ENS 53215
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ENS Event | |
|---|---|
04:53 Feb 16, 2018 | |
| Title | Automatic Reactor Trip Due to Low Departure from Nucleate Boiling Signal |
| 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 February 15, 2018, at approximately 2153 Mountain Standard Time (MST), the Palo Verde Nuclear Generating Station (PVNGS) Unit 1 Control Room received Reactor Protection System alarms for Low Departure from Nucleate Boiling Ratio and an automatic reactor trip occurred. Prior to the reactor trip, Unit 1 was operating normally at 100 percent power. Plant operators entered the emergency operations procedures and diagnosed an uncomplicated reactor trip but noted that Reactor Coolant Pumps 1B and 2B were not running due to a loss of power. All CEAs [Control Element Assemblies] fully inserted into the core. Following the reactor trip, all nuclear instruments responded normally. No emergency classification was required per the PVGS Emergency Plan. The PVGS Unit 1 safety related electrical busses remained energized from normal offsite power during the event. The Unit 1 'B' Diesel Generator is currently removed from service for maintenance. Due to ongoing planned maintenance on NAN-X02, Startup Transformer 2, fast bus transfer for NAN-S02 (from NAN-S04) was blocked. This resulted in a loss of offsite power to NAN-S02 and NBN-S02. The offsite power grid is stable. Unit 1 is currently stable in Mode 3 with the reactor coolant system at normal operating temperature and pressure. 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 Resident Inspector has been informed of the Unit 1 reactor trip.
Unit 1 is stable in Mode 3 following an uncomplicated trip. Offsite power has been restored to non-safety related electrical busses. Troubleshooting continues to determine the cause of the event. During performance of the alarm response procedure, it was identified that the seismic monitoring (SM) system had been in alarm since the reactor trip and was incapable of performing its emergency plan function. Pursuant to 10 CFR 50.72(b)(3)(xiii), this condition constitutes a major loss of emergency assessment capability. Compensatory measures have been implemented in accordance with PVNGS procedures to provide alternative methods for HU2.1 event classification with the SM system out of service. Maintenance is currently in progress to restore SM system functionality. The licensee notified the NRC Resident Inspector. Notified R4DO (Werner).
Station staff completed an evaluation of event EN #53215 reported on February 15, 2018, and determined that the seismic monitoring system remained capable of assessing a seismic event following the reactor trip. Therefore, a major loss of emergency assessment capability pursuant to 10 CFR 50.72(b)(3)(xiii) did not occur as reported in the update on February 16, 2018. The NRC Resident Inspectors have been notified. Notified the R4DO (Gaddy). |
| Where | |
|---|---|
Palo Verde  Arizona (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.72(b)(2)(iv)(B), RPS Actuation 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | |
| Time - Person (Reporting Time:+-2.05 h-0.0854 days <br />-0.0122 weeks <br />-0.00281 months <br />) | |
| Opened: | Jorge Lester 02:50 Feb 16, 2018 |
| NRC Officer: | Jeff Herrera |
| Last Updated: | Mar 30, 2018 |
| 53215 - NRC Website | |
Unit 1 | |
|---|---|
| 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)(xiii), Loss of Emergency Preparedness | |
WEEKMONTHYEARENS 565512023-06-02T11:05:0002 June 2023 11:05:00
[Table view]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 557962022-03-19T20:06:00019 March 2022 20:06:00 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness Loss of Technical Support Center (TSC) 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 554442021-09-01T03:50:0001 September 2021 03:50:00 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness Loss of Seismic Monitoring System 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 542722019-09-12T01:24:00012 September 2019 01:24:00 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness Main Steam Line Radiation Monitor Communication Failure 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 535752018-08-31T07:00:00031 August 2018 07:00:00 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness Unplanned Loss of Steam Line Monitor Channels ENS 535222018-07-23T07:00:00023 July 2018 07:00:00 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness Unplanned Loss of Steam Line Monitor Channels 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 529892017-09-22T22:00:00022 September 2017 22:00:00 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness Seismic Monitoring Computer Out-Of-Service ENS 522292016-09-09T01:56:0009 September 2016 01:56:00 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness Loss of the Seismic Monitoring System Computer 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 510412015-05-04T10:20:0004 May 2015 10:20:00 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness Seismic Monitoring System Out of Service ENS 496162013-12-08T15:00:0008 December 2013 15:00:00 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness Loss of Assessment Due to Technical Support Center Uninterruptable Power Supply Planned Replacement 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 488492013-03-25T17:30:00025 March 2013 17:30:00 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness One Alert Notification Siren Removed from Service for Planned Maintenance 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 472742011-09-18T15:30:00018 September 2011 15:30:00 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness Technical Support Center Out of Service Due to Planned Maintenance ENS 472682011-09-14T17:23:00014 September 2011 17:23:00 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness Loss of Two Public Warning System Sirens 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 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 463312010-10-14T16:15:00014 October 2010 16:15:00 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness Emergency Sirens Will Be Taken Out of Service for Planned Maintenance ENS 461882010-08-18T14:42:00018 August 2010 14:42:00 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness Loss of Several Public Warning System Sirens ENS 461402010-07-30T14:20:00030 July 2010 14:20:00 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness Loss of Emergency Siren ENS 459682010-06-01T14:15:0001 June 2010 14:15:00 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness Public Warning System Siren Out of Service 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 454252009-10-11T11:50:00011 October 2009 11:50:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident, 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness Reactor Water Level Indication Inoperable 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 449242009-03-21T16:00:00021 March 2009 16:00:00 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness Various Control Room Annunciators and Alarms Out of Service Due to Maintenance on Power Supply ENS 446922008-12-02T23:20:0002 December 2008 23:20:00 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness Loss of One (1) Emergency Siren ENS 446062008-10-28T16:00:00028 October 2008 16:00:00 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness Maintenance on Public Prompt Notification System Emergency Sirens 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 438242007-12-04T14:00:0004 December 2007 14:00:00 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness, 10 CFR 50.72(b)(3)(xii), Transport of a Contaminated Person Offsite Offsite Notification Due to Potential Loss of Three Sirens 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 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 427012006-07-12T14:30:00012 July 2006 14:30:00 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness One Siren in Ep Zone Is Out of Service 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 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 419412005-08-23T20:49:00023 August 2005 20:49:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release, 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness Two Emergency Sirens Inoperable ENS 419122005-08-11T15:45:00011 August 2005 15:45:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release, 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness One Emergency Preparedness Siren Out of Service ENS 418742005-07-26T23:35:00026 July 2005 23:35:00 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness Inoperable Single Emergency Siren ENS 418102005-06-29T11:43:00029 June 2005 11:43:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release, 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness Evacuation Siren Inoperable ENS 414862005-03-13T01:45:00013 March 2005 01:45:00 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness Loss of Operability of One Emergency Evacuation Siren ENS 414662005-03-07T15:10:0007 March 2005 15:10:00 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness Two Emergency Sirens Inoperable ENS 414512005-02-28T21:57:00028 February 2005 21:57:00 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness Major Loss of Siren Coverage within the Emergency Planning Zone 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 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 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 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. 2023-06-02T11:05:00 | |
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