United States Nuclear Regulatory Commission - Protecting People and the Environment


ACCESSION #: 9803030035

                       LICENSEE EVENT REPORT (LER)



FACILITY NAME: Virgil C. Summer Nuclear Station           PAGE: 1 OF 4



DOCKET NUMBER:  05000395



TITLE:  10 CFR Part 21 Report on failed electrical governor (EG-

        A) on the "A" Emergency Diesel Generator



EVENT DATE:  01/09/98   LER #:  98-002-0    REPORT DATE:  02/26/98



OTHER FACILITIES INVOLVED:                          DOCKET NO:  05000



OPERATING MODE:  1   POWER LEVEL:  100



THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR

SECTION:

OTHER



LICENSEE CONTACT FOR THIS LER:

NAME:  A.R. Rice, Manager, Nuclear Licensing TELEPHONE:  (803) 345-4232

       & Operating Experience



COMPONENT FAILURE DESCRIPTION:

CAUSE:  X   SYSTEM:  EK   COMPONENT:  DG   MANUFACTURER:  C470

REPORTABLE NPRDS:  Y



SUPPLEMENTAL REPORT EXPECTED:  NO



ABSTRACT:



This notification is made pursuant to 10 CFR Part 21.



On January 9, 1998, Condition Evaluation Report (CER) 98-0038 and

Non-Conformance Notice (NCN) 98-0038 reported the failure of EG-A

control, serial number 1425251.  Due to potential applications in the

industry and the safety significance of its application as a governor

control for Emergency Diesel Generators (EDGs), this failure is

considered to be reportable under 10 CFR Part 21.  In this case, V. C.

Summer Nuclear Station ensured that adequate on site testing had been

performed to the associated EG-A to verify its operable status.  The

vendor, Engine Systems, Incorporated (ESI), has been notified of this

situation and understands that a Part 21 notification is being submitted

based on their certification of the EG-A (with inadequate

post-refurbishment bench testing by the vendor), that did not identify

intermittent failures in electrical components (such as potentiometers

and zener diodes).



A team from VCSNS procurement engineering visited the vendor's repair

facility (Woodward Governor Company) in Fort Collins, CO, to evaluate

their repair program.  Future purchase requisitions for EG-A

repair/refurbishment will include requirements for an extended burn-in

period and bench testing of the EG-A control for detection of

intermittent failures.



END OF ABSTRACT



TEXT                                                          PAGE 2 OF 4



This notification is made pursuant to 10 CFR Part 21.



PLANT IDENTIFICATION:



Westinghouse - Pressurized Water Reactor



EQUIPMENT IDENTIFICATION:



"A" Train Emergency Diesel Generator (XEG0001A) - EIIS - EA



The defective governor component is a Woodward model EGA electrical

governor.



IDENTIFICATION OF EVENT:



On January 9, 1998, Condition Evaluation Report (CER) 98-0038 and

Non-Conformance Notice (NCN) 98-0038 reported the failure of EG-A

control, serial number 1425251.  Due to potential applications in the

industry and the safety significance of its application as a governor

control for Emergency Diesel Generators (EDGs), this failure is

considered to be reportable under 10 CFR Part 21.  In this case, V. C.

Summer Nuclear Station ensured that adequate testing had been performed

on site to the associated EG-A to verify its operable status.  The

vendor, Engine Systems, Incorporated (ESI), has been notified of this

situation and understands that a Part 21 notification is being submitted

based on their certification of the EG-A (with inadequate post-

refurbishment bench testing by the vendor), that did not identify

intermittent failures in electrical components (such as potentiometers

and zener diodes).



A team from VCSNS procurement engineering visited the vendor's repair

facility (Woodward Governor Company) in Fort Collins, CO, to evaluate

their repair program.



EVENT DATE:



January 9, 1998



REPORT DATE:



February 26, 1998



This Licensee Event Report (LER) was initiated by Condition Evaluation

Report (CER) 98-0038.



