View source for 05000388/LER-2025-001, Event Involving the Trip of the Unit 2 Main Generator and Subsequent Automatic Reactor Scram

{{Adams
| number = ML25349A037
| issue date = 12/16/2025
| title = Event Involving the Trip of the Unit 2 Main Generator and Subsequent Automatic Reactor Scram
| author name = Casulli E
| author affiliation = Susquehanna Nuclear, LLC, Talen Energy
| addressee name = 
| addressee affiliation = NRC/NRR, NRC/Document Control Desk
| docket = 05000388
| license number = 
| contact person = 
| case reference number = PLA-8201
| document report number = LER 2025-001-00
| document type = Letter, Licensee Event Report (LER)
| page count = 0
}}
{{LER
| Title = Event Involving the Trip of the Unit 2 Main Generator and Subsequent Automatic Reactor Scram
| Plant = 
| Reporting criterion = 10 CFR 50.73(a)(2)(iv)(A), 10 CFR 50.73(a)(2)
| Power level = 
| Mode = 
| Docket = 05000388
| LER year = 2025
| LER number = 1
| LER revision = 0
| Event date = 
| Report date = 
| ENS = 
| abstract = 
}}

=text=
{{#Wiki_filter:Edward Casulli Chief Nuclear Officer December 16, 2025 Attn: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 Susquehanna Nuclear, LLC 769 Salem Boulevard Berwick, PA 18603 Tel. 570.542.3795 Fax 570.542.1504 Edward.Casull i@TalenEnergy.com SUSQUEHANNA STEAM ELECTRIC STATION LICENSEE EVENT REPORT 50-388/2025-001-00 UNIT 2 LICENSE NO. NPF-22 PLA-8201 TALEN~
ENERGY 10 CPR 50.73 Docket No. 50-388 Attached is Licensee Event Report (LER) 50-388/2025-001-00. The LER reports an event involving the trip of the Unit 2 main generator and subsequent automatic reactor scram that was determined to reportable in accordance with 10 CPR 50.72(b)(2)(iv)(B) and 10 CPR 50.72(b)(2)(xi). This event is also reportable in accordance with 10 CPR 50.73(a)(2)(iv)(A) as an event that resulted in an automatic actuation of the Reactor Protection System (including a reactor scram).
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 5 0-388/2025-001-00 Copy:
NRC Region I Mr. R. Wehrmann, NRC Senior Resident Inspector Mr. R. Guzman, NRC Project Manager Mr. M. Shields, PA DEP/BRP 

Attachment to PLA-8201 LER 50-388/2025-001-00 

=Abstract=
On October 28, 2025, at approximately 19:04, Susquehanna Steam Electric Station (SSES) Unit 2 experienced a main turbine trip followed by an automatic reactor scram when an arc flash on the 500 kilo-volt (kV) lines occurred during manual hydrogen venting activities. The event was reported by Event Notification 58012 in accordance with 10 CFR 50.72(b)(2)(iv)(B) as an event that resulted in an automatic actuation of the Reactor Protection System and 10 CFR 50.72(b)(2)(xi) as an event that resulted in an offsite notification made to the Pennsylvania Emergency Management Agency. This event is also reportable in accordance with 1 O CFR 50.73(a)(2)(iv)(A) as an event that resulted in an automatic actuation of the Reactor Protection System. Following visual inspection and testing of the 500kV lines and a review of the post-trip plant response, SSES Unit 2 was returned to Mode 1 operation on October 31, 2025. An evaluation of the event 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 100% Rated Thermal Power Unit 2: Mode 1, approximately 100% Rated Thermal Power
: 2. DOCKET NUMBER I
00388
: 3. LER NUMBER C::7 NUMBER NO.
I YEAR SEQUENTIAL REV
:- 1 001 1-
There were no inoperable structures, systems, or components at the start of the event that contributed to the event. 

==EVENT DESCRIPTION==
On October 28, 2025, at approximately 19:04, Susquehanna Steam Electric Station (SSES) Unit 2 experienced a main turbine trip [EIIS System Code - IT] followed by an automatic reactor scram when an arc flash on the 500 kilo-volt (kV) lines occurred during manual hydrogen venting activities. The event was reported by Event Notification 58012 in accordance with 10 CFR 50.72(b)(2)(iv)(B) as an event that resulted in an automatic actuation of the Reactor Protection System (including a reactor scram) and 10 CFR 50.72(b)(2)(xi) as an event that resulted in an offsite notification made to the Pennsylvania Emergency Management Agency. This event is also reportable in accordance with 10 CFR 50.73(a)(2)
(iv)(A) as an event that resulted in an automatic actuation of the Reactor Protection System (including a reactor scram).
All plant systems responded normally following the automatic reactor scram. Decay heat was removed by discharging steam to the main condenser using the turbine bypass valves. Unit 1 was unaffected by the event and remained at approximately 100% Rated Thermal Power.
Following visual inspection and testing of the 500kV lines and a review of the post-trip plant response, SSES Unit 2 was returned to Mode 1 operation on October 31, 2025.
An evaluation of the events resulting in the main turbine trip and subsequent automatic scram is in progress. Additional details will be provided in a supplemental LER. 

==CAUSE OF THE EVENT==
A cause evaluation of the event is in progress. Cause(s) will be provided in a supplemental LER.
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
of 2 
~'RREO(l<.r;,, 
~:::;
0~ 
~ 
\\...,.*.,i 
,,:,,....,..*~*
* I I
}}

{{LER-Nav}}