58 AM. (This statement was added by the PRIME system upon its validation)

Figure A5-2: Watts Bar U1R14 Tube Proximity Indications in All SGs 100 SG1 PRX SG2 PRX SG3 PRX SG4 PRX 80 60 Tube Row 40 20 0

0 20 40 60 80 100 120 Tube Column SG-SGMP-17-9 November 2019 Revision 1 Page 49 of 55

• • • This record was final approved on 11/21/2019 10:34:58 AM. (This statement was added by the PRIME system upon its validation)

Attachment 6 - Watts Bar U1R14 MAPOD and Fully Probabilistic Operational Assessment Graphics Figure A6-5: Watts Bar U1R14 U-bend Support and Horizontal ATSG Noise Distributions SG-SGMP-17-9 November 2019 Revision 1 Page 50 of 55

• • • This record was final approved on 11/21/2019 10:34:58 AM. (This statement was added by the PRIME system upon its validation)

Figure A6-6: Watts Bar U1R14 U-bend Support and Horizontal ATSG Noise Distributions Diagonal Bar Noise Distribution Vertical Strap Noise Distribution Horizontal ATSG Noise Distribution SG-SGMP-17-9 November 2019 Revision 1 Page 51 of 55

• • • This record was final approved on 11/21/2019 10:34:58 AM. (This statement was added by the PRIME system upon its validation)

Figure A6-7: Watts Bar U1R14 U-bend Support and ATSG MAPOD Curves Diagonal Bar Wear POD Vertical Strap Wear POD Horizontal ATSG Wear POD SG-SGMP-17-9 November 2019 Revision 1 Page 52 of 55

• • • This record was final approved on 11/21/2019 10:34:58 AM. (This statement was added by the PRIME system upon its validation)

Figure A6-8: Watts Bar U1R14 U-bend Support and ATSG FBM Software Outputs U-bend Support Structure Wear - 4.5 EFPY Horizontal ATSG Wear - 4.5 EFPY SG-SGMP-17-9 November 2019 Revision 1 Page 53 of 55

• • • This record was final approved on 11/21/2019 10:34:58 AM. (This statement was added by the PRIME system upon its validation)

Figure A6-9: Watts Bar U1R14 U-bend Support and ATSG FBM Software Outputs (Continued)

U-bend Support Structure Wear - 4.74 EFPY Horizontal ATSG Wear - 4.74 EFPY SG-SGMP-17-9 November 2019 Revision 1 Page 54 of 55

• • • This record was final approved on 11/21/2019 10:34:58 AM. (This statement was added by the PRIME system upon its validation)

Attachment 7 - Watts Bar U1R14 Support Structure NDE Sizing Methods A change was made to the NDE process for sizing wear indications at Watts Bar leading up to the U1R14 inspection. Indications of support structure wear were sized using the bobbin coil which was calibrated to the flat wear eddy current standard through the U1R11 and U1R8 inspections. However, TVA elected to move to the combination bobbin and Array coil probe for the U1R14 inspection. The combination probe requires the use of different inline calibration standards specific to the Array coil which do not include the eddy current wear flaws used to size support structure wear indications at previous inspections.

Instead, a pre-determined voltage versus depth curve was generated in advance of the inspection in order to allow for sizing of volumetric wear with bobbin and still support use of the Array probe. This canned curve was created based on the tapered wear flaws of the EPRI 27091 series of ETSSs. Data was collected at EPRI on the actual tapered wear standards that makeup the ETSS. These standards are of the same tube material and size as the Watts Bar Unit 1 RSGs. Further, the same data collection process used to capture the data in the EPRI standards was used during the U1R14 inspection. Figure A7-1 shows the voltage versus depth sizing curve used during U1R14 plotted against data points from the P2 mix channel during U1R11 and U1R8. Use of this sizing method is considered supplementary to the application of the condition monitoring limits associated with ETSS 96004.1.

Reviewing the two sizing methods, it becomes apparent that adjustment is necessary when comparing historical wear indications against those from the U1R14 inspection in developing growth rates. This is particularly relevant for historical indications in the range of approximately 0.2 to 0.55 volts where the wide majority of the wear indications reside. Variation in this range is on the order of about 10%TW or less. This adjustment has been made in the process of determining degradation growth rates throughout this operational assessment. TVA currently plans to continue the use of the canned curve for sizing of wear degradation in future outages such that wear depth measurements can be compared directly.

However, if any further changes are made to the degradation sizing process then similar considerations in degradation growth rate development may become necessary.

