PNO-I-06-010, Seabrook Power Station, Shutdown Greater than 72 Hours - Both Emergency Diesel Generators Inoperable Due to Problems in the Voltage Regulation Circuitry
| ML062440470 | |
| Person / Time | |
|---|---|
| Site: | Seabrook  |
| Issue date: | 09/01/2006 |
| From: | Paul Krohn NRC/RGN-I/DRP/PB6 |
| To: | |
| Krohn P, RI/DRP/PB6/610-337-5120 | |
| References | |
| PNO-I-06-010 | |
| Download: ML062440470 (3) | |
DCS No.: 05000443090106 Date: September 1, 2006 PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE -- PNO-I-06-010 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 I staff on this date.
Facility Seabrook Power Station Seabrook, NH Docket: 05000443 Licensee Emergency Classification Notification of Unusual Event Alert Site Area Emergency General Emergency X Not Applicable
SUBJECT:
SHUTDOWN GREATER THAN 72 HOURS - BOTH EMERGENCY DIESEL GENERATORS INOPERABLE DUE TO PROBLEMS IN THE VOLTAGE REGULATION CIRCUITRY On August 31, 2006, at 3:30 p.m., FPL Seabrook operators initiated a plant shutdown per Technical Specification (TS) 3.8.1.1 due to two inoperable emergency diesel generators (EDGs). The shutdown was necessitated by problems in the voltage regulation circuitry of both the A and B EDGs.
Previously, on August 28, the A EDG was removed from service for planned maintenance and declared inoperable. During a slow start maintenance run on August 30, the A EDG came up to rated speed and voltage and was loaded to the E5 safety bus for 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />. During a fast start run on the evening of August 30, the A EDG initially came up to rated speed and voltage (not loaded). However, a diode trouble light illuminated on the local EDG panel during the run.
Because of the potential operability implications of this light, the licensee decided to shutdown the A EDG and to schedule a run of the B EDG per the TS. Concurrently, licensee personnel began troubleshooting activities on the A EDG. During a subsequent fast start operability run on August 31, the A EDG came up to rated speed and voltage (not loaded) with no anomalous indications. The licensee further refined its troubleshooting activities by developing a plan which identified seven likely causes. Later that day, the B EDG was tested per technical specifications and initially came up to rated speed, but output voltage failed high.
The B EDG was promptly shutdown and declared inoperable per TS 3.8.1.1 at 2:15 p.m., on August 31. This TS required the restoration of one EDG to an operable status within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />, or a plant shut down to hot standby within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />. Based on the lack of a clearly definable success path, FPL Seabrook management initiated a plant shutdown per the TS at 3:30 p.m., on August 31. The plant reached Mode 3 (hot shutdown) at normal operating temperature and pressure at approximately 9:00 p.m, August 31.
Throughout the event, the licensee considered the A EDG functional. All off-site power lines, and the supplemental emergency power system (a separate EDG capable of supplying a safety bus), have been maintained available.
The NRC Resident Inspector staff has been following EDG troubleshooting activities since August 28 and observed portions of the Unit shutdown and cooldown. The Senior Resident Inspector accompanied the licensee during its Mode 3 Containment walkdown in which a Safety Injection Vent Valve (SI-V-265) was noted to have a very small active leak which will be addressed prior to startup.
On September 1, at approximately 2:00 p.m., following replacement of several failed capacitors on B EDG and satisfactory post maintenance testing, the B EDG was declared operable.
The facts of this PN were verified with John Dent, Assistant Plant Manager. This information is current as of 2:30 p.m. EST on September 1, 2006.
The Region I Public Affairs Office has responded to media inquiries. The States of Massachusetts and New Hampshire have been informed.
ADAMS Accession Number: ML062440470 CONTACT:
Paul Krohn (610) 337-5120
DISTRIBUTION: (PN Recipient List)
OWFN TWFN LST Chairman Klein Comm.
Lyons NMSS Comm.
Jazcko ACRS Comm.
McGaffigan Jr.
OIG Comm.
Merrifield RES OIP NSIR OCA OGC OPA EDO OE NRR SECY Regional Offices By Fax:
DOT:Trans INPO NSAC RI Resident Office Licensee: Dominion ADAMS Accession Number: ML062440470 SUNSI Review Complete: PGK (Reviewers Initials)
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RI/DRP RI/DRP RI/ORA RI/DRP RI/DR P
NAME SBarber PKrohn NSheehan MMcLaughlin BHolian DATE 09/01/06 09/01/06 09/01/06 09/01/06 09/01/06 OFFICIAL RECORD COPY Region I Form 83 (Rev. July 2, 2003)