Event Notification Report for April 11, 2025
U.S. Nuclear Regulatory Commission
Operations Center
EVENT REPORTS FOR
04/10/2025 - 04/11/2025
EVENT NUMBERS
57743
57743
Power Reactor
Event Number: 57743
Facility: Watts Bar
Region: 2 State: TN
Unit: [2] [] []
RX Type: [1] W-4-LP,[2] W-4-LP
NRC Notified By: Daniel Hudson
HQ OPS Officer: Karen Cotton
Region: 2 State: TN
Unit: [2] [] []
RX Type: [1] W-4-LP,[2] W-4-LP
NRC Notified By: Daniel Hudson
HQ OPS Officer: Karen Cotton
Notification Date: 06/05/2025
Notification Time: 14:50 [ET]
Event Date: 04/11/2025
Event Time: 23:15 [EDT]
Last Update Date: 06/05/2025
Notification Time: 14:50 [ET]
Event Date: 04/11/2025
Event Time: 23:15 [EDT]
Last Update Date: 06/05/2025
Emergency Class: Non Emergency
10 CFR Section:
50.73(a)(1) - Invalid Specif System Actuation
10 CFR Section:
50.73(a)(1) - Invalid Specif System Actuation
Person (Organization):
Blamey, Alan (R2DO)
Blamey, Alan (R2DO)
| Unit | SCRAM Code | RX Crit | Initial PWR | Initial RX Mode | Current PWR | Current RX Mode |
|---|---|---|---|---|---|---|
| 2 | N | Y | 0 | Hot Standby | 100 | Power Operation |
INVALID SPECIFIED SYSTEM ACTUATION
The following information was provided by the licensee via phone and email:
"At 2315 EDT on April 11, 2025, the spare train of Unit 2 auxiliary feedwater (AFW), the turbine-driven AFW pump (TDAFWP), automatically started. At the time, Unit 2 was entering a refueling outage and had been shutdown to hot standby conditions. Sufficient makeup water to the steam generators was being supplied by the 'A' and 'B' trains of AFW, [both] motor-driven AFW pumps. Several hours before this automatic start, feed from all main feedwater pumps (MFWPs) and the TDAFWP had been secured.
"The TDAFWP automatically started during the alignment of Unit 2 balance-of-plant to support the outage. As part of the alignment, condenser vacuum for the '2A' MFWP was broken prior to the de-energization of the '2A' MFWP's turbine trip bus. Even though the '2A' MFWP was incapable of providing any main feedwater flow, the order in which these two events were performed appeared to the protective circuitry as a low-vacuum trip of the '2A' MWFP, and thus a loss of all MFWPs. The loss of all MFWPs is an automatic start signal to the TDAFWP.
"This report is being made under 10 CFR 50.73(a)(2)(iv)(A) as an event that resulted in an invalid actuation of the Unit 2 TDAFWP.
"There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector was notified of the event."
The following information was provided by the licensee via phone and email:
"At 2315 EDT on April 11, 2025, the spare train of Unit 2 auxiliary feedwater (AFW), the turbine-driven AFW pump (TDAFWP), automatically started. At the time, Unit 2 was entering a refueling outage and had been shutdown to hot standby conditions. Sufficient makeup water to the steam generators was being supplied by the 'A' and 'B' trains of AFW, [both] motor-driven AFW pumps. Several hours before this automatic start, feed from all main feedwater pumps (MFWPs) and the TDAFWP had been secured.
"The TDAFWP automatically started during the alignment of Unit 2 balance-of-plant to support the outage. As part of the alignment, condenser vacuum for the '2A' MFWP was broken prior to the de-energization of the '2A' MFWP's turbine trip bus. Even though the '2A' MFWP was incapable of providing any main feedwater flow, the order in which these two events were performed appeared to the protective circuitry as a low-vacuum trip of the '2A' MWFP, and thus a loss of all MFWPs. The loss of all MFWPs is an automatic start signal to the TDAFWP.
"This report is being made under 10 CFR 50.73(a)(2)(iv)(A) as an event that resulted in an invalid actuation of the Unit 2 TDAFWP.
"There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector was notified of the event."