Protecting People and the EnvironmentUNITED STATES NUCLEAR REGULATORY COMMISSION
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555
May 18, 1988
Information Notice No. 88-27: DEFICIENT ELECTRICAL TERMINATIONS
IDENTIFIED IN SAFETY-RELATED COMPONENTS
Addressees:
All holders of operating licenses or construction permits for nuclear power
reactors.
Purpose:
This information notice is being provided to alert addressees of deficiencies
identified in electrical terminations in safety-related components. It is ex-
pected that recipients will review the information for applicability to their
facilities and consider actions, as appropriate, to avoid similar problems.
However, suggestions contained in this information notice do not constitute
NRC requirements; therefore, no specific action or written response is
required.
Description of Circumstances:
The Nuclear Regulatory Commission (NRC) has been notified of several recently
identified deficiencies in electrical terminations in safety-related
components that, if they had remained uncorrected, would have jeopardized the
ability of these components to perform their intended safety function. These
deficiencies were identified at River Bend Station, Unit 1; Shoreham Nuclear
Power Station; Vermont Yankee Nuclear Power Station; and Oyster Creek, Unit 1.
River Bend Station, Unit 1
On January 19, 1988, the Gulf States Utility Company (GSU) submitted a
notification to the NRC, pursuant to 10 CFR Part 21, regarding oversized motor
operator termination lugs in three main steam shutoff valves and two feedwater
isolation valves. GSU reported that during functional testing of a main steam
shutoff valve on December 7, 1987, the valve motor operator experienced a high
current surge, which tripped its motor overload heater and prevented the valve
from fully closing. During GSU's investigation, two motor leads were found
burned and separated from the lugs. A third lug was easily pulled from the
motor lead by GSU personnel after they removed the heat shrink insulation.
The lugs were found to be oversized for the motor lead conductors. In
addition, during maintenance on a feedwater isolation valve, a lug on one
motor lead was found to be
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oversized for the conductor and not crimped. These lugs were manufactured by
Thomas & Betts. They were marked "T&B Navy 23-30 E-6" and were sized for use
with a #5-#6 AWG conductor. The actual motor leads were #10 AWG stranded
conductors.
Further investigation by GSU personnel found that both valves used Limitorque
SMB-4 motor operators with terminal blocks that had one-quarter-inch diameter
terminal screws. The lugs were the correct size for the one-quarter-inch
screw, but not for the conductor. All SMB-4 operators used in safety-related
applications were inspected by the licensee to determine lug size. Ten SMB-4
operators were inspected, and five were found with oversized lugs that were
deemed unreliable by the licensee, although they passed their surveillance
requirements. GSU personnel replaced the defective lugs with correctly sized
lugs. GSU is also revising its procedures for inspecting Limitorque motor
operators when they are received to include inspection of lug size on the
motor leads to prevent recurrence of this condition, since the defective wire
lugs were contained in valve operators supplied by the Limitorque Corporation
during the construction of River Bend Station.
In a separate 10 CFR Part 21 notification dated December 23, 1987, GSU
reported that several defective terminations were identified in electrical
heater panels supplied by NUTHERM International, Inc. The defective wire
terminations were in heater panel circuits of the fuel storage building
engineered safety feature charcoal filters. The deficiency involved improper
stripping of conductors that resulted in insulation under the termination
lugs. This insulation inhibited a good connection and jeopardized the ability
of the filters to perform their function. GSU reported that it had notified
NUTHERM International of the defect.
Shoreham Nuclear Power Station
On October 19, 1987, the Long Island Lighting Company (LILCO) submitted a
notification to the NRC pursuant to 10 CFR Part 21 regarding inadequately
crimped termination lugs discovered at the Shoreham Nuclear Power Station.
The subject lugs, which were manufactured by AMP Special Industries, were
installed in control wiring in 4160-volt switchgear equipment manufactured by
the General Electric Company (GE). The licensee discovered that many of the
GE-installed termination lugs were inadequately crimped to the control wires
and, in some cases, the lugs could be removed by hand. When LILCO personnel
inspected these lugs in equipment supplied by GE, they found that of
approximately 1400 lugs installed by GE, 42% had to be replaced.
GE determined that its personnel had deviated from the crimp process described
in their installation procedures during the manufacture of the equipment.
Therefore, the insulation around the control wires was not properly stripped
before being inserted into the AMP lugs and an AMP crimper was not used as
required. GE also determined that this problem was limited to equipment
supplied to
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Shoreham and Salem. GE stated that it had notified both facilities of the
problem and that its personnel had been requalified on the proper crimping
procedures to preclude any further similar incidents.
Vermont Yankee Nuclear Power Station
On September 28, 1987, Vermont Yankee Nuclear Power Station (Vermont Yankee)
personnel were conducting pre-startup operability tests on the residual heat
removal (RHR) pumps and core spray pumps. During the operability tests, the
"B" RHR pump motor experienced severe arcing problems and was quickly secured,
preventing damage to the motor windings.
Vermont Yankee personnel investigated the problem and found that the arcing
resulted from a failed AMP motor lead to power lead termination lug. Motor
lead and power lead termination lugs were subsequently inspected on three
other RHR pumps and core spray pumps fitted with AMP lugs. Termination lugs
manufactured by Thomas & Betts (T&B) that are used on RHR service water pumps
and station service water pumps also were inspected. These inspections
identified evidence of cracking of varying severity on seven AMP motor lead
termination lugs; however, no cracks were found on power lead terminations.
Little or no cracking was identified on terminations manufactured by T&B. The
AMP motor lead termination lugs were of the ring tongue type, #2 AWG, model
#35184, manufactured by AMP Special Industries. The terminations were
supplied in conjunction with the motors by GE.
Several of the cracked lugs were discovered by direct visual inspection, while
the remainder were identified using 10X magnification and/or dye penetrant
testing. During inspection of the lugs, it appeared that the manufacturer's
stamping on the throat of the lug contributed to the observed cracking because
a shallow "AMP" die stamp was found at the throat section of the lug. A stamp
(a numeral 1, 2, or 3) on the opposite side of the throat, believed to be a
phase indication, was also suspected of being a contributor. The cracking
identified on these lugs was ultimately attributed to excessive bending during
maintenance activities, with the manufacturer's stamping providing
pre-stressed flaws for crack initiation and propagation. The small cramped
work space inside the motor terminal housings, coupled with the rigidity of
the required Raychem splices, contributed to fatiguing the lugs during
maintenance activities.
Oyster Creek, Unit 1
GPU Nuclear Corporation (GPUNC) submitted Licensee Event Report (LER)
219-87-011, Revision 1, to the NRC on May 4, 1987, regarding deficient
electrical terminations at Oyster Creek, Unit 1. GPUNC reported that on
February 10, 1987, an electrical technician who was verifying proper wiring
connections inadvertently moved a wiring harness in a control room panel.
This movement disconnected the "A" feedwater flow rate signal wire and
initiated a sequence of events that resulted in a
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May 18, 1988
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turbine trip and an anticipatory scram. On February 26, 1987, an electrical
technician, performing an inspection of wire terminations in response to the
previous event, disturbed a wire that caused the automatic closure of the main
steam isolation valves.
The GPUNC investigation determined that the cause of the first event was in-
sufficient procedural controls over wire termination practices. The wire
terminations used in the control room panel were compression-type
terminations, which capture wires under a metal plate compressed by a screw,
rather than lug-type terminations. GPUNC personnel found that different size
wires were used in the same termination and that sometimes the plate in the
compression terminations was removed when wires were too large to fit under
the plate. The GPUNC investigation also found terminations with cracked or
broken pressure plates, as well as wires that were unlabeled, unterminated,
and uninsulated. Furthermore, GPUNC personnel discovered that when new cables
were pulled to support modification work, existing wire terminations were
stressed by the new wires that lay on top of the original wiring.
The second event was attributed to faulty wire installation, either during
plant construction or during subsequent maintenance. Inspection of the wire
termination showed that the screw used to fasten the wire was loose. Movement
of this wire caused four relays to deenergize, resulting in automatic closure
of the main steam isolation valves.
GPUNC personnel identified and corrected a total of 123 deficient
terminations, both compression-type and lug-type. GPUNC has revised its
Installation Specifications for wire terminations and Quality Assurance
Procedures for inspecting wire terminations to ensure and verify proper
electrical terminations. These revisions will ensure that an adequate
structural integrity of the termination exists, require that a
post-modification and maintenance tug test be performed, and eliminate the
practice of terminating two wires with significant gauge differences in
compression-type terminations unless it is endorsed by the termination
manufacturer. In addition, GPUNC indicated that it was in the process of
identifying those terminations that are frequently accessed for surveillance
and maintenance purposes and will install test connections to minimize
movement and stress on the terminations.
Discussion:
These examples emphasize the need to carefully monitor the receipt, instal-
lation, and maintenance of safety-related components with respect to their
cable or wire terminations. Licensees may wish to review their current
receipt, installation, and maintenance procedures to assure that proper
quality controls and measures exist to preclude such events as those discussed
above.
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No specific action or written response is required by this information notice.
If you have any questions about this matter, please contact one of the
technical contacts listed below or the Regional Administrator of the
appropriate regional office.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contacts: Jaime Guillen, NRR
(301) 492-1153
Carl S. Schulten, NRR
(301) 492-1192
Attachment: List of Recently Issued NRC Information Notices
. Attachment
IN 88-27
May 18, 1988
Page 1 of 1
LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
_____________________________________________________________________________
Information Date of
Notice No._____Subject_______________________Issuance_______Issued to________
85-35, Failure of Air Check 5/17/88 All holders of OLs
Supplement 1 Valves to Seat or CPs for nuclear
power reactors.
88-26 Falsified Pre-Employment 5/16/88 All holders of OLs
Screening Records or CPs for nuclear
power reactors and
all major fuel
facility
licensees.
88-25 Minimum Edge Distance for 5/16/88 All holders of OLs
Expansion Anchor Bolts or CPs for nuclear
power reactors.
88-24 Failures of Air-Operated 5/13/88 All holders of OLs
Valves Affecting Safety- or CPs for nuclear
Related Systems power reactors.
88-23 Potential for Gas Binding 5/12/88 All holders of OLs
of High-Pressure Safety or CPs for PWRs.
Injection Pumps During a
Loss-of-Coolant Accident
88-22 Disposal of Sludge from 5/12/88 All holders of OLs
Onsite Sewage Treatment or CPs for nuclear
Facilities at Nuclear power reactors.
Power Stations
88-21 Inadvertent Criticality 5/9/88 All holders of OLs
Events at Oskarshamn or CPs for nuclear
and at U.S. Nuclear power reactors.
Power Plants
88-20 Unauthorized Individuals 5/5/88 All holders of OLs
Manipulating Controls and or CPs for nuclear
Performing Control Room power, test and
Activities research reactors,
and all licensed
operators.
_____________________________________________________________________________
OL = Operating License
CP = Construction Permit
