Text

Response to Request for Additional Information Regarding Application to Revise Watts Bar Nuclear Plant (Wbn), Unit 1 Technical Specifications for Steam Generator Tube Inspection Frequency and to Adopt TSTF-510, .
	ML21091A151
Person / Time
Site:	Watts Bar
Issue date:	03/30/2021
From:	Polickoski J; Tennessee Valley Authority
To:	; Document Control Desk, Office of Nuclear Reactor Regulation
Shared Package
ML21091A150	List: CNL-21-021, Response to Request for Additional Information Regarding Application to Revise Watts Bar Nuclear Plant (Wbn), Unit 1 Technical Specifications for Steam Generator Tube Inspection Frequency and to Adopt TSTF-510, .;
References
	CNL-21-021, EPID L-2020-LLA-0161, TSTF-510, WBN-390-TS-20-012
	Download: ML21091A151 (94)
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Proprietary Information Withhold Under 10 CFR § 2.390 This letter is decontrolled when separated from Enclosure 2 1101 Market Street, Chattanooga, Tennessee 37402 CNL-21-021 March 30, 2021 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:

Response to Request for Additional Information Regarding 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-20-078, 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 Sample Selection, (WBN-390-TS-20-012) (EPID L 2020-LLA-0161), dated October 13, 2020 (ML20287A569)

3. NRC Electronic Mail to TVA, Request for Additional Information Regarding TVA's Request to Revise the Watts Bar Nuclear Plant, Unit 1 Technical Specifications Related to Steam Generator Tube Inspection Frequency (EPID L-2020-LLA-0161), dated February 8, 2021 (ML21039A640)

4. NRC Electronic Mail to TVA, RE: Request for Additional Information Regarding TVA's Request to Revise the Watts Bar Nuclear Plant, Unit 1 Technical Specifications Related to Steam Generator Tube Inspection Frequency (EPID L-2020-LLA-0161), dated March 11, 2021 Proprietary Information Withhold Under 10 CFR § 2.390 This letter is decontrolled when separated from Enclosure 2

Proprietary Information Withhold Under 10 CFR § 2.390 This letter is decontrolled when separated from Enclosure 2 U.S. Nuclear Regulatory Commission CNL-21-021 Page 2 March 30, 2021 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 Specification (TS) 3.4.17, "Steam Generator (SG) Tube Integrity," TS 5.7.2.12, Steam Generator (SG) Program, and 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 and to incorporate Technical Specifications Task Force (TSTF) Technical Change Traveler 510, Revision 2, Revision to Steam Generator Program Inspection Frequencies and Tube Sample Selection. In Reference 2, TVA submitted a supplement to the LAR to provide the Nuclear Regulatory Commission (NRC) a copy of Westinghouse Electric Company LLC (Westinghouse) Document, SG-SGMP-17-9, Revision 1, "Watts Bar U1R14 Steam Generator Condition Monitoring and Operational Assessment," to assist the NRC in their review of Reference 1.

In Reference 3, the NRC issued a request for additional information (RAI) and requested TVA respond by March 19, 2021. As noted in Reference 4, the due date for this RAI response was extended to March 31, 2021. Enclosure 1 to this letter provides the TVA response to RAIs 1, 3, 4a, and 6b. Enclosure 2 to this letter contains Westinghouse Letter Report, LTR-CDMP-21-20 P-Attachment Revision 0, which provides the response to RAIs 2, 4, 5, and 6a. contains information that Westinghouse considers to be proprietary in nature pursuant to 10 CFR 2.390, "Public inspections, exemptions, requests for withholding,"

paragraph (a)(4). Enclosure 3 contains a non-proprietary version of Enclosure 2. Enclosure 4 provides the Westinghouse Application for Withholding Proprietary Information from Public Disclosure CAW-21-5163 affidavit supporting this proprietary withholding request. The affidavit sets forth the basis on which the information may be withheld from public disclosure by the NRC and addresses with specificity the considerations listed in paragraph (b)(4) of Section 2.390.

Accordingly, TVA requests that the information, which is proprietary to Westinghouse, be withheld from public disclosure in accordance with 10 CFR Section 2.390. Correspondence with respect to the copyright or proprietary aspects of the items listed above or the supporting Westinghouse affidavit should reference CAW-21-5163 and should be addressed to Zachary S. Harper, Manager, Licensing Engineering, Westinghouse Electric Company, 1000 Westinghouse Drive, Suite 165, Cranberry Township, Pennsylvania 16066.

In response to NRC RAI 1 of Enclosure 1, Enclosure 5 to this letter contains a revised mark-up to the proposed change to WBN Unit 1 TS 5.7.2.12.d.2 and Enclosure 6 to this submittal contains the retyped WBN Unit 1 TS 5.7.2.12.d.2 to show the proposed change. For completeness purposes, Enclosures 5 and 6 also contain the proposed changes to WBN Unit 1 TS 3.4.17 and TS 5.9.9 that was provided in Reference 1. Enclosures 5 and 6 supersede, in their entirety, the proposed TS changes provided in References 1 and 2. In response to RAIs 2 and 6a of Enclosure 2, Enclosure 7 to this letter contains Revision 2 to Westinghouse Proprietary Information Withhold Under 10 CFR § 2.390 This letter is decontrolled when separated from Enclosure 2

Proprietary Information Withhold Under 10 CFR § 2.390 This letter is decontrolled when separated from Enclosure 2 U.S. Nuclear Regulatory Commission CNL-21-021 Page 3 March 30, 2021 Document, SG-SGMP-17-9. The errors identified in RAI 1, 2, and 6 have been entered into the TVA corrective action program.

This letter does not change the no significant hazard considerations or 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. Please address any questions regarding this request to Kimberly D. Hulvey, Senior Manager, Fleet Licensing, at (423) 751-3275.

I declare under penalty of perjury that the foregoing is true and correct. Executed on this 30th day of March 2021.

Respectfully, James T. Polickoski Director, Nuclear Regulatory Affairs

Enclosures:

1. Response to NRC Request for Additional Information

2. Westinghouse Letter Report, LTR-CDMP-21-20 P-Attachment, Revision 0 (Proprietary)

3. Westinghouse Letter Report, LTR-CDMP-21-20 NP-Attachment, Revision 0 (Non-Proprietary)

4. Westinghouse Electric Company LLC Application for Withholding Proprietary Information from Public Disclosure (Affidavit CAW-21-5163)

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

6. Revised TS Changes (Final Typed) for WBN Unit 1

7. Westinghouse Document, SG-SGMP-17-9, Revision 2 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 Proprietary Information Withhold Under 10 CFR § 2.390 This letter is decontrolled when separated from Enclosure 2

Enclosure 1 Response to NRC Request for Additional Information INTRODUCTION By letter dated July 17, 2020 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML20199M346), as supplemented by letter dated October 13, 2020 (ADAMS Accession No. ML20287A569), Tennessee Valley Authority (TVA, the licensee) requested changes to the Technical Specifications (TSs) for Watts Bar Nuclear Plant (Watts Bar), Unit 1. The proposed changes would revise the steam generator (SG) tube inspection frequency requirements in TS 5.7.2.12, Steam Generator (SG) Program, and TS 5.9.9, Steam Generator Tube Inspection Report. The proposed changes include the adoption of Technical Specifications Task Force (TSTF) Technical Change Traveler 510 (TSTF-510), Revision 2, Revision to Steam Generator Program Inspection Frequencies and Tube Sample Selection.

REGULATORY BASIS Section 50.36, Technical specifications," of Title 10 of the Code of Federal Regulations (10 CFR), establishes the regulatory requirements related to the content of the TSs. The TSs for all current pressurized-water reactor licenses require that an SG Program be established and implemented to ensure that SG tube integrity is maintained. Fundamental regulatory requirements with respect to the integrity of the SG tubing are established in 10 CFR Part 50.

Specifically, the general design criteria (GDC) in Appendix A to 10 CFR Part 50 establish minimum requirements for the principal design criteria for nuclear power plants and state that the reactor coolant pressure boundary shall have an extremely low probability of abnormal leakage, of rapidly propagating failure, and of gross rupture (GDC 14); shall be designed with sufficient margin (GDCs 15 and 31); shall be of the highest quality standards practical (GDC 30); and, shall be designed to permit (1) periodic inspection and testingto assess their structural and leak tight integrity (GDC 32). Section 3.1.2 of the Watts Bar UFSAR addresses conformance with the GDC in Appendix A to 10 CFR Part 50 (ADAMS Accession No. ML19176A129).

