ENS Event | |
|---|---|
21:42 Feb 2, 2005 | |
| Title | Single Failure Vulnurability in Ac Auxiliary Power System |
| Event Description | This report is being made pursuant to 10CFR50.72(b)(3)(ii)(B). At 15:42 on 02/02/05 while reviewing Operation Experience from another Nuclear Site, it was discovered that the design of the AC Auxiliary Power System incorporates a common circuit which could result in a bus lockout preventing the re-energization of both the Division 1 and Division 2 Essential Safety Feature (ESF) buses from either onsite or offsite power sources due to a single failure in the common portion of the circuitry. This common circuit includes various metering circuits such as System Auxiliary Transformer Wattmeters and Ammeters. Also connected to these metering loops are ground fault devices that feed breaker lockout relays. Should a failure occur on these common circuits, all breakers supplying power to these ESF Buses would be opened, locked out, and prevented from reclosure onto the buses.
Due to the loss of the ability to accommodate a single failure, one offsite power source and one onsite Diesel Generator have been declared inoperable and Technical Specification 3.8.1 Condition A, Condition B, and Condition E entered. Corrective actions are in progress to isolate the common circuit and eliminate the single point vulnerability. The licensee notified the NRC Resident Inspector. |
| Where | |
|---|---|
LaSalle  Illinois (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | |
| LER: | 05000254/LER-2005-001 Re 4160 Volt Relaying and Metering Single Failure Vulnerability |
| Time - Person (Reporting Time:+-0.72 h-0.03 days <br />-0.00429 weeks <br />-9.86256e-4 months <br />) | |
| Opened: | Harold Vinyard 20:59 Feb 2, 2005 |
| NRC Officer: | Mike Ripley |
| Last Updated: | Feb 2, 2005 |
| 41366 - NRC Website
Loading map... | |
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 (100 %) |
WEEKMONTHYEARENS 532132018-02-15T17:00:00015 February 2018 17:00:00
[Table view]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 Notification of Unanalyzed Condition Affecting Accident Mitigation for Tornado Generated Missiles ENS 506752014-12-12T21:00:00012 December 2014 21:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition with Reactor Core Isolation Cooling ENS 424052006-03-11T06:30:00011 March 2006 06:30:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition 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 418442005-07-14T21:10:00014 July 2005 21:10:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Station Blackout Temperature Analysis Higher than Rcic Governor Documentation ENS 413662005-02-02T21:42:0002 February 2005 21:42:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Single Failure Vulnurability in Ac Auxiliary Power System 2018-02-15T17:00:00 | |