05000410/LER-2024-002, Automatic Reactor Scram on Turbine Trip Due to Failed Breaker
| ML24326A058 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 11/22/2024 |
| From: | Crawford C Constellation Energy Generation |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| NMP2L2891 LER 2024-002-00 | |
| Download: ML24326A058 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 4102024002R00 - NRC Website | |
text
10 CFR 50.73 NMP2L2891 November 22, 2024 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Nine Mile Point Nuclear Station, Unit 2 Renewed Facility Operating License No. NPF-69 Docket No. 50-410
Subject:
NMP2 Licensee Event Report 2024-002, Automatic Reactor Scram on Turbine Trip due to Failed Breaker In accordance with the reporting requirements contained in 10 CFR 50.73(a)(2)(iv)(A), please find enclosed NMP2 Licensee Event Report (LER) 2024-002, Automatic Reactor Scram on Turbine Trip due to Failed Breaker.
There are no regulatory commitments contained in this letter.
Should you have any questions regarding the information in this submittal, please contact Matt Rossi, Site Regulatory Assurance Manager, at (315) 349-7012.
Respectfully, Carl J. Crawford Plant Manager, Nine Mile Point Nuclear Station CJC/MLR
Enclosure:
NMP2 Licensee Event Report 2024-002, Automatic Reactor Scram on Turbine Trip due to Failed Breaker cc:
NRC Regional Administrator, Region I NRC Resident Inspector NRC Project Manager Crawford, Carl Digitally signed by Crawford, Carl Date: 2024.11.20 17:31:54 -05'00'
Enclosure NMP2 Licensee Event Report 2024-002, Automatic Reactor Scram on Turbine Trip due to Failed Breaker Nine Mile Point Nuclear Station, Unit 2 Renewed Facility Operating License No. NPF-69
Abstract
At 07:20 on 9/23/2024 Nine Mile Point Unit 2 (NMP2) Scrammed from 100% power due to Turbine Stop Valve closure on a Turbine Trip following Generator Field Loss of Excitation due to failure of the Main Generator Field Circuit Breaker (41M-2EXSX01). High resistance across the Main Generator Field Circuit Breaker caused a large voltage drop across the breaker main contacts. The main generator field degraded until the loss of field relay picked up and tripped the 86 that subsequently tripped the Auto Voltage Regulator (AVR). The AVR control system responded to the lower excitation through the feedback and increased output to compensate. The increased output resulted in increased voltage drop, heat at the contacts, a subsequent fire, and Generator Field Loss of Excitation. The resulting Turbine Trip and Turbine Stop and Control Valve closure caused an automatic anticipatory RPS actuation. Shifts were in morning briefs. No testing or field work was in progress.
This event is reportable in accordance with 10 CFR 50.73(a)(2)(iv)(A).
X 01 10 2025 11 21 2024 X
TL BD GE YesPage of
- 3. LER NUMBER YEAR SEQUENTIAL NUMBER REV NO.
052 050 A. FAILED COMPONENTS:
Main Generator Field Circuit Breaker (41M-2EXSX01)
B. PREVIOUS LERs on SIMILAR EVENTS:
None 4
4 Nine Mile Point Unit 2 410 2024 002 00