United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 89-29: Potential Failure of ASEA Brown Boveri Circuit Breakers During Seismic Event

                                  UNITED STATES
                          NUCLEAR REGULATORY COMMISSION
                             WASHINGTON, D.C.  20555

                                 March 15, 1989

                                   CIRCUIT BREAKERS DURING SEISMIC EVENT


All holders of operating licenses or construction permits for nuclear power 


This information notice is being provided to alert addressees to potential 
failures of ASEA Brown Boveri (ABB) K-Line circuit breakers (CBs) during a 
seismic event.  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 do not constitute NRC requirements; therefore, no specific action or 
written response is required.

Description of Circumstances:

ABB submitted two letters, dated January 13 and February 16, 1989, to the NRC 
in accordance with the requirements of 10 CFR Part 21 regarding a deficiency 
in K-Line CBs, model numbers K-225 through K-2000, that were delivered to cus-
tomers before July 1974.  These CBs have a slow-close lever that could move 
during a seismic event and prevent the CBs from closing upon an electrical 
demand.  The slow-close lever is used to perform diagnostic checks on the 
CB internals during initial installation.  The lever is located in the rear 
portion of the CB and is only accessible while the CB is out of its cubicle.


In late 1988, Rancho Seco personnel asked ABB why some K-Line CBs used at the 
Rancho Seco plant had springs on the slow-close lever and others did not.  ABB 
investigated the matter and determined that rebound springs were added to CBs 
manufactured after July 1974 as a response to CB failures that occurred during 
seismic testing of K-Line CBs.

The seismic testing was conducted on several sample K-Line CBs at Wyle Labora-
tories in 1974 and consisted of 123 test runs under varying seismic conditions.  
During test run number 100 (which consisted of side-to-side sine dwell at 23 
hertz, amplitude 0.5 g, duration greater than 20 seconds), one K-1600 CB jammed 
and failed to close on demand.  During test run number 101 (which consisted of 

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                                                            March 15, 1989
                                                            Page 2 of 2

side-to-side sine dwell at 30 hertz, amplitude 0.36 g, duration greater than 
20 seconds), a second K-1600 CB failed to close on demand.  The causes of the 
breaker malfunctions were not immediately recognized.  ABB later determined 
that the CBs had failed to close because of vibration-induced movement of the 
slow-close lever to a position where it interfered with the closing mechanism 
of the CB.  As a result, a rebound spring that prevents any undesired movement 
of the slow close lever was added to the CB design and installed in all CBs 
manufactured after mid-1974. 

ABB sent the letters of January 13 and February 16, 1989, to all nuclear power 
plants that have purchased safety-related electrically operated K-Line CBs, 
model numbers K-225 through K-2000, and requested that all users of these 
CBs add rebound springs to the slow-close levers.  The letters are included 
as Attachment 1 and Attachment 2 respectively.  Attachment 1 also includes 
a sketch of the location of the slow-close lever with the rebound spring in 
place and the field installation procedures for adding the rebound spring 
to the slow-close lever.  Additional information on this subject may be 
obtained by contacting the appropriate ABB representative.  
It is important for addressees to determine whether any of the subject CBs, 
regardless of their delivery or installation date, are installed at their 
facilities and to verify that the CBs are seismically qualified.  

In addition, addressees are reminded that component manufacturers do not 
typically notify customers who have procured commercial grade items of design 
changes and deficiencies identified in their components.  Therefore, it is 
important that this fact be considered when purchasing components that were 
procured as commercial grade and dedicated for safety-related applications 
by entities other than the component manufacturer.

No specific action or written response is required by this information notice.  
If you have any questions regarding this matter, please contact the technical 
contact listed below or the Regional Administrator of the appropriate regional 

                                   Charles E. Rossi, Director                
                                   Division of Operational Events Assessment
                                   Office of Nuclear Reactor Regulation

Technical Contact:  Jaime Guillen, NRR
                    (301) 492-1170

1.  ASEA Brown Boveri Letter dated January 13, 1989
2.  ASEA Brown Boveri Letter dated February 16, 1989
3.  List of Recently Issued NRC Information Notices
..                                                            Attachment 3 
                                                            IN 89-29
                                                            March 15, 1989
                                                            Page 1 of 1

                             LIST OF RECENTLY ISSUED
                             NRC INFORMATION NOTICES
Information                                  Date of 
Notice No._____Subject_______________________Issuance_______Issued to________

89-28          Weight and Center of          3/14/89        All holders of OLs
               Gravity Discrepancies                        or CPs for nuclear
               for Copes-Vulcan                             power reactors.
               Air-Operated Valves

89-27          Limitations on the Use        3/8/89         All holders of OLs
               of Waste Forms and High                      or CPs for nuclear
               Integrity Containers for                     power reactors, 
               the Disposal of Low-Level                    fuel cycle 
               Radioactive Waste                            licenses and 
                                                            certain by-product 
                                                            materials licenses.

89-26          Instrument Air Supply to      3/7/89         All holders of OLs
               Safety-Related Equipment                     or CPs for nuclear
                                                            power reactors.

89-25          Unauthorized Transfer of      3/7/89         All U.S. NRC source,
               Ownership or Control of                      byproduct, and 
               Licensed Activities                          special nuclear 

89-24          Nuclear Criticality Safety    3/6/89         All fuel cycle
                                                            licensees and other
                                                            possessing more 
                                                            than critical 
                                                            mass quantities of
                                                            special nuclear 

89-23          Environmental Qualification   3/3/89         All holders of OLs
               of Litton-Veam CIR Series                    or CPs for nuclear
               Electrical Connectors                        power reactors.

89-22          Questionable Certification    3/3/89         All holders of OLs
               of Fasteners                                 or CPs for nuclear
                                                            power reactors.

89-21          Changes in Performance        2/27/89        All holders of OLs
               Characteristics of Molded-                   or CPs for nuclear
               Case Circuit Breakers                        power reactors.

OL = Operating License
CP = Construction Permit 
Page Last Reviewed/Updated Friday, May 22, 2015