ENS 49875
ENS Event | |
|---|---|
15:12 Mar 5, 2014 | |
| Title | Potential Impact On Unfused Direct Current Ammeter Circuits In The Main Control Room |
| 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 a similar condition is applicable to the Waterford 3 Nuclear Station resulting in a potentially unanalyzed condition with respect to 10 CFR 50 Appendix R requirements. The original plant wiring design and associated analysis for an ammeter measuring current from the train AB Class 1E battery to its associated power distribution panel does not include overcurrent protection features to limit the fault current and is routed through multiple fire areas. The ammeter is located on the train AB power distribution panel in the train AB switchgear room.
In the postulated event, a fire could cause one of the ammeter wires to short to ground. Simultaneously, it is postulated that the fire could cause another DC wire from the opposite polarity on the same battery to also short to ground. 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. This condition is being reported in accordance with 10 CFR 50.72(b)(3)(ii)(B). There is no effect on plant operation. Fire watches have been implemented for affected areas of the plant as an interim compensatory measure. The licensee notified the NRC Resident Inspector.
Subsequent engineering evaluation has determined that the circuit for an ammeter measuring current from its Class 1E battery to its associated power distribution panel is not routed through multiple fire areas. Therefore, the IER 13-54 related condition is not, and was not, an unanalyzed condition at Waterford 3 that significantly degraded plant safety, and thus not required to be reported under 10 CFR 50.72(b)(3)(ii)(B). The licensee notified the NRC Resident Inspector. Notified R4DO (Gaddy). |
| Where | |
|---|---|
Waterford  Louisiana (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | |
| Time - Person (Reporting Time:+-1.03 h-0.0429 days <br />-0.00613 weeks <br />-0.00141 months <br />) | |
| Opened: | Cesar Garcia 14:10 Mar 5, 2014 |
| NRC Officer: | Vince Klco |
| Last Updated: | Apr 16, 2014 |
| 49875 - NRC Website
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Unit 3 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
WEEKMONTHYEARENS 568492023-11-10T21:45:00010 November 2023 21:45:00
[Table view]10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Unanalyzed Condition ENS 498752014-03-05T15:12:0005 March 2014 15:12:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Potential Impact on Unfused Direct Current Ammeter Circuits in the Main Control Room ENS 493262013-09-05T21:00:0005 September 2013 21:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Loss of Auxiliary Component Cooling Water Systems ENS 406322004-04-01T01:19:0001 April 2004 01:19:00 Other Unspec Reqmnt, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition New Worst Case Single Failure May Exceed 10 Cfr 50.46 Acceptance Criterion for Sbloca 2023-11-10T21:45:00 | |