Event Notification Report for October 10, 2024
U.S. Nuclear Regulatory Commission
Operations Center
EVENT REPORTS FOR
10/09/2024 - 10/10/2024
Power Reactor
Event Number: 57372
Facility: Calvert Cliffs
Region: 1 State: MD
Unit: [2] [] []
RX Type: [1] CE,[2] CE
NRC Notified By: Ryan Baker
HQ OPS Officer: Natalie Starfish
Region: 1 State: MD
Unit: [2] [] []
RX Type: [1] CE,[2] CE
NRC Notified By: Ryan Baker
HQ OPS Officer: Natalie Starfish
Notification Date: 10/10/2024
Notification Time: 08:45 [ET]
Event Date: 10/10/2024
Event Time: 05:57 [EDT]
Last Update Date: 10/10/2024
Notification Time: 08:45 [ET]
Event Date: 10/10/2024
Event Time: 05:57 [EDT]
Last Update Date: 10/10/2024
Emergency Class: Non Emergency
10 CFR Section:
50.72(b)(2)(iv)(B) - RPS Actuation - Critical
10 CFR Section:
50.72(b)(2)(iv)(B) - RPS Actuation - Critical
Person (Organization):
Arner, Frank (R1DO)
Arner, Frank (R1DO)
| Unit | SCRAM Code | RX Crit | Initial PWR | Initial RX Mode | Current PWR | Current RX Mode |
|---|---|---|---|---|---|---|
| 2 | A/R | Y | 100 | Power Operation | 0 | Hot Standby |
AUTOMATIC REACTOR TRIP DUE TO TURBINE GENERATOR LOSS OF FIELD
The following information was provided by the licensee via phone and email:
"At 0557 EDT on 10/10/2024, with Unit 2 in mode 1 at 100 percent power, the reactor automatically tripped due to turbine generator loss of field. The trip was not complex with all systems responding normally post-trip. Due to the reactor protection system actuation while critical, this event is being reported as a four-hour, non-emergency notification per 10 CFR 50.72(b)(2)(iv)(B).
"Operations responded using EOP-0, post trip immediate actions, and stabilized the plant in mode 3. Decay heat is removed by discharging steam to the main condenser using the turbine bypass valves.
"Unit 1 is not affected.
"There was no impact on the health and safety of the public or plant personnel. 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 exciter is suspected to being the cause and is under investigation. All control rods fully inserted.
The following information was provided by the licensee via phone and email:
"At 0557 EDT on 10/10/2024, with Unit 2 in mode 1 at 100 percent power, the reactor automatically tripped due to turbine generator loss of field. The trip was not complex with all systems responding normally post-trip. Due to the reactor protection system actuation while critical, this event is being reported as a four-hour, non-emergency notification per 10 CFR 50.72(b)(2)(iv)(B).
"Operations responded using EOP-0, post trip immediate actions, and stabilized the plant in mode 3. Decay heat is removed by discharging steam to the main condenser using the turbine bypass valves.
"Unit 1 is not affected.
"There was no impact on the health and safety of the public or plant personnel. 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 exciter is suspected to being the cause and is under investigation. All control rods fully inserted.
Power Reactor
Event Number: 57373
Facility: Davis Besse
Region: 3 State: OH
Unit: [1] [] []
RX Type: [1] B&W-R-LP
NRC Notified By: Michael Boles
HQ OPS Officer: Kerby Scales
Region: 3 State: OH
Unit: [1] [] []
RX Type: [1] B&W-R-LP
NRC Notified By: Michael Boles
HQ OPS Officer: Kerby Scales
Notification Date: 10/10/2024
Notification Time: 11:39 [ET]
Event Date: 10/10/2024
Event Time: 10:45 [EDT]
Last Update Date: 10/10/2024
Notification Time: 11:39 [ET]
Event Date: 10/10/2024
Event Time: 10:45 [EDT]
Last Update Date: 10/10/2024
Emergency Class: Non Emergency
10 CFR Section:
50.72(b)(3)(ii)(B) - Unanalyzed Condition
10 CFR Section:
50.72(b)(3)(ii)(B) - Unanalyzed Condition
Person (Organization):
Orlikowski, Robert (R3DO)
Orlikowski, Robert (R3DO)
| Unit | SCRAM Code | RX Crit | Initial PWR | Initial RX Mode | Current PWR | Current RX Mode |
|---|---|---|---|---|---|---|
| 1 | N | Y | 100 | Power Operation | 100 | Power Operation |
UNANALYZED CONDITION
The following information was provided by the licensee via phone and email:
"On October 10, 2024, at 1045 EDT, it was determined that an additional failure mechanism existed for a previous issue with the emergency diesel generator (EDG) speed switches. As a result, for some initiating events such as a fire or high energy line break potentially causing a ground on the negative buses on both trains of the station direct current (DC) system, both EDG speed switches could have been affected, resulting in a failure of the EDGs to function.