INFORMATION REQUESTED In order to complete its evaluation of whether the proposed TS changes meet the SG Program requirements described above, the U.S. Nuclear Regulatory Commission staff requests the following information.

1. Provide a correction or justification for the one instance of repair criteria in the proposed changes to 5.7.2.12.d.2. To conform to TSTF-510, as corrected by NRC letter to the TSTF dated June 17, 2013 (ADAMS Accession No. ML13120A541), repair criteria in this instance should be replaced with plugging criteria.

Response

Enclosures 5 and 6 to this submittal contain a correction to WBN Unit 1 TS 5.7.2.12.d.2 to replace the one instance of repair criteria with plugging criteria in accordance with the correction to TSTF-510-A, Revision 2 (ML13120A541).

CNL-21-021 E1-1 of 4

Enclosure 1

2. On page 11 of Enclosure 1 to the LAR supplement, the third full paragraph in Section 3.1.2, Mechanical Wear at Horizontal [Advanced Tube Support Grid] ATSGs, contains a sentence about U-bend wear. This sentence appears to be in the wrong section of the report. Confirm the actual operating interval between inspections and the worst-case projected support structure wear indications.

Response

Enclosures 2 and 3 contain the response to this RAI.

3. In Enclosure 1 of the LAR, Section 3.2.7, Discussion of Growth Rates, OA Methods, Projections, and Results, contains a statement that, the observed behavior of ATSG wear growth rates are considered encompassing of that for tube wear occurring at U-bend supports. Clarify the meaning of this statement, considering that the paragraph that follows identifies higher wear growth rates at U-bend supports than at ATSG locations.

Response

The ATSG wear growth rates are considered encompassing of those for U-bend locations based on a comparison of the number and percent through-wall (%TW) depths of indications detected combined with the relative similarities in degradation growth rates. The 95th percentile growth rate is 0.3%TW/effective full power year (EFPY) higher for indications through the U-bend. There were 419 indications of ATSG wear detected with a maximum depth of 37%TW returned to service compared to 59 indications of U-bend support wear detected with a maximum depth of 27%TW. Both forms of degradation are detected and measured with the same bobbin Examination Technique Specification Sheet (ETSS) technique 96004.1 and the associated measurement uncertainties are the same. The projected operating duration between SG eddy current inspections is also the same. The wear growth rate was only slightly higher for U-bend wear; however, the data set with the larger number of indications and maximum %TW depth was ATSG wear. Therefore, on a deterministic operational assessment basis, the degradation growth rates for ATSG wear indications are limiting.

4. Attachment 7 to Enclosure 1 of the LAR supplement describes the process for comparing eddy current wear indications that were sized with the bobbin probe during different inspections. The comparison is complicated by the use of a different probe reference standard in the R14 inspection than in prior inspections. Please provide the following clarifications:

a. Attachment 7 states that adjustment is necessary to compare U1R14 combination bobbin/array probe wear sizing to bobbin probe wear sizing in previous inspections, and that this adjustment is used to develop growth rates.

Describe the adjustment and explain how the adjustment was applied to the tables in Attachments 3 and 4 comparing wear depths from different inspections.

In addition, please clarify whether the wear values for U1R14 in Figure 3 (Enclosure 1) are adjusted in the way described in Attachment 7.

CNL-21-021 E1-2 of 4

Enclosure 1

b. Clarify the meaning of the statement in Attachment 7 that, Use of this sizing method is considered supplementary to the application of the condition monitoring limits associated with ETSS 96004.1. If this was the wear sizing method used in U1R14, and sizing is required to perform condition monitoring, explain why this method is considered supplementary.

Response

Enclosures 2 and 3 contain the response to this RAI. As noted in the Westinghouse response to RAI 4a in Enclosures 2 and 3, Regarding the data in Figure 3 of Enclosure 1 to the License Amendment Request, the U1R14 depths (blue dots) were sized using the method described in of the OA. The U1R11 depths (yellow dots) reflect the original sizing and were not corrected using the canned curve amplitude method from Attachment 7 of the OA. Making the described adjustment to the U1R11 data points in Figure 3 of Enclosure 1 would shift the curve to the right. While a revised Figure 3 of Enclosure 1 to the License Amendment Request (LAR) is not included in this RAI response, if the U1R11 depths (yellow dots) in Figure 3 of to the LAR were corrected using the canned curve amplitude method, they would still be well within the 40%TW plugging limit.

5. Sections 4.1.4 and 4.2.4 of Enclosure 1 of the LAR supplement describe the use of a volume-based wear approach for assessing U-bend support wear and ATSG wear, respectively. The staff requests the following information about the volume-based wear approach.

a. Clarify the description in Section 4.1.4 of how benchmarking was performed for the volumetric wear approach.

b. Explain how the non-matched indications in Figure 4-1 were assigned values of predicted wear (i.e., x-axis values), the basis and meaning of the linear regression of the non-matched indications, and the significance of the upper bound line given that one value is above it.

c. Discuss the statement in Section 4.1.4 that a slope less than unity indicates a conservative condition for application of the benchmarking parameters since it appears this is only true for data points below the red line with a slope of 1.

d. Section 4.2.4 of Enclosure 1 of the LAR supplement states that volumetric wear evaluation for ATSG wear requires two of the flaws to be treated as tapered wear using rotating probe inspection data. The text refers to Figure A4-8 (labeled A4-16 in Attachment 4), which is an array probe terrain plot. Describe how the array probe terrain plots were used to provide the necessary flaw profile information.

e. In the paragraph following Figure 4-1 in Section 4.1.4 of Enclosure 1 of the LAR, clarify the statement that the inputs to the volume-based wear model are measured wear depths from the U1R14 inspection and eddy current look-up depths for these flaws from the U1R8 and UR11 inspections. In addition, if U1R8 depths are used as inputs, explain why growth rates are based only on growth between U1R11 and U1R14.

Response

Enclosures 2 and 3 contain the response to this RAI.

CNL-21-021 E1-3 of 4

Enclosure 1

6. During the review, the NRC staff identified the following apparent discrepancies.

Confirm the correct information.

a. Several figures in Enclosure 1 of the LAR supplement appear to be mis-numbered as identified in the table below.

Table of Contents Text Figure Label Figure A3-1 Figure A3-1 Figure A3-5 Figure A3-2 Figure A3-2 Figure A3-6 Figure A3-3 Figure A3-3 Figure A3-7 Figure A3-4 Figure A3-4 Figure A3-8 Figure A4-1 Figure A4-1 Figure A4-9 Figure A4-2 Figure A4-2 Figure A4-10 Figure A4-3 Figure A4-3 Figure A4-11 Figure A4-4 Figure A4-4 Figure A4-12 Figure A4-5 Figure A4-5 Figure A4-13 Figure A4-6 Figure A4-6 Figure A4-14 Figure A4-7 Figure A4-7 Figure A4-15 Figure A4-8 Figure A4-8 Figure A4-16 Figure A5-1 Not used Figure A5-2 Figure A6-1 Figure A6-1 Figure A6-5 Figure A6-2 Figure A6-2 Figure A6-6 Figure A6-3 Figure A6-3 Figure A6-7 Figure A6-4 Figure A6-4 Figure A6-8 Not Used Not Used Figure A6-9 Figure A7-1 Figure A7-1 Figure A7-2

b. The heading on Page E1-10 of 25 in the LAR identifies the U1R14 outage as occurring in Fall 2016 rather than Spring 2017.

Response

a. Enclosures 2 and 3 contain the response to this RAI.

b. TVA confirms that the heading on Page E1-10 of 25 in the license amendment request should have identified the U1R14 outage as occurring in spring 2017 rather than fall 2016.

CNL-21-021 E1-4 of 4

Proprietary Information Withhold Under 10 CFR § 2.390 Enclosure 2 Westinghouse Letter Report, LTR-CDMP-21-20 P-Attachment, Revision 0 (Proprietary)

CNL-21-021 Proprietary Information Withhold Under 10 CFR § 2.390

Enclosure 3 Westinghouse Letter Report, LTR-CDMP-21-20 NP-Attachment, Revision 0 (Non-Proprietary)

CNL-21-021

Westinghouse Non-Proprietary Class 3

Westinghouse Electric Company LTR-CDMP-21-20 NP-Attachment Revision 0 Responses to NRC Requests for Additional Information on Watts Bar U1R14 Condition Monitoring and Operational Assessment March 2021 Author:

Bradley T. Carpenter*

Component Design and Management Programs Verifier:

Levi Y. Marcus*

Component Design and Management Programs Approved:

Michael E. Bradley*, Manager Component Design & Management Programs

Electronically approved records are authenticated in the Electronic Document Management System.

