RA-22-0210, Supplement to License Amendment Request to Adopt Technical Specifications Task Force (TSTF) Traveler TSTF-577, Revised Frequencies for Steam Generator Tube Inspections

Supplement to License Amendment Request to Adopt Technical Specifications Task Force (TSTF) Traveler TSTF-577, Revised Frequencies for Steam Generator Tube Inspections

ML22209A156
Person / Time
Site:	Robinson
Issue date:	07/28/2022
From:	Flippin N Duke Energy Progress
To:	Document Control Desk, Office of Nuclear Reactor Regulation
Shared Package
ML22209A155	List: RA-22-0210, Supplement to License Amendment Request to Adopt Technical Specifications Task Force (TSTF) Traveler TSTF-577, Revised Frequencies for Steam Generator Tube Inspections
References
RA-22-0210
Download: ML22209A156 (25)

Text

Nicole L. Flippin H. B. Robinson Steam Electric Plant Unit 2 Site Vice President Duke Energy 3581 West Entrance Road Hartsville, SC 29550 O: 843 951 1701 F: 843 857 1319 Nicole.Flippin@Duke-Energy.com PROPRIETARY INFORMATION - WITHHOLD UNDER 10 CFR 2.390 UPON REMOVAL OF ENCLOSURE 1 THIS LETTER IS UNCONTROLLED Serial: RA-22-0210 10 CFR 50.90 July 28, 2022 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 H.B. Robinson Steam Electric Plant, Unit No. 2 Docket No. 50-261 Renewed License No. DPR-23

Subject:

Supplement to License Amendment Request to Adopt Technical Specifications Task Force (TSTF) Traveler TSTF-577, Revised Frequencies for Steam Generator Tube Inspections By letter dated December 9, 2021 (Agencywide Document Access and Management System (ADAMS) Accession No. ML21343A047), as supplemented by letters dated January 6, 2022 (ADAMS Accession No. ML22006A240) and April 28, 2022 (ADAMS Accession No. ML22118A336), Duke Energy Progress, LLC (Duke Energy) requested an amendment to the H.B. Robinson Steam Electric Plant, Unit No. 2 (HBRSEP2) Technical Specifications (TS). The proposed amendment would adopt Technical Specifications Task Force (TSTF) Traveler TSTF-577, Revision 1, Revised Frequencies for Steam Generator Tube Inspections. Additionally, Duke Energy proposed a steam generator tube inspection period of 72 effective full power months (EFPM) for the HBRSEP2 inspection period that began December 8, 2020.

On June 13, 2022, Duke Energy and the U.S. Nuclear Regulatory Commission (NRC) held a closed meeting to discuss the response to a request for additional information (RAI) that was provided on April 28, 2022. Based on those discussions, Duke Energy is revising the responses to RAI questions 1b and 1d. All other RAI responses provided within the enclosures of Duke Energy letter dated April 28, 2022 remain unchanged. provides responses to RAI-1a, 1b, 1d, 2b, 3, 4 and 5 which contain information proprietary to Westinghouse Electric Company LLC (Westinghouse), and the information is supported by an Affidavit (Enclosure 3) signed by Westinghouse, the owner of the information.

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 Title 10 of the Code of Federal Regulations (10 CFR) Part 50, Section 2.390, Public inspections, exemptions, requests for withholding. Accordingly, it is respectfully requested that the information which is PROPRIETARY INFORMATION - WITHHOLD UNDER 10 CFR 2.390 UPON REMOVAL OF ENCLOSURE 1 THIS LETTER IS UNCONTROLLED

PROPRIETARY INFORMATION -WITHHOLD UNDER 10 CFR 2.390 UPON REMOVAL OF ENCLOSURE 1 THIS LETTER IS UNCONTROLLED U.S. Nuclear Regulatory Commission RA-22-0210 Page 2 proprietary to Westinghouse be withheld from public disclosure in accordance with 1 O CFR Section 2.390. The changes associated with the responses to RAI questions 1 b and 1d are identified by a vertical line in the left-hand margin of the affected page.

A non-proprietary version of Enclosure 1 is included in Enclosure 2. The information contained within Enclosure 2 does not change the No Significant Hazards Consideration provided in the original license amendment request (LAR) submittal.

There are no regulatory commitments made in this submittal.

In accordance with 10 CFR 50.91, Duke Energy is notifying the State of South Carolina of the supplement to this LAR by transmitting a copy of this letter and enclosure to the designated State Official.

If there are any questions or if additional information is needed, please contact Mr. Ryan Treadway, Manager - Nuclear Fleet Licensing at 980-373-5873.

I declare under penalty of perjury that the foregoing is true and correct. Executed on July 28, 2022.

