Part 21 Report - 1998-153
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!
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