View source for PNO-II-85-043, on 850425,most Control Room Annunciators Lost Due to Failure of Inverter Power Supply.Possibly Caused by Blown Fuse.One Feedwater Pump Restored to Operation

{{Adams
| number = ML20133E295
| issue date = 04/25/1985
| title = PNO-II-85-043:on 850425,most Control Room Annunciators Lost Due to Failure of Inverter Power Supply.Possibly Caused by Blown Fuse.One Feedwater Pump Restored to Operation
| author name = Brownlee V, Dance H
| author affiliation = NRC OFFICE OF INSPECTION &amp; ENFORCEMENT (IE REGION II)
| addressee name = 
| addressee affiliation = 
| docket = 05000269
| license number = 
| contact person = 
| document report number = PNO-II-85-043, PNO-II-85-43, NUDOCS 8507220455
| document type = PRELIMINARY NOTIFICATION OF EVENT OR OCCURRENCE (PNO,, TEXT-INSPECTION &amp; AUDIT &amp; I&amp;E CIRCULARS
| page count = 3
}}
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April 25,1985-PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE PNO-II-85-43 This preliminary notification constitutes EARLY notice of events of POSSIBLE safety or public interest sigr.ificance. The information is as initially received without veriff-cation or evaluation, and is basically all that is known by the Region II staff on this dat:.
FACILITY: Duke Power Company                       Licensee Emergency Classification:
Oconee Unit 1                              Notification of Unusual Event Docket No. 50-269                       X Alert Seneca, South Carolina                     Site Area Emergency General Emergency Not Applicable

==SUBJECT:==
LOSS OF ANNUNCIATORS AND REACTOR TRIP Duke Power Company declared an alert at 5:12 a.m. (EST) today -- in accordance with the Oconee emergency plan -- after most control room annunciators were lost because of the failure of an inverter power supply. The cause of the power supply loss at present is unknown. The inverter, which was being supplied by battery, normally automatically switches to the AC power line source, but did not in this instance, possibly because of a blown fuse in the switching circuit.
When the power supply was manually transferred to the AC line, oscillations developed in the integrated control system, which was attempting to adjust various components to the requirements of the plant's operation at 100 percent power. These oscillations resulted in the tripping of one main feedwater pump, which initiated an automatic turbine runback.
During the runback, the other main feedwater pump also tripped, which caused the reactor to trip at 5:33 a.m. One feedwater pump was restored to operation at 6:02 a.m. The alert designation ended at 6:33 a.m. The unit is now stable and in hot shutdown. Region II is monitoring the licensee's evaluation of the event.
Duke issued a news announcement at 6:54 a.m. today. Both Duke and the NRC are responding to inquiries.
Oconee Unit 2 is operating at 76 percent power, and Unit 3 is at 100 percent power.
l The State of South Carolina has been informed.
l Duke informed the NRC headquarters incident response center of this incident at 5:30 a.m. l today. This information is current as of 10:30 a.m.                                        l

==Contact:==
H. C. Dance, 242-5533                       V. Brownlee, 242-5583               ,
DISTRIBUTION:
H. Street            MNBB     Phillips     E/W   Willste     MAIL:
Chairman Palladino EIF        NRR g' gOIA    T / NMSS        %URIDMB Trans Only Comm. Roberts        PA /                       RES         DOT:
Applicable State Comm. Asselstine    MPA                   AE0D Comm. Bernthal       ELD Comm. Zech           Air Rights           INPO SECY                      SP              NSAC ACRS CA B507220455 850425
                               $-I!k5-043         PDR L___._._.__

'As PDR Regions:       /         -
Licensee:       V                 i l
(Reactor Licensees)
Applicable Resident Site          l l
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                                                                -   1 FN No. 5-   5 DATE   Y/ OD S$
PRELIMINARY NOTIFICATION (PN) DISTRIBUTION INTERNAL REGION II DISTRIBUTION Regional Administrator Deputy Administrator                            l Assistant to Administrator Di rector, DRB   (3)
Director, DRS (2)
Director, DRSS (2)
Director, State & Government Affairs General Files (SSINS NO. 6810) 8 L}}

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