LTR-CDMP-21-20 NP-Attachment Page 1 of 8

Revision 0

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Westinghouse Non-Proprietary Class 3 Responses to NRC Requests for Additional Information on Watts Bar U1R14 Condition Monitoring and Operational Assessment Information Requested

2. On page 11 of Enclosure 1 to the LAR supplement, the third full paragraph in Section 3.1.2, Mechanical Wear at Horizontal [Advanced Tube Support Grid] ATSGs, contains a sentence about U-bend wear. This sentence appears to be in the wrong section of the report. Confirm the actual operating interval between inspections and the worst-case projected support structure wear indications.

Response

The sentence in Section 3.1.2 Enclosure 1 to the LAR supplement that references U-bend wear is a transcription error in the Condition Monitoring and Operational Assessment (CMOA) that is being corrected in a Revision 2 of the report (SG-SGMP-17-9). Section 3.1.2 is the Condition Monitoring discussion on mechanical wear at horizontal ATSGs. The intent of the statement is to demonstrate that the Operational Assessment (OA) method from U1R11 is conservative in comparison to the inspection results from U1R14. Rather than specifying that the largest projected ATSG wear at U1R14 would have been 42% through-wall (TW) (which was the projection for U-bend wear), the CMOA is being revised to state that the maximum projected ATSG wear at U1R14 would have been 45% TW. A detailed description of the deterministic calculation is being included in the revised CMOA (SG-SGMP-17-9, Revision 2). Enclosure 7 to the RAI response contains the revised CMOA.

4. Attachment 7 to Enclosure 1 of the LAR supplement describes the process for comparing eddy current wear indications that were sized with the bobbin probe during different inspections. The comparison is complicated by the use of a different probe reference standard in the R14 inspection than in prior inspections. Please provide the following clarifications:

a. Attachment 7 states that adjustment is necessary to compare U1R14 combination bobbin/array probe wear sizing to bobbin probe wear sizing in previous inspections, and that this adjustment is used to develop growth rates. Describe the adjustment and explain how the adjustment was applied to the tables in Attachments 3 and 4 comparing wear depths from different inspections. In addition, please clarify whether the wear values for U1R14 in Figure 3 (Enclosure 1) are adjusted in the way described in Attachment 7.

Response

For the U1R8 and U1R11 inspections, tube wear at horizontal ATSG intersections was detected and sized using the bobbin probe and applying Examination Technique Specification Sheet (ETSS) technique 96004.1. For the U1R14 inspection, the combination bobbin and array probe was used for detection and sizing of indications of this type of degradation. As described in the Attachment 7 to the OA, U1R14 ATSG sizing was performed using a canned curve based on measured amplitude from the bobbin probe. The curve is shown in Figure A7-1 of the revised OA. The LTR-CDMP-21-20 NP-Attachment Page 2 of 8 Revision 0

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Westinghouse Non-Proprietary Class 3 primary reason for including this information in the OA is to provide insights into how growth rates from U1R11 to U1R14 were calculated. Because the sizing method was different between the two inspections, the U1R11 flaw depths needed to be re-sized using the U1R11 bobbin voltages and the canned curve to provide a direct comparison between the measurements from successive inspections.

The tables in Attachments 3 and 4 of the OA provide the sizing history for U-bend wear and horizontal ATSG wear flaws, respectively, at Watts Bar Unit 1. The flaw depths in the 2017 column (U1R14) were determined from the signal amplitude and the canned curve described in Attachment 7. The flaw depths in the 2012 column (U1R11) are the U1R11 flaws which have also been sized using the U1R14 canned curve. This is done to provide the direct comparison of each indication between the two inspections and to quantify the change in depth for developing the growth rate distribution. As an example, the sizing history of a few sample ATSG wear indications is shown in the table below.

SG Row Col Loc U1R14 U1R11 U1R14 %TW U1R11 % TW U1R11 %TW Bobbin Bobbin (Sized Using (From (Re-sized Canned 180-day Using Canned Volts Volts Curve) Report) Curve) 3 15 4 C06 0.4 0.22 19 8 15 3 23 124 C06 0.73 0.46 23 12 21 3 92 35 C03 0.93 0.3 25 10 17 Regarding the data in Figure 3 of Enclosure 1 to the License Amendment Request, the U1R14 depths (blue dots) were sized using the method described in Attachment 7 of the OA. The U1R11 depths (yellow dots) reflect the original sizing and were not corrected using the canned curve amplitude method from Attachment 7 of the OA. Making the described adjustment to the U1R11 data points in Figure 3 of Enclosure 1 would shift the curve to the right.

b. Clarify the meaning of the statement in Attachment 7 that, Use of this sizing method is considered supplementary to the application of the condition monitoring limits associated with ETSS 96004.1.

If this was the wear sizing method used in U1R14, and sizing is required to perform condition monitoring, explain why this method is considered supplementary.

Response

The term supplementary in this case means that the NDE sizing method discussed in Attachment 7 of the CMOA was developed for comparison against the condition monitoring limits associated with ETSS technique 96004.1. Supplementary in this case does not mean additional.

LTR-CDMP-21-20 NP-Attachment Page 3 of 8 Revision 0

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Westinghouse Non-Proprietary Class 3

5. Sections 4.1.4 and 4.2.4 of Enclosure 1 of the LAR supplement describe the use of a volume-based wear approach for assessing U-bend support wear and ATSG wear, respectively. The staff requests the following information about the volume-based wear approach.

a. Clarify the description in Section 4.1.4 of how benchmarking was performed for the volumetric wear approach.

Response

Benchmarking in the Westinghouse analysis software WVOL is performed to compare predicted values to measured values in order to define the plant-specific performance parameters for application of the volume-based predictive model. The benchmarking analysis uses two cycles of prior data so that volumetric wear predictions can be compared against the subsequent inspection results to confirm that the model can accurately predict wear growth.

A slope [

]a,c. Figure 4-1 of the CMOA displays this regression with predicted values on the x-axis and measured values on the y-axis.

b. Explain how the non-matched indications in Figure 4-1 were assigned values of predicted wear (i.e., x-axis values), the basis and meaning of the linear regression of the non-matched indications, and the significance of the upper bound line that one value is above it.

Response

Non-matched indications are shown as yellow in Figure 4-1 and represent indications [

]a,c. The x-axis values are the predicted U1R14 depths based on the growth rates [

]a,c. The non-matched indications are included in the benchmark predictions [

]a,c, providing consistency between the benchmark model and the OA prediction model.

The upper bound line for the benchmarking analysis represents the [

]a,c. The intent of this is to identify outliers, which may represent points with [ ]a,c. Indications above the 95th percentile line could be [ ]a,c. The value above the upper bound line is an outlier because it is [

]a,c. For the OA LTR-CDMP-21-20 NP-Attachment Page 4 of 8 Revision 0

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Westinghouse Non-Proprietary Class 3 projection of the yellow non-matched indication above the upper bound line, the volume-based prediction model [

]a,c. As such, the growth for this indication from U1R14 to the next planned inspection will reflect the growth [ ]a,c in order to provide a conservative projection.

c. Discuss the statement in Section 4.1.4 that a slope less than unity indicates a conservative condition for application of the benchmark parameters since it appears this is only true for data points below the red line with a slope of 1.

Response

The statement is referring to the slope of the regression line being less than unity, which is displayed by the green line in Figure 4-1, rather than the red line which is the 1:1 line with a slope of 1. The benchmarking parameters are provided in Table 4-4 of the OA, which shows

[ ]a,c for each case. [ ]a,c for the benchmark regression indicates that as the [

]a,c, indicating that the prediction is conservative. If [

]a,c.

d. Section 4.2.4 of Enclosure 1 of the LAR supplement states that volumetric wear evaluation for ATSG wear requires two of the flaws to be treated as tapered wear using rotating probe inspection data. The text refers to Figure A4-8 (labeled A4-16 in Attachment 4), which is an array probe terrain plot. Describe how the array probe terrain plots were used to provide the necessary flaw profile information.

