ENS 41573
ENS Event | |
|---|---|
21:55 Apr 6, 2005 | |
| Title | Partial Loss of Offsite Power Resulting in Autostart of Emergency Diesel Generators |
| Event Description | At 1655 on April 6, 2005, a trip of the 4A/4B Transformer occurred at Limerick Generating Station in the 500 KV Substation. This de-energized one of the required off site sources and the associated 20 Start-up Bus and 201 Safeguard Bus, causing a valid actuation signal for the D12, D14, D21, and D23 Diesel Generators. All Diesels started and their associated 4 KV buses swapped to the 101 Safeguard Bus as required. Cause of the 4A/4B Transformer trip is under investigation. Power reduction on Unit 2 was performed in response to lowering Main Condenser vacuum during power supply transfers. Condition was stabilized and Unit 2 Reactor power restored to 100 %.
The cause of the lowering main condenser vacuum was that when the bus transfer occurred, several air valves on Unit 2 cycled which caused the lowering vacuum. Once power transferred, Unit 2 stabilized and was restored to 100% power. Unit 1 main condenser vacuum was not affected since power was not transferred on Unit 1. Additionally, a Group 6A valve isolation signal was generated. This caused the purge valves to receive an isolation signal but the purge valves were not in operation nor were they required to be in operation at the time of the isolation signal. Both unit's Reactor Water Clean-up (RWCU) pumps tripped due to the isolation signal. At the time of this report, the isolation signal was reset, Unit 1 RWCU pump has been reset, and preparations are being made to restart Unit 2 RWCU pump. The only other anomaly is that Unit 2 D22 diesel is in a maintenance outage and is scheduled to be returned to service tomorrow. Currently, both units are in a 72-hour LCO action statement due to loss of one offsite power supply. The licensee will inform the NRC resident inspector. |
| Where | |
|---|---|
Limerick  Pennsylvania (NRC Region 1) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(iv)(A), System Actuation | |
| LER: | 05000352/LER-2005-002 |
| Time - Person (Reporting Time:+1.02 h0.0425 days <br />0.00607 weeks <br />0.0014 months <br />) | |
| Opened: | Bob Lance 22:56 Apr 6, 2005 |
| NRC Officer: | Howie Crouch |
| Last Updated: | Apr 6, 2005 |
| 41573 - NRC Website | |
Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (95 %) |
WEEKMONTHYEARENS 511682015-06-21T20:25:00021 June 2015 20:25:00
[Table view]10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Secondary Containment Isolation ENS 509812015-04-13T06:20:00013 April 2015 06:20:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Reactor Scram Initiated ENS 489362013-04-17T01:42:00017 April 2013 01:42:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Specified System Actuation During Turbine Stop Valve Logic Testing While Shutdown ENS 481212012-07-19T19:37:00019 July 2012 19:37:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Reactor Protection Signal Actuation Due to Changing Mode Switch Position During Surveillance Testing ENS 478882012-05-02T11:24:0002 May 2012 11:24:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Initiation of Secondary Containment Isolation ENS 469062011-05-30T15:50:00030 May 2011 15:50:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Specified System Actuation - Manual Reactor Scram Due to Dual Recirc Pump Trip During Startup ENS 449482009-03-31T22:50:00031 March 2009 22:50:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Valid Diesel Start Signal Received During Maintenance Testing of Diesel ENS 438982008-01-12T14:04:00012 January 2008 14:04:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Valid Specified System Actuation During Edg Governor Testing ENS 433152007-04-24T06:10:00024 April 2007 06:10:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation, 10 CFR 50.72(b)(2)(iv)(A), System Actuation - ECCS Discharge Automatic Reactor Scram with Eccs Injection on Lowering Reactor Vessel Water Level ENS 432312007-03-13T11:30:00013 March 2007 11:30:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Low Main Condenser Vacuum Isolation Signal Received During Plant Shutdown ENS 421932005-12-09T14:01:0009 December 2005 14:01:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Trip of a Startup Bus Breaker Results in Start of Emergency Diesel Generators ENS 415732005-04-06T21:55:0006 April 2005 21:55:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Partial Loss of Offsite Power Resulting in Autostart of Emergency Diesel Generators 2015-06-21T20:25:00 | |