Event Notification Report for October 21, 2025
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Event Text
Event Text
U.S. Nuclear Regulatory Commission
Operations Center
EVENT REPORTS FOR
10/20/2025 - 10/21/2025
Power Reactor
Event Number: 57952
Facility: South Texas
Region: 4 State: TX
Unit: [1] [] []
RX Type: [1] W-4-LP,[2] W-4-LP
NRC Notified By: Marc Hill
HQ OPS Officer: Ernest West
Region: 4 State: TX
Unit: [1] [] []
RX Type: [1] W-4-LP,[2] W-4-LP
NRC Notified By: Marc Hill
HQ OPS Officer: Ernest West
Notification Date: 09/25/2025
Notification Time: 17:36 [ET]
Event Date: 09/25/2025
Event Time: 12:29 [CDT]
Last Update Date: 10/20/2025
Notification Time: 17:36 [ET]
Event Date: 09/25/2025
Event Time: 12:29 [CDT]
Last Update Date: 10/20/2025
Emergency Class: Non Emergency
10 CFR Section:
50.72(b)(3)(v)(D) - Accident Mitigation
10 CFR Section:
50.72(b)(3)(v)(D) - Accident Mitigation
Person (Organization):
Drake, James (R4DO)
Drake, James (R4DO)
| Unit | SCRAM Code | RX Crit | Initial PWR | Initial RX Mode | Current PWR | Current RX Mode |
|---|---|---|---|---|---|---|
| 1 | N | Y | 100 | 100 |
EN Revision Imported Date: 10/21/2025
EN Revision Text: TWO TRAINS OF ECCS INOPERABLE
The following information was provided by the licensee via phone and email:
"On 9/23/2025 at 2214 CDT, the South Texas Project Unit 1 (STP-1) train 'B' reactor containment fan cooler (RCFC) chilled water supply outside containment isolation valve, 1-CC-MOV-0137, was declared inoperable due to a material condition. This rendered train 'B' component cooling water inoperable which cascaded to train 'B' emergency core cooling system (ECCS) subsystem to render it inoperable. STP-1 entered technical specification (TS) 3.5.2 action 'A' for train 'B' ECCS, requiring restoration within 7 days or apply the requirements of the Configuration Risk Management Program (CRMP).
"On 09/25/2025 at 1229 CDT, train 'A' essential chiller 12A was declared inoperable due to inability to maintain chiller water outlet temperature less than 52 degrees Fahrenheit. This cascaded down to the train 'A' ECCS subsystem to render it inoperable. STP-1 entered TS 3.5.2 action 'B' due to less than two of the required subsystems operable, to within 1 hour restore at least two subsystems to operable status or apply the requirements of the CRMP, or be in at least hot standby within the next 6 hours and in hot shutdown within the following 6 hours.
"On 09/25/2025 at 1329 CDT, STP-1 entered the CRMP based on two ECCS subsystems remaining inoperable longer than 1 hour. These subsystems are used for accident mitigation. Unit 1 remains in mode 1."
* * * RETRACTION ON 10/20/2025 AT 1636 EDT FROM MARC HILL TO JOSUE RAMIREZ * * *
The following information was provided by the licensee via phone and email:
"The purpose of this notification is to retract EN 57952, which was made on September 25, 2025, at 1736 EDT. [The] notification was initially made due to two of three trains of emergency core cooling system (ECCS) being declared inoperable. After the notification was made, South Texas Project determined using an engineering evaluation, that one of the two inoperable ECCS trains was operable because the elevated chilled water outlet temperature of the associated essential chiller (Train A) did not impact the technical specification specified function.
"Therefore, this event was not a condition that could have prevented fulfillment of a safety function.
"The NRC Resident Inspector has been notified."
