ML21253A087
| ML21253A087 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  |
| Issue date: | 09/15/2021 |
| From: | Kimberly Green Plant Licensing Branch II |
| To: | Tennessee Valley Authority |
| Green K | |
| References | |
| EPID L-2021-LRM-0067 | |
| Download: ML21253A087 (4) | |
Text
September 15, 2021 LICENSEE: Tennessee Valley Authority FACILITY: Watts Bar Nuclear Plant, Unit 2
SUBJECT:
SUMMARY
OF AUGUST 19, 2021, PARTIALLY CLOSED MEETING WITH TENNESSEE VALLEY AUTHORITY TO DISCUSS MID-CYCLE OUTAGE CONTINGENCIES (EPID L-2021-LRM-0067)
On August 19, 2021, the U.S. Nuclear Regulatory Commission (NRC) staff held a partially closed meeting with representatives of Tennessee Valley Authority (TVA or the licensee) to discuss potential mid-cycle outage contingencies and steam generator (SG) tube locking as a basis for reducing burst probability at Watts Bar Nuclear Plant, Unit 2 (Watts Bar). The meeting notice and agenda for this meeting, dated July 27, 2021, are available in the Agencywide Documents Access and Management System (ADAMS) at Accession No. ML21218A015. A list of attendees is enclosed. No regulatory decisions were made at this meeting.
During the licensees public presentation (ADAMS Accession No. ML21229A199), it described the current licensing basis for the Watts Bar, Unit 2, SG program regarding tube inspections.
Watts Bar, Unit 2, was previously approved to use the alternate SG tube repair criteria applicable specifically to outer diameter stress corrosion cracking (ODSCC) at the tube-to-tube support plate intersections in Westinghouse Electric Company (Westinghouse) designed SGs having drilled-hole tube support plates (TSPs) and alloy 600 tubing described in Generic Letter (GL) 95-05, Voltage-Based Repair Criteria for Westinghouse Steam Generator Tubes Affected by Outside Diameter Stress Corrosion Cracking. During the Unit 2 Cycle 3 refueling outage, TVA employed the GL 95-05 alternate repair criteria. TVA stated that the condition monitoring requirements were met for all degradation mechanisms except for the conditional burst probability in SG number 3. This led TVA to request a license amendment that would permit the use of alternate probabilities of detection for indications less than 3.2 volts, greater than or equal to 3.2 volts and less than 6 volts, and greater than or equal to 6.0 volts. The NRC approved the amendment on February 9, 2021 (ADAMS Accession No. ML21027A167). TVA subsequently requested an amendment to apply a temperature adjustment to the voltage growth rate for the GL 95-05 alternate repair criteria. The NRC approved this amendment on June 24, 2021 (ADAMS Accession No. ML21161A239). These amendments enabled Watts Bar, Unit 2, to operate until September 11, 2021, when it will conduct a mid-cycle inspection to determine the structural and leakage integrity of the SG tubes.
The licensee then described its overall contingency strategy for the mid-cycle outage. TVA stated that if the results are as expected, based on the condition monitoring and operational assessment (CMOA), and support continued operation until the planned SG replacement in March 2022, then no additional contingencies will be needed. However, TVA is working with Westinghouse on TSP locking/displacement contingency if the CMOA does not support an additional 6 months of operation until the replacement outage. Locking of a TSP would limit the displacement of that TSP during a main steam line break, thereby minimizing contribution to probability of burst. The modification of TSPs would be accomplished placing sleeves in the
inner diameter of certain SG tubes to create bulges above and below the TSP. TVA stated that this modification itself will be implemented under Section 50.59 of Title 10 of the Code of Federal Regulations process. However, the analysis based on displacement is an exception to the GL 95-05 methodology and requires a license amendment request. The NRC questioned why the modification would not require an amendment. TVA stated that the sleeve it would use is not a leak-limiting sleeve and that tubes fitted with these sleeves will be plugged and taken out of service. TVA noted that TSP locking had been previously approved for use at South Texas Project, Unit 2, in March 2001.
The TSP displacement/locking modification was discussed in detail during the closed portion of the meeting.
Please direct any inquiries to me at 301-415-1627 or Kimberly.Green@nrc.gov.
/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:
List of Attendees cc: Listserv
LIST OF ATTENDEES AUGUST 19, 2021, PUBLIC PORTION OF PARTIALLY CLOSED MEETING WITH TENNESSEE VALLEY AUTHORITY REGARDING MID-CYCLE OUTAGE CONTINGENCIES Name Organization Kim Green U.S. Nuclear Regulatory Commission (NRC)
Luke Haeg NRC Dave Wrona NRC Steve Bloom NRC Paul Klein NRC Greg Makar NRC Binoy Desai NRC Al Butcavage NRC Wes Deschaine NRC Jeremy Dean NRC Paula Cooper NRC Ed Miller NRC Allen Hiser NRC Russ Wells Tennessee Valley Authority (TVA)
Kim Hulvey TVA Ron Rogers TVA Tony Brown TVA Jeremy Mayo TVA Dean Baker TVA John Pope TVA Dave Goetcheus TVA Robert Chappo Westinghouse Electric Company, LLC (Westinghouse)
Jim Smith Westinghouse Michael Bradley Westinghouse John Carlson Westinghouse Gary Whiteman Westinghouse Tyler Bro Westinghouse Enclosure
ML21253A087 OFFICE NRR/DORL/LPL2-2/PM NRR/DORL/LPL2-2/LA NRR/DORL/LPL2-2/BC NRR/DORL/LPL2-2/PM NAME KGreen RButler DWrona KGreen DATE 9/10/2021 9/13/2021 9/14/2021 9/15/2021