Sincerely, Nicole L. Flippin Site Vice President

Enclosures:

1. Response to Request for Additional Information RAl-1a, 1b, 1d, 2b, 3, 4, 5 (Westinghouse Proprietary)

2. Response to Request for Additional Information RAl-1a, 1b, 1d, 2b, 3, 4, 5 (Redacted)

3. Affidavit of Westinghouse PROPRIETARY INFORMATION -WITHHOLD UNDER 10 CFR 2.390 UPON REMOVAL OF ENCLOSURE 1 THIS LETTER IS UNCONTROLLED

PROPRIETARY INFORMATION - WITHHOLD UNDER 10 CFR 2.390 UPON REMOVAL OF ENCLOSURE 1 THIS LETTER IS UNCONTROLLED U.S. Nuclear Regulatory Commission RA-22-0210 Page 3 cc (with Enclosures):

L. Dudes, USNRC Region II - Regional Administrator J. Zeiler, USNRC Senior Resident Inspector - RNP L. Haeg, NRR Project Manager A. Nair, Director, Division of Environmental Response (SC)

A. Wilson, Attorney General (SC)

L. Garner, Manager, Radioactive and Infectious Waste Management (SC)

PROPRIETARY INFORMATION - WITHHOLD UNDER 10 CFR 2.390 UPON REMOVAL OF ENCLOSURE 1 THIS LETTER IS UNCONTROLLED

RA-22-0210 Enclosure 1 Response to Request for Additional Information RAI-1a, 1b, 1d, 2b, 3, 4, 5 (Westinghouse Proprietary)

[16 pages follow this cover page]

RA-22-0210 Enclosure 2 Response to Request for Additional Information RAI-1a, 1b, 1d, 2b, 3, 4, 5 (Redacted)

[16 pages follow this cover page]

Westinghouse Non-Proprietary Class 3 Westinghouse Electric Company CPL-NRCD-RF-LR-000001 NP-Attachment Revision 2 H.B. Robinson Steam Electric Plant, Unit 2- Responses to NRC Request for Additional Information from the Application to Adopt Technical Specifications Task Force (TSTF)

Traveler TSTF 577, Revision 1, Revised Frequencies for Steam Generator Tube Inspections (ADAMS Accession No. ML21060B434)

July 2022 Author:

Jay R. Smith*

Component Design and Management Programs Verifier:

Levi Y. Marcus*

Component Design and Management Programs Reviewer:

Gary W. Whiteman*

Licensing Engineering Approved:

Robert S. Chappo, Jr.*

Manager, Component Design and Management Programs

©2022 Westinghouse Electric Company LLC All Rights Reserved

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

CPL-NRCD-RF-LR-000001 NP-Attachment Page 1 of 16 Rev. 2

• • • This record was final approved on 7/22/2022, 3:13:37 PM. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3 H.B. Robinson Steam Electric Plant, Unit 2- Responses to NRC Request for Additional Information from the Application to Adopt Technical Specifications Task Force (TSTF) Traveler TSTF 577, Revision 1, Revised Frequencies for Steam Generator Tube Inspections (ADAMS Accession No. ML21060B434)

Background

By letter dated December 9, 2021, as supplemented by letter dated January 6, 2022 (Agencywide Documents Access and Management System Accession No. ML21343A047 and ML22006A240, respectively), Duke Energy Progress, LLC submitted a license amendment request for H.B. Robinson Steam Electric Plant, Unit No. 2 (Robinson). The proposed amendment would adopt Technical Specifications Task Force (TSTF) Traveler TSTF 577, Revision 1, Revised Frequencies for Steam Generator Tube Inspections (ADAMS Accession No. ML21060B434).

Title 10 of the Code of Federal Regulations (10 CFR) Part 50, Domestic Licensing of Production and Utilization Facilities, Section 50.36, Technical specifications, establishes the regulatory requirements related to the content of Technical Specifications (TSs). Section 50.36(c)(5), Administrative Controls, states in part, that administrative controls are the provisions relating to organization and management, procedures, recordkeeping, review and audit, and reporting necessary to assure operation of the facility in a safe manner. All pressurized water reactors have TSs according to 10 CFR 50.36 that include a steam generator (SG) Program with specific criteria for the structural and leakage integrity, repair, and inspection of SG tubes. At Robinson, programs established by Duke Energy Progress, LLC, including the SG Program, are listed in the administrative controls section of the TS to operate the facility in a safe manner.

The U.S. Nuclear Regulatory Commission staff has reviewed the information submitted by Duke Energy Progress, LLC and determined that additional information is required to complete its review. Responses to the specific requests for additional information are provided below. The responses to RAI Question #1b and #1d have been revised to provide additional supplemental information as a result of a clarification call with the NRR staff on 6/13/22. All changes are identified by a vertical line (bar) in the left-hand margin of the affected page. The revision bars in the left-hand margin have been retained from Revision 1 to Revision 2 for completeness and clarity.

Responses to Request for Additional Information In order to complete the review of the License Amendment Request (LAR), the Nuclear Regulatory Commission (NRC) Staff has requested the following information:

RAI-1

Discuss in greater detail how potential cracking at tube support plates (TSPs) was analyzed, including:

a. Did the analysis consider cracking only in the high stress tubes or a greater sub-population of tubes? If tubes that were inspected with the bobbin probe only were included in the subpopulation of potentially susceptible tubes, please discuss how these tubes were analyzed and combined with those tubes inspected with a combination bobbin probe/array probe to develop the overall probability of burst and probability of leakage.

