ENS 42050
ENS Event | |
|---|---|
23:02 Oct 11, 2005 | |
| Title | Tech Spec Required Shutdown of Both Unit 2 and 3 |
| 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 October 11, 2005 Palo Verde Nuclear Generating Station (PVNGS) Units 2 and 3 at approximately 1602 and 1655 Mountain Standard Time (MST), respectively commenced reactor shutdowns required by Technical Specification 3.0.3. Engineering personnel were unable to demonstrate that the original design of the Emergency Core Cooling System (ECCS) could perform its safety function for its mission time under certain postulated accident scenarios. Specifically, the Refueling Water Tank (RWT) is designed with baffles to prevent a vortex from developing and air binding the Safety Injection pumps during a Loss of Coolant Accident (LOCA). On a LOCA, the High Pressure Safety Injection pumps take a suction from the RWT and inject borated water into the Reactor Coolant System (RCS). At 7.4 percent RWT level, the source of borated water by design automatically shifts from the RWT to the containment sump. However, for small break LOCA there may be insufficient containment pressure to ensure inventory is not continuing to be drawn from the RWT. This may allow the baffles in the bottom of the RWT to uncover. With the RWT baffles uncovered, a vortex may develop, leading to potential air binding of the Safety Injection pumps before the operator manually isolates the RWT. At approximately 1333 Mountain Standard Time, based on the inability to demonstrate that the ECCS can perform its safety function under certain accident scenarios, Palo Verde Units 2 and 3 entered Technical Specification 3.0.3. Engineering continues to evaluate this condition. There were no RPS/ESF actuations, and none were required. There were no structures, systems or components that were inoperable at the start of event that contributed to the event. This condition did not result in any challenges to the fission product barrier or result in any releases of radioactive materials. There were no adverse safety consequences or implications as a result of this event. This condition did not adversely affect the safe operation of the plant or health and safety of the public. The NRC Resident Inspector has been notified of this condition and this ENS notification. |
| Where | |
|---|---|
Palo Verde  Arizona (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
| Time - Person (Reporting Time:+-0.5 h-0.0208 days <br />-0.00298 weeks <br />-6.849e-4 months <br />) | |
| Opened: | Duane Kanitz 22:32 Oct 11, 2005 |
| NRC Officer: | Bill Huffman |
| Last Updated: | Oct 11, 2005 |
| 42050 - NRC Website
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Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Hot Standby (0 %) |
Unit 3 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Hot Standby (0 %) |
Palo Verde with 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat, 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition, 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown | |
WEEKMONTHYEARENS 576332025-03-28T08:06:00028 March 2025 08:06:00
[Table view]10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident High Pressure Safety Injection Pump Inoperable ENS 539682019-04-01T03:06:0001 April 2019 03:06:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition, 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material Unanalyzed Condition Due to Eccs Leakage ENS 520832016-07-12T20:00:00012 July 2016 20:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Degraded Fire Barrier ENS 506002014-11-06T18:16:0006 November 2014 18:16:00 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown Technical Specification Required Shutdown Due to Dropped Control Element Assembly ENS 496012013-12-03T06:24:0003 December 2013 06:24:00 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown Tech Spec Required Shutdown Due to Dropped Control Element Assembly ENS 494112013-10-04T16:46:0004 October 2013 16:46:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Postulated Fire Event Could Result in a Hot Short That Could Adversely Impact Safe Shutdown Equipment ENS 488142013-03-09T02:21:0009 March 2013 02:21:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Spent Fuel Pool Criticality Analysis of Record Not Revised Following Power Uprate ENS 474592011-11-19T15:28:00019 November 2011 15:28:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition the Low Pressure Safety Injection System Was Subjected to High Pressure Resulting in Both Trains Being Declared Inoperable 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 448462009-02-11T20:18:00011 February 2009 20:18:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Possibly Inadequate Backup Nitrogen Supply for Atmospheric Dump Operation ENS 442742008-06-06T06:56:0006 June 2008 06:56:00 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown Tech Spec Required Shutdown Due to Leak in Safety Injection Tank Vent Line ENS 438042007-11-24T05:26:00024 November 2007 05:26:00 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown Technical Specification Required Plant Shutdown Due to Inoperable Load Sequencer ENS 437362007-10-22T10:11:00022 October 2007 10:11:00 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown Shutdown Due to Inoperable Steam Driven Auxiliary Feedwater Pump ENS 431732007-02-19T21:57:00019 February 2007 21:57:00 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown Unit 2 Performed a Ts Required Shutdown ENS 431402007-02-03T19:32:0003 February 2007 19:32:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Technical Specification 3.0.3 Entered During Routine Surveillance Testing of Control Element Assemblies (Cea'S) ENS 428472006-09-19T08:05:00019 September 2006 08:05:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition, 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown Pressurizer Heater Capacity Less than Tech Spec Limit ENS 427322006-07-27T02:00:00027 July 2006 02:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Limiting Condition for Operation 3.7.4 Deemed to Be Nonconservative ENS 426512006-06-18T21:55:00018 June 2006 21:55:00 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat, 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident Loss of Onsite Emergency Safety Function - "B" Edg Failed to Start During Test Run ENS 424872006-04-10T19:33:00010 April 2006 19:33:00 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown Unit 2 Entered a Ts Required Shutdown Due to Inoperable Auxiliary Feedwater Pumps ENS 420502005-10-11T23:02:00011 October 2005 23:02:00 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat, 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition, 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown Tech Spec Required Shutdown of Both Unit 2 and 3 ENS 419392005-08-22T23:05:00022 August 2005 23:05:00 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown Technical Specification Shutdown Due to Core Protection Calculator System (Cpcs) Software Not Consistent with System Design Requirements. ENS 419132005-08-12T07:19:00012 August 2005 07:19:00 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown Plant Entered Lco Action Statement 3.8.1 to Be in Mode 5 Due to Unit 1 "B" Diesel Gen. Being Declared Inoperable ENS 417892005-06-23T15:23:00023 June 2005 15:23:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unit 2 Aux Feedwater Train Separation Not Maintained During Operation ENS 415022005-03-18T22:00:00018 March 2005 22:00:00 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown Technical Specification Required Shutdown Due to Inoperable Diesel Generator ENS 413892005-02-09T08:04:0009 February 2005 08:04:00 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown Technical Specifications Required Shutdown Due to Loss of Normal and Alternate Power to Safety Bus ENS 412242004-11-24T19:20:00024 November 2004 19:20:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident Eccs Loops Declared Inoperable in Support of Log Term Accident Mitigation ENS 409132004-07-31T01:45:00031 July 2004 01:45:00 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat, 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident Air Void in Post-Loca Recirculation Piping System ENS 405032004-02-03T22:35:0003 February 2004 22:35:00 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown, 10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded Technical Specification Required Shutdown Due to Rcs Pressure Boundary Leakage 2025-03-28T08:06:00 | |