ENS 41370
ENS Event | |
|---|---|
01:15 Feb 4, 2005 | |
| Title | 4160 Volt Relaying and Metering Single Failure Vulnerability |
| Event Description | The licensee provided the following report via facsimile:
On February 3, 2005 at 1915 hours0.0222 days <br />0.532 hours <br />0.00317 weeks <br />7.286575e-4 months <br />, DNPS confirmed a vulnerability with a 4160 VAC relaying and metering current transformer (CT) associated with the Unit and Reserve Auxiliary Transformers (i.e., the UAT and RAT) on both Units. Although the CT is currently fully operable, failure of the CT circuitry will cause the neutral overcurrent relay to trip (and lockout) the main, reserve and tie feed breakers. These combined protective relay trips will act to trip and lock out the circuit breakers supplying feeds to buses 23 (33) and 24 (34), essentially isolating them from their normal and emergency power sources. Emergency power (i.e., the emergency diesel generator) would still be available to safety related buses 23-1 (33-1) and 24-1 (34-1), but the Containment Cooling Service Water (CCSW) system would remain without a power source. If this failure occurred during a LOCA, then the CCSW pumps may not be able to be started within ten minutes. A modification is in progress to eliminate this vulnerability. This event is being reported as a potential loss of safety function (10CFR50.72(b)(3)(v)(B)) and a degraded or unanalyzed condition (10CFR50.72(b)(3)(ii)(B)). The NRC Resident Inspector has been notified. See similar events #41362 (Crystal River), #41366 (LaSalle), and #41369 (Quad Cities). |
| Where | |
|---|---|
Dresden  Illinois (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat | |
| Time - Person (Reporting Time:+-0.87 h-0.0363 days <br />-0.00518 weeks <br />-0.00119 months <br />) | |
| Opened: | Paul Salgado 00:23 Feb 4, 2005 |
| NRC Officer: | Bill Huffman |
| Last Updated: | Feb 4, 2005 |
| 41370 - NRC Website | |
Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (95 %) |
| After | Power Operation (95 %) |
Unit 3 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (96 %) |
| After | Power Operation (96 %) |
Dresden with 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | |
WEEKMONTHYEARENS 560232022-07-30T03:17:00030 July 2022 03:17:00
[Table view]10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat RHR Capability Lost Due to Suction Bay Level ENS 532042018-02-12T18:00:00012 February 2018 18:00:00 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)(B), Unanalyzed Condition En Revision Imported Date 10/14/2019 ENS 488452012-11-20T00:00:00020 November 2012 00:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Control Rod Drive Check Valve in Service Leak Test Failure ENS 480802012-07-10T07:36:00010 July 2012 07:36:00 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat Invalid Group 5 Isolation Due to Failed Test Switch During Surveillance ENS 468572011-05-17T15:30:00017 May 2011 15:30:00 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat Temporary Blockage of Suction Source for Containment Cooling Service Water ENS 454722009-11-02T12:12:0002 November 2009 12:12:00 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat Loss of Shutdown Cooling ENS 446262008-11-03T12:52:0003 November 2008 12:52:00 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat Recirc Loop Temperature Element Failed ENS 444702008-09-07T13:05:0007 September 2008 13:05:00 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat Isolation Condenser Declared Inoperable Following Surveillance Testing ENS 441682008-04-25T16:30:00025 April 2008 16:30:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Non-Conservative Core Spray Flow in Dresden Nuclear Power Station Loca Analysis ENS 441402008-04-15T12:00:00015 April 2008 12:00:00 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat, 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident High Pressure Coolant Injection Declared Inoperable ENS 413702005-02-04T01:15:0004 February 2005 01:15:00 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition 4160 Volt Relaying and Metering Single Failure Vulnerability ENS 407032004-04-24T15:50:00024 April 2004 15:50:00 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat Isolation Condenser Declared Inoperable ENS 403112003-11-10T13:20:00010 November 2003 13:20:00 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)(B), Unanalyzed Condition Bypassing the Pressure Suppression Function of the Torus 2022-07-30T03:17:00 | |