05000364/LER-2025-004, Manual Reactor Trip Due to Loss of Main Condenser Vacuum
| ML25230A243 | |
| Person / Time | |
|---|---|
| Site: | Farley  |
| Issue date: | 08/18/2025 |
| From: | Carroll J Southern Nuclear Operating Co |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| NL-25-0306 LER 2025-004-00 | |
| Download: ML25230A243 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(iv)(B), System Actuation |
| 3642025004R00 - NRC Website | |
text
"" Southern Nuclear August 18,2025 Docket No.:
50-364 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555-0001 Joshua W. Carroll Vice President - Farley Joseph M. Farley Nuclear Plant - Unit 2 Licensee Event Report 2025-004-00 Joseph M. Farley Nuclear Plant 7388 North State Hwy 95 Columbia. Alabama 36319 334.661.2101 tel 334.661.2512 fax JCARROLL@southcmco.com NL-25-0306 Manual Reactor Trip due to Loss of Main Condenser Vacuum Ladies and Gendemen:
In accordance with the requirements of 10 CFR 50.73(a)(2)(iv)(A), Southern Nuclear Company is submitting the enclosed Licensee Event Report for Unit 2.
This letter contains no NRC commitments. If you have any questions regarding this submittal, please contact Gene Surber, Licensing Manager, at (334) 661-2265.
Respectfully submitted, f:71-- µ)_J\\-*J Nf' Joshua W. Carroll Vice President - Farley JC/rgs/cbg Enclosure: Unit 2 Licensee Event Report 2025-004-00 Cc: Regional Administrator, Region II NRR Project Manager - Farley Nuclear Plant Senior Resident Inspector - Farley Nuclear Plant RTYPE: CFA04.054
Joseph M. Farley Nuclear Plant - Unit 2 Licensee Event Report 2025-004-00 Manual Reactor Trip due to Loss of Main Condenser Vacuum Enclosure Unit 2 Licensee Event Report 2025-004-00
Abstract
On June 27, 2025, at 22:09 CDT while in Mode 1 and at 100% power, plant operators initiated a manual reactor trip on Unit 2 due to low main condenser vacuum. All systems worked as designed and decay heat was removed by Auxiliary Feed Water and Steam Generators by steaming to atmosphere.
The event was due to the failure of the 2B Steam Generator Feed Pump Turbine (SGFPT) Exhaust Diaphragm (Rupture Disc) leak which led to the loss of vacuum. The SGFPT Exhaust Rupture Disc had been replaced incorrectly in the previous April outage.
The 2B SGFPT Exhaust Rupture Disc was replaced. Unit 2 exited the forced outage on June 30, 2025.
This event is reportable under 10 CFR 50.73(a)(2)(iv)(A) due to the automatic actuation of multiple systems listed in 10 CFR 50.73(a)(2)(iv)(B). FNP Unit 1 was not affected during this event.
Plant Conditions/ Event Description:
- 2. DOCKET NUMBER
- 3. LER NUMBER I
364 NUMBER NO.
I YEAR SEQUENTIAL REV
~-I 004 1-G On June 27, 2025, at 22:09 CDT while in Mode 1 and 100% power, plant operators initiated a manual reactor trip on Unit 2 due to low main condenser [EIIS: SG] vacuum. All systems worked as design and decay heat was removed by Auxiliary Feed Water (AFW) [EIIS: BA] and Steam Generators [EIIS: AB/SG] by steaming to atmosphere. No equipment was out of service at the time of the event that contributed to the event.
Event Analysis
At approximately 22:04 on June 27, 2025, Unit 2 main condenser vacuum began degrading from 1 _6 psia, and electrical output began lowering at the same time. Unit 2 operators entered abnormal operating procedures and manually tripped Unit 2 at 22:09 CDT. AFW automatically actuated on low SG level which is normal for plant design. The plant entered Mode 3 with all safety systems operating normally.
The 28 SGFPT (Steam Generator Feed Pump Turbine) Exhaust Rupture Diaphragm (Rupture Disc) [EIIS: SJ/ RPO] was discovered to have an approximately 5 sq. inch hole in the upper portion of the disk.
It was determined that the failed rupture disc (Manufacturer: Siemens/Westinghouse; Part: 16G0477050) had been replaced during the previous outage on April 25, 2025, by supplemental turbine personnel. The 28 SGFPT Rupture Disc was replaced and Unit 2 exited the forced outage on June 30, 2025.
Reportability and Safety Assessment
There were no actual safety consequences because of this event. All safety related systems functioned as designed during this event. The Operating crew responded correctly to the event. The applicable abnormal / emergency operating procedures were properly entered, and the plant was stabilized. The event was within the analysis of the Updated Final Safety Analysis Report (UFSAR) Chapter 15.
The event is reportable per 10 CFR 50_ 73(a)(2)(iv)(A) as any event or condition that resulted in the manual or automatic actuation of any of the systems listed in paragraph (a)(2)(iv)(B) of this section. Systems that were actuated during this event include: the Reactor Protection System (RPS)(EIIS Code: IG) and AFW.
Cause(s)
The 28 SGFPT Exhaust Rupture Disc failed due to improper installation. Upon performing the as-found inspection and removal of the 28 SGFPT Rupture Disc assembly the installed backing plate of the rupture disc was found misaligned. It was noted that the backing plate was not in its recession and the lower portion of the rupture disc had been pinched/crushed underneath the backing plate.
Corrective Actions
A replacement 28 SGFPT Discharge Rupture Diaphragm was installed. Additional Corrective actions include updating pre-job brief for task and modifying planning sequence to incorporate operating experience, establish assembly verifications, torque validations by supervision, and post installation testing to verify proper backing plate position and rupture disk integrity.
Previous Similar Events
None Page 2
of 2