Protecting People and the EnvironmentUNITED STATES NUCLEAR REGULATORY COMMISSION
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555-0001
August 12, 1996
NRC INFORMATION NOTICE 96-46: ZINC PLATING OF HARDENED METAL PARTS AND
REMOVAL OF PROTECTIVE COATINGS IN REFURBISHED
CIRCUIT BREAKERS
Addressees
All holders of operating licenses or construction permits for nuclear power
reactors.
Purpose
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information
notice to alert addressees that inadequate licensee review of procedures
employed by a circuit breaker refurbishing contractor resulted in breakage of
hardened metal parts and potentially increased wear of other metal parts that
could cause the refurbished breakers to fail to operate. It is expected 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 are not NRC requirements;
therefore, no specific action or written response is required.
Description of Circumstances
In May 1996, technicians employed by Public Service Electric & Gas (PSE&G) at
its Salem Generating Station (Salem) observed broken lock washers in the arc
chute holddown assembly of a General Electric (GE) 4.16-kV AM-type Magne-Blast
circuit breaker during a receipt inspection. Nuclear Logistics Incorporated
(NLI), a breaker refurbishing contractor, refurbished the breaker. NLI used a
subcontractor, National Switchgear Systems (NSS), to perform the
refurbishment. The licensee determined that NSS did not remove or mask the
lock washers during the zinc-plating of the arc chute holddown assembly.
On July 16, 1996, during preinstallation testing of another Magne-Blast
breaker, technicians at Salem noted that the inner latch pawl spring retainer
roll pin of the spring charging mechanism was broken longitudinally. The pin
had been zinc plated during refurbishment at NSS. Failure of the pin may
cause the failure of the spring charging mechanism to charge the spring and
cause the breaker to fail to operate on demand (open or close). However, if
the springs were charged when the breaker was closed, failure of the pin would
not prevent the breaker from opening.
9608090035
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Discussion
Low and medium voltage circuit breakers are refurbished periodically to assure
reliable operation by implementing manufacturer maintenance recommendations.
This service may be performed by the original manufacturer or by contractors
who implement a quality assurance program that meets 10 CFR Part 50,
Appendix B for safety-related equipment. In addition to establishing and
maintaining an acceptable licensee/vendor interface program to remain current
with manufacturer maintenance recommendations (in accordance with Generic
Letters 83-28 and 90-03), licensees are expected to assure that vendors (or
contractors) translate manufacturer recommendations into their procedures.
To enhance the appearance of some metal parts, NLI/NSS plated them with zinc
without realizing that hydrogen generated during the plating process can
diffuse into hardened metal parts. The diffusion of hydrogen into the
hardened metal may cause embrittlement and result in cracking and breakage of
the metal if heat treatment is not applied to desorb the hydrogen. Subsequent
to problems identified at Salem, NLI deleted the zinc plating of metal parts
from its breaker refurbishment procedure.
During an inspection at NLI, the NRC determined that NLI/NSS refurbished
various types of low and medium voltage circuit breakers used in the nuclear
power industry, including 4.16-kV and 480 V breakers made by GE and
Westinghouse. In addition to the GE Magne-Blast breakers at Salem, NLI/NSS
also plated several parts in a Magne-Blast breaker for Entergy Operations,
Inc, GE model AK breakers for Northeast Utilities Company, and a Westinghouse
DB-50 breaker for Carolina Power & Light Company. Work also was done for GPU
Nuclear Corporation.
NLI has informed affected customers that the breakers with the identified
zinc-plated parts should be returned to NLI so that the parts can be replaced.
However, the NRC is concerned that NLI/NSS may not have identified all of the
zinc-plated parts in all of the different breakers that it refurbished because
the zinc-plating was performed on assemblies consisting of several smaller
piece parts. Some of the piece parts may not have been identified. NLI is
currently evaluating the implications of the plated parts and removal of the
dry film lubricant on other projects.
Technicians at Salem also noticed that some metal parts on GE-refurbished
breakers appeared darker than similar parts in the NLI/NSS-refurbished
breakers. Upon inquiry, GE informed Salem that the darker color resulted from
a dry film lubricant that GE applied to the parts to reduce wear between
metal-to-metal contact surfaces in accordance with GE Service Advisory Letter
(SAL) 354.1, "Lubrication Recommendations Type AM Circuit Breakers ML13 & ML
13A Mechanisms," dated August 25, 1995, which states, in part, "And finally, a
spray-on, MoS2 (molybdenum disulfide) dry film lubricant is also being made
available, and it is recommended for use during general overhaul maintenance
periods to lubricate certain hardened surfaces."
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The dry film lubricant is applied to the following parts: (1) the ratchet
wheel, (2) the latch pawl tips, (3) the drive pawl tip, (4) the front and top
surfaces of the prop, (5) the main cam outer surface, and (6) the spring motor
limit switch cam. NLI/NSS inadvertently removed this lubricant when the metal
parts were glass bead blasted as part of the cleaning process, and did not re-
coat the parts with the lubricant.
The work performed by NLI/NSS was detailed in a procedure that was reviewed
and approved by PSE&G prior to refurbishment of any of the Salem breakers.
Ensuring that contractor procedures receive proper technical review, and that
the latest vendor recommendations are incorporated before the procedures are
approved, may help licensees avoid the type of problems described in this
notice.
Related Generic Communications
NRC Generic Letter No. 83-28, "Required Actions Based on Generic Implications
of Salem ATWS Events," issued July 8, 1983.
NRC Generic Letter No. 90-03, "Relaxation of Staff Position in Generic Letter
83-28, Item 2.2 Part 2 - Vendor Interface for Safety-Related Components,"
issued March 20, 1990.
NRC Generic Letter No. 90-03, Supplement 1, "Relaxation of Staff Position in
Generic Letter 83-28, Item 2.2 Part 2 - Vendor Interface for Safety-Related
Components," issued May 14, 1990.
NRC Information Notice 96-43, "Failures of General Electric Magne-Blast
Circuit Breakers," issued August 2, 1996, alerted licensees to a failure of a
Magne-Blast breaker to open on demand at Dresden Nuclear Power Station because
of hardened grease, and a failure of Magne-Blast breakers at Salem Generating
Station and Maine Yankee Atomic Power Plant to latch closed because of a
problem with the prop not resetting under the prop pin during the closing
cycle.
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This information notice requires no specific action or written response. If
you have any questions about the information in this notice, please contact
one of the technical contacts listed below or the appropriate Office of
Nuclear Reactor Regulation (NRR) project manager.
signed by
Brian K. Grimes, Acting Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts: David Skeen, NRR
(301) 415-1174
E-mail: dls@nrc.gov
Kamalakar Naidu, NRR
(301) 415-2980
E-mail: krn@nrc.gov
