05000251/LER-2025-002, Emergency Diesel Generator Actuation
| ML25129A103 | |
| Person / Time | |
|---|---|
| Site: | Turkey Point  |
| Issue date: | 05/09/2025 |
| From: | Mack K Florida Power & Light Co |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| L-2025-097 LER 2025-002-00 | |
| Download: ML25129A103 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 2512025002R00 - NRC Website | |
text
U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 Re:
Turkey Point Unit 4 Docket No. 50-251 Renewed Facility Operating License No. DPR-41 Reportable Event: 2025-02-00 Date of Event: March 13, 2025 Emergency Diesel Generator Actuation May 9, 2025 L-2025-097 10 CFR 50.73 The attached Licensee Event Report (LER), Turkey Point Unit 4 LER 2025-02-00, Emergency Diesel Generator Actuation, is being submitted pursuant to the requirements of 10 CFR 50.73(a)(2)(iv)(A), System Actuation.
This event did not have an adverse effect on the health and safety of the public.
Should you have any questions regarding this submission, please contact Maribel Valdez, Fleet Licensing Manager, at 561-904-5164.
This letter contains no new or modified regulatory commitments.
Sincerely, ~~
Ke~ck Director, Licensing and Regulatory Compliance Florida Power & Light Company Attachment: Turkey Point Unit 4 LER 2025-02-00, Emergency Diesel Generator Actuation cc:
USNRC Regional Administrator, Region II USNRC Project Manager, Turkey Point Nuclear Plant USNRC Senior Resident Inspector, Turkey Point Nuclear Plant Mr. Clark Eldredge, Florida Department of Health Florida Power & Light Company 9760 SW 344th Street, Homestead, FL 33035
Attachment Turkey Point Unit 4 LER 2025-02-00 Turkey Point Unit 4 LER 2025-02-00, Emergency Diesel Generator Actuation Florida Power & Light Company 9760 SW 344*h Street, Homestead, FL 33035
Abstract
At 1847 EDT on March 13, 2025, while at zero percent power and in Mode 5 (reactor coolant temperature</= 200 degrees), Turkey Point Unit 4 Startup Transformer (SUT) [EIIS: EA] feeder breaker, 4AB05 [EIIS: EB], tripped while supplying power to the 48 4kV Switchgear. At the time of the breaker trip, the unit was in a planned refueling outage with the 4A 4kV Switchgear out-of-service for planned breaker replacements. The breaker trip was caused by a spurious trip signal from the bus differential current interposing protective relay, 94/HFA53K91 H [EIIS: FA] which caused the breaker to open. This resulted in a momentary de-energization of the 48 4kV Bus. As designed, the 48 Emergency Diesel Generator {EOG) [EIIS: EK] and 48 Sequencer responded automatically to restore power to the 48 4kV Bus. At the time of the feeder breaker trip, the site inaccurately classified the event as an Unusual Event under the loss of offsite power criteria, which was later retracted under Event Notification {EN) 57603. Due to the automatic start of the 48 EOG, this event is being reported pursuant to 10 CFR 50. 73(a)(2)(iv)(A), System Actuation.
Description of Event
- 2. DOCKET NUMBER
- 3. LER NUMBER I
00251 D
NUMBER NO.
I YEAR SEQUENTIAL REV
~-I 02 I-~
At 1847 EDT on March 13, 2025, while at zero percent power and in Mode 5 (reactor coolant temperature </= 200 degrees), Turkey Point Unit 4 Startup Transformer (SUT) [EIIS: EA] feeder breaker, 4AB05 [EIIS: EB], tripped while supplying power to the 48 4kV Switchgear. At the time of the breaker trip, the unit was in a planned refueling outage with the 4A 4kV Switchgear out-of-service for planned breaker replacements. The breaker trip was caused by a spurious trip signal from the bus differential current interposing protective relay, 94/HFA53K91 H [EIIS: FA] which caused the breaker to open. This resulted in a momentary de-energization of the 48 4kV Bus. As designed, the 48 Emergency Diesel Generator (EOG) [EIIS: EK] and 48 Sequencer responded automatically to restore power to the 48 4kV Bus.
There were no structures, systems, or components inoperable at the start of the event that contributed to the event other than the 4A 4kV bus.
Cause of Event
An interposing relay (94/HFA53K91 H) in the Unit 4 SUT feeder breaker, 4AB05 trip circuit scheme spuriously actuated causing breaker 4AB05 to open. The spurious actuation was caused by a cable short-circuit between switchyard lock-out relays and interposing relay 94/HFA53K91 H.
Analysis of Event
The safety significance of this event is minimal based on having more than one emergency power source available (48 EOG and D bus station blackout tie) to perform the safety function of providing emergency power to the 48 4 kV bus. This event did not challenge maintaining safe shutdown conditions, removal of residual heat, controlling the release of radioactive material, or mitigating the consequences of an accident.
This event is being reported pursuant to 10 CFR 50. 73(a)(2)(iv)(A), System Actuation.
This event did not result in a Safety System Functional Failure.
Corrective Actions
Actions Completed:
The issue was corrected by lifting leads and electrically isolating relay 94/HFA53K91 H from breaker 4AB05 protection scheme which removed the locked-in trip signal.
Actions Planned:
Actions are planned to replace the cable from the switchyard to relay 94/HFA53K91 H. In addition, actions are planned to address any potential extent of condition issues. Page 2
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