United States Nuclear Regulatory Commission - Protecting People and the Environment

ACCESSION #: 9812300181


GE Nuclear Energy

General Electric Company
175 Curtner Ave., San Jose, CA 95125

December 22, 1998
98-17NRC.DOC
MFN 054-98

Document Control Desk
United States Nuclear Regulatory Commission
Washington, DC 20555

Subject: Terminal Block Cracking in GE Type DC2800 or IC2800 Series DC Contactors

This letter provides information concerning potential failure of GE Type DC2800 or IC2800 Series DC contactors due to terminal block phenolic cracking. Cracking in the terminal block phenolic material has been observed by a licensee in two separate instances in contactors manufactured seven years apart. Though no other instances of cracking have been reported to GE in over forty years of contactor manufacture and service, and there have been no known operational failures as a result of such cracking, GE Nuclear Energy (GE-NE) is conservatively assuming that all Type DC2900 or IC2800 Series contactors supplied to date may be subject to this failure mode.

GE Type DC2800 and IC2800 Series DC contactors are manufactured and supplied by GE Industrial Systems (formerly GE Drive Systems), Salem, VA as commercial grade items. GE-NE has dedicated these contactors (and the terminal blocks) and supplied them to several nuclear power plants as basic components for unspecified, safety related applications. They may also have been supplied as subcomponents of DC Motor Control Centers furnished as complete assemblies by GE Industrial Systems (formerly GE Electrical Distribution and Control), Mebane, NC and other vendors. Since the specific applications and associated safety functions of the contactors are not known to GE-NE, we have transferred information to those licensees known to be affected pursuant to 10 CFR Part 21.21(b). However, since additional licensees may have obtained these devices through other vendors or dedicating entities, we cannot assure ourselves that all end-users have been notified. We are therefore providing this information to the NRC for appropriate action.

The basic component of concern is GE-NE terminal block Q144A1364G1 (GE Industrial Systems part numbers 144A1364G1 and 808651P1), a renewal part for some GE Type DC2800 or IC2800 Series DC contactors. It has also been supplied as part of new and replacement DC2800 or IC2800 Series contactors. GE-NE has provided safety related replacement DC2800 and IC2800 Series contactors as DD317A7888P001-P008.

According to the published catalog information, these contactors have not been commercially, available since December 1982. The terminal block is available as a renewal part, but is not utilized in any current production devices. The terminal block may also have been utilized in similar DC contactors manufactured during the same period, but this has not been confirmed.

In October 1998, a licensee reported that cracks had been found in spare terminal blocks that were received by the licensee and had been in storage since 1993. This was the second reported instance of cracking, the first report having come from the same licensee in 1993 when cracks were found in contactors that were received in 1986.

Cracks have only been found adjacent to the terminal nut inserts of the outer two poles of the terminal block, radiating outward from the terminal point. The most probable cause of the cracking is excessive flaring of the terminal nut during the assembly process. This creates stresses that eventually cause the terminal block to crack.

It is postulated that the terminal block phenolic material may crack and break away from the female brass terminal nut inserts, such that the device control wiring is dislodged and the wire terminations short circuit during normal operation or a seismic event. This could prevent proper operation of the individual DC contactor in its safety system or create a condition where the Class eH power supply is degraded, affecting the proper operation of other safety related devices.

It is suggested that, at the next scheduled maintenance or inspection of GE Type DC2800 or IC2800 Series DC contactors installed in safety related applications, individual contactors be replaced if cracking of the terminal block phenolic material is observed.

Unless it can be determined that they do not contain the subject terminal block, similar DC products (Types identified as DC28xx or IC28xx) should also be examined for terminal block cracking.

New replacement contactors do not contain the same terminal block design identified in this letter.

If you have any questions, please call me at (408) 925-1019.

Sincerely,

Michael A. Smith, Manager
Safety Evaluations, Procedures & Training

cc: S. D. Alexander (NRC-NRR/DISP/PSIB)
G. C. Cwalina (NRC-NRR/DISP/PSIB)
J. F. Quirk (GE-NE)
H. J. Neems (GE-NE)
T. S. Panetta (GE-NE)
G. W. Sanders (GE-NE)
J. A. Steininger (GE-NE)

PRC File

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