CPL-NRCD-RF-LR-000001 NP-Attachment Page 2 of 16 Rev. 2

• • • This record was final approved on 7/22/2022, 3:13:37 PM. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3

Response

The Robinson Refueling Outage 32 (RO32) condition monitoring and operational assessment (Reference 1) performed forward-looking tube burst and leakage projections for a 3-cycle inspection interval following RO32 for three potential degradation mechanisms that were judged to be more likely to occur based on operating experience of similar plants. H.B. Robinson has no history of tube cracking in any location. The three potential degradation mechanisms evaluated in the RO32 CMOA (Reference 1) were axial and circumferential outer diameter stress corrosion cracking (ODSCC) at tubesheet expansion transitions and axial ODSCC at tube support plate (TSP) intersections. The focus of this response is ODSCC at TSP intersections in Alloy 600 thermally treated (A600TT) tubes with potentially high residual stress from cold working during fabrication.

A fully probabilistic operational assessment (OA) has been performed following the guidance in the Reference 2 EPRI SG Integrity Assessment Guidelines (IAGL) and an updated evaluation is described in detail in the response to RAI Question #1b. An input to the fully probabilistic analysis is the assumed population of undetected flaws and flaws assumed to initiate during the subsequent inspection interval.

The population of tubes considered in the RO32 CMOA for axial ODSCC at TSP intersections was the total population of high stress tubes identified at Robinson. The total population of high stress tubes was assumed to be in a single SG and assumed four TSP intersections per tube were susceptible. This assumption resulted in evaluating four times the actual number of high stress tubes identified and applied all to a single steam generator. For Robinson, axial ODSCC at TSP locations in non-residual stressed cold worked tubes was characterized as a potential degradation mechanism less likely to occur than the three mechanisms in evaluated in the RO32 CMOA. This conclusion was based on industry experience of cracking in A600TT tubed SGs presented in the Reference 5 EPRI Feasibility Study for Multi-Cycle 600TT Operational Assessments (EPRI Feasibility Study) that all traditional axial ODSCC flaws at TSP intersections (81 indications) have been within cold worked tubes with potential higher residual stress.

Traditional axial ODSCC flaws were defined as cracking directly underneath the TSP land and initiating near the center of the TSP width. More recent industry experience showed two occurrences of non-traditional cracking in broached TSP flow holes and just above a TSP in the freespan in non-stressed tubes. These indications were believed to be related to deposit conditions and not due to the stress condition. The deposit related cracking mechanism was also considered a degradation mechanism less likely to occur than the three mechanisms evaluated in the RO32 CMOA. Additionally, Robinson operating temperature (605°F) is significantly less than other A600TT plants that have experienced cracking at TSP locations (611°F to 621°F), thus reducing the susceptibility to cracking.

b. Provide more details about how the undetected total flaw length distribution was derived from industry experience for potential axial outside diameter stress corrosion at the TSP.

Response

The undetected total flaw length distribution for axial ODSCC at TSP intersections was derived from reanalysis of +POINT probe data from similar plants that had experienced axial ODSCC at TSP intersections. The total flaw length data set consisted of 81 indications from domestic plants with thermally treated Alloy 600 (A600TT) tubed SGs as provided in the EPRI Feasibility Study CPL-NRCD-RF-LR-000001 NP-Attachment Page 3 of 16 Rev. 2

• • • This record was final approved on 7/22/2022, 3:13:37 PM. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3 (Reference 5). The flaws were sized with Electric Power Research Institute (EPRI) +POINT probe sizing eddy current examination technique specification sheet (ETSS) I28432 applicable to axial ODSCC at broached TSP intersections. Subsequent review of the RO32 CMOA methodology for the degradation mechanism revealed that the distribution of non-destructive examination (NDE) measured total lengths was used as the end-of-cycle (EOC) distribution without adjustment. However, when using NDE measured flaw data for OA calculations it is standard practice to adjust the NDE flaw sizes by the mean sizing regression to estimate the actual metallurgical flaw size or truth. Also, when using a detected flaw length EOC distribution for the beginning-of-cycle (BOC) undetected flaw length distribution for OAs greater than 48 effective full power months (EFPM), further flaw growth should be considered.

Both of these practices were not applied in the Reference 1 OA for this degradation mechanism. These issues were entered into the Westinghouse Corrective Action Program and the OA was reperformed using a redefined total flaw length distribution and the results presented in this response.

The re-calculation of the OA for axial ODSCC at TSP intersections used a total length flaw distribution derived from the industry A600TT +POINT probe sizing of 81 detected flaws adjusted for NDE measurement uncertainty and included a 1-cycle (2.0 EFPY) growth allowance.

In addition to updating the total flaw length distribution, the recalculation of the RO32 CMOA (Reference 1) also updated the array probe maximum depth probability of detection (POD) curve with recently published EPRI methodology for developing array probe PODs as provided in the Reference 4 EPRI Plus-Point to X-Probe Amplitude Transfer Function and Probability of Detection report (EPRI Transfer Function Report). The original POD curve for axial ODSCC at TSP intersections described in the Reference 1 RO32 CMOA was developed using the array probe ETSS 20402.1 data set which was very limited in the number of detected flaws (12) and limited in flaw size (62%TW to 97%TW). This produced a very conservative and steep array probe POD curve due to the lack of Ahat data points below 62%TW. The 95th and 50th percentiles of the original POD curve were 83%TW and 56%TW, respectively. The Reference 4 EPRI Transfer Function Report describes a methodology to correlate

+POINT probe voltage amplitudes to array probe voltage amplitudes using a transfer function. This produces additional data necessary to generate more accurate and reliable array probe POD curves by providing Ahat data for flaws below 62%TW. Using the EPRI Transfer Function Report methodology, a more robust flaw Ahat data set was generated using 60 axial ODSCC flaws ranging from 22%TW to 99%TW to generate a noise-based array probe POD using the Robinson RO32 array probe TSP noise distribution. The resultant array probe maximum depth POD curve for axial ODSCC at TSP intersections has a 95th percentile of 74%TW and a 50th percentile of 37%TW as shown in Figure 1.

A fully probabilistic OA was performed using the updated total length distribution and the updated array probe POD curve (Figure 1) as described above. The undetected maximum depth distribution that was input to the OA was derived from [

]a,c,e, since all high stress tubes were inspected with both probe types. The bobbin coil ETSS I28413 log-logistic POD produces a 95th percentile value of 100%TW and a 50th percentile 21%TW. This type of flat POD curve is not reasonable for having very good detection at shallow depths and poor detection at higher depths. This shape of curve is a function of the log-logistic algorithm that artificially passes through the origin (0, 0) while maintaining a balance of the curves centroid. In contrast, the logistic curve algorithm does not alter the shape of the curve but may produce negative POD values as in the case with the ETSS I28413 logistic POD curve. Therefore, the logistic CPL-NRCD-RF-LR-000001 NP-Attachment Page 4 of 16 Rev. 2

• • • This record was final approved on 7/22/2022, 3:13:37 PM. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3 curve is considered more accurate for larger flaw depths. The bobbin coil ETSS I28413 log-logistic POD curve was modified [ ]a,c,e`. The modified log-logistic POD curve passes through about 37%TW at a POD of 0.5, which is conservative compared to the ETSS log-logistic and logistic curve values of 21%TW and 22%TW. The 95th percentile from this modified log-logistic curve is 79.5%TW. The EPRI typical flaw growth rates for maximum depth and total length were applied. As described above, a 2.0 EFPY growth allowance was applied to the total length distribution since a detected flaw length distribution was used as the BOC distribution. The population of flaws and flaw initiation rate inputs used are described in the response to RAI Question #1a. The 3-cycle (72 EFPM) fully probabilistic OA resulted in a probability of burst (POB) of 3.78% and a probability of accident induced leakage (POL) of 2.42%, thus satisfying the <5% probability acceptance criteria (see Table 1, Base Case). Other POD assumptions were also evaluated as further discussed below.

The method described above using the EPRI transfer function is referred to as the Base Case OA and contains conservative input assumptions for the Weibull flaw initiation function, the normal operating pressure differential (PNOP), and the operating cycle duration. Alternate fully probabilistic OA calculations were also performed using more representative values for these inputs and different POD assumptions that do not rely upon using the Reference 4 EPRI array probe transfer.

The Weibull flaw initiation function used in the original OA (Reference 1) and in the Base Case OA described above was conservatively performed using a reference temperature of 611°F, which is the typical industry reference temperature, whereas the actual primary side hot leg operating temperature is 605°F. A 6°F reduction in temperature reduces the crack initiation rate by a factor of [ ]a,c,e using the Arrhenius temperature correction equation with an activation energy of [ ]a,c,e as recommended by the EPRI SG Integrity Assessment Guidelines (Reference 2). With the temperature correction of the Weibull flaw initiation function to the actual plant operating temperature, the number of postulated undetected flaws at the beginning of the OA interval is reduced from 2 flaws to 1 flaw. Also with the reduced temperature, the number of cracks that initiate over the 2-cycle and 3-cycle OA interval are similarly reduced to 3 flaws and 5 flaws respectively.

The Base Case OA and the original Reference 1 CMOA used conservative inputs for the normal operating differential pressure across the tubes (PNOP) and for the operating cycle burn-up assumptions over the next OA interval. The predicted PNOP over the next 3-cycles of operation is bound by 1450 psi. A conservative PNOP value of 1500 psi will be used in the alternate OA calculation. This provides a conservative margin of 50 psi to the normal operating pressure and 150 psi margin to the minimum burst pressure requirement of 3PNOP. The estimated plant operating duration for the next 3-cycles is 5.8 effective full power years (EFPY), while the Base Case OA and the original Reference 1 CMOA used a conservative input of 6.0 EFPY (2.0 EFPY per cycle). A conservative estimate of 5.9 EFPY (1.97 EFPY per cycle) provides a 36-day margin to the projected 5.8 EFPY duration. An alternate OA calculation, (OA Case 4, described below) was performed using the updated PNOP input of 1500 psi and an OA interval of 5.9 EFPY.

