Protecting People and the EnvironmentUNITED STATES NUCLEAR REGULATORY COMMISSION
SSINS No.: 6835
IN 84-29
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, D.C. 20555
April 17, 1984
Information Notice No. 84-29: GENERAL ELECTRIC MAGNE-BLAST CIRCUIT BREAKER
PROBLEMS
Addressees:
All nuclear power reactor facilities holding an operating license (OL) or
construction permit (CP).
Purpose:
This information notice is being issued to inform the license and
construction permit holders of a potential generic problem concerning
wornout sleeve bearings that recently have caused circuit breaker closure
failures at the Diablo Canyon nuclear station. Information also is presented
on recommended actions by the breaker manufacturer (GE)*. These actions, if
implemented, can significantly alleviate the cause of the wear problem in
the breaker sleeve bearing. It is expected that recipients will review the
information for applicability to their facilities and consider actions, if
appropriate, to preclude a similar problem occurring at their facilities.
However, suggestions contained in this information notice do not constitute
NRC requirements and, therefore, no specific action or written response is
required.
Background:
Many nuclear power plants use a substantial number of the GE Magne-Blast
circuit breakers with the M-13 operating mechanism on 4kV systems. The M-13
operating mechanism employs a Tuf-Loc sleeve bearing that consists of
teflon-coated fiberglass. A few cases involving a more-than-normal-wear
condition of the Tuf-Loc sleeve bearing, were reported by GE as early as
1977.
To minimize the possibility of a circuit breaker problem and to increase the
life of the sleeve bearings, GE issued the referenced Service Advice letters
to the end-users. The letters identified the problem and provided corrective
actions to resolve the issue. At that time, GE recommended that customers
"promptly and regularly" inspect the breaker for excessive play and wear of
the bearings in the linkages and pawls and for difficulty in holding the
required breaker adjustments including the contact wipes to the breaker. GE
also recommended replacement of the Tuf-Loc bearings with the longer life
and more
*General Electric Installation and Service Engineering Service Advice
Letters; Numbers 318.1 (February 17, 1977), 318.1A (March 29, 1977), and
318.2 (March 22, 1979); subject: ML-13 Mechanism Sleeve Bearing Replacement.
8403140280
.
IN 84-25
April 17, 1984
Page 2 of 2
suitable Aluminum Bronze bearings. According to GE the Aluminum Bronze
bearing design was qualified and introduced into similar applications of all
new breakers of the Magne-Blast type since 1975.
Discussion:
A licensee recently reported experiencing "more than normal wear" on one of
its Magne-Blast breakers. Subsequently, one of the emergency diesel
generator output breakers (Magne-Blast type) failed to close during a test.
Investigation into the failure revealed that the teflon sleeve bearing was
deteriorated to the point of metal-to-metal contact. Further investigation
into the problem, found that the licensee had no record of receiving the GE
Service Advice letters related to this problem. Subsequently, the licensee
received the GE letters and has now initiated a replacement program for
Magne-Blast circuit breakers. Since the licensee has initiated the
replacement program, two additional breaker failures that are related to the
bearing wear problem have been found.
In contrast, another licensee stated that they replaced the teflon sleeve
bearing several years ago with the Aluminium Bronze bearing in all safety-
related Magne-Blast circuit breakers. This licensee indicated that the re-
placement program was initiated after receiving the GE Service Advice
letters on the sleeve bearing issue and experiencing bearing wear problems
in the Magne-Blast circuit breakers at their facility. Approximately 80
Magne-Blast circuit breakers, 40 per unit, were involved in the sleeve
bearing replacement effort. Their operating experience has been good
subsequent to the bearing replacement.
To ensure that all nuclear power plants are aware of the GE Service Advice
letters pertaining to this issue, we request all licensees and holders of
construction permits to review this notice and the referenced GE letters for
applicability to their plant and to take appropriate action.
If you have any questions regarding this 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: V. D. Thomas, IE
(301) 492-4755
Attachments
1. GE Service Advice Letter No. 318.1
2. List of Recently Issued IE Information Notices
