ML25219A178
| ML25219A178 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  |
| Issue date: | 08/06/2025 |
| From: | Kimberly Green Plant Licensing Branch II |
| To: | Hughes S Tennessee Valley Authority |
| Green K | |
| References | |
| EPID L-2025-LRO-0031 | |
| Download: ML25219A178 (3) | |
Text
From:
Kimberly Green To:
Hughes, Shawna
Subject:
Request for Additional Information -TVA 180-Day SGTI Report for Watts Bar Unit 1, Cycle 19 (EPID L-2025-LRO-0031)
Date:
Wednesday, August 6, 2025 8:23:00 AM Attachments:
WBN1 SGTIR Final RAI and RCI 08-06-25.docx
Dear Shawna Hughes:
By letter dated May 21, 2025 (Agencywide Documents Access and Management System Accession No. ML25151A010), Tennessee Valley Authority (TVA) submitted the 180-day steam generator (SG) tube inspection report for the Watts Bar Unit 1, Cycle 19 outage.
The U.S. Nuclear Regulatory Commission (NRC) staff is reviewing your submittal and has identified areas where additional information or confirmation of information is needed to complete its review. A draft request for additional information (RAI) and request for confirmation of information (RCI) was previously sent to you via email on August 4, 2025.
At your request, a clarification call was held on August 5th, to clarify the NRC staffs request. As a result of the clarification call, the NRC staff revised RAI 1.a as follows (additions in red, deletions in red strikethrough):
- a. Clarify the difference between the 2020 and 2024 descriptions of the shape of ATSG wear indications and, if applicable, describe any effects of the change in the wear indication shapes on the structural limits calculated for condition monitoring and operational assessment CM and OA calculations.
A response to the attached RAI and RCI is due within 30 days from the date of this email.
The NRC staff considers that timely responses to RAIs help ensure sufficient time is available for staff review and contribute toward the NRCs goal of efficient and effective use of staff resources. If circumstances result in the need to revise the requested response date, please me at (301)415-1627 or via email atKimberly.Green@nrc.gov.
Sincerely, Kimberly J. Green, Senior Project Manager Plant Licensing Branch II-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation
REQUEST FOR ADDITIONAL INFORMATION AND REQUEST FOR CONFIRMATION OF INFORMATION FOR WATTS BAR NUCLEAR PLANT, UNIT 1 STEAM GENERATOR TUBE INSPECTION REPORT FOR CYCLE 19 TENNESSEE VALLEY AUTHORITY DOCKET NO. 50-390
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Background===
By letter dated May 21, 2025 (Agencywide Documents Access System (ADAMS) Accession Number ML25141A010), Tennessee Valley Authority (TVA), submitted information summarizing the results of the fall 2024 steam generator (SG) tube inspections performed at Watts Bar Nuclear Plant, Unit 1 (Watts Bar, Unit 1) during refueling outage 19 (U1R19). Documents related to condition monitoring (CM) and operational assessment (OA) for the inspection in 2024 and the most recent prior inspection (2017) are listed as references below.
References
- 1. ML17209A554 (7/28/2017), SG tube inspection report from U1R14 (spring 2017), the last SG tube inspection before 2024.
- 2. ML20199M346 (7/17/2020), license amendment request (LAR) to revise the Watts Bar, Unit 1 technical specifications for SG tube inspection frequency and adoption of TSTF-510.
- 3. ML20287A569 (10/13/2020), supplement to the 2020 LAR, including the supporting Condition Monitoring and Operational Assessment (CMOA) report for U1R14, revised in 2019.
- 4. ML21091A151 (3/30/2021), response to request for additional information on the 2020 LAR, including the updated CMOA dated March 2021.
- 5. ML25141A010 (5/21/2025), SG tube inspection report from U1R19 (fall 2024), which summarizes information from the corresponding CMOA.
Regulatory Basis Watts Bar, Unit 1, Technical Specification (TS) 5.5.9 requires that a report be submitted within 180 days after the initial entry into hot shutdown (MODE 4) following completion of an inspection of the SGs performed in accordance with TS 5.7.2.12, which requires that a SG Program be established and implemented to ensure SG tube integrity is maintained.
2 Requests To complete its review of the inspection report, the U.S. Nuclear Regulatory Commission (NRC) staff requests the following information:
RAI 1
The 2024 inspection report states in Table 4-1 that all advanced tube support grid (ATSG) wear indications were flat. Previously, the 2019 OA included in the supplement to the 2020 LAR (Reference 3) stated that the Watts Bar ATSG wear flaws have been observed to be primarily tapered wear, as opposed to flat (or uniform depth) wear. However, that OA conservatively assumed flat wear, except for two indications that did not meet the tube integrity criteria when projected for five cycles as flat wear. Those two indications were confirmed to be tapered based on the 2017 array probe data (Reference 4).
- a. Clarify the difference between the 2020 and 2024 descriptions of the shape of ATSG wear indications and, if applicable, describe any effects of the change in the wear indication shapes on the structural limits calculated for condition monitoring and operational assessment.
- b. For the two indications evaluated as tapered wear for the 2020 LAR, discuss whether they changed from tapered wear to flat wear during the subsequent operating cycles.
RCI 1:
As noted in Table 10-1 of the 2024 inspection report, there were 29 previously plugged tubes in the Watts Bar Unit 1 SGs. However, section 2 and section 13 of the report refer to 29 previously installed plugs. Given that each plugged tube has two plugs, confirm that sections 2 and 13 should state that there were 58 total plugs installed and all were inspected with no leakage or degradation detected.