Event Notification Report for November 10, 2002
U.S. Nuclear Regulatory Commission
Operations Center
EVENT REPORTS FOR
11/09/2002 - 11/10/2002
EVENT NUMBERS
39361
Power Reactor
Event Number: 39361
Facility: PALO VERDE
Region: 4 State: AZ
Unit: [1] [] []
RX Type: [1] CE,[2] CE,[3] CE
NRC Notified By: RAY BUZZARD
HQ OPS Officer: GERRY WAIG
Region: 4 State: AZ
Unit: [1] [] []
RX Type: [1] CE,[2] CE,[3] CE
NRC Notified By: RAY BUZZARD
HQ OPS Officer: GERRY WAIG
Notification Date: 11/11/2002
Notification Time: 04:28 [ET]
Event Date: 11/10/2002
Event Time: 22:50 [MST]
Last Update Date: 11/11/2002
Notification Time: 04:28 [ET]
Event Date: 11/10/2002
Event Time: 22:50 [MST]
Last Update Date: 11/11/2002
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):
TROY PRUETT (R4)
TROY PRUETT (R4)
| Unit | SCRAM Code | RX Crit | Initial PWR | Initial RX Mode | Current PWR | Current RX Mode |
|---|---|---|---|---|---|---|
| 1 | A/R | Y | 63 | Power Operation | 0 | Hot Standby |
AUTOMATIC REACTOR TRIP - RPS ACTUATION FROM LOW DNBR SIGNAL
"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 10CFR50.73.
"At approximately 2250 Mountain Standard Time (MST) Palo Verde Nuclear Generating Station Unit 1 experienced an automatic reactor trip. The trip is believed to have been caused by a control element assembly deviation that resulted in the generation of a low departure from nucleate boiling (DNBR) trip signal. The cause of the CEA deviation is not known at this time. At the time of the trip the plant was being shutdown in a planned effort to effect repairs on the A train shutdown cooling suction line that had been experiencing high vibration.
"All CEAs inserted into the core and safety systems actuated as expected. No other essential safety system actuations occurred and none were required. The plant did experience a loss of letdown flow when nuclear cooling water to the letdown heat exchanger was sensed as being low. Letdown has been restored.
"The plant is currently operating in Mode 3, Hot Shutdown. Safety and non-safety related electrical buses remained energized during and following the reactor trip. The offsite power grid is stable. No major equipment was inoperable prior to the event that contributed to the event."
The licensee has notified the NRC Resident Inspector of this event.
"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 10CFR50.73.
"At approximately 2250 Mountain Standard Time (MST) Palo Verde Nuclear Generating Station Unit 1 experienced an automatic reactor trip. The trip is believed to have been caused by a control element assembly deviation that resulted in the generation of a low departure from nucleate boiling (DNBR) trip signal. The cause of the CEA deviation is not known at this time. At the time of the trip the plant was being shutdown in a planned effort to effect repairs on the A train shutdown cooling suction line that had been experiencing high vibration.
"All CEAs inserted into the core and safety systems actuated as expected. No other essential safety system actuations occurred and none were required. The plant did experience a loss of letdown flow when nuclear cooling water to the letdown heat exchanger was sensed as being low. Letdown has been restored.
"The plant is currently operating in Mode 3, Hot Shutdown. Safety and non-safety related electrical buses remained energized during and following the reactor trip. The offsite power grid is stable. No major equipment was inoperable prior to the event that contributed to the event."
The licensee has notified the NRC Resident Inspector of this event.