Protecting People and the EnvironmentUNITED STATES NUCLEAR REGULATORY COMMISSION
SSINS No.: 6835
IN 87-08
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, D.C. 20555
February 4, 1987
Information Notice No. 87-08: DEGRADED MOTOR LEADS IN LIMITORQUE DC
MOTOR OPERATORS
Addressees:
All nuclear power reactor facilities holding an operating license (OL) or a
construction permit (CP).
Purpose:
This notice is provided to alert recipients of potentially defective dc
motors installed in Limitorque motor operators. The motors in question were
manufactured at H. K. Porter (now Peerless-Winsmith) between December 1984
and December 1985. The motors are fitted with Nomex-Kapton insulated leads
that are susceptible to insulation degradation and subsequent short circuit
failure. The Nomex-Kapton leads are different than the leads which were
tested and reported in Limitorque Qualification Report B-0009 dated April
30, 1976. Valves with these Nomex-Kapton leads have recently failed to
actuate on demand at two nuclear plant sites. It is expected that recipients
will review this information for applicability to their facilities and
consider actions, if appropriate, to preclude a similar problem from
occurring at their facilities. However, suggestions contained in this notice
do not constitute NRC requirements; therefore, no specific action or written
response is required.
Description of Circumstances:
On May 6, 1986 the NRC received from Portland General Electric Company a 10
CFR 21 report concerning a motor failure which occurred at its Trojan
Nuclear Power Plant. The failure involved shorting of the motor leads inside
a Limitorque motor operator connected to an auxiliary feedwater flow control
valve. Upon inspection it was determined that the failure was the result of
insulation degradation of the motor leads that had allowed two leads to
short together. Further, inspection at Trojan revealed three similar motors
that also had experienced insulation degradation.
Recently, the NRC has also learned of a failure at the Turkey Point Nuclear
Power Plant in which the steam supply valve for the auxiliary feedwater
turbine failed to operate after a Limitorque motor operator experienced a
similar motor lead short circuit. The Trojan and the Turkey Point Limitorque
operators were found to contain motors manufactured with Nomex-Kapton
insulated leads.
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IN 87-08
February 4, 1987
Page 2 of 3
On January 12-14, 1987, the NRC conducted an inspection at
Peerless-Winsmith, Inc., manufacturer of dc motors for Limitorque Co. During
this inspection it was determined that the failed Nomex-Kapton leads were
different than the leads which were fitted to the motors, tested, and
documented in Limitorque Qualification Report B-0009 for dc motor operators.
The leads attached to the tested motors were insulated with Nomex plus an
epoxy impregnated braided fiberglass sleeve. The NRC knows of no analysis or
testing that has been performed to show the Nomex-Kapton leads are
acceptable for use in an application requiring environmental qualification.
Further, it should be noted that the failures cited above occurred under
normal operating conditions, not under the harsh conditions which could
occur in areas where environmental qualification is required.
On December 19, 1986, Limitorque notified 30 plant sites (Attachment 1) that
had received affected motors and recommended the sleeving of existing
Nomex-Kapton motor leads. The sleeving system is still under development and
Limitorque expects to have this system tested for environmental
qualification by the third quarter of 1987.
Discussion: The Peerless-Winsmith motors were manufactured between December
1984 and December 1985 and can be identified by the first two letters of the
serial number data code on the motors. Motor serial numbers beginning with
the letters ZM, NN, PN, QN, RN, SN, TN, UN, VN, WN, XN, YN, and ZN likely
contain the Nomex-Kapton leads. The lead insulation consists of one layer of
50 percent overlapped 0.003 inch Nomex plus a 50 percent overlapped layer of
0.0012 inch F616 Kapton/FEP. This insulation system is about one-sixth the
thickness of the leads which were part of the Limitorque qualified motor.
Peerless-Winsmith has since switched to a third type of insulated lead
similar to the ones used originally. No failures with this type of lead have
been reported; however, qualification of this type wire also needs to be
ensured.
Previous, unrelated problems involving wiring installed in Limitorque motor
actuators have been identified in Information Notices 83-72, 86-03 and
86-71.
Although no written response to this notice is required, it is expected that
holders of OLs or CPs will review the information in this notice for
applicability at their facilities. Because of the failures such as those
discussed above and the lack of demonstrated environmental qualification,
NRC's evaluation of this problem is continuing. Depending on the result of
the evaluation, specific actions may be requested. If you have any questions
regarding this
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IN 87-08
February 4, 1987
Page 3 of 3
matter, please contact the Regional Administrator of the appropriate NRC
Regional Office, or this office.
Edward L. Jordan Director
Division of Emergency Preparedness
and Engineering Response
Office of Inspection and Enforcement
Technical Contact: J. Jacobson, IE
(301) 492-8845
Attachments:
1. List of Affected Plants
2. List of Recently Issued IE Information Notices
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