United States Nuclear Regulatory Commission - Protecting People and the Environment


ACCESSION #: 9805140315



POWER REACTOR                                EVENT NUMBER: 34194



FACILITY:  CLINTON       REGION: 3      NOTIFICATION DATE: 05/08/98

UNIT: [1] [ ]  [ ]       STATE: IL      NOTIFICATION TIME: 13:44 [ET]

RX TYPE: [1] GE-6                       EVENT DATE:        05/08/98

                                        EVENT TIME:        00:00[CDT]

NRC NOTIFIED BY:  BYRON SHERMAN         LAST UPDATE DATE:  05/08/98

HQ OPS OFFICER:   BOB STRANSKY

                                                  NOTIFICATIONS

EMERGENCY CLASS:  NOT APPLICABLE

10 CFR SECTION:                         PATRICK HILAND     RDO

CDEG 21.21(c)(3)(i)   DEFECTS/NONCOMPLIANCE

                                        VERN HODGE         NRR



UNIT SCRAM CODE  RX CRIT  INIT PWR  INIT RX MODE  CURR PWR  CURR RX

MODE

  1       N         N         0     COLD SHUTDOWN      0    COLD SHUTDOWN



                               EVENT TEXT



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 KEPCO, INC. MODEL

RMW12-D-20993.  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.



Initial notification by facsimile of 10CFR, Part 21, Report No. 21-98-022



     On February 13, 1998, a Nuclear Systems Power System (NSPS) 12 volt

direct current (VDC) power supply failed causing the Division II NSPS

inverter to reverse transfer to a de-energized bypass transformer.  This

caused a loss of shutdown cooling as described in Licensee Event Report

(LER) 98-003, dated March 16, 1998.  The cause of the power supply

failure was an inadequately designed output transistor pair combined with

degraded capacitors.



(i)       Walter G. MacFarland, IV, Senior Vice President and Chief

          Nuclear Officer of Illinois Power, Clinton Power Station, Post

          Office Box 678, Highway 54, Six Miles East, Clinton, Illinois,

          61727, is informing the Nuclear Regulatory Commission (NRC) of

          a condition reportable under the provisions of 10CFR, Part 21.



(ii)      The component involved in this report is a 12 VDC power supply,

          model number RMX12-D-20993 supplied to Clinton Power Station.



(iii)     This power supply is manufactured by KEPCO, Incorporated, and

          was purchased by General Electric (GE) as a non-safety related

          component.  Subsequently, the power supply was installed during

          construction of Clinton Power Station as part of a panel

          supplied by GE as a safety related component.



(iv)      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 NSPS bus loads

          which included the primary valve for the shutdown cooling mode

          at the time of the event.



(v)       IP identified on March 12, 1998, that the power supply failed

          during startup of the division 2 NSPS inverter on February 13,

          1998, and determined that it was potentially reportable under

          10CFR21.



(vi)      RMX type KEPCO, Inc. power supplies are in use at CPS for all

          four divisions of NSPS (16 total), Neutron Monitoring System

          (24 total), and the Display Control System (2 total).

          Currently, CPS is evaluating the impact on all KEPCO supplied

          power supplies.



(vii)     Corrective actions to be taken by IP will be to replace the

          output transistors and degraded capacitors, due to premature

          aging, of all KEPCO RMX type power supplies and refurbish these

          power supplies on a routine basis under a normal preventive

          maintenance program.



(viii)    IP recommends evaluation of all RMX type power supplies

          manufactured by KEPCO, Inc. to determine impact of this

          condition.



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