ENS 49478
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ENS Event | |
|---|---|
17:30 Oct 28, 2013 | |
| Title | Postulated Event Could Result In A Hot Short That Could Adversely Impact Safe Shutdown Equipment |
| Event Description | A review of industry operating experience regarding the impact of unfused direct current (DC) ammeter circuits in the control room has determined that the condition described below applies to Fort Calhoun Nuclear Station. This could result in an unanalyzed condition with respect to 10 CFR 50 Appendix R analysis requirements.
The control room ampere indications for the Class 1E batteries and their chargers do not include over-current protection to limit fault current. In a postulated event, a fire in the control room could cause one of the ammeter wires to hot-short to the ground plane. Simultaneously, the event could cause another DC wire from the opposite polarity on the same battery to hot-short to the ground plane. This would cause a ground-loop through unprotected ammeter wiring. Since this circuit is not protected (not fused), this event could result in excessive current flow in the ammeter wiring to the point of causing a secondary fire in the associated raceway system. This could potentially cause the loss of the ability to conduct a safe shutdown as required by 10CFR50 Appendix R. This condition is being reported in accordance with 10 CFR 50.72(b)(3)(ii)(B) as an unanalyzed condition that significantly degrades plant safety. Compensatory measures (fire watches) have been implemented for affected areas of the plant. The NRC Resident Inspector has been notified. |
| Where | |
|---|---|
Fort Calhoun  Nebraska (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | |
| Time - Person (Reporting Time:+0.53 h0.0221 days <br />0.00315 weeks <br />7.25994e-4 months <br />) | |
| Opened: | David Ortiz 18:02 Oct 28, 2013 |
| NRC Officer: | John Shoemaker |
| Last Updated: | Oct 28, 2013 |
| 49478 - NRC Website
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Unit 1 | |
|---|---|
| Reactor critical | Not Critical |
| Scram | No |
| Before | Cold Shutdown (0 %) |
| After | Cold Shutdown (0 %) |
WEEKMONTHYEARENS 522012016-08-25T20:23:00025 August 2016 20:23:00
[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 Unanalyzed Condition Involving Potential Tornado Missile Damage ENS 519172016-05-10T16:38:00010 May 2016 16:38:00 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 Containment Cooling Water System Inoperable Due to Unanalyzed Condition ENS 514872015-10-21T18:50:00021 October 2015 18:50:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition Due to Pressurizer Heater Bank Potential Circuit Failure Vulnerability ENS 508002015-02-09T23:30:0009 February 2015 23:30:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Safety Injection Tank Level Results in an Unanalyzed Condition ENS 494782013-10-28T17:30:00028 October 2013 17:30:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Postulated Event Could Result in a Hot Short That Could Adversely Impact Safe Shutdown Equipment ENS 493782013-09-23T18:40:00023 September 2013 18:40:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition - 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Guidance Not Adequate to Mitigate a Design Basis Flood ENS 478482011-10-06T18:44:0006 October 2011 18:44:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Waste Disposal System Class One Seismic Support Inoperable ENS 470882011-07-22T13:30:00022 July 2011 13:30:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Fire Supression Pumps Inoperable ENS 469652011-06-16T17:30:00016 June 2011 17:30:00 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 Additional Penetration Identified for Mitigation During Walkdown ENS 462972010-09-30T21:16:00030 September 2010 21:16:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition Due to Potential Flooding Via Condensate Drain Lines ENS 458282010-04-08T21:22:0008 April 2010 21:22:00 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(b)(2)(i), Tech Spec Required Shutdown Technical Specification Required Shutdown Due to Inoperable Steam Generator Inlet Isolation Valve ENS 454672009-10-26T15:50:00026 October 2009 15:50:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Pressurizer and Feedwater Storage Tank Level Indications Do Not Meet Appendix R Requirements ENS 429432006-10-28T22:09:00028 October 2006 22:09:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition ENS 429022006-10-12T22:30:00012 October 2006 22:30:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Steam Generator Instrumentation Nonconformance ENS 428962006-10-10T20:00:00010 October 2006 20:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Containment Spray Valve Mispositioned 2016-08-25T20:23:00 | |
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