ML20211L822
| ML20211L822 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  |
| Issue date: | 08/10/2020 |
| From: | Kimberly Green Plant Licensing Branch II |
| To: | |
| Green K | |
| References | |
| EPID L-2020-LRM-0051 | |
| Download: ML20211L822 (4) | |
Text
August 10, 2020 LICENSEE:
Tennessee Valley Authority FACILITY:
Watts Bar Nuclear Plant, Unit 1
SUBJECT:
SUMMARY
OF THE JUNE 25, 2020, TELECONFERENCE CALL WITH THE TENNESSEE VALLEY AUTHORITY REGARDING A PLANNED LICENSE AMENDMENT REQUEST FOR WATTS BAR NUCLEAR PLANT, UNIT 1 (EPID L-2020-LRM-0051)
On June 25, 2020, a Category 1 public teleconference call was held between the U.S. Nuclear Regulatory Commission (NRC) staff and representatives of the Tennessee Valley Authority (TVA). The purpose of the meeting was to discuss TVAs planned license amendment request (LAR) for Watts Bar Nuclear Plant (WBN), Unit 1. The purpose of the LAR is to revise the WBN Unit 1, Technical Specification (TS) for the steam generator (SG) inspection intervals for the life of the plant and to adopt Technical Specification Task Force (TSTF)-510, Revision to Steam Generator Program Inspection Frequencies and Tube Sample Selection.
The meeting notice and agenda, dated June 10, 2020, are available at Agencywide Documents Access and Management System (ADAMS) Accession No. ML20163A011. TVAs slides for the meeting are available at ADAMS Accession No. ML20169A522. A list of participants is provided as an enclosure to this summary. No regulatory decisions were made during this meeting.
TVA began the presentation by providing background information regarding the development of the current TS. According to TVA, the TS inspection intervals were developed under TSTF-449.
The inspection intervals developed under TSTF-449 considered uncertainties associated with Alloy 690TT tubing performance. The proposed changes to TSTF-510 are based on 15 years of operating experience with Alloy 690TT.
TVA briefly described the current and proposed WBN Unit 1 SG sequential inspection periods (slide 9). The NRC staff asked TVA which of the rows are stress relieved. TVA did not have the immediate answer and subsequently responded to this question by email. TVAs email stated that the Watts Bar Unit 1 replacement steam generator project strategy was to stress relieve the largest diameter U-bend that the tube manufacturers furnace would accommodate. Based on the bend radii of the tubing, the U-bend regions of tube Rows 1 through 38 received a supplemental stress relief thermal treatment. The NRC staff asked if SG Rows 1 - 4 are physically limited with regard to the type of inspection method that can be deployed. TVA stated that for rows 1 - 4 the U-bend sections were inspected with a singular bobbin probe due to dimensional constraints.
Currently, the WBN Unit 1 SG TS maximum inspection interval consists of either 72 effective full power months (EFPM) or three refueling outages. Moreover, as it relates to the SG tube inspections, WBN Unit 1 must inspect 100 percent of the SG tubes during the first 144 EFPM after the first refueling outage following SG installation (the first inspection period). After the completion of the first inspection, WBN Unit 1 must inspect 100 percent of the SG tubes within the next 108 EFPM (the second inspection period). After the completion of the second inspection, WBN Unit 1 must inspect 100 percent of the SG tubes within the next 72 EFPM (the third inspection period). Once the third inspection is completed, WBN Unit 1 must inspect 100 percent of the SG tubes every 60 EFPM thereafter (the fourth and subsequent inspection periods).
TVA plans to request that the 100 percent inspection for the second and subsequent inspection periods be completed within the next 96 EFPM. Additionally, TVA will propose a revision to the TS for the Steam Generator Tube Inspection Report to require discussion of trending of tube degradation over the inspection interval and provide comparison of the prior operational assessment degradation projections to the as-found condition. The proposed changes to the TS are consistent with similar a LAR for Sequoyah Unit 1 submitted to the NRC on February 24, 2020 (ADAMS Accession No. ML20056C857).
TVA described the operational assessment of the U1R14 100 percent inspection. TVA stated that the largest U-bend support wear left in-service is 27 percent through wall (TW); the largest advanced tube support grid (ATSG) wear left in-service is 37 percent TW; and the 95th percentile growth rate of 5.4 percent TW/effective full power year. The staff asked if the 95th percentile growth rate was a bounding 95th percentile value for both the ATSG and upper support wear. TVA confirmed that it is a bounding value. The NRC staff suggested that it would be helpful if the operational assessment is included in the LAR. TVA stated that this information was not included in the Sequoyah LAR. The NRC staff indicated that they would contact the licensee after internal discussions to communicate whether the OA information should be submitted or made available on a portal for audit by the staff.
TVA plans to submit the LAR by August 2020 and will request approval within one year.
One member of the public asked the NRC staff about statistical modeling and if it could be used to predict the SG leakage rate or degradation. The NRC staff were not able to answer the member of the publics question because it was not clear to which specific statistical model the member of the public was referring.
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. 50-390
Enclosure:
List of Participants cc: Listserv
Enclosure LIST OF PARTICIPANTS JUNE 25, 2020, PUBLIC TELECONFERENCE CALL TENNESSEE VALLEY AUTHORITY REGARDING PLANNED LICENSE AMENDMENT REQUEST WATTS BAR NUCLEAR PLANT, UNIT 1 Name Organization Kim Green U.S. Nuclear Regulatory Commission (NRC)
Steve Bloom NRC Allen Hiser NRC Andrew Johnson NRC Paul Klein NRC Greg Makar NRC Darrell Murdock NRC Ethan Shek NRC Tom Stephen NRC Clint Ashley NRC Jesse Baron Tennessee Valley Authority (TVA)
Tammy Sears TVA Gordon Williams TVA Russ Wells TVA Anne Robinson-Givens TVA Jeremy Mayo TVA Mark Ceraldi Framatome Yan Peng China Institute of Atomic Energy
- via e-mail OFFICE NRR/DORL/LPL2-2/PM NRR/DORL/LPL2-2/LA*
NRR/DORL/LPL2-2/BC*
NRR/DORL/LPL2-2/PM*
NAME KGreen BAbeywickrama UShoop KGreen DATE 08/03/2020 08/03/2020 08/10/2020 08/10/2020