OA Case 1 was calculated using the plant temperature corrected Weibull flaw initiation function and used only the bobbin coil ETSS I28413 maximum depth modified log-logistic POD curve described above for flaw detection and determination of the depth distribution of undetected flaws. The number of undetected flaws at the beginning of the OA interval was assumed to be 1 and the plant temperature corrected CPL-NRCD-RF-LR-000001 NP-Attachment Page 5 of 16 Rev. 2

• • • This record was final approved on 7/22/2022, 3:13:37 PM. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3 Weibull initiation function was used to initiate flaw over a 3-cycle OA interval. The conservative inputs of 2.0 EFPY per cycle and PNOP of 1550 psi were used. All other inputs remained the same as the Base Case OA. The results for OA Case 1 successfully satisfied all SG performance criteria and are shown in Table 1.

OA Case 2 was calculated using both the original array probe POD curve discussed above and the modified log-logistic ETSS I28413 bobbin coil POD curve also discussed above to produce the undetected maximum depth size distribution. All other inputs were the same as the inputs to the Base Case OA as shown in Table 1. The results for OA Case 2 successfully satisfied all SG performance criteria and are shown in Table 1.

OA Case 3 is the same as OA Case 2, except OA Case 3 conservatively assumed 2 undetected flaws and refined differential pressure and cycle duration inputs as discussed above. The assumed normal operating tube differential pressure for this case was 1500 psi and a per cycle duration of 1.97 EFPY. The plant temperature corrected Weibull flaw initiation function was used to determine flaw initiations over the 3-cycle OA interval. All other inputs were the same as the inputs to the Base Case OA as shown in Table 1.

The results for OA Case 3 successfully satisfied all SG performance criteria and are shown in Table 1.

CPL-NRCD-RF-LR-000001 NP-Attachment Page 6 of 16 Rev. 2

• • • This record was final approved on 7/22/2022, 3:13:37 PM. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3 Table 1: Axial ODSCC at TSPs FBM Simulation Results Summary Case POD Assumption # PNOP Prob. of Prob. of Burst SLB Leak Cycle

1. Un-Detected (psid) # OA Burst Leakage Pressure Rate at Duration Flaws Cycles (POB) (POL) at Lower Lower (EFPY) 5%, psi 5%, gpm Base Double Processed POD(1) 2 2.0 1550 3 3.78% 2.42% 4865 0 1 Bobbin 1 2.0 1550 3 4.04% 3.09% 4818 0.006 2 Double Processed POD(2) 1 2.0 1550 3 2.90% 1.99% 5062 0 3 Double Processed POD(2) 2 1.97 1500 3 4.49% 3.77% 4571 0.031 Acceptance Criterion 5% 5% 4650 0.06 Notes:

(1) The double processed POD used the bobbin coil ETSS I28413 modified POD curve and the array probe POD using the EPRI transfer function from Reference 4.

(2) The double processed POD used the ETSS I28413 modified POD curve and the ETSS 20402.1 array probe POD (without the EPRI transfer function).

CPL-NRCD-RF-LR-000001 NP-Attachment Page 7 of 16 Rev. 2

• • • This record was final approved on 7/22/2022, 3:13:37 PM. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3 a,c,e Figure 1. Site Specific Maximum Depth Array Probe POD for Axial ODSCC at TSP Intersections

c. Compare the tube support plate deposits at Robinson relative to the Duke unit that experienced cracking in a few non-high stress tubes in 2019 near the top of a TSP. Discuss the likelihood of similar tube cracking at Robinson based on deposit amounts or composition.

Response

Duke Energy Progress, LLC to provide response.

d. Provide the 95th percentile probability of detection value for the bobbin probe and the combined bobbin-array probe.

Response

CPL-NRCD-RF-LR-000001 NP-Attachment Page 8 of 16 Rev. 2

• • • This record was final approved on 7/22/2022, 3:13:37 PM. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3 POD curves are used in fully probabilistic operational assessments to determine the undetected flaw size distribution for the inspection techniques used to detect the degradation mechanism. For the Robinson potential degradation mechanism of axial ODSCC at TSP intersections, all high stress tubes were inspected with both the bobbin coil probe and the array probe. The inspection with two different probe designs can result in improved overall detection capabilities afforded by the individual features of each probe type and techniques. As an example, a flaw may not be detected by one probe type but could be detected by the second probe type. For inspections with two probe types, in this case the bobbin coil and the array probe, a singular combined bobbin-array POD was not developed to derive the undetected flaw size distribution for input to the OA model; instead, [

]a,c,e Detection of axial ODSCC flaws at TSP intersections with the bobbin coil probe is accomplished using EPRI ETSS I28413. The maximum depth 95th percentile value from the ETSS I28413 modified log-logistic POD curve is 79.5%TW.

Detection of axial ODSCC flaws at TSP intersection with the array probe is accomplished using EPRI ETSS 20402.1. Development of the POD is provided in RAI Question #1b. The array probe POD curve developed using the array probe ETSS 20402.1 dataset was used directly for the derivation of the Ahat regression and the RO32 measured TSP noise distribution as inputs to the noise-based Model Assisted Probability of Detection (MAPOD) methodology. The maximum depth 95th percentile value from the array probe POD curve is 83%TW.

