ENS 51697
ENS Event | |
|---|---|
15:20 Jan 29, 2016 | |
| Title | Offsite Power Declared Inoperable Due to Lowering Generator Voltage |
| Event Description | At 0920 CST on 1/29/16, while performing main generator voltage adjustments at the direction of the transmission operator, Duane Arnold Energy Center (DAEC) switchyard voltage lowered to the calculated point where offsite sources were considered inoperable. During this event, both onsite emergency diesel generators were fully operable and capable of performing their intended safety function.
While no safety concerns arose, Technical Specification (TS) Limiting Condition for Operability (LCO) 3.8.1.a Condition C was entered due to two offsite electric power circuits being inoperable. Immediate actions were taken to adjust main generator voltage to restore switchyard voltage. In less than 10 minutes, both offsite circuits were declared operable and LCO 3.8.1.a Condition C was exited. This resulted in a reportable event pursuant to 10CFR50.72(b)(3)(v)(D). During the time of reduced grid voltage, no bus low-voltage alarms nor any equipment issues occurred. The cause of this event is under investigation, and there are not any current operability concerns with the offsite power circuits. The licensee has notified the NRC Resident Inspector.
The purpose of this notification is to retract a previous report made on 1/29/16 at 1709 (EST). NRC notification was initially made as a result of offsite power sources being declared inoperable due to the identification of a low voltage condition by the grid operator. Subsequent to the initial report, NextEra Energy Duane Arnold (NextEra) has determined that the offsite power grid conditions were above the required limit and were therefore operable. It was determined that a trip of the DAEC turbine/generator would not have led to fluctuations in voltages in the DAEC switchyard below the trip setpoints for Loss of Power. Based on this, the safety-related buses and loads were fully capable of performing their intended design basis function. The degraded voltage relays setpoint were not reached; therefore, the essential electrical buses remained connected to offsite power. Therefore, the low voltage condition does not meet the reporting requirements of 10 CFR 50.72 or 10 CFR 50.73 The Resident Inspector has been notified. Notified R3DO (Kozak). |
| Where | |
|---|---|
Duane Arnold  Iowa (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
| Time - Person (Reporting Time:+1.82 h0.0758 days <br />0.0108 weeks <br />0.00249 months <br />) | |
| Opened: | Terry Brandt 17:09 Jan 29, 2016 |
| NRC Officer: | Dong Park |
| Last Updated: | Feb 5, 2016 |
| 51697 - NRC Website
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Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
Duane Arnold with 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
WEEKMONTHYEARENS 528812017-08-01T14:34:0001 August 2017 14:34:00
[Table view]10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident High Pressure Coolant Injection Steam Supply Valve Failed to Reposition ENS 516972016-01-29T15:20:00029 January 2016 15:20:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident Offsite Power Declared Inoperable Due to Lowering Generator Voltage ENS 510062015-04-23T15:50:00023 April 2015 15:50:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident Safety Systems Declared Inoperable Due to Equipment Malfunction ENS 508912015-03-13T17:30:00013 March 2015 17:30:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident Low Pressure Coolant Injection Declared Inoperable ENS 501542014-05-30T15:43:00030 May 2014 15:43:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident High Pressure Coolant Injection Pump Received an Invalid Isolation Signal ENS 495662013-11-21T08:29:00021 November 2013 08:29:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident Diesel Generator Inoperability ENS 480642012-07-02T20:05:0002 July 2012 20:05:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident Hpci Declared Inoperable ENS 475612011-12-30T02:09:00030 December 2011 02:09:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident Lpci Instrumentation Required Repair and Recalibration ENS 466452011-02-26T15:48:00026 February 2011 15:48:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident High Pressure Coolant Injection System Inoperable ENS 450102009-04-23T00:45:00023 April 2009 00:45:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident High Pressure Coolant Injection (Hpci) System Declared Inoperable ENS 436922007-10-05T09:08:0005 October 2007 09:08:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident Loss of Both Emergency Service Water Pumps ENS 436022007-08-27T05:00:00027 August 2007 05:00:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident One Channel of Low Main Steam Line Pressure Signal Mistakenly Removed from Service for 33 Minutes ENS 433312007-05-01T01:17:0001 May 2007 01:17:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident Hpci Declared Inoperable Due to Primary Containment Nitrogen Leak ENS 432622007-03-28T18:41:00028 March 2007 18:41:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident Hpci Inoperable Due to Surveillance Test Failure ENS 431612007-02-12T16:52:00012 February 2007 16:52:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident Both Standby Filter Units Inoperable ENS 431182007-01-24T15:55:00024 January 2007 15:55:00 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)(A), Seriously Degraded Missing Pipe Clamp Bolt Found on High Pressure Coolant Injection (Hpci) System ENS 428352006-09-08T09:01:0008 September 2006 09:01:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident Containment Atmospheric Dilution (Cad) System Inoperable ENS 420252005-09-29T20:34:00029 September 2005 20:34:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident High Pressure Coolant Injection (Hpci) Declared Inoperable 2017-08-01T14:34:00 | |