CONDITIONS PRIOR TO EVENT:



Model 1 - Reactor Power 100%.



TEXT                                                          PAGE 3 OF 4



DESCRIPTION OF EVENT:



On January 9, 1998, Condition Evaluation Report (CER) 98-0038 and

Non-Conformance Notice (NCN) 98-0038 reported the failure of EG-A

control, serial number 1425251.  Due to potential applications in the

industry and the safety significance of its application as a governor

control for Emergency Diesel Generators (EDGs), this failure is

considered to be reportable under 10 CFR Part 21.  In this case, V. C.

Summer Nuclear Station ensured that adequate testing had been performed

on site to the associated EG-A to verify its operable status.  The

vendor, Engine Systems, Incorporated (ESI), has been notified of this

situation and understands that a Part 21 notification is being submitted

based on their certification of the EG-A (with inadequate

post-refurbishment bench testing by the vendor), that did not identify

intermittent failures in electrical components (such as zener diodes).



VCSNS sent EG-A serial number 1425251 to the vendor for repair, due to

intermittent spiking problems.  Following vendor refurbishment and

testing, VCSNS tests showed that the problem still existed.  The EG-A

unit was sent back to the vendor, where they again performed their

required tests with satisfactory results.  They next duplicated our test

by monitoring the device output over a period of time to look for

intermittent output problems.  At this point, the vendor observed the

problem and replaced two additional components.



Intermittent failures of this type can result in operation of components

outside of their design basis requirements.  The diesel's design basis

function is to carry its associated 7.2kV bus, without being paralleled

to the off-site grid.  In this configuration, EG-A control output spiking

results in diesel speed (frequency) changes.  Adverse affects resulting

from spurious speed changes can include:

     1.   The ready for load permissive will not allow diesel breaker

          closure if the frequency is below 58.8 hertz. (Ref. DG DBD

          section 3.9.4)

     2.   Plant ESF motors are not required by design, to accelerate

          equipment to rated speed if the frequency is more than 5% below

          rated (i.e. 57 hertz).  (Ref. FSAR section 8.3.1.1.4.2)

     3.   When ESF sequencer load blocks are loaded on the diesel,

          frequency is required to remain above 55.5 hertz.  (Ref. FSAR

          section 8.3.1.1.2.4)

     4.   When ESF sequencer load blocks are loaded on the diesel,

          frequency is required to return to within 2% of 60 hertz within

          2 seconds. (Ref. FSAR section 8.3.1.1.2.4)

     5.   Motor speeds vary in direct proportion to engine frequency; and

          systems with centrifugal pumps experience flow changes in

          direct proportion to speed changes.  Therefore, frequency dips

          could decrease system flows below their design requirements.

     6.   The diesel generator, step-down transformers, and motors could

          exceed their design volts/hertz limits.  As frequency drops,

          the voltage regulator tends to maintain voltage, so the volts

          per hertz ratio increases.  If this ratio gets above the flux

          saturation limit for the iron in the device, excessive heating

          and premature failure can occur.



The EG-A spikes and erratic changes varied in magnitude and duration.

Therefore, it is very hard to put a bound on the lower limit of possible

frequency dips.  Increases in frequency would be bounded by the

mechanical governor speed setting.



This programmatic repair/testing deficiency creates the potential for

common mode failures and operation outside of the plant design basis.

Therefore, based on the above affects, a substantial safety hazard could

be introduced.



A team from VCSNS procurement engineering visited the vendor's repair

facility (Woodward Governor Company) in Fort Collins, CO, to evaluate

their repair program.  It was determined that inadequate

post-refurbishment bench testing by the vendor was being conducted.

Future purchase requisitions for EG-A repair/refurbishment will include

requirements for an extended burn-in period and bench testing of the EG-A

control for detection of intermittent failures.



