05000387/LER-2025-001, Manual Reactor Scram Following Partial Loss of Cooling to Main Transformer
| ML25265A118 | |
| Person / Time | |
|---|---|
| Site: | Susquehanna  |
| Issue date: | 09/22/2025 |
| From: | Casulli E Susquehanna, Talen Energy |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| PLA-8191 LER 2025-001-00 | |
| Download: ML25265A118 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 3872025001R00 - NRC Website | |
text
Edward Casulli Site Vice President September 22, 2025 Attn: Document Control Desk U. S. Nuclear Regulatory Commission Washington, DC 20555-0001 Susquehanna Nuclear, LLC 769 Salem Boulevard Berwick, PA I 8603 Tel. 570.542.3795 Fax 570.542.1504 Edward.Casulli@TalenEnergy.com SUSQUEHANNA STEAM ELECTRIC STATION LICENSEE EVENT REPORT 50-387/2025-001-00 UNIT 1 LICENSE NO. NPF-14 PLA-8191 TALEN~,
ENERGY 10 CFR 50.73 Docket No. 50-387 Attached is Licensee Event Report (LER) 50-387/2025-001-00. The LER reports an event involving a manual scram following the partial loss of Main Transformer cooling that was determined to be reportable in accordance with 10 CFR 50.72(b)(2)(iv)(A), 10 CFR 50.72(b)(2)(iv)(B) and 10 CFR 50.72(b)(3)(iv)(A). This event is also reportable in accordance with 10 CFR 50.73(a)(2)(iv)(A) as an event that resulted in a manual actuation of the Reactor Protection System (including a reactor scram) and actuation of an emergency core cooling system.
There were no actual consequences to the health and safety of the public as a result of this event.
This letter contains no new or revised regulatory commitments.
E. Casulli Attachment: LER 50-3 87/2025-001-00 Copy:
NRC Region I Ms. E. Brady, NRC Resident Inspector Mr. R. Guzman, NRC Project Manager Mr. M. Shields, PA DEP/BRP
Attachment to PLA-8191 LER 50-387/2025-001-00
Abstract
On July 22, 2025, at approximately 15:10, Susquehanna Steam Electric Station (SSES) Unit 1 was manually scrammed following a partial loss of cooling to the main transformer (one of two cooling fan groups were found tripped). The event was reported by Event Notification 57822 in accordance with 1 O CFR 50.72(b)(2)(iv)(A), 1 O CFR 50.72{b)(2)(iv)(B) and 1 O CFR 50.72(b)(3)(iv)(A). This event is also reportable in accordance with 10 CFR 50.73{a)(2)(iv)(A) as an event that resulted in a manual actuation of the Reactor Protection System (including a reactor scram) and actuation of the emergency core cooling system. Following restoration of both cooling fan groups, SSES Unit 1 was restored to Mode 1 operation on July 25, 2025.
An evaluation of the events is in progress. Additional details will be provided in a supplemental LER.
There were no actual consequences to the health and safety of the public as a result of this event.
CONDITIONS PRIOR TO THE EVENT:
050 052 Unit 1: Mode 1, approximately 96% Rated Thermal Power Unit 2: Mode 1, approximately 100% Rated Thermal Power
- 2. DOCKET NUMBER
- 3. LER NUMBER I
00387 D
NUMBER NO.
I YEAR SEQUENTIAL REV
~-I 001 1-0 There were no inoperable structures, systems, or components at the start of the event that contributed to the event.
EVENT DESCRIPTION
On July 22, 2025, at approximately 15:10, Susquehanna Steam Electric Station (SSES) Unit 1 was manually scrammed following a loss of cooling to the Main Transformer 1X101 [EIIS System Code/ Component Code - EL/ XFMR]. One of two cooling fan groups [IEEE Component Code - FAN] was found tripped. The event was reported by Event Notification 57822 in accordance with 10 CFR 50.72(b)(2)(iv)(A), 10 CFR 50.72(b)(2)(iv)(B) and 10 CFR 50.72(b)(3)(iv)(A). This event is also reportable in accordance with 10 CFR 50.73(a)(2)(iv)(A) as an event that resulted in a manual actuation of the Reactor Protection System (including a reactor scram) and actuation of the emergency core coolant system.
All systems responded normally following the manual scram. High Pressure Coolant Injection [EIIS System Code - BJ]
actuated briefly to assist in restoring reactor water level. The 1 B Reactor Feedwater Pump [EIIS System Code/
Component Code - SJ/ P] stabilized and maintained reactor water level. Decay heat was removed by discharging steam to the main condenser using the turbine bypass valves.
Following restoration of both cooling fan groups, SSES Unit 1 was returned to Mode 1 operation on July 25, 2025.
An evaluation of the events resulting in the manual scram is in progress. Additional details will be provided in a supplemental LER.
CAUSE OF THE EVENT
A cause evaluation of the event and the contributing factors is in progress. A supplemental LER will be issued to provide information on the cause(s) following completion and approval of the evaluation.
ANALYSIS/ SAFETY SIGNIFIGANCE Safety significance information will be provided in a supplemental LER.
CORRECTIVE ACTIONS
Corrective actions will be provided In a supplemental LER.
COMPONENT FAILURE INFORMATION
None
PREVIOUS OCCURRENCES
Previous occurrences, if any, will be provided in a supplemental LER. Page 2
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