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On December 3, 2009 at approximately 04:30 … On December 3, 2009 at approximately 04:30 Mountain Standard Time (MST) Palo Verde Unit 3 operators manually tripped the reactor from approximately 100% rated thermal power due to loss of Instrument Air (IA) to Containment. This loss was apparently caused by a failure (closed) of the outboard IA Containment Isolation Valve (CIV) solenoid valve. Loss of IA to Containment resulted in closure of the inboard Reactor Coolant Pump (RCP) controlled seal bleedoff CIV. The RCP seal bleedoff was then being diverted via relief valve to the Reactor Drain Tank (RDT) inside Containment.</br>Following the manual reactor trip all CEAs (Control Element Assemblies) fully inserted into the reactor core. All 4 RCPs were stopped to allow for isolation of bleedoff to the RDT. Upon completion of Standard Post Trip Actions, the crew entered the Optimal Recovery Procedure for Loss of Forced Circulation. 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. LCO 3.6.3 was entered due to failure of the IA CIV. No major equipment was inoperable prior to the event which contributed to the need for manual reactor trip.</br>The reactor was manually tripped for equipment preservation. No safety or relief valves lifted other than noted above. After the trip, decay heat was being removed using the turbine bypass valves and steam generator level was being maintained with the auxiliary feedwater pumps. The licensee also entered LCO 3.4.5, "RCS Loop Operability" because the RCPs were stopped.</br>The licensee notified the NRC Resident Inspector.ensee notified the NRC Resident Inspector. +
11:30:00, 3 December 2009 +
45,537 +
09:14:00, 3 December 2009 +
11:30:00, 3 December 2009 +
On December 3, 2009 at approximately 04:30 … On December 3, 2009 at approximately 04:30 Mountain Standard Time (MST) Palo Verde Unit 3 operators manually tripped the reactor from approximately 100% rated thermal power due to loss of Instrument Air (IA) to Containment. This loss was apparently caused by a failure (closed) of the outboard IA Containment Isolation Valve (CIV) solenoid valve. Loss of IA to Containment resulted in closure of the inboard Reactor Coolant Pump (RCP) controlled seal bleedoff CIV. The RCP seal bleedoff was then being diverted via relief valve to the Reactor Drain Tank (RDT) inside Containment.</br>Following the manual reactor trip all CEAs (Control Element Assemblies) fully inserted into the reactor core. All 4 RCPs were stopped to allow for isolation of bleedoff to the RDT. Upon completion of Standard Post Trip Actions, the crew entered the Optimal Recovery Procedure for Loss of Forced Circulation. 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. LCO 3.6.3 was entered due to failure of the IA CIV. No major equipment was inoperable prior to the event which contributed to the need for manual reactor trip.</br>The reactor was manually tripped for equipment preservation. No safety or relief valves lifted other than noted above. After the trip, decay heat was being removed using the turbine bypass valves and steam generator level was being maintained with the auxiliary feedwater pumps. The licensee also entered LCO 3.4.5, "RCS Loop Operability" because the RCPs were stopped.</br>The licensee notified the NRC Resident Inspector.ensee notified the NRC Resident Inspector. +
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