Response

In both the Electric Power Research Institute (EPRI) Steam Generator (SG) Integrity Assessment Guidelines (IAGL) (Reference 1) and the SG Degradation Specific Management Flaw Handbook (Reference 2), support structure wear is typically considered to have a tapered wear profile as opposed to being flat wear. The volumetric wear evaluation utilizes the wear profile (flat versus tapered) both as an input for the volumetric growth calculation and as the basis for the structural acceptance criteria.

Section 4.2.4 of the CMOA states that the typical approach used for the Watts Bar Unit 1 OA is to assume all wear indications are flat wear, which is conservative since more tube wall volume would be removed to reach the same depth as a tapered wear flaw. In this case, two of the larger indications returned to service (37 %TW and 34% TW) were reviewed and determined to be tapered wear. The array probe flaw graphic of ATSG wear at SG2 R88C95 C03 was referenced as an example of an image that could be reviewed to determine the wear profile of the flaws. Array probe graphics can be reviewed in the same manner as rotating LTR-CDMP-21-20 NP-Attachment Page 5 of 8 Revision 0

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Westinghouse Non-Proprietary Class 3

probe graphics since the shape of the flaw is apparent from the terrain plot. A flaw profile that displays a similar entrance slope to the maximum depth as the exit slope back to null (and resembles the shape of a normal distribution), is representative of flat wear. A steeper entrance or exit of the flaw would represent a tapered wear condition. In the case of this particular graphic that was used as an example, the taper appears to be slight with a minor amount of asymmetry between the entrance and the exit of the flaw.

If a review were performed of all horizontal ATSG flaws from U1R14 it is likely that a great number of them would be representative of tapered wear, which would add margin back to the OA EOC projections. Many of the horizontal ATSG wear indications, including the 37% TW and 34% TW indications referenced above (detected at -1.17 inch and -1.04 inch from the centerline of the support structure, respectively), are detected at the tube location where the edge of the support structure intersects. This is indicative of a tapered wear profile due to the nature of the structure to tube interaction at that location.

It is also important to note that the nondestructive examination (NDE) sizing method applied at U1R14 was amplitude based with the use of a canned curve developed from tapered wear standards used in creation of the EPRI ETSS 27091 series.

e. In the paragraph following Figure 4-1 in Section 4.1.4 of Enclosure 1 of the LAR, clarify the statement that the inputs to the volume-based wear model are measured wear depths from the U1R14 inspection and eddy current look-up depths for these flaws from the U1R8 and U1R11 inspections. In addition, if U1R8 depths are used as inputs, explain why growth rates are based only on growth between U1R11 and U1R14.

Response

The volume-based wear model uses the current wear depth (U1R14), previous wear depth (U1R11) and prior cycle length in the calculation, and therefore does not use the U1R8 depths for the OA projections. The U1R8 data is used for the benchmark calculation, not as an input for the OA projections. This statement is being slightly revised in the CMOA revision to remove mention of the U1R8 data as being used as historical measurements for the U1R14 flaw depths.

LTR-CDMP-21-20 NP-Attachment Page 6 of 8

Revision 0

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Westinghouse Non-Proprietary Class 3

6. During the review, the NRC staff identified the following apparent discrepancies. Confirm the correct information.

a. Several figures in Enclosure 1 of the LAR supplement appear to be mis-numbered as identified in the table below.

Table of Content Text Figure Label Figure A3-1 Figure A3-1 Figure A3-5 Figure A3-2 Figure A3-2 Figure A3-6 Figure A3-2 Figure A3-2 Figure A3-7 Figure A3-4 Figure A3-4 Figure A3-8 Figure A4-1 Figure A4-1 Figure A4-9 Figure A4-2 Figure A4-2 Figure A4-10 Figure A4-3 Figure A4-3 Figure A4-11 Figure A4-4 Figure A4-4 Figure A4-12 Figure A4-5 Figure A4-5 Figure A4-13 Figure A4-6 Figure A4-6 Figure A4-14 Figure A4-7 Figure A4-7 Figure A4-15 Figure A4-8 Figure A4-8 Figure A4-16 Figure A5-1 Figure A5-1 Figure A5-2 Figure A6-1 Figure A6-1 Figure A6-5 Figure A6-2 Figure A6-2 Figure A6-6 Figure A6-3 Figure A6-3 Figure A6-7 Figure A6-4 Figure A6-4 Figure A6-8 Not Used Not Used Figure A6-9 Figure A7-1 Figure A7-1 Figure A7-2 LTR-CDMP-21-20 NP-Attachment Page 7 of 8 Revision 0

- - This record was final approved on 3/15/2021 2:36:49 PM. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3

Response

These editorial corrections are being made to Revision 2 of the Watts Bar U1R14 CMOA (SG-SGMP-17-9), which is provided as Enclosure 7 to the RAI response.

References:

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

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

LTR-CDMP-21-20 NP-Attachment Page 8 of 8 Revision 0

- - This record was final approved on 3/15/2021 2:36:49 PM. (This statement was added by the PRIME system upon its validation)

Enclosure 4 Westinghouse Electric Company LLC Application for Withholding Proprietary Information from Public Disclosure (Affidavit CAW-21-5163)

CNL-21-021

Westinghouse Non-Proprietary Class 3 CAW-21-5163 Page 1 of 3 COMMONWEALTH OF PENNSYLVANIA:

COUNTY OF BUTLER:

(1) I, Zachary S. Harper, have been specifically delegated and authorized to apply for withholding and execute this Affidavit on behalf of Westinghouse Electric Company LLC (Westinghouse).

(2) I am requesting the proprietary portions of LTR-CDMP-21-20 P-Attachment, Revision 0, Responses to NRC Requests for Additional Information on Watts Bar U1R14 Condition Monitoring and Operational Assessment, be withheld from public disclosure under 10 CFR 2.390.

(3) I have personal knowledge of the criteria and procedures utilized by Westinghouse in designating information as a trade secret, privileged, or as confidential commercial or financial information.

(4) Pursuant to 10 CFR 2.390, the following is furnished for consideration by the Commission in determining whether the information sought to be withheld from public disclosure should be withheld.

(i) The information sought to be withheld from public disclosure is owned and has been held in confidence by Westinghouse and is not customarily disclosed to the public.

(ii) The information sought to be withheld is being transmitted to the Commission in confidence and, to Westinghouses knowledge, is not available in public sources.

(iii) Westinghouse notes that a showing of substantial harm is no longer an applicable criterion for analyzing whether a document should be withheld from public disclosure. Nevertheless, public disclosure of this proprietary information is likely to cause substantial harm to the competitive position of Westinghouse because it would enhance the ability of competitors to provide similar technical evaluation

Westinghouse Non-Proprietary Class 3 CAW-21-5163 Page 2 of 3 justifications and licensing defense services for commercial power reactors without commensurate expenses. Also, public disclosure of the information would enable others to use the information to meet NRC requirements for licensing documentation without purchasing the right to use the information.

(5) Westinghouse has policies in place to identify proprietary information. Under that system, information is held in confidence if it falls in one or more of several types, the release of which might result in the loss of an existing or potential competitive advantage, as follows:

(a) The information reveals the distinguishing aspects of a process (or component, structure, tool, method, etc.) where prevention of its use by any of Westinghouse's competitors without license from Westinghouse constitutes a competitive economic advantage over other companies.

(b) It consists of supporting data, including test data, relative to a process (or component, structure, tool, method, etc.), the application of which data secures a competitive economic advantage (e.g., by optimization or improved marketability).

(c) Its use by a competitor would reduce his expenditure of resources or improve his competitive position in the design, manufacture, shipment, installation, assurance of quality, or licensing a similar product.

(d) It reveals cost or price information, production capacities, budget levels, or commercial strategies of Westinghouse, its customers or suppliers.

(e) It reveals aspects of past, present, or future Westinghouse or customer funded development plans and programs of potential commercial value to Westinghouse.

(f) It contains patentable ideas, for which patent protection may be desirable.

Enclosure 5 Revised TS Changes (Mark-Ups) for WBN Unit 1 CNL-21-021

SG Tube Integrity 3.4.17 3.4 REACTOR COOLANT SYSTEM (RCS) 3.4.17 STEAM GENERATOR (SG) TUBE INTEGRITY LCO 3.4.17 SG tube integrity shall be maintained AND All SG tubes satisfying the tube repairplugging criteria shall be plugged in accordance with the Steam Generator Program.

APPLICABILITY: MODES 1, 2, 3, and 4.

ACTIONS

NOTE--------------------------------------------------------

Separate Condition entry is allowed for each SG tube.