[

]a,c,e that has a 95th percentile value of 50.1%TW.

RAI-2

During Refueling Outage 32 (RO32), 20 new foreign object wear indications were detected. A significant number of these indications occurred at support plates with the largest measured at 30-31 percent through wall (TW). No possible loose part signals were detected in any of the tubes with foreign object wear. In addition, four previous indications of foreign object wear without associated possible loose part signals exhibited 1-3 percent TW/effective full power years (EFPY) growth since the previous inspection.

a. Provide a copy of Reference 6 from the RO32 Condition Monitoring and Operational Assessment: Disposition of Foreign Object(s) Remaining in Robinson RSGs.

Response

Duke Energy Progress, LLC to provide response.

CPL-NRCD-RF-LR-000001 NP-Attachment Page 9 of 16 Rev. 2

• • • This record was final approved on 7/22/2022, 3:13:37 PM. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3

b. Discuss for each of the four indications mentioned above that exhibited growth, whether the measured growth is judged to result from eddy current measurement uncertainty or additional wear from a loose part that did not produce a possible loose part indication. Discuss why loose part wear is not expected to challenge tube integrity during a 72 EFPM inspection cycle.

Response

All four of the indications that exhibited growth were reevaluated and show no change between RO30 and RO32. Since these four indications did not have a PLP detected by eddy current and showed no change in depth from the previous eddy current inspection, loose part wear is not expected to challenge tube integrity during a 72 EFPM inspection cycle.

RAI-3

Please provide insights as to why the array probe 95th percentile probability of detection for circumferential ODSCC cracking in the tubesheet expansion zone is more favorable than for axial ODSCC cracking. Is the probability of detection for axial cracks at the tubesheet expansion zone more favorable than circumferential cracks when the cracks are smaller?

Response

The primary elements and inputs for developing probability of detection (POD) curves include the flaw metallurgical depth to flaw voltage amplitude regression (Ahat) for the degradation mechanism and the eddy current noise voltage amplitude distribution for the region of interest. The Ahat regression and noise distribution are probabilistically sampled to calculate flaw signal-to-noise (S/N) ratios which are used to determine whether sampled flaw depths are detected or not detected. The detected and non-detected flaw sizes are used to develop the POD curve. Larger S/N ratios tend to result in more flaw detection and thus more favorable POD curves. Larger S/N ratios occur from larger flaw signals from the Ahat regression or from smaller noise signals from the noise distribution.

The tubesheet expansion transition noise measurements and distributions used in the Reference 1 RO32 CMOA were collected with the array probe during the Robinson RO32 outage. The array probe contains axial sensitive coils and circumferential sensitive coils. Consequently, two noise distributions were developed, a noise distribution for axially oriented flaws and a noise distribution for circumferentially oriented flaws. The axial noise distribution contained higher noise levels than the circumferential noise distribution. The 95th percentile of the axial noise distribution was 0.34 volts as compared to 0.27 volts for the circumferential noise distribution. Therefore, the probability of detection would be more favorable for circumferential flaws at the tubesheet expansion transition based upon the noise levels.

The Ahat array probe regressions for axial and circumferential ODSCC at tubesheet expansion transitions that were used in the Reference 1 RO32 CMOA were compared for trends that could explain differences in POD impact for axial and circumferential flaws. The Ahat comparison showed that the circumferential ODSCC Ahat regression has larger flaw voltages than the axial ODSCC Ahat for same sized flaws up to about 94% TW, where the two regressions cross. The larger circumferential ODSCC Ahat regression would also produce more favorable probability of detection than for axial ODSCC.

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• • • This record was final approved on 7/22/2022, 3:13:37 PM. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3 The higher noise level for the axial sensitive array probe coils and larger Ahat regression for the circumferential sensitive coils could be explained by the array probe design. The array probe consists of two bands of axial sensitive and circumferential sensitive coils. Multiple coils of each type are placed around the circumference of the probe to provide 360-degree coil coverage. [

]a,c,e Given the higher voltage amplitude noise levels from the array probe axial sensitive coils and the lower Ahat flaw depth to voltage correlation than the array probe circumferential sensitive coils, the probability of detection for shallow axial flaws would be expected to be less favorable than for circumferential flaws of the same depth. This conclusion is demonstrated through comparison of axial and circumferential probability of detection curves developed from the recent EPRI Transfer Function Report (Reference 4) derivations of Ahat regressions and the noise-based Model Assisted Probability of Detection (MAPOD) methodology using RO32 axial and circumferential noise distributions. Figure 2 provides the developed log-logistic and logistic probability of detection curves for axial and circumferential ODSCC flaws at the tubesheet expansion transition using the array probe.

