ENS 51559
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ENS Event | |
|---|---|
13:44 Nov 23, 2015 | |
| Title | Manual Reactor Trip After Partial Msiv Closure |
| Event Description | At 0820 EST on 11/23/2015, Sequoyah Unit 1 was at 100% power when operators identified the Loop #3 Main Steam Isolation Valve (MSIV) came off its full open seat. This was evidenced by no OPEN indication on the main control board, dual indication on the post accident monitoring panel, and a change in both Tavg and steam pressure. Operators were dispatched locally to the MSIV and to the battery board room to investigate if a cause could be identified for the MSIV movement. The field investigation identified no issues. The operating crew manually tripped the reactor at 0844 EST due to an increasing Tavg-Tref mismatch.
Following the reactor trip, all safety-related equipment operated as designed. Auxiliary Feedwater automatically initiated as expected from the feedwater isolation signal. Unit 1 is currently being maintained in Mode 3 at normal operating temperature and pressure, approximately 547 degrees F and 2235 psig, with auxiliary feedwater supplying the steam generators and decay heat removal via the condenser steam dumps. There is no indication of any primary to secondary leakage. All control rods fully inserted on the reactor trip and remain inserted. The electrical alignment is normal with shutdown power supplied from off-site power. There is no operational impact to Unit 2 as it continues through the refueling outage with the core off-loaded. There was no impact on public health and safety. Post-trip investigation is in progress and planned restart timeline has not yet been determined. The licensee notified the NRC Resident Inspector. All control rods fully inserted during the reactor trip. The atmospheric steam dumps did operate during the transient and then shut. After the trip, the MSIV re-opened. |
| Where | |
|---|---|
Sequoyah  Tennessee (NRC Region 2) | |
| 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:+-1.87 h-0.0779 days <br />-0.0111 weeks <br />-0.00256 months <br />) | |
| Opened: | Frank Schulte 11:52 Nov 23, 2015 |
| NRC Officer: | Mark Abramovitz |
| Last Updated: | Nov 23, 2015 |
| 51559 - NRC Website | |
Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | Yes, Manual Scram |
| Before | Power Operation (100 %) |
| After | Hot Standby (0 %) |
Sequoyah with 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation | |
WEEKMONTHYEARENS 552722021-05-24T13:16:00024 May 2021 13:16:00
[Table view]10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation on 5/24/21 at 0916 Edt, an Automatic Reactor Trip on Unit 1 Occurred. All Safety Systems Responded Normally and the Plant Is Currently Stable in Mode 3 (Hot Standby) at Normal Operating Temperature and Pressure. Preliminary Indications Are That the Unit Trip Was Caused by a High Neutron Flux Rate Detected by the Power Range Nuclear Instruments. Troubleshooting and Investigation Are Ongoing to Determine the Initiating Cause. ENS 544462019-12-16T08:58:00016 December 2019 08:58:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Emergency Diesel Generator Autostart Due to Loss of Power to 1B Shutdown Board ENS 544382019-12-12T09:33:00012 December 2019 09:33:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation ENS 542422019-08-27T05:09:00027 August 2019 05:09:00 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 539992019-04-14T07:20:00014 April 2019 07:20:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation En Revision Imported Date 8/7/2019 ENS 527692017-05-24T03:30:00024 May 2017 03:30:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation All Four Edgs Autostarted During Transfer of Shutdown Board to Normal Power Source for Unit 2 Testing ENS 524692016-12-30T18:05:00030 December 2016 18:05:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Reactor Trip Due to Control Rod Not Withdrawing as Expected ENS 517202016-02-09T19:15:0009 February 2016 19:15:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation, 10 CFR 50.72(b)(2)(iv)(A), System Actuation - ECCS Discharge Eccs Discharge to Rcs Via Charging System ENS 515592015-11-23T13:44:00023 November 2015 13:44:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Reactor Trip After Partial Msiv Closure ENS 513922015-09-14T08:26:00014 September 2015 08:26:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Reactor Trip Due to Loss of Power to Vital Instrument Board