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Event Notification Report for September 29, 2008

U.S. Nuclear Regulatory Commission
Operations Center

Event Reports For
09/26/2008 - 09/29/2008

** EVENT NUMBERS **


44525

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Power Reactor Event Number: 44525
Facility: PALO VERDE
Region: 4 State: AZ
Unit: [ ] [ ] [3]
RX Type: [1] CE,[2] CE,[3] CE
NRC Notified By: JOHN ARONSON
HQ OPS Officer: STEVE SANDIN
Notification Date: 09/28/2008
Notification Time: 02:35 [ET]
Event Date: 09/27/2008
Event Time: 21:51 [MST]
Last Update Date: 09/28/2008
Emergency Class: NON EMERGENCY
10 CFR Section:
50.72(b)(2)(iv)(B) - RPS ACTUATION - CRITICAL
Person (Organization):
WILLIAM JONES (R4)

Unit SCRAM Code RX CRIT Initial PWR Initial RX Mode Current PWR Current RX Mode
3 M/R Y 34 Power Operation 0 Hot Standby

Event Text

UNIT 3 REACTOR MANUALLY TRIPPED FOLLOWING AUTOMATIC TURBINE TRIP ON HIGH VIBRATION

"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 under the reporting requirements of 10CFR50.73.

"On September 27, 2008, at approximately 21:51 Mountain Standard Time (MST) Palo Verde Unit 3 operators manually tripped the reactor from approximately 34% rated thermal power in response to an automatic trip of the main turbine. The unit was being shutdown from 100% power due to a chemistry excursion in the secondary plant. Following the manual reactor trip all CEAs fully inserted into the reactor core. This was an uncomplicated reactor trip. No emergency classification was required per the Emergency Plan. No automatic ESF actuations occurred and none were required. Safety related buses remained energized during and following the reactor trip. The Emergency Diesel Generators did not start and were not required. The offsite power grid is stable. No LCOs have been entered as a result of this event. No major equipment was inoperable prior to the event that contributed to the event.

"Unit 3 is stable at normal operating temperature and pressure in Mode 3. Decay heat removal is via the Steam Generators and Main Feedwater to the Main Condenser using the Steam Bypass Control System. The event did not result in any challenges to fission product barriers and there were no adverse safety consequences as a result of this event. The event did not adversely affect the safe operation of the plant or the health and safety of the public.

"The main turbine tripped on high vibration.

"The Senior Resident Inspector was informed of the Unit 3 reactor trip."

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Thursday, March 29, 2012