"This condition is not bounded by existing design and licensing documents; however, it poses no impact to the health and safety of the public or plant personnel, as the EDG speed switches were replaced in January 2022 with a different design that is not susceptible to grounds on the station DC system. This event is being reported as an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(ii)(B).
"The NRC Resident Inspector has been notified."
The following information was provided by the licensee via phone and email:
"On October 10, 2024, at 1045 EDT, it was determined that an additional failure mechanism existed for a previous issue with the emergency diesel generator (EDG) speed switches. As a result, for some initiating events such as a fire or high energy line break potentially causing a ground on the negative buses on both trains of the station direct current (DC) system, both EDG speed switches could have been affected, resulting in a failure of the EDGs to function.
"This condition is not bounded by existing design and licensing documents; however, it poses no impact to the health and safety of the public or plant personnel, as the EDG speed switches were replaced in January 2022 with a different design that is not susceptible to grounds on the station DC system. This event is being reported as an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(ii)(B).
"The NRC Resident Inspector has been notified."
Power Reactor
Event Number: 57422
Facility: Millstone
Region: 1 State: CT
Unit: [3] [] []
RX Type: [1] GE-3,[2] CE,[3] W-4-LP
NRC Notified By: Robert Mello
HQ OPS Officer: Tenisha Meadows
Region: 1 State: CT
Unit: [3] [] []
RX Type: [1] GE-3,[2] CE,[3] W-4-LP
NRC Notified By: Robert Mello
HQ OPS Officer: Tenisha Meadows
Notification Date: 11/13/2024
Notification Time: 13:38 [ET]
Event Date: 10/10/2024
Event Time: 09:02 [EST]
Last Update Date: 11/13/2024
Notification Time: 13:38 [ET]
Event Date: 10/10/2024
Event Time: 09:02 [EST]
Last Update Date: 11/13/2024
Emergency Class: Non Emergency
10 CFR Section:
50.72(b)(3)(v)(C) - Pot Uncntrl Rad Rel 50.72(b)(3)(v)(D) - Accident Mitigation
10 CFR Section:
50.72(b)(3)(v)(C) - Pot Uncntrl Rad Rel 50.72(b)(3)(v)(D) - Accident Mitigation
Person (Organization):
Lilliendahl, Jon (R1DO)
Lilliendahl, Jon (R1DO)
| Unit | SCRAM Code | RX Crit | Initial PWR | Initial RX Mode | Current PWR | Current RX Mode |
|---|---|---|---|---|---|---|
| 3 | N | Y | 100 | Power Operation | 100 | Power Operation |
SECONDARY CONTAINMENT BOUNDARY INOPERABLE
The following information was provided by the licensee via phone and email:
"At 0902 EST, on 10/10/2024, with Millstone Unit 3 in mode 1 at 100 percent power, it was discovered that the secondary containment boundary was inoperable when the latch that secured a hatch that was part of the secondary containment boundary was not functional. The latch was repaired by 1115, on 10/10/2024, and the secondary containment boundary was declared operable at 1200, on 10/10/2024. The initial assessment of reportability concluded that an immediate report was not required. However, upon additional review, it has been determined that because the secondary containment boundary is a single-train system that performs a safety function, an 8-hour report was required in accordance with 10 CFR 50. 72 (b)(3)(v)(C) and (D).
"This report should have been made on 10/10/2024 and is late.
"There has been no impact to Unit 2, and Unit 3 continues to operate in mode 1 at 100 percent power.
"There is no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified."
The following information was provided by the licensee via phone and email:
"At 0902 EST, on 10/10/2024, with Millstone Unit 3 in mode 1 at 100 percent power, it was discovered that the secondary containment boundary was inoperable when the latch that secured a hatch that was part of the secondary containment boundary was not functional. The latch was repaired by 1115, on 10/10/2024, and the secondary containment boundary was declared operable at 1200, on 10/10/2024. The initial assessment of reportability concluded that an immediate report was not required. However, upon additional review, it has been determined that because the secondary containment boundary is a single-train system that performs a safety function, an 8-hour report was required in accordance with 10 CFR 50. 72 (b)(3)(v)(C) and (D).
"This report should have been made on 10/10/2024 and is late.
"There has been no impact to Unit 2, and Unit 3 continues to operate in mode 1 at 100 percent power.
"There is no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified."