United States Nuclear Regulatory Commission - Protecting People and the Environment



CR79017 

                              August 9, 1979 

MEMORANDUM FOR:     B. H. Grier, Director, Region I 
                    J. P. O'Reilly, Director, Region II 
                    J. G. Keppler, Director, Region III 
                    K. V. Seyfrit, Director, Region IV 
                    R. H. Engelken, Director, Region V 

FROM:               Harold D. Thornburg, Director, Division of Reactor 
                      Construction Inspection, IE 

SUBJECT:            IE CIRCULAR NO. 79-17 - CONTACT PROBLEM IN SB-12 
                    SWITCHES ON GENERAL ELECTRIC COMPANY METALCLAD CIRCUIT 
                    BREAKERS 

     The subject circular should be dispatched for action to all power 
reactor licensees with a construction permit and/or operating license no 
later than August 14, 1979. The text of the circular and draft letter to 
licensees are enclosed for this purpose. 


                                   Harold D. Thornburg, Director 
                                   Division of Reactor Construction 
                                     Inspection  
                                   Office of Inspection and Enforcement 

Enclosures: 
1.   Draft Transmittal Letter 
2.   IE Circular No. 79-17 

CONTACT:  W. Laudan, IE 
          49-27551 
.

(Draft letter to all holders of Reactor Operating Licenses and Construction 
Permits) 

                                                      IE Circular No. 79-17 

Addressee: 

This Circular is provided as an early notification of a possible significant
matter. It is expected that recipients will review the information for 
possible applicability to their facilities. No specific action or response 
is requested at this time. If further NRC evaluations so indicate, an IE 
Bulletin will be issued to recommend or request specific licensee actions. 
If you have questions regarding this matter, please contact the Director of 
the appropriate NRC Regional Office. 

                                        Sincerely, 


                                        Signature 
                                        (Regional Director) 

Enclosures:
1.   IE Circular No. 79-17 
2.   List of IE Circulars Issued 
       in the Last 12 Months
.

                                            Accession No: 7908090272 
                                             SSINS:  6830 

                              UNITED STATES 
                      NUCLEAR REGULATORY COMMISSION 
                   OFFICE OF INSPECTION AND ENFORCEMENT 
                          WASHINGTON, D.C. 20555 
                                     
                             August 14, 1979  

                                                      IE Circular No. 79-17 

CONTACT PROBLEM IN SB-12 SWITCHES ON GENERAL ELECTRIC METALCLAD CIRCUIT 
BREAKERS 

The General Electric Company, Switchgear Department in Philadelphia, 
reported to the NRC on July 3, 1979, an intermittent contact problem in 
SB-12 switches.  This intermittent contact problem will cause a lack of 
continuity through the "a" contact of the switch that is used to energize 
the trip coil of the circuit breaker. Investigation disclosed that a die 
used to form a hole in the contact arms of the switch had worn, resulting in 
elongated holes. This condition could permit the contact bridge member to 
move laterally relative to the contact arm, occasionally resulting in 
improper "a" contact wipe.  The worn die has been corrected, and all 
switches shipped on or after July 1, 1979, include this correction. A review 
of the history of these components indicates that switches shipped in the 
time period of August 1, 1978, to July 1, 1979, could have this problem.  
The trip coil and auxiliary switch portion of the trip circuit is monitored 
for continuity by a red light on the front door of the switchgear.  This 
light is lit when the breaker is closed and the control circuits are 
energized.  If the red light is lit, this indicates that the "a" contacts of 
the switch are closed, and that a trip signal will trip the breaker. 

Based on the above, the licensees are advised to do the following: 

     1.   Insure that all General Electric Company Metelclad Circuit 
          Breakers shipped to your facilities during the period from August 
          1, 1978 to July 1, 1979 and used in or affecting the operation of 
          safety related equipment are furnished with new SB-12 control 
          switches as promptly as possible. 
          
     2.   Pending replacement of SB-12 control switches administrative 
          controls should be initiated to assure the red light which 
          demonstrates contact continuity, is lit and remains lit each time 
          these circuit breakers are closed. 

No written response to this circular is required.  If you require additional
information regarding this subject, contact the Director of the appropriate 
NRC Regional Office. 


Page Last Reviewed/Updated Thursday, March 29, 2012