ENS 47510: Difference between revisions
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| event date = 12/08/2011 05:00 CST | | event date = 12/08/2011 05:00 CST | ||
| last update date = 12/08/2011 | | last update date = 12/08/2011 | ||
| title = Unanalyzed Condition - Non Fused Dc Bus Ammeters Could Short | | title = Unanalyzed Condition - Non Fused Dc Bus Ammeters Could Short and Cause a Fire | ||
| event text = During Operating Experience (OPEX) review of Browns Ferry Fire Protection ENS 47374, 'Deficiency Identified in Transition to Performance Based Standard for Fire Protection,' a similar condition was identified at Clinton Power Station. | | event text = During Operating Experience (OPEX) review of Browns Ferry Fire Protection ENS 47374, 'Deficiency Identified in Transition to Performance Based Standard for Fire Protection,' a similar condition was identified at Clinton Power Station. | ||
During site review, it was determined that original plant wiring design for the station battery ammeter contains a 'shunt' in the current flow from each direct current (DC) battery. Bolted on the shunt bar are two IEEE 383 qualified leads to a current meter in the main control room (MCR). The small difference in voltage between the two taps on the shunt is enough to deflect the current gauge in the MCR when current flows from the battery through the shunt. The ammeter wiring attached to the shunt does not have fuses, and if one of these ammeter wires shorts to ground at the same time another DC wire from the opposite polarity on the same battery also shorts to ground, a ground loop through the unfused ammeter cable could occur. With enough current going through the cable, the potential exists that a fire in the raceway system or MCR could occur wherever the cable is routed. | During site review, it was determined that original plant wiring design for the station battery ammeter contains a 'shunt' in the current flow from each direct current (DC) battery. Bolted on the shunt bar are two IEEE 383 qualified leads to a current meter in the main control room (MCR). The small difference in voltage between the two taps on the shunt is enough to deflect the current gauge in the MCR when current flows from the battery through the shunt. The ammeter wiring attached to the shunt does not have fuses, and if one of these ammeter wires shorts to ground at the same time another DC wire from the opposite polarity on the same battery also shorts to ground, a ground loop through the unfused ammeter cable could occur. With enough current going through the cable, the potential exists that a fire in the raceway system or MCR could occur wherever the cable is routed. | ||
Latest revision as of 22:05, 1 March 2018
| Where | |
|---|---|
Clinton  Illinois (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | |
| Time - Person (Reporting Time:+2.5 h0.104 days <br />0.0149 weeks <br />0.00342 months <br />) | |
| Opened: | Ed Tiedenmann 13:30 Dec 8, 2011 |
| NRC Officer: | John Shoemaker |
| Last Updated: | Dec 8, 2011 |
| 47510 - NRC Website
| |