Notified R4DO (Vossmar)
EN Revision Text: TWO TRAINS OF ECCS INOPERABLE
The following information was provided by the licensee via phone and email:
"On 9/23/2025 at 2214 CDT, the South Texas Project Unit 1 (STP-1) train 'B' reactor containment fan cooler (RCFC) chilled water supply outside containment isolation valve, 1-CC-MOV-0137, was declared inoperable due to a material condition. This rendered train 'B' component cooling water inoperable which cascaded to train 'B' emergency core cooling system (ECCS) subsystem to render it inoperable. STP-1 entered technical specification (TS) 3.5.2 action 'A' for train 'B' ECCS, requiring restoration within 7 days or apply the requirements of the Configuration Risk Management Program (CRMP).
"On 09/25/2025 at 1229 CDT, train 'A' essential chiller 12A was declared inoperable due to inability to maintain chiller water outlet temperature less than 52 degrees Fahrenheit. This cascaded down to the train 'A' ECCS subsystem to render it inoperable. STP-1 entered TS 3.5.2 action 'B' due to less than two of the required subsystems operable, to within 1 hour restore at least two subsystems to operable status or apply the requirements of the CRMP, or be in at least hot standby within the next 6 hours and in hot shutdown within the following 6 hours.
"On 09/25/2025 at 1329 CDT, STP-1 entered the CRMP based on two ECCS subsystems remaining inoperable longer than 1 hour. These subsystems are used for accident mitigation. Unit 1 remains in mode 1."
* * * RETRACTION ON 10/20/2025 AT 1636 EDT FROM MARC HILL TO JOSUE RAMIREZ * * *
The following information was provided by the licensee via phone and email:
"The purpose of this notification is to retract EN 57952, which was made on September 25, 2025, at 1736 EDT. [The] notification was initially made due to two of three trains of emergency core cooling system (ECCS) being declared inoperable. After the notification was made, South Texas Project determined using an engineering evaluation, that one of the two inoperable ECCS trains was operable because the elevated chilled water outlet temperature of the associated essential chiller (Train A) did not impact the technical specification specified function.
"Therefore, this event was not a condition that could have prevented fulfillment of a safety function.
"The NRC Resident Inspector has been notified."
Notified R4DO (Vossmar)
Power Reactor
Event Number: 57963
Facility: South Texas
Region: 4 State: TX
Unit: [1] [] []
RX Type: [1] W-4-LP,[2] W-4-LP
NRC Notified By: Long Han
HQ OPS Officer: Jordan Wingate
Region: 4 State: TX
Unit: [1] [] []
RX Type: [1] W-4-LP,[2] W-4-LP
NRC Notified By: Long Han
HQ OPS Officer: Jordan Wingate
Notification Date: 10/02/2025
Notification Time: 20:55 [ET]
Event Date: 10/02/2025
Event Time: 16:52 [CDT]
Last Update Date: 10/20/2025
Notification Time: 20:55 [ET]
Event Date: 10/02/2025
Event Time: 16:52 [CDT]
Last Update Date: 10/20/2025
Emergency Class: Non Emergency
10 CFR Section:
50.72(b)(3)(v)(D) - Accident Mitigation
10 CFR Section:
50.72(b)(3)(v)(D) - Accident Mitigation
Person (Organization):
Vossmar, Patricia (R4DO)
Vossmar, Patricia (R4DO)
| Unit | SCRAM Code | RX Crit | Initial PWR | Initial RX Mode | Current PWR | Current RX Mode |
|---|---|---|---|---|---|---|
| 1 | N | Y | 100 | 100 |
EN Revision Imported Date: 10/21/2025
EN Revision Text: TWO TRAINS OF ECCS INOPERABLE
The following information was provided by the licensee via phone and email:
"On October 2, 2025, at 1651 CDT, essential cooling water pump '1C' tripped. Essential chiller '1C' and cascading equipment, including emergency core cooling system (ECCS) train '1C,' was declared inoperable.
"Essential chiller '12A' and cascading equipment, including ECCS train '1A,' was concurrently inoperable for ongoing maintenance.
"This condition resulted in an inoperable condition on 2 out of 3 safety trains for the accident mitigating functions, including the train 'A' and train 'C' high head safety injection (SI), low head SI, containment spray, electrical auxiliary building heating ventilation and air conditioning (HVAC), and essential chilled water. All 'B' train safety related equipment remains operable. There was no impact on the health and safety of the public or plant personnel.
"The repair timeline is unknown. We have already entered the configuration risk management program to mitigate additional maintenance induced risk with a risk informed completion time of October 19, 2025, at 1140 CDT. We are limited by TS 3.7.7.C to restore 1 train of control room HVAC by October 5, 2025, at 1651 CDT.
"This condition is being reported as an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(v)(D).
"The NRC Resident Inspector has been notified."
The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance:
The 'C' emergency diesel generator is unavailable due to the loss of cooling water. Maintenance on the ECCS train '1A' is partially complete and operators are working to restore the train to an operable status prior to the technical specification deadline. The essential cooling water pump trip was due to a hot spot causing the pump to overheat. The cause of the hot spot is still under investigation.
* * * RETRACTION ON 10/20/2025 AT 1636 EDT FROM MARC HILL TO JOSUE RAMIREZ * * *
The following information was provided by the licensee via phone and email:
"The purpose of this notification is to retract EN 57963, which was made on October 2, 2025, at 2055 EDT. [The] notification was initially made due to two of three trains of emergency core cooling system (ECCS) being declared inoperable. After the notification was made, South Texas Project determined, using an engineering evaluation, that one of the two inoperable ECCS trains was operable because the elevated chilled water outlet temperature of the associated essential chiller (Train A) did not impact the technical specification specified function.
"Therefore, this event was not a condition that could have prevented fulfillment of a safety function.
"The NRC Resident Inspector has been notified."
Notified R4DO (Vossmar)
EN Revision Text: TWO TRAINS OF ECCS INOPERABLE
The following information was provided by the licensee via phone and email:
"On October 2, 2025, at 1651 CDT, essential cooling water pump '1C' tripped. Essential chiller '1C' and cascading equipment, including emergency core cooling system (ECCS) train '1C,' was declared inoperable.
"Essential chiller '12A' and cascading equipment, including ECCS train '1A,' was concurrently inoperable for ongoing maintenance.
"This condition resulted in an inoperable condition on 2 out of 3 safety trains for the accident mitigating functions, including the train 'A' and train 'C' high head safety injection (SI), low head SI, containment spray, electrical auxiliary building heating ventilation and air conditioning (HVAC), and essential chilled water. All 'B' train safety related equipment remains operable. There was no impact on the health and safety of the public or plant personnel.
"The repair timeline is unknown. We have already entered the configuration risk management program to mitigate additional maintenance induced risk with a risk informed completion time of October 19, 2025, at 1140 CDT. We are limited by TS 3.7.7.C to restore 1 train of control room HVAC by October 5, 2025, at 1651 CDT.
"This condition is being reported as an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(v)(D).
"The NRC Resident Inspector has been notified."
The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance:
The 'C' emergency diesel generator is unavailable due to the loss of cooling water. Maintenance on the ECCS train '1A' is partially complete and operators are working to restore the train to an operable status prior to the technical specification deadline. The essential cooling water pump trip was due to a hot spot causing the pump to overheat. The cause of the hot spot is still under investigation.
* * * RETRACTION ON 10/20/2025 AT 1636 EDT FROM MARC HILL TO JOSUE RAMIREZ * * *
The following information was provided by the licensee via phone and email:
"The purpose of this notification is to retract EN 57963, which was made on October 2, 2025, at 2055 EDT. [The] notification was initially made due to two of three trains of emergency core cooling system (ECCS) being declared inoperable. After the notification was made, South Texas Project determined, using an engineering evaluation, that one of the two inoperable ECCS trains was operable because the elevated chilled water outlet temperature of the associated essential chiller (Train A) did not impact the technical specification specified function.
"Therefore, this event was not a condition that could have prevented fulfillment of a safety function.
"The NRC Resident Inspector has been notified."
