Protecting People and the EnvironmentUNITED STATES NUCLEAR REGULATORY COMMISSION
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555
June 9, 1992
NRC INFORMATION NOTICE 92-43: DEFECTIVE MOLDED PHENOLIC ARMATURE CARRIERS
FOUND ON ELMWOOD CONTACTORS
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 to fractures found in the molded phenolic
armature carrier blocks (armature carriers) in certain Elmwood and Fasco
electrical contactors. 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 1990, Fasco Industries, Incorporated (Fasco) took over the manufacture
of Elmwood Sensors, Incorporated (Elmwood) electrical contactors. Elmwood
and Fasco were sister companies. Before this change, the contactors were
identified as Elmwood contactors with part numbers prefixed by "30D,"
"30E," or "30F." After the change, the contactors were identified as
Fasco contactors with part numbers prefixed by either "2M" or "3M."
Nutherm International, Incorporated (Nutherm) examined the Fasco and
Elmwood contactor models discussed in this notice and determined them to
be identical.
In October 1991, the Georgia Power Company (GPC) informed Nutherm that it
was experiencing problems with Elmwood model 30FO30 contactors supplied
to GPC by Nutherm. Nutherm had dedicated and qualified these components,
and sold them to GPC as Class 1E components. GPC informed Nutherm that
several Elmwood model 30FO30 contactors used in safety-related
applications had failed. GPC had determined that the phenolic armature
carrier in the contactors shrank slightly such that the designed clearance
fit between the armature carrier and the laminated steel armature became
an interference fit. This condition then caused the armature carrier to
fracture. The fractured armature carriers caused Elmwood contactors at
GPC's Vogtle Electric Generating Plant (Vogtle) to fail, and resulted in
a safety-related system malfunction. GPC was concerned that similar
failures could occur in other Elmwood or Fasco
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June 9, 1992
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contactors used in safety-related applications at Vogtle. Therefore, GPC
replaced all of the Elmwood and Fasco contactors that were installed in
safety-related applications.
After being informed of the contactor failures by GPC, Nutherm tested the
contactors and determined that the shrinkage of the contactor carrier
exceeded the amount provided for in the design. Nutherm found the maximum
shrinkage of the contactor carrier to be 0.018 inch whereas the design of
the armature carrier slot allowed for a shrinkage of 0.015 inch. Nutherm
determined this deficiency to be reportable under Part 21 of Title 10 of
the Code of Federal Regulations (10 CFR Part 21) and reported it to the
NRC.
GPC documented its evaluation of the failed Elmwood contactors on Vogtle
"Deficiency Card," (DC) 191-209 of August 27, 1991, and DC 291-162 of
September 30, 1991. In DC 191-209, GPC stated that similar failures
(fracture of the armature carrier) of Elmwood's model 30FO30 contactor had
occurred in other safety-related and nonsafety-related applications at
Vogtle. One contactor that failed was installed in an electrical panel
with an ambient temperature of about 90øF, had been in service 4 years,
and had operated for less than 100 cycles. In the root cause
determination for DC 191-209, GPC concluded that, in part, "...this
shrinkage is of a magnitude exceeding that which can be accommodated by
the [armature carrier]...design without failure, and a consequent re-
evaluation of the qualified life is necessary." Most, if not all, of the
Elmwood contactors replaced by GPC and subsequently tested were identi-
fied with the manufacturer's date codes for 1982 or 1983. However, the
Fasco staff stated that the design of the armature carrier slot had not
changed until Nutherm and GPC informed Fasco of this problem in 1991.
Upon reviewing the results of GPC's evaluation and Nutherm's testing of
armature carrier specimens, Fasco revised its phenolic armature carrier
manufacturing process to enlarge the armature carrier slot from 2.110
inches to 2.115 inches. Fasco informed Nutherm that this change should
reduce the potential for future armature carrier fractures. Fasco stated
that it began incorporating the newly modified armature carriers into its
"2M" and "3M" contactors about April 13, 1992. However, Fasco stated that
the suspect armature carrier assemblies had been used in all of its "2M"
and "3M" contactors and in Elmwood's "30D," "30E," and "30F" contactors
manufactured before this date.
These contactors were manufactured and marketed as commercial-grade items
by Elmwood or Fasco and were subsequently dedicated for safety-related
use. The failures of the contactors after dedication suggests that
certain requirements of Criterion III, "Design Control," of Appendix B to
10 CFR Part 50 (Criterion III) were not appropriately addressed during the
dedication process. Criterion III requires, in part, that measures be
established to review the suitability of application of materials and
parts that are essential to the functions of safety-related structures,
systems, and components.
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June 9, 1992
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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.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical contacts: Randolph N. Moist, NRR
(301) 504-2945
Joseph J. Petrosino, NRR
(301) 504-2979
Attachment: List of Recently Issued NRC Information Notices
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