CONDITION REQUIRED ACTION COMPLETION TIME A. One or more SG tubes A.1 Verify tube integrity of the 7 days satisfying the tube affected tube(s) is maintained pluggingrepair criteria and not until the next refueling outage plugged in accordance with or SG tube inspection.

the Steam Generator Program AND A.2 Plug the affected tube(s) in Prior to entering accordance with the Steam MODE 4 following Generator Program. the next refueling outage or SG tube inspection B. Required Action and B.1 Be in MODE 3. 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months associated Completion Time of Condition A not met. AND OR B.2 Be in MODE 5. 36 hours4.166667e-4 days 0.01 hours 5.952381e-5 weeks 1.3698e-5 months SG tube integrity not maintained Watts Bar-Unit 1 3.4-43 Amendment 65, 112,

SG Tube Integrity 3.4.17 SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY SR 3.4.17.1 Verify steam generator tube integrity in accordance with the In accordance with Steam Generator Program. the Steam Generator Program SR 3.4.17.2 Verify that each inspected SG tube that satisfies the tube Prior to entering repairplugging criteria is plugged in accordance with the MODE 4 following a Steam Generator Program. SG tube inspection.

Watts Bar-Unit 1 3.4-44 Amendment 65,

Procedures, Programs, and Manuals 5.7 5.7 Procedures, Programs, and Manuals (continued) 5.7.2.12 Steam Generator (SG) Program A Steam Generator Program shall be established and implemented to ensure that SG tube integrity is maintained. In addition, the Steam Generator Program shall include the following provisions:

a. Provisions for condition monitoring assessments. Condition monitoring assessment means an evaluation of the as found condition of the tubing with respect to the performance criteria for structural integrity and accident induced leakage. The as found condition refers to the condition of the tubing during an SG inspection outage, as determined from the inservice inspection results or by other means, prior to the plugging of tubes. Condition monitoring assessments shall be conducted during each outage during which the SG tubes are inspected or plugged, to confirm that the performance criteria are being met.

b. Performance criteria for SG tube integrity. SG tube integrity shall be maintained by meeting the performance criteria for tube structural integrity, accident induced leakage, and operational LEAKAGE.

1. Structural integrity performance criterion: All in-service steam generator tubes shall retain structural integrity over the full range of normal operating conditions (including startup, operation in the power range, hot standby, cooldown), and all anticipated transients included in the design specification), and design basis accidents. This includes retaining a safety factor of 3.0 against burst under normal steady state full power operation primary-to-secondary pressure differential and a safety factor of 1.4 against burst applied to the design basis accident primary-to-secondary pressure differentials. Apart from the above requirements, additional loading conditions associated with the design basis accidents, or combination of accidents in accordance with the design and licensing basis, shall also be evaluated to determine if the associated loads contribute significantly to burst or collapse. In the assessment of tube integrity, those loads that do significantly affect burst or collapse shall be determined and assessed in combination with the loads due to pressure with a safety factor of 1.2 on the combined primary loads and 1.0 on axial secondary loads.

2. Accident induced leakage performance criterion: The primary-to-secondary accident induced leakage rate for any design basis accident, other than a SG tube rupture, shall not exceed the leakage rate assumed in the accident analysis in terms of total leakage rate for all SGs and leakage rate for an individual SG. Leakage for all degradation mechanisms is not to exceed 150 gpd for each unfaulted SG. Leakage for all degradation mechanisms is not to exceed 1 gpm in the faulted SGFor design basis accidents that have a faulted steam generator, accident induced leakage is not to exceed 1.0 gallon per minute (gpm) for the faulted steam generator and 150 gallons per day (gpd) for the non-faulted steam generators. For design basis accidents that do not (continued)

Watts Bar-Unit 1 5.0-15 Amendment 27, 38, 44, 65,

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Reporting Requirements 5.9 5.9 Reporting Requirements (continued) 5.9.7 EDG Failures Report If an individual emergency diesel generator (EDG) experiences four or more valid failures in the last 25 demands, these failures and any nonvalid failures experienced by that EDG in that time period shall be reported within 30 days. Reports on EDG failures shall include the information recommended in Regulatory Guide 1.9, Revision 3, Regulatory Position C.4, or existing Regulatory Guide 1.108 reporting requirement.

5.9.8 PAMS Report When a Report is required by Condition B or F of LCO 3.3.3, Post Accident Monitoring (PAM)

Instrumentation, a report shall be submitted within the following 14 days. The report shall outline the preplanned alternate method of monitoring, the cause of the inoperability, and the plans and schedule for restoring the instrumentation channels of the Function to OPERABLE status.

5.9.9 Steam Generator Tube Inspection Report A report shall be submitted within 180 days after the initial entry into MODE 4 following completion of an inspection performed in accordance with the Specification 5.7.2.12, Steam Generator (SG) Program. The report shall include:

a. The scope of inspections performed on each SG,

b. Active dDegradation mechanisms found,

c. Nondestructive examination techniques utilized for each degradation mechanism,

d. Location, orientation (if linear), and measured sizes (if available) of service induced indications,

e. Number of tubes plugged during the inspection outage for each active degradation mechanism,

f. The number and percentage of tubes plugged to date, and effective plugging percentage in each steam generatorTotal number and percentage of tubes plugged to date,

g. The results of condition monitoring, including the results of tube pulls and in-situ testing, and

h. Discuss trending of tube degradation over the inspection interval and provide comparison of the prior operational assessment degradation projections to the as-found condition.The effective plugging percentage for all plugging in each SG.

Watts Bar-Unit 1 5.0-32 Amendment 27, 38, 65, 96,

Enclosure 6 Revised TS Changes (Final Typed) for WBN Unit 1 CNL-21-021

SG Tube Integrity 3.4.17 3.4 REACTOR COOLANT SYSTEM (RCS) 3.4.17 STEAM GENERATOR (SG) TUBE INTEGRITY LCO 3.4.17 SG tube integrity shall be maintained AND All SG tubes satisfying the tube plugging criteria shall be plugged in accordance with the Steam Generator Program.

APPLICABILITY: MODES 1, 2, 3, and 4.

ACTIONS

NOTE--------------------------------------------------------

Separate Condition entry is allowed for each SG tube.

CONDITION REQUIRED ACTION COMPLETION TIME A. One or more SG tubes A.1 Verify tube integrity of the 7 days satisfying the tube plugging affected tube(s) is maintained criteria and not plugged in until the next refueling outage accordance with the Steam or SG tube inspection.

Generator Program AND A.2 Plug the affected tube(s) in Prior to entering accordance with the Steam MODE 4 following Generator Program. the next refueling outage or SG tube inspection B. Required Action and B.1 Be in MODE 3. 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months associated Completion Time of Condition A not met. AND OR B.2 Be in MODE 5. 36 hours4.166667e-4 days 0.01 hours 5.952381e-5 weeks 1.3698e-5 months SG tube integrity not maintained Watts Bar-Unit 1 3.4-43 Amendment 65, 112,

SG Tube Integrity 3.4.17 SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY SR 3.4.17.1 Verify steam generator tube integrity in accordance with the In accordance with Steam Generator Program. the Steam Generator Program SR 3.4.17.2 Verify that each inspected SG tube that satisfies the tube Prior to entering plugging criteria is plugged in accordance with the Steam MODE 4 following a Generator Program. SG tube inspection.

Watts Bar-Unit 1 3.4-44 Amendment 65,

Procedures, Programs, and Manuals 5.7 5.7 Procedures, Programs, and Manuals (continued) 5.7.2.12 Steam Generator (SG) Program A Steam Generator Program shall be established and implemented to ensure that SG tube integrity is maintained. In addition, the Steam Generator Program shall include the following:

a. Provisions for condition monitoring assessments. Condition monitoring assessment means an evaluation of the as found condition of the tubing with respect to the performance criteria for structural integrity and accident induced leakage. The as found condition refers to the condition of the tubing during an SG inspection outage, as determined from the inservice inspection results or by other means, prior to the plugging of tubes. Condition monitoring assessments shall be conducted during each outage during which the SG tubes are inspected or plugged, to confirm that the performance criteria are being met.

b. Performance criteria for SG tube integrity. SG tube integrity shall be maintained by meeting the performance criteria for tube structural integrity, accident induced leakage, and operational LEAKAGE.