Figure A7-2: Watts Bar U1R14 Support Structure Wear Sizing Method Comparisons 33 32 31 30 29 28 27 26 25 24 23 22 21 20

% Throughwall Depth 19 18 17 16 15 14 13 U1R14 Canned Curve 12 11 U1R11 Wear Standard 10 U1R8 Wear Standard 9

8 7

6 5

4 3

2 1

0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 Bobbin Voltage SG-SGMP-17-9 November 2019 Revision 1 Page 55 of 55

• • • This record was final approved on 11/21/2019 10:34:58 AM. (This statement was added by the PRIME system upon its validation)

Enclosure 2 Revised TS Changes (Mark-Ups) for WBN Unit 1 CNL-20-078

Procedures, Programs, and Manuals 5.7 non-faulted steam generators. For design basis accidents that do not have a faulted steam generator, accident induced leakage is not to exceed 150 gpd per steam generator.

5.7 Procedures, Programs, and Manuals5.7 Procedures, Programs, and Manuals 5.7.2.12 Steam Generator (SG) Program (continued)

3. The operational leakage performance criterion is specified in LCO 3.4.13, RCS Operational LEAKAGE.

c. Provisions for SG tube pluggingrepair criteria. Tubes found by inservice inspection to contain flaws with a depth equal to or exceeding 40% of the nominal tube wall thickness shall be plugged.

d. Provisions for SG tube inspections. Periodic SG tube inspections shall be performed. The number and portions of the tubes inspected and methods of inspection shall be performed with the objective of detecting flaws of any type (e.g., volumetric flaws, axial and circumferential cracks) that may be present along the length of the tube, from the tube-to-tubesheet weld at the tube inlet to the tube-to-tubesheet weld at the tube outlet, and that may satisfy the applicable tube pluggingrepair criteria. The tube-to-tubesheet weld is not part of the tube.

In addition to meeting the requirements of d.1, d.2, and d.3 below, the inspection scope, inspection methods, and inspection intervals shall be such as to ensure that SG tube integrity is maintained until the next SG inspection. An assessment of degradation assessment shall be performed to determine the type and location of flaws to which the tubes may be susceptible and, based on this assessment, to determine which inspection methods need to be employed and at what locations.

1. Inspect 100% of the tubes in each SG during the first refueling outage following SG replacemeninstallationt.

2. After the first refueling outage following SG installation, inspect each SG at least every 96 effective full power months. Tube inspections shall be performed using equivalent to or better than array probe technology.

For regions where a tube inspection with array probe technology is not possible (such as due to dimensional constraints or tube specific conditions), the tube inspection techniques applied shall be capable of detecting all forms of existing and potential degradation in that region.

In addition, the minimum number of tubes inspected at each scheduled inspection shall be the number of tubes in all SGs divided by the number of SG inspection outages scheduled in each inspection period as defined in a and b below. If a degradation assessment indicates the potential for a type of degradation to occur at a location not previously inspected with a technique capable of detecting this type of degradation at this location and that may satisfy the applicable tube repair criteria, (continued)

Watts Bar-Unit 1 5.0-16 Amendment 27, 38, 44, 65, XXXAmendment 99

Procedures, Programs, and Manuals 5.7 the minimum number of locations inspected with such a capable inspection technique during the remainder of the inspection period may be prorated. The fraction of locations to be inspected for this potential type of degradation at this location at the end of the inspection period shall be no less than the ratio of the number of times the SG is scheduled to be inspected in the inspection period after the determination that a new form of degradation could potentially be occurring at this location divided by the total number of times the SG is (continued)

Watts Bar-Unit 1 5.0-17 Amendment 27, 38, 44, 65, XXXAmendment 99

Procedures, Programs, and Manuals 5.7 5.7 Procedures, Programs, and Manuals 5.7.2.12 Steam Generator (SG) Program (continued) scheduled to be inspected in the inspection period. Each inspection period defined below may be extended up to 3 effective full power months to include a SG inspection outage in an inspection period and the subsequent inspection period begins at the conclusion of the included SG inspection outage.

a) After the first refueling outage following SG installation, inspect 100% of the tubes during the next 144 effective full power months.

This constitutes the first inspection period.

b) During the next 96 effective full power months, inspect 100% of the tubes. This constitutes the second and subsequent inspection periods.Inspect 100% of the tubes at sequential periods of 144, 108, 72, and thereafter, 60 effective full power months. The first sequential period shall be considered to begin after the first inservice inspection of the SGs. In addition, inspect 50% of the tubes by the refueling outage nearest the midpoint of the period and the remaining 50% by the refueling outage nearest the end of the period. No SGs shall operate for more than 72 effective full power months or three refueling outages (whichever is less) without being inspected.