Notified R4DO (Vossmar)
Agreement State
Event Number: 57965
Rep Org: Arkansas Department of Health
Licensee: Domtar AW LLC
Region: 4
City: Ashdown State: AR
County:
License #: ARK-0354-03120
Agreement: Y
Docket:
NRC Notified By: Hunter Broadaway
HQ OPS Officer: Robert A. Thompson
Licensee: Domtar AW LLC
Region: 4
City: Ashdown State: AR
County:
License #: ARK-0354-03120
Agreement: Y
Docket:
NRC Notified By: Hunter Broadaway
HQ OPS Officer: Robert A. Thompson
Notification Date: 10/03/2025
Notification Time: 13:56 [ET]
Event Date: 10/02/2025
Event Time: 00:00 [CDT]
Last Update Date: 10/20/2025
Notification Time: 13:56 [ET]
Event Date: 10/02/2025
Event Time: 00:00 [CDT]
Last Update Date: 10/20/2025
Emergency Class: Non Emergency
10 CFR Section:
Agreement State
10 CFR Section:
Agreement State
Person (Organization):
Vossmar, Patricia (R4DO)
NMSS_EVENTS_NOTIFICATION (EMAIL)
Vossmar, Patricia (R4DO)
NMSS_EVENTS_NOTIFICATION (EMAIL)
EN Revision Imported Date: 10/21/2025
EN Revision Text: AGREEMENT STATE REPORT - STUCK OPEN GAUGE SHUTTER
The following information is a summary of information provided by the Arkansas Department of Health (the Department) via email:
During routine gauge shutter checks conducted by the licensee on October 2, 2025, the licensee found the shutters of three Berthold Technologies model LB300L fixed gauges stuck in the open position. The licensee has flagged the gauges, placed barriers around the gauges, and suspended any work in the area. The licensee is arranging for a Berthold field representative to perform maintenance on the gauges to attempt to close the gauges.
Gauge 1: 0.2 mCi Co-60
Gauge 2: 0.5 mCi Co-60
Gauge 3: 1.8 mCi Co-60
Arkansas event: AR-2025-013
* * * UPDATE ON 10/20/2025 AT 1617 EDT FROM HUNTER BROADAWAY TO JOSUE RAMIREZ * * *
The following information is a summary of information provided by the Arkansas Department of Health (the Department) via email:
On October 20, 2025, a response from DOMTAR A.W. LLC, Arkansas Licensee ARK-0354-03120, reports that under the direction of a Berthold Technologies representative, the three shutters were able to be cycled and are once again functional. Maintenance and leak testing were performed on the three gauges.
Arkansas event AR-2025-013 is considered closed by the Department.
EN Revision Text: AGREEMENT STATE REPORT - STUCK OPEN GAUGE SHUTTER
The following information is a summary of information provided by the Arkansas Department of Health (the Department) via email:
During routine gauge shutter checks conducted by the licensee on October 2, 2025, the licensee found the shutters of three Berthold Technologies model LB300L fixed gauges stuck in the open position. The licensee has flagged the gauges, placed barriers around the gauges, and suspended any work in the area. The licensee is arranging for a Berthold field representative to perform maintenance on the gauges to attempt to close the gauges.
Gauge 1: 0.2 mCi Co-60
Gauge 2: 0.5 mCi Co-60
Gauge 3: 1.8 mCi Co-60
Arkansas event: AR-2025-013
* * * UPDATE ON 10/20/2025 AT 1617 EDT FROM HUNTER BROADAWAY TO JOSUE RAMIREZ * * *
The following information is a summary of information provided by the Arkansas Department of Health (the Department) via email:
On October 20, 2025, a response from DOMTAR A.W. LLC, Arkansas Licensee ARK-0354-03120, reports that under the direction of a Berthold Technologies representative, the three shutters were able to be cycled and are once again functional. Maintenance and leak testing were performed on the three gauges.
Arkansas event AR-2025-013 is considered closed by the Department.
Page Last Reviewed/Updated October 21, 2025