ENS 46556
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ENS Event | |
|---|---|
01:41 Jan 20, 2011 | |
| Title | Reactor Trip Due to Main Feedwater Pump Trip |
| Event Description | 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.
On January 19, 2011, at approximately 1840 Mountain Standard Time (MST), Palo Verde Unit 3 received a Reactor Power Cutback (RPCB) due to the 'B' Main Feedwater Pump (MFP) tripping on low suction pressure in response to the 'A' MFP mini-flow valve failing open. Reactor power lowered to approximately 60% in response to the RPCB. Steam Generator levels continued to decrease and a Reactor Trip occurred on Low Steam Generator #1 level at 18:41. Unit 3 was at normal operating temperature and pressure prior to the trip. Following the automatic reactor trip all CEAs [Control Element Assemblies] inserted fully into the reactor core. No emergency classification was required per the Emergency Plan. An AFAS-2 [Auxiliary Feedwater Actuation Signal] occurred at 1844 on low Steam Generator #2 level. Safety related busses remained energized during and following the reactor trip. The Emergency Diesel Generators started in response to the AFAS-2 actuation but did not energize the class 4.16kV buses as they remained energized from off-site power. The offsite power grid is stable. 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 feeding the steam generators with Auxiliary Feedwater pump 'B'. 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 [NRC] Senior Resident Inspector was informed of the Unit 3 reactor trip. Unit 3 is in a normal post-trip electrical lineup. Decay heat is being removed via the turbine bypass valves to the main condenser. No safety valves on the secondary or primary side opened. |
| Where | |
|---|---|
Palo Verde  Arizona (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.72(b)(2)(iv)(B), RPS Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | |
| Time - Person (Reporting Time:+-1.55 h-0.0646 days <br />-0.00923 weeks <br />-0.00212 months <br />) | |
| Opened: | Rob Warner 00:08 Jan 20, 2011 |
| NRC Officer: | Donald Norwood |
| Last Updated: | Jan 20, 2011 |
| 46556 - NRC Website
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Unit 3 | |
|---|---|
| Reactor critical | Critical |
| Scram | A/R |
| Before | Power Operation (100 %) |
| After | Hot Standby (0 %) |
Palo Verde with 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation | |
WEEKMONTHYEARENS 576592025-04-10T14:11:00010 April 2025 14:11:00
[Table view]10 CFR 50.72(a)(1)(i), Emergency Class Declaration, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Unusual Event - Loss of All But One AC Power Source to Emergency Buses ENS 576562025-04-09T02:24:0009 April 2025 02:24:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Valid Actuation of Emergency AC Electrical Power Systems ENS 570472024-03-24T23:34:00024 March 2024 23:34:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Valid Specified System Actuations of Unit 2 Train B Emergency Diesel Generator and Train B Auxiliary Feedwater ENS 565512023-06-02T11:05:0002 June 2023 11:05:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Reactor Trip ENS 564592023-04-09T04:44:0009 April 2023 04:44:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Reactor Trip Due to Loss of Reactor Coolant Pumps ENS 560442022-08-15T00:02:00015 August 2022 00:02:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Valid Actuations of Unit 1 and Unit 3 Emergency Diesel Generators and Unit 1 Auxiliary Feedwater Pump ENS 558782022-05-05T02:55:0005 May 2022 02:55:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Valid Actuation of Unit 2 and Unit 3 Emergency Diesel Generators and Unit 3 Auxiliary Feedwater Pump ENS 556262021-12-06T19:03:0006 December 2021 19:03:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Unit 3 Automatic Trip ENS 555342021-10-20T21:46:00020 October 2021 21:46:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Valid Specified System Actuations of Unit 1 and Unit 3 Emergency Diesel Generators ENS 552652021-05-19T10:15:00019 May 2021 10:15:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Automatic Reactor Trip Due to High Pressurizer Pressure ENS 551142021-02-26T17:33:00026 February 2021 17:33:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Reactor Trip Due to Loss of Two Reactor Coolant Pumps ENS 545602020-03-04T03:50:0004 March 2020 03:50:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Reactor Trip Due to Low Steam Generator Level ENS 542242019-08-16T15:21:00016 August 2019 15:21:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Reactor Trip Due to Turbine Trip ENS 534772018-06-27T07:00:00027 June 2018 07:00:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Reactor Trip on Low Steam Generator Water Level ENS 534242018-05-23T18:28:00023 May 2018 18:28:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Automatic Reactor Trip on Low Departure from Nucleate Boiling Ratio ENS 532152018-02-16T04:53:00016 February 2018 04:53:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness Automatic Reactor Trip Due to Low Departure from Nucleate Boiling Signal ENS 522262016-09-08T04:31:0008 September 2016 04:31:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Manual Reactor Trip Due to Stuck Open Pressurizer Main Spray Valve ENS 496002013-12-03T00:58:0003 December 2013 00:58:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Automatic Reactor Trip Following the Loss of the 1A Reactor Coolant Pump ENS 478372012-04-15T19:20:00015 April 2012 19:20:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Manual Reactor Trip Due to Control Rod Deviation During Startup ENS 