ENS 41787
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ENS Event | |
|---|---|
04:40 Jun 22, 2005 | |
| Title | Multiple Specified Systems Actuations Due To Loss Of Ac Safety Related Buses |
| Event Description | At 23:40 CDST, LaSalle Unit 2 experienced a trip of the 4160 Volt AC feed breaker to 480 Volt AC Safety Related buses 235X & 235Y. As a result of this feed breaker trip, containment isolation valves closed in multiple systems. The systems which isolated included Containment Monitoring System, Drywell Floor Drains and Drywell Equipment Drains, Reactor Recirculation Flow Control Hydraulic System, Drywell Instrument Nitrogen System, Reactor Water Cleanup System, and Reactor Recirculation Sample System. This event is reportable under 10 CFR50.72(b)(3)(iv)(A). In addition to the- above mentioned system isolations, the following plant responses occurred due to the loss of these 480 Volt AC buses: Reactor Building Ventilation was lost due to the closure of the secondary containment isolation dampers; Multiple Division 1 containment isolation valves lost their AC power source, a 1/2-SCRAM occurred due to the loss of the 2A Reactor Protection System Motor-Generator set, the DC charger feed to the Division 1 DC Battery/Bus was lost, and the battery is currently maintaining availability of DC power to the bus. Troubleshooting has determined that the cause of the breaker trip was due to a defective neutral ground current protective relay. This relay has been replaced and the buses have been re-energized. System restoration is currently in progress.
The licensee informed the NRC Resident Inspector.
The following is an update to EN 41787. Restoration of all required safety systems with the exception of the Reactor Core Isolation Cooling (RCIC) system has been completed. The associated ECCS systems were filled, vented and restored to an available status at 0630 CDST and full operability established at 0803 CDST. The Division 1 DC battery was fully recharged and returned to an operable status at 0803 CDST. Restoration of the RCIC system and investigation into the cause of the relay failure is currently in progress. The licensee has notified the NRC Resident Inspector. Notified R3DO (Bruce Burgess). |
| Where | |
|---|---|
LaSalle  Illinois (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(iv)(A), System Actuation | |
| Time - Person (Reporting Time:+1.27 h0.0529 days <br />0.00756 weeks <br />0.00174 months <br />) | |
| Opened: | John Washko 05:56 Jun 22, 2005 |
| NRC Officer: | John Knoke |
| Last Updated: | Jun 23, 2005 |
| 41787 - NRC Website
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Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
WEEKMONTHYEARENS 570832024-04-20T12:04:00020 April 2024 12:04:00
[Table view]10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Actuation of Emergency Diesel Generators ENS 563892023-03-04T15:10:0004 March 2023 15:10:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Actuation of Reactor Protection System (RPS) ENS 539032019-03-01T04:17:0001 March 2019 04:17:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Specified System Actuation - Trip of Safety Related Bus ENS 503462014-08-05T22:34:0005 August 2014 22:34:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Reactor Scram ENS 489392013-04-17T20:11:00017 April 2013 20:11:00 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, 10 CFR 50.72(b)(2)(iv)(A), System Actuation - ECCS Discharge Notification of Unusual Event Declared Due to Loss of Offsite Power from a Lightning Strike ENS 423482006-02-20T06:23:00020 February 2006 06:23:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition, 10 CFR 50.72(a)(1)(i), Emergency Class Declaration, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Site Area Emergency - Reactor Scram ENS 417872005-06-22T04:40:00022 June 2005 04:40:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Multiple Specified Systems Actuations Due to Loss of Ac Safety Related Buses ENS 404952004-02-02T04:34:0002 February 2004 04:34:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation One Half Scram Signal Due to the Loss of the "B" Reactor Protection System Bus. 2024-04-20T12:04:00 | |
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