05000260/LER-2024-002-01, Browns Ferry Nuclear Plant, Unit 2, High Pressure Coolant Injection Inoperable Due to Rupture Disc Failure and Resulting System Isolation
| ML24330A077 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 11/25/2024 |
| From: | Komm D Tennessee Valley Authority |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| LER 2024-002-01 | |
| Download: ML24330A077 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 2602024002R01 - NRC Website | |
text
Post Office Box 2000, Decatur, Alabama 35609-2000 November 25, 2024 10 CFR 50.73 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Browns Ferry Nuclear Plant, Unit 2 Renewed Facility Operating License No. DPR-52 NRC Docket No. 50-260
Subject:
Licensee Event Report 50-260/2024-002 High Pressure Coolant Injection Inoperable and Isolated due to Rupture Disc Failure
References:
- 1. Letter from NRC to TVA, Browns Ferry Nuclear Plant - NRC Inspection Report 05000260/2024090; and Apparent Violation dated September 17, 2024. (ML24255A027) 2.
Letter from TVA to NRC, Licensee Event Report 50-260/2024-002-00
- - High Pressure Coolant Injection Inoperable due to Rupture Disc Failure and Resulting System Isolation, dated May 20, 2024 (ML24141A246)
The enclosed Licensee Event Report provides details of an isolation of the High Pressure Coolant Injection (HPCI) system on Browns Ferry Nuclear Plant, Unit 2. The Tennessee Valley Authority is submitting this report in accordance with Title 10 of the Code of Federal Regulations (10 CFR) 50.73(a)(2)(v)(D), as any event or condition which could have prevented the fulfillment of the safety function of a system that is needed to mitigate the consequences of an accident; and 10 CFR 50.73(a)(2)(i)(B), as any operation or condition which was prohibited by the plants Technical Specifications.
There are no new regulatory commitments contained in this letter. Should you have any questions concerning this submittal, please contact David J. Renn, Nuclear Site Licensing Manager, at (256) 729-2636.
Respectfully, Daniel A. Komm Site Vice President
U.S. Nuclear Regulatory Commission Page 2 November 25, 2024 Enclosure: Licensee Event Report 50-260/2024-002 High Pressure Coolant Injection Inoperable due to Rupture Disc Failure and Resulting System Isolation.
cc (w/ Enclosure):
NRC Regional Administrator - Region II NRC Senior Resident Inspector - Browns Ferry Nuclear Plant NRC Project Manager - Browns Ferry Nuclear Plant
ENCLOSURE Browns Ferry Nuclear Plant Unit 2 Licensee Event Report 50-260/2024-002-01 HPCI Inoperable due to Rupture Disc Failure and Resulting System Isolation.
See Enclosed
Abstract
On March 19, 2024, at 1030 Central Daylight Time (CDT), during performance of 2-SR-3.5.1.7, High Pressure Coolant Injection (HPCI) Flowrate at Rated Reactor Pressure, after operating the Unit 2 HPCI system for approximately 37 minutes at rated pressure and flow, BFN Unit 2 received indications of high rupture disc pressure, HPCI Turbine trip, and HPCI isolation. Operations personnel verified HPCI isolated as expected, declared HPCI inoperable, verified BFN Unit 2 Reactor Core Isolation Cooling (RCIC) operability, and entered 2-AOI-64-2B for isolation. On March 19, 2024, at 1719 CDT, Event Notification 57036 was made to the NRC. BFN Unit 2 remained in Technical Specification (TS) Limiting Condition for Operation (LCO) 3.5.1 until the rupture disc was replaced and the HPCI system was declared operable at 1051 CDT on March 25, 2024.
The root cause of this event was that the operating ratio of the rupture disc was not used to develop effective operating limits to protect the integrity of the disc. The corrective actions taken to prevent recurrence will be to create or revise a design output document to determine the operating pressure limit for the HPCI and RCIC System turbine exhaust line rupture discs, to revise affected drawings and procedures to specify the operating pressure limit for the rupture discs, and to revise installation and maintenance instructions to include all pertinent operating limits for operating rupture discs on HPCI systems.
- 3. Revise the following procedures to specify the operating pressure limit for the turbine exhaust line rupture discs:
a.
1-, 2-, 3-OI-71, Reactor Core Isolation Cooling System [Note: Changes needed for Section 3.0 Precautions and Limitations, and Section 8.4. RCIC Turbine Trip]
b.
1-, 2-, 3-OI-73, High Pressure Coolant Injection System [Note: Changes needed for Section 3.0 Precautions and Limitations, and Section 8.3 HPCI Turbine Trip]
c.
1-, 2-, 3-ARP-9-3B, Alarm Response Procedure [Note: Changes needed for Window 28 alarm response. (RCIC)]
d.
1-, 2-, 3-ARP-9-3F, Alarm Response Procedure [Note: Changes needed for Window 25 alarm response. (HPCI)]
- 4. Revise Vendor Manual BFN-VTD-F103-0050, Installation and Maintenance Instructions for Fike Rupture Disc Assemblies, to include all pertinent operating limits for operating rupture discs on HPCI systems.
Additionally, BFN plans to implement the following Corrective Actions to address contributing
causes
- 1. Revise Vendor Manual BFN-VTD-F103-0050, Installation and Maintenance Instructions for Fike Rupture Disc Assemblies, to include all pertinent operating limits for operating rupture discs on RCIC systems.
- 2. Revise ODM 4.7, Operations Work Control Interface, Attachment 2, to warn against the possibility of over pressurizing low pressure system components during online maintenance, such as when closing the HPCI/RCIC steam exhaust isolation valve with potential valve leak by.
VII. Previous Similar Events at the Same Site
A review of the BFN CAP and Licensee Event Reports (LERs) for Units 1, 2, and 3 revealed no rupture disc failures resulting in the inoperability of BFN HPCI systems for the last three years.
VIII. Additional Information
There is no additional information.
IX. Commitments There are no new commitments.