1. Structural integrity performance criterion: All in-service steam generator tubes shall retain structural integrity over the full range of normal operating conditions (including startup, operation in the power range, hot standby, cooldown), all anticipated transients included in the design specification, and design basis accidents. This includes retaining a safety factor of 3.0 against burst under normal steady state full power operation primary-to-secondary pressure differential and a safety factor of 1.4 against burst applied to the design basis accident primary-to-secondary pressure differentials. Apart from the above requirements, additional loading conditions associated with the design basis accidents, or combination of accidents in accordance with the design and licensing basis, shall also be evaluated to determine if the associated loads contribute significantly to burst or collapse. In the assessment of tube integrity, those loads that do significantly affect burst or collapse shall be determined and assessed in combination with the loads due to pressure with a safety factor of 1.2 on the combined primary loads and 1.0 on axial secondary loads.

2. Accident induced leakage performance criterion: The primary-to-secondary accident induced leakage rate for any design basis accident, other than a SG tube rupture, shall not exceed the leakage rate assumed in the accident analysis in terms of total leakage rate for all SGs and leakage rate for an individual SG. Leakage for all degradation mechanisms is not to exceed 150 gpd for each unfaulted SG. Leakage for all degradation mechanisms is not to exceed 1 gpm in the faulted SG.

(continued)

Watts Bar-Unit 1 5.0-15 Amendment 27, 38, 44, 65,

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Reporting Requirements 5.9 5.9 Reporting Requirements (continued) 5.9.7 EDG Failures Report If an individual emergency diesel generator (EDG) experiences four or more valid failures in the last 25 demands, these failures and any nonvalid failures experienced by that EDG in that time period shall be reported within 30 days. Reports on EDG failures shall include the information recommended in Regulatory Guide 1.9, Revision 3, Regulatory Position C.4, or existing Regulatory Guide 1.108 reporting requirement.

5.9.8 PAMS Report When a Report is required by Condition B or F of LCO 3.3.3, Post Accident Monitoring (PAM)

Instrumentation, a report shall be submitted within the following 14 days. The report shall outline the preplanned alternate method of monitoring, the cause of the inoperability, and the plans and schedule for restoring the instrumentation channels of the Function to OPERABLE status.

5.9.9 Steam Generator Tube Inspection Report A report shall be submitted within 180 days after the initial entry into MODE 4 following completion of an inspection performed in accordance with the Specification 5.7.2.12, Steam Generator (SG) Program. The report shall include:

a. The scope of inspections performed on each SG,

b. Degradation mechanisms found,

c. Nondestructive examination techniques utilized for each degradation mechanism,

d. Location, orientation (if linear), and measured sizes (if available) of service induced indications,

e. Number of tubes plugged during the inspection outage for each degradation mechanism,

f. The number and percentage of tubes plugged to date, and effective plugging percentage in each steam generator,

g. The results of condition monitoring, including the results of tube pulls and in-situ testing, and

h. Discuss trending of tube degradation over the inspection interval and provide comparison of the prior operational assessment degradation projections to the as-found condition.

Watts Bar-Unit 1 5.0-32 Amendment 27, 38, 65, 96,

Enclosure 7 Westinghouse Document, SG-SGMP-17-9, Revision 2 CNL-21-021

WESTINGHOUSE NON-PROPRIETARY CLASS 3 SG-SGMP-17-9 March 2021 Revision 2 Watts Bar U1R14 Steam Generator Condition Monitoring and Operational Assessment

- - This record was final approved on 3/16/2021 9:29:20 AM. (This statement was added by the PRIME system upon its validation)

WESTINGHOUSE NON-PROPRIETARY CLASS 3 SG-SGMP-17-9 Revision 2 Watts Bar U1R14 Steam Generator Condition Monitoring and Operational Assessment Prepared for:

Tennessee Valley Authority Authors Name: Signature / Date For Pages Logan T. Clark *Electronically Approved All Component Engineering and Chemistry Operations Verifiers Name: Signature / Date For Pages Bradley T. Carpenter *Electronically Approved All Component Design and Management Programs Manager Name: Signature / Date For Pages Michael E. Bradley, Manager *Electronically Approved All Component Design and Management Programs

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

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WESTINGHOUSE NON-PROPRIETARY CLASS 3 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 0

2017 preparation for Mode 4 return to power.

Inspection interval investigated.

November 1 19, 2019 (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.)

This revision was created to make editorial and consistency changes associated with NRC RAIs. Specifically, Section 3.1.1 and 3.1.2 were updated with U1R14 projections of max wear depth for U-bend and horizontal ATSG wear. Section 4.1.4 removed mention of U1R8 data being used as historical wear data for W-VOL OA projections. Section 4.2.4 was updated to note that non-rotating array See probe, in addition to array probe, graphics can be reviewed to determine flaw 2

EDMS profile. Additionally several table and figure numbers were updated throughout that were misnumbered in the prior revision.

(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 March 2021 Revision 2 Page 3 of 57

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WESTINGHOUSE NON-PROPRIETARY CLASS 3 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 ....................................................................................................... 13 3.3 Resolution for Classification of Indications ................................................................................ 13 3.4 SG Channel Head Primary Side Bowl and Tube Plug Visual Inspections ................................. 14 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 ............................................................................................. 15 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 - Deterministic (Depth-Based) Approach ........................................... 17 4.1.3 Operational Assessment - Monte Carlo (Depth-Based) Approach ............................................ 17 4.1.4 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 - Deterministic (Depth-Based) Approach ........................................... 20 4.2.3 Operational Assessment - Monte Carlo (Depth-Based) Approach ............................................ 20 4.2.4 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 .............................................................................................. 23 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 March 2021 Revision 2 Page 4 of 57

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WESTINGHOUSE NON-PROPRIETARY CLASS 3 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 .................................... 31 Table A4-1: Watts Bar U1R14 ATSG Wear Indications - SG1 ......................................................................... 35 Table A4-2: Watts Bar U1R14 ATSG Wear Indications - SG2 ......................................................................... 36 Table A4-3: Watts Bar U1R14 ATSG Wear Indications - SG3 ......................................................................... 38 Table A4-4: Watts Bar U1R14 ATSG Wear Indications - SG4 ......................................................................... 39 Table A5-1: Watts Bar U1R14 Tube Proximity Indications (PRX) - All SGs................................................... 49 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 ..... 32 Figure A3-2: Watts Bar U1R14 U-bend Wear Growth Cumulative Frequency Distribution - All SGs ............ 33 Figure A3-3: Watts Bar U1R14 U-bend Support Structure Wear - Monte Carlo Simulation ............................ 33 Figure A3-4: Watts Bar U1R14 U-bend Support Wear Indication - SG3 R81C56 VS4 Array Graphic 2017 .. 34 Figure A4-1: Watts Bar U1R14 Horizontal ATSG Wear Indications Map - SG1 ............................................. 42 Figure A4-2: Watts Bar U1R14 Horizontal ATSG Wear Indications Map - SG2 ............................................. 43 Figure A4-3: Watts Bar U1R14 Horizontal ATSG Wear Indications Map - SG3 ............................................. 44 Figure A4-4: Watts Bar U1R14 Horizontal ATSG Wear Indications Map - SG4 ............................................. 45 Figure A4-5: Watts Bar U1R14 Horizontal ATSG Wear Growth Cumulative Frequency Distributions .......... 46 Figure A4-6: Watts Bar U1R14 Horizontal ATSG Wear Indication Growth Rates Map - All SGs.................. 47 Figure A4-7: Watts Bar U1R14 Horizontal ATSG Wear - Monte Carlo Simulation ......................................... 48 Figure A4-8: Watts Bar U1R14 Horizontal ATSG Wear Indication - SG2 R88C95 C03 Array Graphic 2017 48 Figure A5-1: Watts Bar U1R14 Tube Proximity Indications in All SGs ........................................................... 50 Figure A6-1: Watts Bar U1R14 U-bend Support and Horizontal ATSG Noise Distributions ........................... 51 Figure A6-2: Watts Bar U1R14 U-bend Support and Horizontal ATSG Noise Distributions ........................... 52 Figure A6-3: Watts Bar U1R14 U-bend Support and ATSG MAPOD Curves.................................................. 53 Figure A6-4: Watts Bar U1R14 U-bend Support and ATSG FBM Software Outputs ....................................... 54 Figure A6-5: Watts Bar U1R14 U-bend Support and ATSG FBM Software Outputs ....................................... 55 Figure A7-1: Watts Bar U1R14 Support Structure Wear Sizing Method Comparisons .................................... 57 List of Attachments - Watts Bar U1R14 As-Implemented SG Inspection Scope.................................................. 27 - Watts Bar U1R14 SG Tube Structural and Condition Monitoring Limits ...................... 30 - Watts Bar U1R14 U-bend Support Structure Wear Indications ...................................... 31 - Watts Bar U1R14 ATSG Wear Indications......................................................................... 35 - Watts Bar U1R14 Tube Proximity Indications ................................................................... 49 - Watts Bar U1R14 MAPOD and Fully Probabilistic Operational Assessment Graphics 51 - Watts Bar U1R14 Support Structure NDE Sizing Methods .............................................. 56 SG-SGMP-17-9 March 2021 Revision 2 Page 5 of 57

- - This record was final approved on 3/16/2021 9:29:20 AM. (This statement was added by the PRIME system upon its validation)

WESTINGHOUSE NON-PROPRIETARY CLASS 3 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:

x Mechanical Wear at U-bend Support Structures x 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.

