Protecting People and the EnvironmentUNITED STATES NUCLEAR REGULATORY COMMISSION
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555-0001
November 21, 1994
NRC INFORMATION NOTICE 94-78: ELECTRICAL COMPONENT FAILURE DUE TO DEGRADATION
OF POLYVINYL CHLORIDE WIRE INSULATION
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 the possibility that polyvinyl chloride (PVC)
insulation, used on electrical wire, may degrade and cause electrical
components to fail. 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
On April 14, 1993, at the St. Lucie Nuclear Plant, Unit 1, a nonsafety-related
ABB/Westinghouse model CO-9 overcurrent protective relay failed to operate
during calibration testing. The relay failed because a green substance from
the internal wiring had coated the instantaneous trip unit. Electrical tests
indicated that the substance was insulating the instantaneous contacts and
preventing the relay from operating even at twice the normal trip current.
The licensee identified the wiring insulation as polyvinyl chloride (PVC).
The licensee inspected all ABB/Westinghouse relays in Unit 1 (most with 1970
date codes) and Unit 2 (most with 1975 date codes) and found relays in both
units which contained PVC-insulated wire (black insulation with white
lettering which identified it as 105øC, 18 AWG, manufactured by the
Philadelphia Insulated Wire Co.). The licensee had ABB/Westinghouse models
CO-7, CO-9, KC-4, COM-5, CV-2, and CVE installed.
The licensee found that numerous Unit 1 relays contained the green substance
and replaced all PVC-insulated wire with a cross-linked polyethylene-insulated
wire. However, the licensee found no relays in Unit 2 with the green
substance. The licensee also replaced all Unit 1 indicating switch coils of
the ABB/Westinghouse relays because it could not identify the coil lead wiring
and could not determine the type of insulation. The relays, used in both
safety-related and nonsafety-related applications, had been supplied as
original plant equipment.
9411150578
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November 21, 1994
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Discussion
The licensee did a laboratory analysis and identified the green substance as a
copper chelate of the polyester plasticizer from the PVC insulation on the
internal wire of the relay. The licensee also found that overheating of the
wiring could have caused the release of the plasticizer. ABB analyzed the
substance and also concluded that the green substance was produced when a
plasticizer released from the PVC insulation, which had decomposed at high
temperatures, oxidized and interacted with the copper.
ABB stated that until 1989, Westinghouse manufactured the relays as a joint
venture with ABB. Since 1990, ABB has manufactured the relays and also has
labeled the relays according to the period of production. Before 1977
ABB/Westinghouse supplied only commercial grade relays and used PVC-insulated
wire for the internal wiring in each relay manufactured. From 1977-1992,
ABB/Westinghouse supplied commercial grade relays that used PVC insulated wire
and safety-related relays that did not use PVC insulated wire. In November of
1992, ABB/Westinghouse began using wire without PVC insulation for both
commercial grade and safety-related relays.
This information is of particular interest to licensees which have
ABB/Westinghouse relays, installed in safety-related applications, which were
procured from ABB/Westinghouse before 1977 or were procured from
ABB/Westinghouse as commercial grade between 1977 and 1992 (and later
dedicated by the licensee or other party). Relays supplied by
ABB/Westinghouse as safety-related (available since 1977) were not
manufactured with PVC wire. The four-digit date code typically stamped inside
the latch handle on each relay indicates the month and year of manufacture
(for example, 1192 for November 92).
Related Generic Communication
Various manufacturers have used PVC-insulated wire in a variety of electrical
components. NRC addressed a similar condition in Information Notice 91-20,
"Electric Wire Insulation Degradation Caused Failure In a Safety-Related Motor
Control Center," in which the staff discussed the decomposition of PVC
insulation in motor control centers and containment fan coolers at
H. B. Robinson and in a motor control center at San Onofre Nuclear Generating
Station, Unit 1.
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November 21, 1994
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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 B.D. Liaw for
Brian K. Grimes, Director
Division of Project Support
Office of Nuclear Reactor Regulation
Technical contacts: George T. MacDonald, RII
(404) 331-5576
Thomas Koshy, NRR
(301) 504-1176
Bill H. Rogers, NRR
(301) 504-2945
Attachment:
List of Recently Issued NRC Information Notices