Figure 2 shows that the circumferential ODSCC probability of detection is more favorable than the axial probability of detection for both the log-logistic and logistic POD functions for flaw depths larger than about 25%TW. For shallower depths less than about 25%TW the axial and circumferential flaw POD functions are similar. It is noted from Figure 2 that the log-logistic POD functions are less favorable than the logistic POD functions for larger flaw depths and the log-logistic function slope becomes nearly flat also for larger flaw depths. This is because the log-logistic function passes the curve through the origin (0, 0) which artificially lowers the tail of the curve at larger depths. The logistic POD function does not artificially pass through the origin but allows the curve to become negative. Therefore, the logistic curve is considered more accurate for larger flaw depths. It is believed that the reason for the axial and circumferential POD curves are similar for shallow depths is due to decreased sensitivity of both coil orientations for shallow depths (i.e., both coil orientations have difficulty detecting flaws with shallow depths).

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• • • This record was final approved on 7/22/2022, 3:13:37 PM. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3 a,c,e Figure 2. Axial and Circumferential ODSCC at Expansion Transition POD

RAI-4

Page 2 of Attachment 3 in the license amendment request (LAR) states: Recent (April 2021) operating experience within the Duke Energy fleet at Catawba Nuclear Station, Unit 2 demonstrated that an inspection using enhanced probes did not identify additional crack like indications. The NRC staff interprets this statement to mean that the use of the array probe, in addition to the bobbin probe, does not necessarily mean that additional cracks will be detected. Please confirm if the NRC staffs understanding is correct and discuss the relative crack detection capability of the array probe as compared to the bobbin only probe.

Response

Page 2 of Attachment 3 in the LAR stated Recent (April 2021) operating experience within the Duke Energy fleet at Catawba Nuclear Station, Unit 2 demonstrated that an inspection using enhanced probes did not identify additional crack like indications. This statement was intended to be a statement of fact that during the April 2021 Catawba Unit 2 inspection the array probe did not identify additional crack like flaws that were not detected by the bobbin coil probe. The bobbin coil probe also did not identify crack-like flaws during this inspection.

The detection of cracks is dependent on various factors including the crack size and the inspection probe.

There is an increasing probability of detecting a flaw as the flaw size increases as represented in a POD CPL-NRCD-RF-LR-000001 NP-Attachment Page 12 of 16 Rev. 2

• • • This record was final approved on 7/22/2022, 3:13:37 PM. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3 curve. A defined probability of flaw detection or non-detection for each probe type can be determined for a given flaw depth. Each probe type has a specific probability of detecting or not detecting the same flaw. Therefore, there are three outcomes of flaw detection when inspected by both probes: 1) the flaw is detected by both probes, 2) the flaw is detected by one probe and not the other, and 3) the flaw is not detected by either probe. If no flaws are detected by either probe it may also signify that there were no flaws present to detect. Therefore, the NRC Staffs understanding is correct in that use of the array probe in addition to the bobbin probe does not necessarily mean that more cracks will be detected.

The bobbin coil probe and array probe are both qualified to detect axial ODSCC at TSP intersections, but the designs and techniques differ. The bobbin coil probe contains two circumferentially wound coils that produce magnetic fields that can detect flaws in the differential mode which detects field variations between the two probe coils and in the absolute mode which detects field variations from one coil on the probe to a reference probe outside the tube. The bobbin coil detects magnetic field variations due to flaws for the entire tube circumference without the ability to distinguish multiple flaws at the same elevation.

Due to the coil winding and magnetic field orientation, the bobbin coil can detect axial and volumetric flaws but not circumferentially oriented flaws. The array probe contains two bands of multiple coil pairs that are spaced circumferentially around the entire circumference of the probe. Each coil pair consists of a magnetic field driver coil and a pickup coil. The array probe has one ring of coil pairs to provide detection capability for axial oriented flaws and one ring for circumferentially oriented flaws. The array probe can discern multiple flaws at the same elevation. Although the bobbin coil probe and array probe are designed to detect flaws differently, both probes are qualified to the same minimum acceptance standards and detection requirements provided in the EPRI Steam Generator Examination Guidelines (Reference 3). Therefore, the probability of detection of each probe type is expected to be similar. Figure 3 provides a comparison of the POD curves for the bobbin coil and array probes for axial ODSCC at TSP intersections. Figure 3 shows that the POD curves are similar, but the array probe provides more favorable detection at larger depths than the bobbin coil probe.

CPL-NRCD-RF-LR-000001 NP-Attachment Page 13 of 16 Rev. 2

• • • This record was final approved on 7/22/2022, 3:13:37 PM. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3 a,c,e Figure 3. Bobbin Coil and Array Probe POD Comparison, Axial ODSCC at TSP Intersections

RAI-5

The NRC staff noted in the supplemental letter dated January 6, 2022 potential typographical errors.

Please assess and correct any typographical errors in the following items:

a. Table 2-3, the indication location (01C +51.21) shown for Tube R6 C76 in SGC.

Response: The location is correct at 0.6 inches below the second tube support plate.

b. Section 4.1, Anti-Vibration Bars Wear maximum growth occurred at multiple indications, which exhibited growth of 2.0 percent TW, or 0.91 percent TW/EFPY.

Response: The maximum growth of 3% TW occurred at a single location, SG C R35 C61 03A, which results in a growth rate of 0.91 %TW/EFPY

c. Section 4.5 inspection interval of 4.0 EFPY covering three cycles of operation to RO34 Response: An inspection interval of 4.0 EFPY was applied for evaluations covering two cycles of operation to RO34.

d. Section 4.5.1, the performance criteria was also met for a total duration of 4.0 EFPY until RO24.

