ML22070A002
| ML22070A002 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  |
| Issue date: | 03/28/2022 |
| From: | Kimberly Green Plant Licensing Branch II |
| To: | Jim Barstow Tennessee Valley Authority |
| Green K | |
| References | |
| EPID L-2021-LRO-0071 | |
| Download: ML22070A002 (4) | |
Text
March 28, 2022 Mr. James Barstow Vice President, Nuclear Regulatory Affairs and Support Services Tennessee Valley Authority 1101 Market Street, LP 4A-C Chattanooga, TN 37402-2801
SUBJECT:
WATTS BAR NUCLEAR PLANT, UNIT 2 - REVIEW OF THE FALL 2021 MID-CYCLE GENERIC LETTER 95-05 VOLTAGE-BASED ALTERNATE REPAIR CRITERIA REPORT (EPID L-2021-LRO-0071)
Dear Mr. Barstow:
By letter dated December 16, 2021, Tennessee Valley Authority (TVA) submitted information summarizing the results of the fall 2021 mid-cycle outage steam generator tube inspections that were performed at Watts Bar Nuclear Plant, Unit 2, following Cycle 4a.
The U.S. Nuclear Regulatory Commission (NRC) staff has completed its review of the information provided and concludes that TVA provided the information required by the Watts Bar Nuclear Plant, Unit 2, technical specifications and that no follow-up is needed at this time.
The staffs review summary is enclosed.
If you have any questions, please contact me at 301-415-1627 or via e-mail at Kimberly.Green@nrc.gov.
Sincerely,
/RA/
Kimberly J. Green, Senior Project Manager Plant Licensing Branch II-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-391
Enclosure:
As stated cc: Listserv
Enclosure REVIEW OF THE FALL 2021 MID-CYCLE GENERIC LETTER 95-05 VOLTAGE-BASED ALTERNATE REPAIR CRITERIA REPORT TENNESSEE VALLEY AUTHORITY WATTS BAR NUCLEAR PLANT, UNIT 2 DOCKET NO. 50-391 By letter dated December 16, 2021 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML21350A209), Tennessee Valley Authority (TVA, the licensee) submitted the fall 2021 Generic Letter (GL) 95-05 Voltage-Based Alternate Repair Criteria Steam Generator (SG) Report for Watts Bar Nuclear Plant (Watts Bar), Unit 2. The SG tube inspections were performed during the mid-cycle outage (F214) following Cycle 4a. The report also serves as the licensees operational assessment (OA) for the Cycle 4b indications of axial outside diameter stress corrosion cracking (ODSCC) at tube support plate (TSP) intersections evaluated according to GL 95-05. By letter dated March 2, 2022 (ADAMS Accession No. ML22062A001), the licensee responded to a request from the U.S. Nuclear Regulatory Commission (NRC) staff for confirmation of information that did not result in any changes to the report. Replacement of the SGs is scheduled for the refueling outage following Cycle 4b in spring 2022.
The licensee submitted the report in accordance with Technical Specifications (TS)
Section 5.9.9, Steam Generator Tube Inspection Report, which requires that a report be submitted within 90 days after the initial entry into hot shutdown (i.e., MODE 4) following completion of an inspection of the SGs performed in accordance with TS Section 5.7.2.12, Steam Generator (SG) Program. The SG Program is required by TS Section 5.7.2.12 to be established and implemented to ensure SG tube integrity is maintained. The report reflects NRC approval (ADAMS Accession No. ML21027A167) of a license amendment request for using site-specific GL 95-05 probability of detection values, and NRC approval (ADAMS Accession No. ML21161A239) of a license amendment request for applying a reduced operating temperature to the GL 95-05 methodology.
Based on the review of the information provided, the NRC staff has the following observations:
The GL 95-05 condition monitoring criteria for tube structural and leakage integrity were met for all tubes during Cycle 4a.
The number of bobbin probe distorted support indications (DSIs) and distorted dent indications (DDIs) associated with axial ODSCC at TSP and flow distribution baffle intersections increased from 1,240 in the previous refueling outage (RFO 3) inspection to 1,583 in the F214 mid-cycle inspection.
Of the 1,583 DSIs, two were designated DDI, meaning the voltages were distorted by pre-existing dents. Based on having bobbin probe dent voltages less than 5.0 volts, the indications were acceptable for application of the GL 95-05 criteria.
Four of the 1,583 DSIs had bobbin probe voltage exceeding the upper repair limit of 2.85 volts, and the tubes were plugged.
The NRC staff confirmed that the licensee is using conservative voltage growth projections until the scheduled steam generator replacement.
Based on a review of the information provided, the NRC staff concludes that the licensee provided the information required by their TS. In addition, the staff concludes that there are no technical issues that warrant additional follow-up action at this time, since the licensee implemented the GL 95-05 voltage-based repair criteria in accordance with the methodology approved in the plant TS.
- by e-mail OFFICE NRR/DORL/LPL2-2/PM NRR/DORL/LPL2-2/LA NRR/DNLR/NCSG/BC NAME KGreen RButler SBloom DATE 03/10/22 03/15/22 03/09/22 OFFICE NRR/DORL/LPL2-2/BC NRR/DORL/LPL2-2/PM NAME DWrona KGreen DATE 03/16/22 03/28/22