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.

Revision 2 of this OA report was created to make editorial and consistency corrections associated with USNRC (US Nuclear Regulatory Commission) Requests for Additional Information (RAIs).

SG-SGMP-17-9 March 2021 Revision 2 Page 6 of 57

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WESTINGHOUSE NON-PROPRIETARY CLASS 3 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).

SG-SGMP-17-9 March 2021 Revision 2 Page 7 of 57

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WESTINGHOUSE NON-PROPRIETARY CLASS 3 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% DUUD\SUREHH[DPLQDWLRQRIGHQWVYolts 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 Attachment 1.

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'2 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 March 2021 Revision 2 Page 8 of 57

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WESTINGHOUSE NON-PROPRIETARY CLASS 3 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 x SG 1: SG1_ENGINEERING_DUMP_FINAL.XLS x SG 2: SG2_ENGINEERING_DUMP_FINAL.XLS x SG 3: SG3_ENGINEERING_DUMP_FINAL.XLS x 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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WESTINGHOUSE NON-PROPRIETARY CLASS 3 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 inspections (Reference 12). Using the actual operating interval between inspections of 4.07 EFPY, the worst-case projected U-bend wear indication would have been 31%TW at the U1R14 inspection, using the equation EOC Maximum Depth = (0.98

X + 2.89 %TW) + (1.645

1.12

4.19

%TW) + (4.07 EFPY

2.06 %TW/EFPY), whereas X represents the maximum measured wear depth reported during U1R11 (12 %TW) with no NDE uncertainty. This projection is based on U1R11 measurements and does not consider bobbin lookups performed after the fact during U1R14. The regression equation from ETSS 96004.1 (Reference 3) is used and bounding growth rate of 2.06% TW/EFPY (Reference 3) is applied.

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.

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WESTINGHOUSE NON-PROPRIETARY CLASS 3 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-WKURXJKLVPXFKVPDOOHUWKDQ¨3NO 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.

45 40 Number of indications 35 30 25 20 15 10 5

0 0 5 10 15 20 25 30 35 40 45 U1R14

%TW Indication Size 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 Attachment 4 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 horizontal ASTG wear indication would have been 45%TW at the U1R14 inspection, using the equation EOC Maximum Depth = (0.98

X + 2.89 %TW) + (1.645

1.12

4.19 %TW) + (4.07 EFPY

5.15 %TW/EFPY), whereas X represents the maximum measured wear depth reported during U1R11 (14 %TW) with no NDE uncertainty. This projection is based on U1R11 measurements and does not consider bobbin lookups performed after the fact during U1R14. The regression equation from ETSS 96004.1 (Reference 3) is used and the bounding growth rate of 5.15% TW/EFPY (Reference 3) is applied. 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 SG-SGMP-17-9 March 2021 Revision 2 Page 11 of 57

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WESTINGHOUSE NON-PROPRIETARY CLASS 3 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-WKURXJKLVPXFKVPDOOHUWKDQ¨3NO 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.

Watts Bar U1R14 SG 1 ATSG Wear Indications Watts Bar U1R14 SG 2 ATSG Wear Indications 55 50 100 Number of indications Number of indications 45 40 80 35 30 60 25 20 40 15 10 20 5

0 0 0 5 10 15 20 25 30 35 40 45 0 5 10 15 20 25 30 35 40 45

%TW Indication Size %TW Indication Size U1R14 U1R14 Watts Bar U1R14 SG 3 ATSG Wear Indications Watts Bar U1R14 SG 4 ATSG Wear Indications 60 80 Number of indications Number of indications 50 70 60 40 50 30 40 20 30 20 10 10 0 0 0 5 10 15 20 25 30 35 40 45 0 5 10 15 20 25 30 35 40 45 U1R14 U1R14

%TW Indication Size %TW Indication Size Figure 3-1: 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 SG-SGMP-17-9 March 2021 Revision 2 Page 12 of 57

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WESTINGHOUSE NON-PROPRIETARY CLASS 3 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 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 Attachment 5, Table A5-1 and in Figure 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.

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WESTINGHOUSE NON-PROPRIETARY CLASS 3 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 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 SG-SGMP-17-9 March 2021 Revision 2 Page 14 of 57

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WESTINGHOUSE NON-PROPRIETARY CLASS 3 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 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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WESTINGHOUSE NON-PROPRIETARY CLASS 3 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 wear SG-SGMP-17-9 March 2021 Revision 2 Page 16 of 57

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WESTINGHOUSE NON-PROPRIETARY CLASS 3 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-WKURXJKLVPXFKVPDOOHUWKDQ¨3NO.

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WESTINGHOUSE NON-PROPRIETARY CLASS 3 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 4.1.4 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 U1R11 inspection. 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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WESTINGHOUSE NON-PROPRIETARY CLASS 3 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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WESTINGHOUSE NON-PROPRIETARY CLASS 3 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.

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WESTINGHOUSE NON-PROPRIETARY CLASS 3 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.

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-WKURXJKLVPXFKVPDOOHUWKDQ¨3NO.

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 or non-rotating array 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.

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WESTINGHOUSE NON-PROPRIETARY CLASS 3 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:

x SG2-R88C95-C03 was 37%TW at U1R14 and 21%TW at U1R11 x 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).

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WESTINGHOUSE NON-PROPRIETARY CLASS 3 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 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 SG-SGMP-17-9 March 2021 Revision 2 Page 23 of 57

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WESTINGHOUSE NON-PROPRIETARY CLASS 3 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.

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 and Figure A6-5. 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 SG-SGMP-17-9 March 2021 Revision 2 Page 24 of 57

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WESTINGHOUSE NON-PROPRIETARY CLASS 3 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.

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. FurthermoreIRUWXEHZHDUWRDSSURDFK¨3EXUVWGLPHQVLRQVWKHGHSWKPXVWH[FHHGWKH

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-WKURXJKLVPXFKVPDOOHUWKDQ¨3NO. 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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WESTINGHOUSE NON-PROPRIETARY CLASS 3 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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WESTINGHOUSE NON-PROPRIETARY CLASS 3 Attachment 1 - Watts Bar U1R14 As-Implemented SG Inspection Scope SG-SGMP-17-9 March 2021 Revision 2 Page 27 of 57

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WESTINGHOUSE NON-PROPRIETARY CLASS 3 SG-SGMP-17-9 March 2021 Revision 2 Page 28 of 57

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WESTINGHOUSE NON-PROPRIETARY CLASS 3 SG-SGMP-17-9 March 2021 Revision 2 Page 29 of 57

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WESTINGHOUSE NON-PROPRIETARY CLASS 3 Attachment 2 - Watts Bar U1R14 SG Tube Structural and Condition Monitoring Limits Degradation Condition Plugging Structural Limit Mechanism Monitoring Limit Existing Wear at 40% TW 62% TW 51% TW for 2.5 U-bend Support for 2.5 inch 96004.1 Revision 13 Structures Wear at 40% TW 63% TW 52% TW for 2.0 Horizontal 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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WESTINGHOUSE NON-PROPRIETARY CLASS 3 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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WESTINGHOUSE NON-PROPRIETARY CLASS 3 Figure A3-1: 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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WESTINGHOUSE NON-PROPRIETARY CLASS 3 Figure A3-2: 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 A3-3: Watts Bar U1R14 U-bend Support Structure Wear - Monte Carlo Simulation SG-SGMP-17-9 March 2021 Revision 2 Page 33 of 57

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WESTINGHOUSE NON-PROPRIETARY CLASS 3 Figure A3-4: Watts Bar U1R14 U-bend Support Wear Indication - SG3 R81C56 VS4 Array Graphic 2017 SG-SGMP-17-9 March 2021 Revision 2 Page 34 of 57

