ML24176A125

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Summary of Partially Closed Meeting with Tennessee Valley Authority to Discuss a Proposed License Amendment Request Regarding the Hydrologic Analysis Updates
ML24176A125
Person / Time
Site: Browns Ferry  Tennessee Valley Authority icon.png
Issue date: 06/28/2024
From: Kimberly Green
Plant Licensing Branch II
To:
Tennessee Valley Authority
Green K
Shared Package
ML24176A127 List:
References
EPID L-2024-LRM-0053
Download: ML24176A125 (4)


Text

June 28, 2024

LICENSEE: Tennessee Valley Authority

FACILITY: Browns Ferry Nuclear Plant, Units 1, 2, and 3

SUBJECT:

SUMMARY

OF MAY 29, 2024, PARTIALLY CLOSED MEETING WITH TENNESSEE VALLEY AUTHORITY TO DISCUSS A PROPOSED LICENSE AMENDMENT REQUEST REGARDING THE HYDROLOGIC ANALYSIS UPDATES (EPID L-2024-LRM-0053)

On May 29, 2024, the U.S. Nuclear Regulatory Co mmission (NRC) staff held a partially closed meeting with representatives of the Tennessee Valley Authority (TVA, the licensee) to discuss a proposed license amendment request (LAR) for Browns Ferry Nuclear Plant, Units 1, 2, and 3 (Browns Ferry). The meeting notice and agenda for this meeting, dated April 16, 2024, are available at Agencywide Documents Access and Management System (ADAMS) Accession No. ML24122A556. The licensees slides for the public portion of the meeting are available at ADAMS Accession No. ML24149A133. A list of the meeting attendees is enclosed.

The Browns Ferry design basis hydrological model is described in Section 2.4, Appendix 2.4A, of the Browns Ferry Updated Final Safety Analysis Report. Currently, the model uses historical TVA unsteady flow software called Simulated Open Channel Hydraulics (SOCH), which has limited capability, requiring manual interface s between multiple river model segments and dam rating curve balancing in the performance of hydrological analysis. TVA identified issues with spillway dam stability assumptions, which required an update of the design basis model. TVA decided to utilize the US Army Corps of Engineer (USACE) Hydraulics Engineering Center-River Analysis Software (HEC-RAS) for t he update and to apply the NRC-approved Topical Report TVA-NPG-AWA16-A for probable maximum pr ecipitation (PMP) for consistency with the assumptions (except Chickamauga Dam boundary assumptions) in the Sequoyah Nuclear Plant and Watts Bar Nuclear LARs.

TVA briefly described the PMP methodology employed in Topical Report TVA-NPG-AWA16-A.

The methodology defines rainfall depth-area-duration data for three storm types (i.e., local, general, and tropical) on a gridded network over the TVA drainage basin comprising dozens of sub-basins. Browns Ferry is located in sub-basin 65. TVA described the areal distribution of gridded rainfall which utilizes PMP nesting criteria. Nested total rainfall depths were developed for certain time increments from 1 to 72-hour durations and applied to each of the TVA sub-basins. TVA noted that use of gridded rainfall allows a more detailed analysis of PMP events.

TVA described the seven key updates for the hydrologic analysis, which are: (1) changed PMP bases document and application of precipitation to the upstream drainage basins; (2) revised process of determining the controlling PMP storms and resulting probable maximum flood; (3) changed hydrological modeling software to HEC-RAS, utilizing the same basic model as Sequoyah and Watts Bar; (4) updated the criteria applied in the determination of dam stability and applied revised stability results in the model; (5) updated overland windspeed data; (6)

added the seismically-induced dam failure flooding analysis; and (7) revised the warning time hydrologic basis for rainfall on rivers and streams and seismically-induced dam failure floods.

TVA noted that the scope of the Browns Ferry LAR is the same as the scope of the Sequoyah amendment, which was approved on March 26, 2024. TVA plans to submit the LAR for Browns Ferry in September 2024. The NRC staff asked TVA why it decided to prepare an LAR rather than perform the update to analysis under the criteria in section 50.59 of Title 10 of the Code of Federal Regulations. TVA stated that the NRC staffs safety evaluation for the topical report indicated that an LAR should be submitted.

No regulatory decisions were made at this meeting.

No comments or public meeting feedback forms were received.

Please direct any inquiries to me at 301-415-1627 or Kimberly.Green@nrc.gov.

/RA/

Kimberly J. Green, Project Manager Plant Licensing Branch II-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation

Docket Nos. 50-259, 50-260, and 50-296

Enclosure:

List of Attendees

cc: Listserv LIST OF ATTENDEES

MAY 29, 2024, PARTIALLY CLOSED MEET ING WITH TENNESSEE VALLEY AUTHORITY

PROPOSED LICENSE AMENDMENT REQUEST REGARDING HYDROLOGIC ANALYSIS

UPDATES FOR BROWNS FERRY NUCLEAR PLANT, UNITS 1, 2, AND 3

Name Organization Kim Green U.S. Nuclear Regulatory Commission (NRC)

Ken See NRC Deanna Zhang NRC Barbara Hayes NRC Perry Buckberg NRC Scott DeNeale Oak Ridge National Laboratory

Andy Taylor Tennessee Valley Authority (TVA)

Karen Carboni TVA Dennis Lundy TVA Steve Carlyle TVA Don Lewis TVA Janelle Schlamp TVA Tom Spink TVA Stu Henry Barge Design Robbie Blackwell Barge Design

Rajiv Prasad Pacific Northwest National Laboratory Sheryl Sweet Florida Power and Light Chris Rochon EPRI

Enclosure

ML24176A127 (Package)

ML24176A125 (Meeting Summary)

ML24122A556 (Meeting Notice)

ML24149A133 (Slides)

OFFICE NRR/DORL/LPL2-2/PM NRR/DORL/LPL2-2/LA NRR/DORL/LPL2-2/BC NRR/DORL/LPL2-2/PM NAME KGreen ABaxter DWrona KGreen DATE 06/21/24 06/27/24 06/27/24 06/28/24