3. If crack indications are found in any SG tube, then the next inspection for each affected and potentially affected SG for the degradation mechanism that caused the crack indication shall not exceed 24 effective full power months or one refueling outage (whichever results in more frequent inspectionsis less). If definitive information, such as from examination of a pulled tube, diagnostic non-destructive testing, or engineering evaluation indicates that a crack-like indication is not associated with a crack(s), then the indication need not be treated as a crack.

e. Provisions for monitoring operational primary-to-secondary LEAKAGE.

(continued)

Watts Bar-Unit 1 5.0-16a Amendment 27, 38, 44, 65, XXXAmendment 99

Enclosure 3 Revised TS Changes (Final Typed) for WBN Unit 1 CNL-20-078

Procedures, Programs, and Manuals 5.7 5.7 Procedures, Programs, and Manuals 5.7.2.12 Steam Generator (SG) Program (continued)

3. The operational leakage performance criterion is specified in LCO 3.4.13, RCS Operational LEAKAGE.

c. Provisions for SG tube plugging criteria. Tubes found by inservice inspection to contain flaws with a depth equal to or exceeding 40% of the nominal tube wall thickness shall be plugged.

d. Provisions for SG tube inspections. Periodic SG tube inspections shall be performed. The number and portions of the tubes inspected and methods of inspection shall be performed with the objective of detecting flaws of any type (e.g., volumetric flaws, axial and circumferential cracks) that may be present along the length of the tube, from the tube-to-tubesheet weld at the tube inlet to the tube-to-tubesheet weld at the tube outlet, and that may satisfy the applicable tube plugging criteria. The tube-to-tubesheet weld is not part of the tube. In addition to meeting the requirements of d.1, d.2, and d.3 below, the inspection scope, inspection methods, and inspection intervals shall be such as to ensure that SG tube integrity is maintained until the next SG inspection. A degradation assessment shall be performed to determine the type and location of flaws to which the tubes may be susceptible and, based on this assessment, to determine which inspection methods need to be employed and at what locations.

1. Inspect 100% of the tubes in each SG during the first refueling outage following SG installation.

2. After the first refueling outage following SG installation, inspect each SG at least every 96 effective full power months. Tube inspections shall be performed using equivalent to or better than array probe technology. For regions where a tube inspection with array probe technology is not possible (such as due to dimensional constraints or tube specific conditions), the tube inspection techniques applied shall be capable of detecting all forms of existing and potential degradation in that region. In addition, the minimum number of tubes inspected at each scheduled inspection shall be the number of tubes in all SGs divided by the number of SG inspection outages scheduled in each inspection period as defined in a and b below. If a degradation assessment indicates the potential for a type of degradation to occur at a location not previously inspected with a technique capable of detecting this type of degradation at this location and that may satisfy the applicable tube repair criteria, the minimum number of locations inspected with such a capable inspection technique during the remainder of the inspection period may be prorated. The fraction of locations to be inspected for this potential type of degradation at this location at the end of the inspection period shall be no less than the ratio of the number of times the SG is scheduled to be inspected in the inspection period after the determination that a new form of degradation could potentially be occurring at this location divided by the (continued)

Watts Bar-Unit 1 5.0-16 Amendment 27, 38, 44, 65, XXX

Procedures, Programs, and Manuals 5.7 5.7 Procedures, Programs, and Manuals 5.7.2.12 Steam Generator (SG) Program (continued) total number of times the SG is scheduled to be inspected in the inspection period. Each inspection period defined below may be extended up to 3 effective full power months to include a SG inspection outage in an inspection period and the subsequent inspection period begins at the conclusion of the included SG inspection outage.

a) After the first refueling outage following SG installation, inspect 100% of the tubes during the next 144 effective full power months.

This constitutes the first inspection period.

b) During the next 96 effective full power months, inspect 100% of the tubes. This constitutes the second and subsequent inspection periods.

3. If crack indications are found in any SG tube, then the next inspection for each affected and potentially affected SG for the degradation mechanism that caused the crack indication shall not exceed 24 effective full power months or one refueling outage (whichever results in more frequent inspections). If definitive information, such as from examination of a pulled tube, diagnostic non-destructive testing, or engineering evaluation indicates that a crack-like indication is not associated with a crack(s), then the indication need not be treated as a crack.

e. Provisions for monitoring operational primary-to-secondary LEAKAGE.

(continued)

Watts Bar-Unit 1 5.0-16a Amendment 27, 38, 44, 65, XXX