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WESTINGHOUSE NON-PROPRIETARY CLASS 3 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 SG-SGMP-17-9 March 2021 Revision 2 Page 35 of 57

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WESTINGHOUSE NON-PROPRIETARY CLASS 3 Per 20171 Per 20121 Delta SG Row Col Locn Inch1 Ind

(%TW) (%TW) (%TW/EFPY) 1 98 85 C03 0.73 PCT 20 15 1.2 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 SG-SGMP-17-9 March 2021 Revision 2 Page 36 of 57

- - This record was final approved on 3/16/2021 9:29:20 AM. (This statement was added by the PRIME system upon its validation)

WESTINGHOUSE NON-PROPRIETARY CLASS 3 Per 20171 Per 20121 Per 20081 Delta SG Row Col Locn Inch1 Ind

(%TW) (%TW) (%TW) (%TW/EFPY) 2 27 124 C05 -0.98 PCT 19 2 28 119 C06 -0.82 PCT 21 17 1.0 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 SG-SGMP-17-9 March 2021 Revision 2 Page 37 of 57

- - This record was final approved on 3/16/2021 9:29:20 AM. (This statement was added by the PRIME system upon its validation)

WESTINGHOUSE NON-PROPRIETARY CLASS 3 Per 20171 Per 20121 Per 20081 Delta SG Row Col Locn Inch1 Ind

(%TW) (%TW) (%TW) (%TW/EFPY) 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 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 SG-SGMP-17-9 March 2021 Revision 2 Page 38 of 57

- - This record was final approved on 3/16/2021 9:29:20 AM. (This statement was added by the PRIME system upon its validation)

WESTINGHOUSE NON-PROPRIETARY CLASS 3 Per 20171 Per 20121 Delta SG Row Col Locn Inch1 Ind

(%TW) (%TW) (%TW/EFPY) 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 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.

SG-SGMP-17-9 March 2021 Revision 2 Page 39 of 57

- - This record was final approved on 3/16/2021 9:29:20 AM. (This statement was added by the PRIME system upon its validation)

WESTINGHOUSE NON-PROPRIETARY CLASS 3 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 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 SG-SGMP-17-9 March 2021 Revision 2 Page 40 of 57

- - This record was final approved on 3/16/2021 9:29:20 AM. (This statement was added by the PRIME system upon its validation)

WESTINGHOUSE NON-PROPRIETARY CLASS 3 Per 20171 Per 20121 Delta SG Row Col Locn Inch1 Ind

(%TW) (%TW) (%TW/EFPY) 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 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 March 2021 Revision 2 Page 41 of 57

- - This record was final approved on 3/16/2021 9:29:20 AM. (This statement was added by the PRIME system upon its validation)

WESTINGHOUSE NON-PROPRIETARY CLASS 3 Figure A4-1: 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 March 2021 Revision 2 Page 42 of 57

- - This record was final approved on 3/16/2021 9:29:20 AM. (This statement was added by the PRIME system upon its validation)

WESTINGHOUSE NON-PROPRIETARY CLASS 3 Figure A4-2: 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 March 2021 Revision 2 Page 43 of 57

- - This record was final approved on 3/16/2021 9:29:20 AM. (This statement was added by the PRIME system upon its validation)

WESTINGHOUSE NON-PROPRIETARY CLASS 3 Figure A4-3: 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 March 2021 Revision 2 Page 44 of 57

- - This record was final approved on 3/16/2021 9:29:20 AM. (This statement was added by the PRIME system upon its validation)

WESTINGHOUSE NON-PROPRIETARY CLASS 3 Figure A4-4: 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 March 2021 Revision 2 Page 45 of 57

- - This record was final approved on 3/16/2021 9:29:20 AM. (This statement was added by the PRIME system upon its validation)

WESTINGHOUSE NON-PROPRIETARY CLASS 3 Figure A4-5: 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 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 CUMULATIVE FREQUENCY DISTRIBUTION (CDF) CUMULATIVE FREQUENCY DISTRIBUTION (CDF) 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 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 CUMULATIVE FREQUENCY DISTRIBUTION (CDF) CUMULATIVE FREQUENCY DISTRIBUTION (CDF) 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 March 2021 Revision 2 Page 46 of 57

- - This record was final approved on 3/16/2021 9:29:20 AM. (This statement was added by the PRIME system upon its validation)

WESTINGHOUSE NON-PROPRIETARY CLASS 3 Figure A4-6: 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 March 2021 Revision 2 Page 47 of 57

- - This record was final approved on 3/16/2021 9:29:20 AM. (This statement was added by the PRIME system upon its validation)

WESTINGHOUSE NON-PROPRIETARY CLASS 3 Figure A4-7: Watts Bar U1R14 Horizontal ATSG Wear - Monte Carlo Simulation Figure A4-8: Watts Bar U1R14 Horizontal ATSG Wear Indication - SG2 R88C95 C03 Array Graphic 2017 SG-SGMP-17-9 March 2021 Revision 2 Page 48 of 57

- - This record was final approved on 3/16/2021 9:29:20 AM. (This statement was added by the PRIME system upon its validation)

WESTINGHOUSE NON-PROPRIETARY CLASS 3 - 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 March 2021 Revision 2 Page 49 of 57

- - This record was final approved on 3/16/2021 9:29:20 AM. (This statement was added by the PRIME system upon its validation)

WESTINGHOUSE NON-PROPRIETARY CLASS 3 Figure A5-1: 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 March 2021 Revision 2 Page 50 of 57

- - This record was final approved on 3/16/2021 9:29:20 AM. (This statement was added by the PRIME system upon its validation)

WESTINGHOUSE NON-PROPRIETARY CLASS 3 Attachment 6 - Watts Bar U1R14 MAPOD and Fully Probabilistic Operational Assessment Graphics Figure A6-1: Watts Bar U1R14 U-bend Support and Horizontal ATSG Noise Distributions SG-SGMP-17-9 March 2021 Revision 2 Page 51 of 57

- - This record was final approved on 3/16/2021 9:29:20 AM. (This statement was added by the PRIME system upon its validation)

WESTINGHOUSE NON-PROPRIETARY CLASS 3 Figure A6-2: 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 March 2021 Revision 2 Page 52 of 57

- - This record was final approved on 3/16/2021 9:29:20 AM. (This statement was added by the PRIME system upon its validation)

WESTINGHOUSE NON-PROPRIETARY CLASS 3 Figure A6-3: 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 March 2021 Revision 2 Page 53 of 57

- - This record was final approved on 3/16/2021 9:29:20 AM. (This statement was added by the PRIME system upon its validation)

WESTINGHOUSE NON-PROPRIETARY CLASS 3 Figure A6-4: 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 March 2021 Revision 2 Page 54 of 57

- - This record was final approved on 3/16/2021 9:29:20 AM. (This statement was added by the PRIME system upon its validation)

WESTINGHOUSE NON-PROPRIETARY CLASS 3 Figure A6-5: Watts Bar U1R14 U-bend Support and ATSG FBM Software Outputs U-bend Support Structure Wear - 4.74 EFPY Horizontal ATSG Wear - 4.74 EFPY SG-SGMP-17-9 March 2021 Revision 2 Page 55 of 57

- - This record was final approved on 3/16/2021 9:29:20 AM. (This statement was added by the PRIME system upon its validation)

WESTINGHOUSE NON-PROPRIETARY CLASS 3 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.

SG-SGMP-17-9 March 2021 Revision 2 Page 56 of 57

- - This record was final approved on 3/16/2021 9:29:20 AM. (This statement was added by the PRIME system upon its validation)

WESTINGHOUSE NON-PROPRIETARY CLASS 3 Figure A7-1: 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 March 2021 Revision 2 Page 57 of 57

- - This record was final approved on 3/16/2021 9:29:20 AM. (This statement was added by the PRIME system upon its validation)

v t e Letter Sequence Response to RAI
EPID:L-2020-LLA-0161, TSTF-510 (Approved, Closed)
Initiation Request, Request, Request Acceptance... Supplement Administration Withholding Request Acceptance Questions 8 February 2021 Answers 30 March 2021 Results Approval Other:
MONTHYEAR2021-02-08 [Table View]

CNL-21-021, Response to Request for Additional Information Regarding Application to Revise Watts Bar Nuclear Plant (Wbn), Unit 1 Technical Specifications for Steam Generator Tube Inspection Frequency and to Adopt TSTF-510, .

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