United States Nuclear Regulatory Commission - Protecting People and the Environment


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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