PNO-I-12-004, Limerick, Unit1, Notification of Unusual Event Declared Due to Electrical Fault in Non-Safety Related Transformer 7-18-2012
| ML12201A869 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 07/19/2012 |
| From: | Paul Krohn Reactor Projects Region 1 Branch 4 |
| To: | |
| KROHN, PG | |
| References | |
| PNO-I-12-004 | |
| Download: ML12201A869 (2) | |
Date: July 19, 2012 PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE -- PNO-I-12-004 This preliminary notification constitutes EARLY notice of events of POSSIBLE safety or public interest significance. Some of the information may not yet be fully verified or evaluated by the Region Staff.
Facility Licensee Emergency Classification Exelon Generating Company LLC. X Notification of Unusual Event Limerick Unit 1 __ Alert Pottstown, PA Site Area Emergency Docket: 50-352 General Emergency Not Applicable
SUBJECT:
NOTIFICATION OF UNUSUAL EVENT DECLARED DUE TO AN ELECTRICAL FAULT IN A NON-SAFETY RELATED TRANSFORMER; ITEM OF POTENTIAL MEDIA INTEREST On July 18, 2012 at 8:39 a.m., Exelon declared an Unusual Event (UE) due to an electrical disturbance on a non-safety related transformer located in the control enclosure inside the Protected Area (PA). The UE declaration was based on operator assessment of damage to the transformer and surrounding equipment which included some deformation and charring on the exterior of the cabinet. Safety-related equipment and off-site power sources were not impacted.
The UE was terminated by Exelon at 9:46 a.m.
Earlier, at 8:15 a.m., Exelon personnel had manually scrammed the reactor in response to the automatic tripping of the two reactor recirculation pumps. An electrical fault interrupted power to the operating main generator stator cooling water pump which, by design, caused a main generator runback and subsequent trip of the reactor recirculation pumps. The reactor scram was not complicated and the plant was stabilized with decay heat being removed by the main condenser via the turbine bypass valves. The NRC resident inspectors were on site and responded to control room and closely monitored licensee actions to stabilize the plant and implement operating response procedures. The NRC remained in the normal mode of operation throughout this event. The NRC staff continues to assess Exelons response and communications with regard to this event. Unit 2 was not affected.
Prior to this event Exelon personnel had been monitoring the condition of the recirculation pump shaft seals. The primary seals on both pumps were showing signs of degrading performance and the licensee was planning a forced maintenance outage at a future date to replace the seals. Following this event, Exelon management decided to take the unit to cold shutdown and replace the affected pump seals.
The Commonwealth of Pennsylvania has been informed. Region I Public Affairs is prepared to respond to media inquiries. Exelon has issued a press release.
NRC received initial notification of this occurrence from Exelon, via a telephone call to the NRC Emergency Operations Duty Center Officer, on July 17, 2012, at 9:32 a.m. The information presented herein has been discussed with Exelon and is current as of July 18, 2012, at 1:00 p.m.
ADAMS Accession Number: ML12201A869 CONTACT: Paul Krohn (610) 337-5120 Paul.krohn@nrc.gov
ML12201A869 Non-Sensitive Publicly Available SUNSI Review Sensitive Non-Publicly Available OFFICE RI/DRP RI/DRP RI/SLO RI/PAO RI/ORA NAME PKrohn/SM for DRoberts/DJR NMcNamara/NM DScrenci/DS DLew/DCL DATE 07/18 /12 07/ 19/12 07/18 /12 07/ 18/12 07/ 19/12