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 | |
| LER: | 05000285/LER-2013-018 Regarding Postulated Fire Event Could Result in Shorts Impacting Safe Shutdown |
| 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
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