ENS 512652015-07-27T14:43:00027 July 2015 14:43:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Reactor/Turbine Trip ENS 512592015-07-24T17:51:00024 July 2015 17:51:00 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 on Main Generator Lockout ENS 508782015-03-11T10:21:00011 March 2015 10:21:00 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 a Nuclear Instrumentation Signal ENS 508562015-03-02T11:45:0002 March 2015 11:45:00 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 487782013-02-24T17:05:00024 February 2013 17:05:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Reactor Trip Due to Loss of Condenser Vacuum Indication ENS 481982012-08-16T23:26:00016 August 2012 23:26:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Reactor Trip from a Reactor Coolant Pump Trip ENS 471692011-08-19T02:50:00019 August 2011 02:50:00 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 Reactor Coolant Pump Bus Undervoltage ENS 470812011-07-21T01:29:00021 July 2011 01:29:00 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 Negative Rate Trip Following Rapid Turbine Load Reduction ENS 469912011-06-26T20:14:00026 June 2011 20:14:00 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 464922010-12-20T05:50:00020 December 2010 05:50:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Reactor Trip Due to a Fire in the Main Generator Bus Duct ENS 464242010-11-17T03:10:00017 November 2010 03:10:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Reactor Trip Based on Decreasing Steam Generator Level ENS 455202009-11-26T07:42:00026 November 2009 07:42:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Trip Due to Loss of Vacuum on Turbine Driven Feedwater Pump ENS 450972009-05-27T23:04:00027 May 2009 23:04:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Reactor Trip from Power Range High Neutron Flux Rate ENS 450452009-05-07T02:56:0007 May 2009 02:56:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Reactor Trip Due to Feed Regulating Valve Failure ENS 450292009-04-29T01:59:00029 April 2009 01:59:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Reactor Trip Initiated as a Result of a Loss of Condensate Flow ENS 449352009-03-26T08:52:00026 March 2009 08:52:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Reactor Trip and Aux Feed Water Start Due to Loss of an Off Site Power Source ENS 449342009-03-26T08:52:00026 March 2009 08:52:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Reactor Trip and Aux Feed Water Start Due to Loss of an Off Site Power Source ENS 446492008-11-09T23:21:0009 November 2008 23:21:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Reactor Trip Breakers Opened Manually Due to Indicated Dropped Control Rod ENS 446272008-11-04T04:22:0004 November 2008 04:22:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Manual Reactor Trip Due to Feedwater Reg Valve Failure ENS 439092008-01-17T00:25:00017 January 2008 00:25:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Reactor Trip Due to Lowering Steam Generator Level ENS 432332007-03-13T19:27:00013 March 2007 19:27:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Reactor Trip Due to "a" Main Feedwater Pump ENS 431152007-01-23T17:44:00023 January 2007 17:44:00 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 Feedwater Regulating Valve Failure ENS 424442006-03-22T21:24:00022 March 2006 21:24:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Turbine Trip / Reactor Trip Caused by Main Generator Trip ENS 415832005-04-09T15:11:0009 April 2005 15:11:00 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 Turbine Trip Due to Low Auto Stop Oil Pressure on Pressure Switches ENS 414372005-02-24T02:06:00024 February 2005 02:06:00 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-Low Steam Generator Level ENS 405892004-03-15T20:18:00015 March 2004 20:18:00 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 Main Generator Electrical Fault Signal ENS 404752004-01-25T08:16:00025 January 2004 08:16:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Unplanned Auto Start of Turbine Driven Auxiliary Feedwater Pump ENS 403052003-11-10T04:15:00010 November 2003 04:15:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Sequoyah Unit 2 Auxiliary Feedwater Actuation During Outage ENS 401132003-08-28T20:04:00028 August 2003 20:04:00 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 Due to Reactor Protection System Failure 2021-05-24T13:16:00 | |
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