ENS 49487
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ENS Event | |
|---|---|
19:25 Oct 30, 2013 | |
| Title | Postulated Hot Short Fire Event That Could Adversly 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 the described condition to be applicable to Millstone Power Station Unit 2 resulting in an unanalyzed condition with respect to 10 CFR 50 Appendix R analysis requirements. The original plant wiring design and associated analysis for the Class 1E batteries control room ampere indications do not include overcurrent protection features to limit the fault current.
In the postulated event, a fire in the control room could cause one of the ammeter wires to short to the ground plane. Simultaneously, it is postulated that the fire causes another DC wire from the opposite polarity on the same battery to also short to the ground plane. This could cause a ground loop through the unprotected ammeter wiring. This event could result in excessive current flow (i.e., heating) in the ammeter wiring to the point of causing a secondary fire in the raceway system. The secondary fire could adversely affect safe shutdown equipment and potentially cause the loss of the ability to conduct a safe shutdown as required by 10 CFR 50 Appendix R. Interim compensatory measures (i.e., fire watches) have been implemented for affected areas of the plant. This condition is being reported pursuant to 10 CFR 50.72(b)(3)(ii)(B). The licensee notified the NRC Resident Inspector. |
| Where | |
|---|---|
Millstone  Connecticut (NRC Region 1) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | |
| LER: | 05000336/LER-2013-003 |
| Time - Person (Reporting Time:+-2.68 h-0.112 days <br />-0.016 weeks <br />-0.00367 months <br />) | |
| Opened: | Todd Perkins 16:44 Oct 30, 2013 |
| NRC Officer: | Pete Snyder |
| Last Updated: | Oct 30, 2013 |
| 49487 - NRC Website
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Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
WEEKMONTHYEARENS 566102023-07-06T16:32:0006 July 2023 16:32:00
[Table view]10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition ENS 555762021-11-14T16:50:00014 November 2021 16:50:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition NON-FUNCTIONAL Steam Supply Check Valve to Turbine Driven Auxiliary Feedwater Pump ENS 555652021-11-06T15:00:0006 November 2021 15:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Steam Supply Check Failure to Turbine Driven Auxillary Feedwater ENS 499022014-03-12T18:00:00012 March 2014 18:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition Due to a Postulated Hot Short That Could Affect Safe Shutdown Equipment ENS 499032014-03-12T18:00:00012 March 2014 18:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition Due to a Postulated Hot Short That Could Affect Safe Shutdown Equipment ENS 494872013-10-30T19:25:00030 October 2013 19:25:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Postulated Hot Short Fire Event That Could Adversly Impact Safe Shutdown Equipment ENS 490472013-05-17T08:39:00017 May 2013 08:39:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition for Reactor Coolant System Temperature Below Required Value ENS 444502008-08-29T14:07:00029 August 2008 14:07:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition Related to Certain Fire Conditions ENS 437192007-10-12T17:30:00012 October 2007 17:30:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition Affecting Fire Safe Shutdown ENS 436752007-09-28T21:00:00028 September 2007 21:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Reactor Vessel Head Vent May Not Be Isolable During a Fire 2023-07-06T16:32:00 | |
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