United States Nuclear Regulatory Commission - Protecting People and the Environment

ACCESSION #: 9505310088

                                             Illinois Power
Company
                                             Clinton Power
Station
                                             P.O. Box 678
                                             Clinton, IL 61727
                                             Tel 217 935-5623
                                             Fax 217 935-4632

                                             John G. Cook
                                             Vice President
ILLINOIS                                          U-602446
  POWER                                           L16-95(05 -22
)LP
                                                  4F.140
                                                  JGC-218-95
                                                  May 22, 1995
Docket No. 50-461                                 10CFR21.21

Document Control Desk
Nuclear Regulatory Commission
Washington, D.C.  20555

Subject:       10CFR21 Interim Report 21-95-010: Elgar
               Inverter PWM Drive Logic Card (J4) Failure

Dear Sir:

          On March 24, 1995, a new PWM drive logic card (J4) was
installed in the Division 2 Nuclear Systems Protection System
(NSPS)
inverter at Clinton Power Station (CPS) and failed after four to
six
hours of operation during calibration of the inverter.  At the
time of
the failure, the inverter was out of service to replace the logic
card
with a revised card in accordance with a scheduled maintenance
activity.
Illinois Power (IP) does not know the cause of the card failure
but has
returned the logic card to the supplier for failure analysis.

          On March 25, 1995, IP determined that the failure of
the logic
card was a condition potentially reportable under the provisions
of
10CFR21.  IP expects to complete the evaluation of this issue by
June 30,
1995.

          IP provides the following interim information in
accordance
with 10CFR21.21(c)(4).  Initial notification of this matter will
be
provided by facsimile of this letter to the NRC Operations Center
in
accordance with 10CFR21.21(c)(3) on the date this letter is
signed by the
responsible officer.

(i)       J. G. Cook, Vice President of Illinois Power, Clinton
Power
          Station, Post Office Box 678, Clinton, Illinois, 61727,
is the
          responsible officer informing the Nuclear Regulatory
Commission
          (NRC) of a condition reportable under the provisions of
10CFR,
          Part 21, by means of this report.

(ii)      The basic component involved in this condition is a PWM
drive
          logic card, part number 642-108-40, revision F.  The
logic card
          was installed in the Division 2 NSPS inverter.  The
inverter
          provides 120 volts alternating current (AC)
uninterruptible
          power to loads such as NSPS logic power, neutron
monitoring,

                                                  U-602446
                                                  Page 2

          process radiation monitoring, portions of the leak
detection
          system, nuclear steam supply shutoff system valves and
loss of
          coolant accident bypass relays during all modes of
operation
          including abnormal and accident conditions.  The logic
card
          provides control signals to the SCR (silicon controlled
          rectifier) drives.  The same logic card part can be
used in the
          Divisions 1, 2, 3, and 4 NSPS inverters but the revised
card
          was never installed in the Divisions 3 and 4 inverters.

(iii)     The logic card was manufactured by Elgar Corporation
and
          supplied to CPS by Elgar Corporation/General Electric.

(iv)      IP installed the logic card in the inverter during a
scheduled
          maintenance activity.  During calibration of the
inverter, the
          logic card operated for four to six hours and then
failed for
          no known reason.

          The failure of the logic card causes the inverter to
shut down.
          When this occurs, the inverter loads are transferred to
the
          alternate AC source of power.  During the failure of
the logic
          card at CPS, the inverter was out of service for
scheduled
          maintenance and not required to be operable.  However,
if the
          logic card had failed during a loss of offsite power
(LOOP)
          condition, the NSPS loads would be transferred to the
alternate
          AC power source which may not be available due to the
LOOP
          condition and the NSPS loads would lose power.

(v)       The logic card failure was discovered on March 24,
1995.  On
          March 25, 1995, IP determined that the failure was
potentially
          reportable under the provisions of 10CFR, Part 21.

(vi)      IP received one other logic card part number
642-108-40,
          revision F.  This logic card was identified as
deficient when
          it was initially installed in the Division 1 NSPS
inverter
          during a similar maintenance activity and the Division
1 NSPS
          inverter would not operate, that is, the inverter SCR
drive
          section operation would not function.  The failure of
the card
          installed in the Division 1 NSPS inverter was obvious
and could
          not have gone undetected since the inverter could not
be
          declared operable if the SCR drives were inoperable. 
IP has no
          information about logic cards that may have been
supplied to
          other purchasers.

(vii)     The logic card that failed in the Division 1 NSPS
inverter has
          been replaced with the original logic card, part number
642-
          108-40, revision A.  The logic card that failed in the
Division
          2 NSPS inverter has been replaced with a logic card
part number
          642-108-40, revision E.  Both logic cards that failed
have been
          returned to Elgar Corporation for failure analysis.

(viii)    IP has no advice to offer other purchasers or licensees
about
          this issue at this time.  Additional information about
this
          issue may be obtained by contacting D. G. Lukach,
system
          engineer, at (217) 935-8881, extension 3952.

                                                  U-602446
                                                  Page 3

          IP will provide a final report regarding this issue
following
completion of the evaluation.

                              Sincerely yours,

                              J. G. Cook
                              Vice President

RSF/csm

cc:  NRC Clinton Licensing Project Manager
     NRC Resident Office, V-690
     Regional Administrator, Region III, USNRC
     INPO Records Center
     Illinois Department of Nuclear Safety
     Elgar Corporation

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