Response: the performance criteria was also met for a total duration of 4.0 EFPY until RO34.

CPL-NRCD-RF-LR-000001 NP-Attachment Page 14 of 16 Rev. 2

• • • This record was final approved on 7/22/2022, 3:13:37 PM. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3

e. Section 4.5.2, therefore, circumferential ODSCC, at the hot expansion transition meets the OA performance criteria for structural and leakage integrity for two and three full cycles of operation.

Response: therefore, axial ODSCC, at the hot expansion transition meets the OA performance criteria for structural and leakage integrity for two and three full cycles of operation.

f. Section 4.5.3, The performance criteria was also met for a total duration of 4.0 EFPY until RO24.

Response: The performance criteria was also met for a total duration of 4.0 EFPY until RO34.

g. Section 4.5.3, in the paragraph following Table 4-4, the POL of 0.936% corresponds to three cycles.

Response: The POL of 0.936% corresponded to two cycles. Note that the POL values have been updated in the response to RAI Question #1b (Table 1).

RAI-6

The LAR description of TS 5.5.9.d introductory paragraph does not appear to align with the current TS description. For example, the LAR version of the last sentence in TS 5.5.9.d introductory paragraph, states, An degradation mechanism whereas the current TS states, A degradation mechanism (emphasis added). This change was not identified as a variation and appears to be a typographical error that was introduced when preparing LAR Attachments 1 (proposed TS changes) and 2 (revised TS pages).

Please assess and correct any typographical errors.

Response

Duke Energy Progress, LLC to provide response.

RAI-7

TS 5.5.9.d would be revised by adding a phrase regarding portions of the tube that are exempt from inspection by alternate repair criteria (see LAR Attachment 1, INSERT 1). However, LAR INSERT 1 appears to contain additional punctuation (unnecessary comma between outlet and except) that is not consistent with TSTF-577. Please assess and correct any typographical errors.

Response

Duke Energy Progress, LLC to provide response.

CPL-NRCD-RF-LR-000001 NP-Attachment Page 15 of 16 Rev. 2

• • • This record was final approved on 7/22/2022, 3:13:37 PM. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3

RAI-8

TS 5.5.9.d.3 would be revised by adding a phrase regarding portions of the tube that are exempt from inspection by alternate repair criteria that replaces the phrase not excluded above (see LAR , INSERT 3). However, LAR INSERT 3 appears to contain additional punctuation (unnecessary comma between tube and excluding) that is not consistent with TSTF-577. Please assess and correct any typographical errors.

Response

Duke Energy Progress, LLC to provide response.

References

1. Westinghouse Report SG-CDMP-20-25, Revision 1, H.B. Robinson Unit 2 RO32 Steam Generator Condition Monitoring and Final Operational Assessment, November 2021.

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

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

4. EPRI Technical Report 3002022466, Plus Point to X-Probe Amplitude Transfer Function and Probability of Detection, December 2021.

5. Steam Generator Management Program: Feasibility Study for Multi-Cycle 600TT Operational Assessments. EPRI, Palo Alto, CA: 2020. 3002018258.

CPL-NRCD-RF-LR-000001 NP-Attachment Page 16 of 16 Rev. 2

• • • This record was final approved on 7/22/2022, 3:13:37 PM. (This statement was added by the PRIME system upon its validation)

RA-22-0210 Enclosure 3 Affidavit of Westinghouse

[3 pages follow this cover page]

Westinghouse Non-Proprietary Class 3 AFFIDAVIT CAW-22-035 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 CPL-NRCD-RF-LR-000001 P-Attachment, Revision 2, H.B. Robinson Steam Electric Plant, Unit 2- Responses to NRC Request for Additional Information from the Application to Adopt Technical Specifications Task Force (TSTF) Traveler TSTF 577, Revision 1, Revised Frequencies for Steam Generator Tube Inspections (ADAMS Accession No. ML21060B434), 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

• • • This record was final approved on 7/21/2022, 6:13:04 PM. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3 AFFIDAVIT CAW-22-035 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.

• • • This record was final approved on 7/21/2022, 6:13:04 PM. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3 AFFIDAVIT CAW-22-035 Page 3 of 3 (6) The attached documents are bracketed and marked to indicate the bases for withholding. The justification for withholding is indicated in both versions by means of lower-case letters (a) through (f) located as a superscript immediately following the brackets enclosing each item of information being identified as proprietary or in the margin opposite such information. These lower-case letters refer to the types of information Westinghouse customarily holds in confidence identified in Sections (5)(a) through (f) of this Affidavit.

I declare that the averments of fact set forth in this Affidavit are true and correct to the best of my knowledge, information, and belief.

I declare under penalty of perjury that the foregoing is true and correct.

Executed on: 7/21/2022 ________________________

Zachary S. Harper, Manager Licensing Engineering

• • • This record was final approved on 7/21/2022, 6:13:04 PM. (This statement was added by the PRIME system upon its validation)