474722011-11-23T02:25:00023 November 2011 02:25:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Manual Reactor Trip Due to Control Element Deviation ENS 471332011-08-06T18:19:0006 August 2011 18:19:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Automatic Reactor Trip Due to Dropped Control Element Assembly ENS 466332011-02-22T03:01:00022 February 2011 03:01:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Auto Start and Load of Edgs on Units 1&3 Following Loss of Start-Up Transformer ENS 465562011-01-20T01:41:00020 January 2011 01:41:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Reactor Trip Due to Main Feedwater Pump Trip ENS 457482010-03-07T18:24:0007 March 2010 18:24:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(a)(1)(i), Emergency Class Declaration Notification of Unusual Event Due to Electrical Fault Causing Damage to Equipment ENS 455372009-12-03T11:30:0003 December 2009 11:30:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Manual Reactor Trip After Loss of Instrument Air to Containment ENS 449702009-04-04T06:54:0004 April 2009 06:54:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Manual Reactor Scram Due to High Vibrations in the Turbine ENS 445252008-09-28T04:51:00028 September 2008 04:51:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Unit 3 Reactor Manually Tripped Following Automatic Turbine Trip on High Vibration ENS 444962008-09-16T21:00:00016 September 2008 21:00:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Manual Reactor Trip During Troubleshooting of Control Rod Drive Mechanism Motor Generators ENS 442462008-05-29T04:34:00029 May 2008 04:34:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Manual Reactor Trip Due to Improper Movement of Cea'S ENS 436972007-10-06T17:59:0006 October 2007 17:59:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Manual Reactor Trip Due to Condenser Tube Rupture ENS 429382006-10-27T06:53:00027 October 2006 06:53:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Loss of Power to the Unit 1 and Unit 3 Train B Safety Buses with Emergency Diesel Generator Actuation ENS 429252006-10-21T22:48:00021 October 2006 22:48:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Automatic Reactor Trip Due to Control Element Assembly Position Transmitter Output Deviations ENS 429202006-10-19T18:47:00019 October 2006 18:47:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Manual Reactor Trip Following the Trip of Secondary Condensate Pumps ENS 427302006-07-26T14:35:00026 July 2006 14:35:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Variable Overpower Reactor Trip Following Turbine Control Valve Maintenance ENS 426812006-07-02T02:28:0002 July 2006 02:28:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Manual Reactor Trip Following Large Leak in Condensate System ENS 426092006-05-30T15:13:00030 May 2006 15:13:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Loss of Power to Train "a" 4 Kv Safety Bus ENS 425592006-05-06T23:35:0006 May 2006 23:35:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Valid Actuation of Emergency Diesel Generator Due to Low Voltage Condition ENS 424682006-04-03T03:54:0003 April 2006 03:54:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Emergency Diesel Trip During Testing ENS 423872006-03-05T14:10:0005 March 2006 14:10:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Automatic Reactor Trip Due to Low Departure from Nucleate Boiling Ratio. ENS 419512005-08-27T01:24:00027 August 2005 01:24:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Rps Actuation - Reactor Scram on High Steam Generator Level ENS 413792005-02-07T05:19:0007 February 2005 05:19:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Emergency Diesel Start Due to Bus Deenergization ENS 413042004-12-31T17:42:00031 December 2004 17:42:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Plant Had Auto Start and Loading of Two Emergency Diesel Gererators ENS 408702004-07-14T08:35:00014 July 2004 08:35:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Automatic Reactor Trip Following a Main Generator Trip ENS 408162004-06-14T14:44:00014 June 2004 14:44:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release, 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(a)(1)(i), Emergency Class Declaration, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Unusual Event Due to Reactor Trip Due to Loss of Off Site Power ENS 408152004-06-14T14:44:00014 June 2004 14:44:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release, 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(a)(1)(i), Emergency Class Declaration, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Unusual Event Declared Due to Reactor Trip Due to Loss of Off Site Power ENS 408142004-06-14T14:44:00014 June 2004 14:44:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release, 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(a)(1)(i), Emergency Class Declaration, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Alert Declared - Reactor Trip Due to Loss of Off Site Power ENS 407952004-06-07T21:58:0007 June 2004 21:58:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Reactor Trip Due to Main Turbine Electro-Hydraulic Control System Failure ENS 407372004-05-09T03:39:0009 May 2004 03:39:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Manual Reactor Trip During Physics Testing Due to Control Element Assembly Slipping 6 Inches. ENS 403492003-11-22T05:53:00022 November 2003 05:53:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Valid Actuation of the "a" Emergency Diesel Generator During Testing 2025-04-09T02:24:00 | |
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