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{{Adams
#REDIRECT [[PNO-III-11-001, ; Palisades, Unusual Event and 72-Hour Limiting Condition for Operation Due to 4160 V Ground Fault]]
| number = ML110110273
| issue date = 01/11/2011
| title = PNO-III-11-001; Palisades, Unusual Event and 72-Hour Limiting Condition for Operation Due to 4160 V Ground Fault
| author name = Ellegood J A, Giessner J B
| author affiliation = NRC/RGN-III/DRP/RPB4
| addressee name =
| addressee affiliation =
| docket = 05000255
| license number = DPR-020
| contact person =
| document report number = PNO-III-11-001
| document type = NRC Preliminary Notification of Event/Occurrence
| page count = 2
}}
 
=Text=
{{#Wiki_filter:PRELIMINARY NOTIFICATION- REGION III January 11, 2011 PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE - PNO-III-11-001
 
This preliminary notification constitutes EARLY notice of events of POSSIBLE safety or public interest significance. The information is as initially received without verification or evaluation, and is basically all that is known by the Region III staff on this date.
 
Facility Palisades Nuclear Plant Entergy Nuclear Operations, Inc.
Covert, MI Docket:  50-255 License:  DPR-20 Licensee Emergency Classification X  Notification of Unusual Event Alert      Site Area Emergency General Emergency
_  Not Applicable
 
==SUBJECT:==
PALISADES UNUSUAL EVENT AND 72-HOUR LIMITING CONDITION FOR OPERATION DUE TO 4160 V GROUND FAULT DESCRIPTION:
 
At 1:03 p.m. (EST) on January 8, 2011, the licensee declared an Unusual Event as a result of a fault on a nonsafety-related buss. The fault resulted in loss of power to the buss, including power to a circulating water pump to a mechanical draft cooling water tower. The licensee reduced power to 53 percent due to this loss. The licensee believes the fault originated in or near an open breaker that could power the buss from off-site. As a result of the fault, the breaker from a station power transformer opened and de-energized the buss. The fault resulted in a small explosion that damaged the breaker and cubicle. With the plant at reduced power and stable, the Unusual Event was exited at 12:43 a.m. (EST) on January 9, 2011.
Although other breakers actuated as expected to isolate the fault, the resulting electrical transient may have affected some of the station supply transformers. In addition, the opening of the breakers removed one of the two available sources of off-site power. The other off-site power source was available and in service. However, this condition placed the site in a 72-hour Limiting Condition for Operation (LCO), which meant that if the other off-site power source was not restored within 72 hours, the plant would be required to shut down. The licensee restored the second off-site power source and exited the LCO at 7:51 a.m. (EST) on January 11, 2011. Before restoring the isolated source of off-site power, the licensee confirmed that the station supply transformers that could have been affected are functioning properly.
The licensee is evaluating the condition of the affected breaker and electrical buss and will perform the necessary repairs.
The State of Michigan has been informed by telephone.
 
NRC Resident Inspectors responded to the site during the Unusual Event and continue to monitor the electrical troubleshooting and repair activities.
 
2  Region III received initial notification of this occurrence by telephone notification to the Resident Inspectors from the licensee on January 8, 2011. The information in this preliminary notification has been reviewed with licensee management and is current as of 08:00 a.m. (EST) on January 11, 2011.
ADAMS Accession Number ML110110273
 
CONTACTS: John Ellegood  John Giessner  269/764-8971  630/829-9619}}

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