Event Notification Report for April 11, 2023
U.S. Nuclear Regulatory Commission
Operations Center
EVENT REPORTS FOR
04/10/2023 - 04/11/2023
Power Reactor
Event Number: 56459
Facility: Palo Verde
Region: 4 State: AZ
Unit: [1] [] []
RX Type: [1] CE,[2] CE,[3] CE
NRC Notified By: Yolanda Good
HQ OPS Officer: Donald Norwood
Notification Date: 04/09/2023
Notification Time: 04:42 [ET]
Event Date: 04/08/2023
Event Time: 21:44 [MST]
Last Update Date: 04/09/2023
Emergency Class: Non Emergency
10 CFR Section:
50.72(b)(2)(iv)(B) - RPS Actuation - Critical
50.72(b)(3)(iv)(A) - Valid Specif Sys Actuation
Person (Organization):
Warnick, Greg (R4DO)
Power Reactor Unit Info
Unit |
SCRAM Code |
RX Crit |
Initial PWR |
Initial RX Mode |
Current PWR |
Current RX Mode |
1 |
A/R |
Y |
100 |
Power Operation |
0 |
Hot Standby |
Event Text
AUTOMATIC REACTOR TRIP DUE TO LOSS OF REACTOR COOLANT PUMPS
The following information was provided by the licensee via email:
"The following event description is based on information currently available. If through subsequent reviews of this event additional information is identified that is pertinent to this event or alters the information being provided at this time a follow-up notification will be made via the ENS or under the reporting requirements of 10 CFR 50.73.
"At 2144 MST on April 8, 2023, the Unit 1 reactor automatically tripped due to the loss of reactor coolant pumps stemming from the loss of 13.8 kV power to the pumps.
"Prior to the reactor trip, the main turbine tripped due to a loss of hydraulic pressure. The main generator output breakers did not automatically open on the turbine trip as expected so the control room operators opened the breakers per procedural guidance. Once the breakers were opened, the two 13.8 kV electrical distribution buses failed to complete a fast bus transfer, which resulted in the loss of power to the reactor coolant pumps, initiating the reactor trip. The control room operators manually actuated a main steam isolation signal per procedure, requiring use of the atmospheric dump valves.
"Following the reactor trip, all control element assemblies inserted fully into the core. No automatic specified system actuation was required or occurred. No emergency plan classification was required per the Emergency Plan. Safety related buses remained powered from offsite power during the event and the offsite power grid is stable. Unit 1 is stable and in Mode 3. Decay heat is being removed by the atmospheric dump valves and the class 1E powered motor driven auxiliary feedwater pump.
"The loss of hydraulic pressure, the main generator output breakers failing to automatically open and the fast bus transfer not actuating are being investigated.
"This event is being reported as a reactor protection system actuation in accordance with the reporting criteria of 10 CFR 50.72(b)(2)(iv)(B).
"The NRC Senior Resident Inspector has been informed.
"Unit 2 is in a refueling outage in Mode 5 and Unit 3 is in Mode 1 at 100 percent power."
* * * UPDATE ON 4/9/23 AT 0835 EDT FROM TANNER GOODMAN TO ADAM KOZIOL * * *
"This update is being made to report the manual actuation of the B-train auxiliary feedwater pump and manual main steam isolation signal (MSIS) actuation affecting multiple main steam isolation valves (MSIVs) following the reactor trip.
"This event is being reported as a reactor protection system actuation in accordance with the reporting criteria of 10 CFR 50.72(b)(2)(iv)(B) and a specified system actuation in accordance with 10 CFR 50.72(b)(3)(iv)(A).
"The NRC Senior Resident Inspector has been informed of the update."
Power Reactor
Event Number: 56460
Facility: Vogtle 3/4
Region: 2 State: GA
Unit: [3] [] []
RX Type: [3] W-AP1000,[4] W-AP1000
NRC Notified By: Tommie Sweat
HQ OPS Officer: Adam Koziol
Notification Date: 04/10/2023
Notification Time: 04:34 [ET]
Event Date: 04/10/2023
Event Time: 00:48 [EDT]
Last Update Date: 04/10/2023
Emergency Class: Non Emergency
10 CFR Section:
50.72(b)(2)(iv)(B) - RPS Actuation - Critical
Person (Organization):
Miller, Mark (R2DO)
Power Reactor Unit Info
Unit |
SCRAM Code |
RX Crit |
Initial PWR |
Initial RX Mode |
Current PWR |
Current RX Mode |
3 |
A/R |
Y |
18 |
Power Operation |
0 |
Hot Standby |
Event Text
AUTOMATIC REACTOR TRIP
The following information was provided by the licensee via email:
"At 0048 EDT on 4/10/2023, with Unit 3 in Mode 1 at 18 percent power, the reactor automatically tripped due to low reactor coolant flow due to voltage decaying to the reactor coolant pumps during main generator testing activities. The trip was not complex, with all safety-related systems responding normally post-trip.
"Operations responded and stabilized the plant. Decay heat is being removed by discharging steam via steam generator power operated relief valves to atmosphere. Units 1, 2, and 4 are not affected.
"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).
"There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified."