05000259/LER-2020-001-01, Manual Reactor Shutdown of Two Units on Decreasing Condenser Vacuum Due to Eel Grass Intrusion

Manual Reactor Shutdown of Two Units on Decreasing Condenser Vacuum Due to Eel Grass Intrusion

ML20322A440
Person / Time
Site:	Browns Ferry
Issue date:	11/17/2020
From:	Rasmussen M Tennessee Valley Authority
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
LER 2020-001-01
Download: ML20322A440 (8)

LER-2020-001, Manual Reactor Shutdown of Two Units on Decreasing Condenser Vacuum Due to Eel Grass Intrusion

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(iv)(A), System Actuation
2592020001R01 - NRC Website

text

Tennessee Valley Authority, Post Office Box 2000, Decatur, Alabama 35609-2000 November 17, 2020 10 CFR 50.73 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Browns Ferry Nuclear Plant, Units 1 and 2 Renewed Facility Operating License Nos. DPR-33 and DPR-52 NRC Docket Nos. 50-259 and 50-260

Subject:

Licensee Event Report 50-259/2020-001 Manual Reactor Shutdown of Two Units on Decreasing Condenser Vacuum due to Eel Grass Intrusion The enclosed Licensee Event Report (LER) provides details of the manual reactor shutdown of two units on decreasing condenser vacuum due to eel grass intrusion. The Tennessee Valley Authority is submitting this report in accordance with Title 10 CFR 50.73(a)(2)(iv)(A), as any event or condition that resulted in a manual or automatic actuation of any of the systems listed in paragraph (a)(2)(iv)(B). The enclosed LER has been revised to update the cause of the event and the corrective actions.

There are no new regulatory commitments contained in this letter. Should you have any questions concerning this submittal, please contact J. L. Paul, Site Licensing Manager, at (256) 729-2636.

Respectfully, Matthew Rasmussen Site Vice President Enclosure: Licensee Event Report 50-259/2020-001 Manual Reactor Shutdown of Two Units on Decreasing Condenser Vacuum due to Eel Grass Intrusion cc (w/ Enclosure):

NRC Regional Administrator - Region II NRC Senior Resident Inspector - Browns Ferry Nuclear Plant NRC Project Manager - Browns Ferry Nuclear Plant Respecctfully, Matthew Rasmussen

Abstract

On July 20, 2020, at approximately 0955 Central Daylight Time (CDT), the Unit 1 control room received the traveling screen differential pressure high alarm. Assistant Unit Operators dispatched to the condenser circulating water (CCW) system forebay reported large masses of eel grass. The influx of eel grass resulted in fouling of the trash racks and traveling water screens for all three units which reduced the CCW flows during this event.

As a result of degrading condenser vacuum on Unit 2, operators manually scrammed the reactor at 1325 CDT. On July 21, 2020, as Unit 1 condenser vacuum continued to degrade to the turbine trip setpoint, the Unit 1 operators manually scrammed the reactor at 0435 CDT.

The root cause of the event is that existing permanently installed plant equipment at the BFN forebay was not adequate to mitigate the newly developed threat presented by large scale eel grass accumulation on Wheeler Lake.

The action plan for addressing the root cause of this event has been developed which consists of deciding which equipment upgrades will be the most effective based on studies of river flow and environmental conditions, funding these upgrades, issuing design packages, and implementing the final designs.

VIII. Additional Information

There is no additional information.

IX.

Commitments

There are no new commitments.