TEXT                                                          PAGE 4 OF 4



CAUSE OF EVENT:



The cause of the "A" EDG frequency oscillations was inadequate

post-refurbishment bench testing by the vendor, that did not identify

intermittent failures in electrical components (such as potentiometers

and zener diodes).  Follow-up testing by the governor manufacturer showed

the EG-A unit was unstable.  Additional vendor evaluation is ongoing to

include possible enhancements to their test program.  Future SCE&G

purchase requisitions for diesel generator EG-A repair/refurbishment will

include requirements for an extended burn-in period and bench testing of

the EG-A control for detection of intermittent failures.



ANALYSIS OF EVENT:



A team from VCSNS procurement engineering visited the vendor's repair

facility (Woodward Governor Company) in Fort Collins, CO, to evaluate

their repair program.  The cause of the 'A' EDG frequency oscillations

was inadequate post-refurbishment bench testing by the vendor, that did

not identify intermittent failures in electrical components (such as

potentiometers and zener diodes).  Future SCE&G purchase requisitions for

EG-A repair/refurbishment will include requirements for an extended

burn-in period and bench testing of the EG-A control for detection of

intermittent failures.



There are no adverse consequences for the event.  The defective EG-A was

discovered by on site bench testing which was confirmed at the vendor's

facility.  The replacement EG-A was satisfactorily tested prior to

installation on "A" EDG.



IMMEDIATE CORRECTIVE ACTIONS:



o    The vendor, Engine Systems, Incorporated (ESI), was notified of this

     situation and understands that a Part 21 notification has been made.



o    Vendor satisfactorily repaired and tested the associated EG-A.



ADDITIONAL CORRECTIVE ACTIONS:



o    Future purchase requisitions for EG-A repair/refurbishment will

     include requirements for an extended burn-in period and bench

     testing of the EG-A control for detection of intermittent failures.



o    SCE&G is continuing to monitor vendor evaluation of this event.  Any

     additional recommended corrective actions by the vendor will be

     reviewed for applicability to the V. C. Summer Nuclear Station.



PRIOR OCCURRENCES:



None.



ATTACHMENT TO 9803030035                                      PAGE 1 OF 1



                    South Carolina Electric &     Gary J.Taylor

                      Gas Company

                    P.O. Box 88                   Vice President

                    Jenkinsville, SC 29065        Nuclear Operations

                    (803) 345-4344



SCE&G                      February 26, 1998

                           RC-98-0036



Document Control Desk

U. S. Nuclear Regulatory Commission

Washington, DC 20555



Gentlemen:



Subject:       VIRGIL C. SUMMER NUCLEAR STATION

               DOCKET NO. 50/395

               OPERATING LICENSE NO. NPF-12

               LICENSEE EVENT REPORT (LER 98-002)



Attached is Licensee Event Report (LER) No. 98-002 for the Virgil C.

Summer Nuclear Station.  This report is submitted pursuant to the

requirements of 10 CFR 21.21(a)(1).



Should you have any questions, please call Mr. Michael J. Zaccone at

(803) 345-4328.



                                   Very truly yours,



GJT/mjz                            Gary J. Taylor

Attachment



c:   J. L. Skolds                  D. L. Abstance

     W. F. Conway                  R. J. Waselus

     R. R. Mahan (w/o attachment   R. L. Osborne

     R. J. White                   R. E. Slone

     L. A. Reyes                   G. A. Robertson

     L. M. Padovan                 J. B. Knotts Jr.

     R. B. Clary                   NRC Resident Inspector

     S. F. Fipps                   INPO Records Center

     A. R. Koon                    Marsh & McLennan

     G. E. Williams                NSRC

     T. L. Matlosz                 RTS (LER 980002, SSH 980001)

     B. C. Williams                Files (818.07, 818.18)

     P. Ledbetter                  DMS RC-98-0036



                NUCLEAR EXCELLENCE - A SUMMER TRADITION!



*** END OF DOCUMENT ***







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