View source for PNO-I-97-045, on 970801,electricians Restoring One Set of Main Generator Exciter Brushes,Following Routine Surveillance,When One of Brushes Sparked Excessively & Disintegrated.Electricians Exited Area & Notified CR

{{Adams
| number = ML20196J537
| issue date = 08/04/1997
| title = PNO-I-97-045:on 970801,electricians Restoring One Set of Main Generator Exciter Brushes,Following Routine Surveillance,When One of Brushes Sparked Excessively & Disintegrated.Electricians Exited Area & Notified CR
| author name = Eselgroth P, Shoppy J
| author affiliation = NRC OFFICE OF INSPECTION &amp; ENFORCEMENT (IE REGION I)
| addressee name = 
| addressee affiliation = 
| docket = 05000219
| license number = 
| contact person = 
| document report number = PNO-I-97-045, PNO-I-97-45, NUDOCS 9708040218
| document type = PRELIMINARY NOTIFICATION OF EVENT OR OCCURRENCE (PNO,, TEXT-INSPECTION &amp; AUDIT &amp; I&amp;E CIRCULARS
| page count = 2
}}
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      .                                                        August              4, 1997 PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE PNO-I-97-045 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 Region I staff in King of Prussia, Pennsylvania on this date.
Facility                                              Licensee Emeraency Classification Gpu Wuclear Corp.                                       Notification of Unusual Event Oyster Creek 1                                          Alert Forked River,New Jersey                                 Site Area Emergency Dockets: 50-219                                         General Emergency X Not Applicable

==Subject:==
PLANT SHUTDOWN GREATER THAN 72 HOURS On August 1,       1997, electricians were restoring one set of main generator exciter brushes, following a routine surveillance, when one of the brushes sparked excessively and disintegrated. The sparks contacted the exciter housing insulation and resulted in a smoke-filled exciter housing.        Electricians exited the area and notified the control room.
Control room operators promptly manually initiated a reactor shutdown (scram) at 1:40 P.M. An in-plant senior reactor operator manually activated the exciter CO2 system to suppress the sparks. Any fire was I
confirmed to be extinguished within several minutes.
Following the reactor scram, the turbine tripped and the startup transformers energized the two non-vital 4160V buses as designed to provide offsite power. However, the two 4160V vital bus voltages did not recover within the required 10 seconds. The undervoltage protective relays actuated, the vital buses tripped, and the emergency diesel generators started automatically and sequenced safety loads onto the vital buses. Off-site power continued to power the non-vital buses through the startup transformers.            The emergency diesel generators were secured in about 40 minutes and vital buses were powered from offsite.
The momentary loss of power to the vital buses de-energized both channels of the reactor protection system.            This failsafe feature resulted in closure of the main steam isolation valves, tripping of all five reactor recirculation pumps and initiation of the standby gas treatment system.
The unexpected undervoltage condition on the vital buses following the reactor scram complicated the plant recovery and further challenged the operators.
Engineering reported that control rod insertion times, as measured by the scram brush recorder, were all within Technical Specification limits. The licensee noted that safety loads sequenced onto the emergency diesel generators as expected; however, the control rod drive (CRD) pumps automatically started and then tripped.            Operators eventually restored the CRD pumps after manipulating the associated breakers and close-fuses.
Operators are maintaining the plant in the cold shutdown condition.
The licensee is investigating the overall electrical system response, including the causes of the degraded voltage on the vital buses and the electrical problems associated with the CRD pump breakers.                        The resident inspectors are following the licensee's actions.
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The State of New Jersey has been notified.       -
,   The licensee has issued a press release.

==Contact:==
Peter W. Eselgroth    Joseph Shoppy (610)337-5234         (609)693-0702 I
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