05000315/LER-1985-052, :on 851012,failure of Critical Control Room Power Inverter Resulted in Momentary Loss of 120-volt Regulated Control Room Power.Caused by Shorted Diode & Capacitor & Blown Fuses.Components Replaced

:on 851012,failure of Critical Control Room Power Inverter Resulted in Momentary Loss of 120-volt Regulated Control Room Power.Caused by Shorted Diode & Capacitor & Blown Fuses.Components Replaced

ML20136E628
Person / Time
Site:	Cook
Issue date:	11/11/1985
From:	Lauren Gibson INDIANA MICHIGAN POWER CO. (FORMERLY INDIANA & MICHIG
To:
Shared Package
ML20136E625	List: 05000315/LER-1985-052, :on 851012,failure of Critical Control Room Power Inverter Resulted in Momentary Loss of 120-volt Regulated Control Room Power.Caused by Shorted Diode & Capacitor & Blown Fuses.Components Replaced 05000315/LER-1985-053, :on 851011,determined That in Event of Actuation of CO2 Suppression Sys Protecting Fire Zones 41 or 45,fire Dampers Not Designed to Close Allowing Gas to Flow Out of Zone.Openings Closed Permanently ML20136E619
References
LER-85-052, LER-85-52, NUDOCS 8511210539
Download: ML20136E628 (1)

LER-1985-052, on 851012,failure of Critical Control Room Power Inverter Resulted in Momentary Loss of 120-volt Regulated Control Room Power.Caused by Shorted Diode & Capacitor & Blown Fuses.Components Replaced

Event date:
Report date:
3151985052R00 - NRC Website

text

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AS$TR ACT #Lemer to f 400 meces to. sesses.saefery rarreen mare asece erse=certoa maes# Hei ON OCTOBER 12, 1985, AT 0111 HOURS, WHILE IN COLD SHUTDOWN (MODE 5),

FAILURE OF THE CRITICAL CONTROL ROOM POWER (CCRP) INVERTER (IEEE/INVT) RESULTED IN A MOMENTARY LOSS OF 120 VOLT REGULATED CONTROL ROOM POWER WHILE AN AUTOMATIC BUS TRANSFER SWITCH SHIFTED TO THE BACKUP UNREGULATED POWER SUPPLY.

THE MOMENTARY LOSS OF POWER RESULTED IN AN AUTOMATIC ENGINEERED SAFETY FEATURES ACTUATION.

THE CAUSE OF THE CCRP FAILURE COULD NOT BE CONCLUSIVELY DETERMINED.

INVESTIGATION REVEALED A SHORTED DIODE (IEEE/ RECT),

SHORTED CAPACITOR (IEEE/ CAP), AND TWO BLOWN FUSES (IEEE/FU).

THE FAILED COMPONENTS WERE REPLACED AS WERE OTHER DIODES, SILICON CONTROLLED RECTIFIERS,-AND CAPACITORS THAT HAD NOT FAILED BUT MAY HAVE SUFFERED DEGRADATION AS A RESULT OF THE INCIDENT.

THE ENGINEERED SAFETY FEATURES ACTUATION CONSISTED OF A CONTAINMENT PURGE ISOLATION SIGNAL.

BECAUSE PURGE IS NOT REQUIRED IN MODE 5, THE SIGNAL WAS BLOCKED WHICH PREVENTED ANY EQUIPMENT ACTUATION. IMMEDIATE ACTION WAS TAKEN BY OPERATIONS PERSONNEL TO RESTORE PURGE TO PRE-EVENT STATUS.

THE INVERTER WAS RETURNED TO SERVICE ON OCTOBER 16, 1985 AT 1416 HOURS.

PROPER FUNCTIONING OF AUTOMATIC TRANSFER TO ALTERNATE POWER ENSURED THERE WERE NO ADVERSE SAFETY CONSEQUENCES OR IMPLICATIONS.

ALL EQUIPMENT PERFORMED AS DESIGNED.

NO PREVIOUS OCCURRENCES ARE KNOWN.

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