Part 21 Report - 1998-370

LICENSEE: ILLINOIS POWER CO. SITE: CLINTON 1 EN NUMBER:34194 DOCKET: 05000461 EVENT DATE: 05-08-98 RX TYPE: BWR EVENT TIME: 00:00 VENDORS: GE-6 NOTIFY DATE: 05-08-98 EMERGENCY CLASS: N/A REGION: 3 STATE: IL TIME: 13:44 OPS OFFICER: BOB STRANSKY 10 CFR SECTION: CDEG 21.21(c)(3)(i) DEFECTS/NONCOMPLIANCE UNIT SCRAM RX INIT INITIAL MODE CURR CURRENT MODE CODE CRIT PWR PWR 1 N N 0 COLD SHUTDOWN 0 COLD SHUTDOWN 10 CFR PART 21 REPORT REGARDING FAILURE OF 12 VDC INVERTER POWER SUPPLY ON 2/13/98, A NUCLEAR SYSTEMS POWER SYSTEM (NSPS) 12 VOLT DC POWER SUPPLY FAILED, CAUSING THE DIVISION II NSPS INVERTER TO REVERSE TRANSFER TO A DEENERGIZED BYPASS TRANSFORMER. THIS CAUSED A LOSS OF SHUTDOWN COOLING AS DESCRIBED IN LER 98-003, DATED 3/16/98. THE CAUSE OF THE FAILURE WAS AN INADEQUATELY SIZED OUTPUT TRANSISTOR PAIR COMBINED WITH DEGRADED CAPACITORS. THE 12 VDC POWER SUPPLY INVOLVED IN THIS REPORT IS MODEL RMW12-D-20993, MANUFACTURED BY KEPCO, INC. IT WAS PURCHASED BY GENERAL ELECTRIC (GE) AS A NON-SAFETY RELATED COMPONENT, BUT WAS SUBSEQUENTLY INSTALLED AT CLINTON AS PART OF A PANEL SUPPLIED BY GE AS A SAFETY RELATED COMPONENT. KEPCO TYPE RMX POWER SUPPLIES ARE IN USE AT CLINTON FOR ALL FOUR DIVISIONS OF NSPS (16 TOTAL), NEUTRON MONITORING SYSTEM (24 TOTAL), AND THE DISPLAY CONTROL SYSTEM (2 TOTAL). THE SUPPLIER PROVIDED MARGINALLY RATED OUTPUT TRANSISTORS IN THE POWER SUPPLIES. THIS CONDITION, COUPLED WITH PREMATURE AGE RELATED DEGRADATION OF ELECTROLYTIC CAPACITORS, RESULTED IN A LARGE CURRENT DRAW WHICH CAUSED THE INVERTER TO TRANSFER TO ITS ALTERNATE SOURCE. SINCE THE ALTERNATE SOURCE WAS UNAVAILABLE, THE CONDITION RESULTED IN A LOSS OF POWER TO THE NSPS BUS LOADS. THE LICENSEE PLANS TO REPLACE ALL OUTPUT TRANSISTORS AND DEGRADED CAPACITORS IN ALL KEPCO TYPE RMX POWER SUPPLIES AND REFURBISH THESE POWER SUPPLIES ON A ROUTINE BASIS UNDER A NORMAL PREVENTIVE MAINTENANCE PROGRAM.

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