United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 84-46: Circuit Breaker Position Verification

                                                            SSINS No.: 6835 
                                                            IN 84-46       

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

                                June 13, 1984

Information Notice No. 84-46:   CIRCUIT BREAKER POSITION VERIFICATION 

Addressees: 

All holders of a nuclear power operating license (OL) or construction permit
(CP). 

Purpose: 

This information notice is provided to notify licensees of a recent event 
that may have safety significance. It is expected that recipients will 
review the information for applicability to their facilities. However, 
suggestions contained in this notice do not constitute NRC requirements and, 
therefore, no specific action or response is required. 

Description of Circumstances: 

On February 13, 1984, at the McGuire Nuclear Station, breaker no. 1EPA-10, 
which controls the 1A centrifugal charging pump (CCP), was racked to the 
DISCONNECT position so that a routine oil sample could be collected from the
pump. Sampling was complete 2 hours later and the circuit breaker was 
supposedly returned to the CONNECT position. The assistant shift supervisor 
and a control room operator then independently confirmed that the breaker 
was in a CONNECT position by status indication lights on the control board. 
However, on February 20, 1984, during normal equipment rotation, it was 
discovered that the CCP-1A breaker had not been returned to the CONNECT 
position and that CCP-1A had been in an inoperable state for 7 days. This 
occurred because the assistant shift supervisor and a control room operator 
had used an invalid indication to verify that the breaker was in a CONNECT 
position. 

Discussion: 

The CCP breaker is a drawout circuit breaker, ITE Model 3 used in 4,160 volt
applications. A similar model ITE 03-B is also used at McGuire in 6,900 volt
applications. Drawout circuit breakers can be disconnected by moving the 
breakers physically away from the bus. This is done with a racking wrench 
that is manually connected to the breaker. The breaker moves from the 
CONNECT position to the TEST position, and then to the DISCONNECT position. 
An interlock is provided to prevent operation of the circuit breaker at any 
point between these three discreet positions. The interlock also functions 
to mechanically control the breaker tripping mechanism. That is, when the 
rack release lever is manually moved to the left the racking screw is 
released and the breaker is mechanically tripped, preventing closing of the 
breaker. As the 

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                                                              June 13, 1984 
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breaker is moved by turning the racking screw into one of the three discreet
positions, he racking release lever simultaneously arrests the racking screw
and releases the trip mechanism. The rack release lever must be in the 
extreme counterclockwise position for breaker operation. 

Control power is supplied to the circuit breaker through a separate 
connecting device. This device consists of a sliding contact strip with one 
part mounted on the back of the cubicle at the floor and the other part 
mounted on the circuit breaker. Contact is made between the two parts when 
the circuit breaker is moved to the TEST position and continues as the 
breaker is moved to the CONNECT position. Consequently, the status light 
indication observed in the control room or on the front of the breaker is 
not a conclusive indication of breaker position or operability. 

To perform a verification of breaker position and operability, all four of 
the following items must be ensured: 

1.   Indication on the floor of the circuit breaker housing corresponds to 
     the markings on the circuit breaker. 

2.   Racking release lever is fully in the CONNECT position (extreme 
     counterclockwise position). 

3.   The spring motor toggle switch is in the ON position and the springs 
     are charged. 

4.   The control power fuse is in place and power is available. 

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
                    J. K. Rausch, R II (404) 242-5554

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