Part 21 Report - 1996-851

 
 

ACCESSION #: 9612300113



                                        Illinois Power Company

                                        Clinton Power Station

                                        P.O. Box 678

                                        Clinton, IL 61727

                                        Tel 217 935-5621

                                        Fax 217 935-4632



                                        Wilfred Connell

                                        Vice President



ILLINOIS                                 U-602677

POWER                                    4F.140



                                         WC-383-96

                                         December 20, 1996



Docket No. 50-461

                                         10CFR21.21



Document Control Desk

Nuclear Regulatory Commission

Washington, D. C. 20555



Subject:  10CFR21 Final Report 21-96-025: Failure of Westinghouse DHP

          Breaker to Close Due to Dirty and Binding Motor Cut-Off Switch

          and Spring Charge Indicator Mechanism



Dear Madame or Sir:



     On October 27, 1996, Illinois Power (IP) identified the failure of a

Westinghouse DHP circuit breaker to close on demand during a surveillance

test as a potentially reportable condition under the provisions of 10CFR,

Part 21.  The affected breaker is the Division 1 Reserve Auxiliary

Transformer (RAT) main feed breaker.  The breaker is required to close to

supply the Division 1 4160-volt safety-related bus.  Failure of the

breaker to close on demand during a Loss of Coolant Accident (LOCA) could

prevent safety-related equipment from performing its intended function.



     An investigation identified that the cause of the failure to close

was a dirty and binding motor cut-off switch and spring charge indicator

mechanism.  The vendor literature provided for the breaker did not

include guidance for inspecting, cleaning, adjusting, or lubricating the

motor cut-off switch and spring charge indicator mechanism Westinghouse

has indicated that another purchaser experienced a similar deficiency.



     At IP's request, Westinghouse provided instructions for inspecting,

cleaning, adjusting, and lubricating the motor cut-off switch and spring

charge indicator mechanism.



     IP has evaluated this issue and concluded that it is reportable

under the provisions of 10CFR, Part 21.



     IP is providing the following information in accordance with

10CFR21.21(c)(4).  Initial notification of this matter will be provided

by facsimile of this letter to the NRC Operations Center in accordance

with 10CFR 21.21(c)(3) within two days of the date the responsible

officer signs this letter.





(i)       Wilfred Connell, Vice President of IP, Clinton Power Station,

          Post Office Box 678, Clinton, Illinois, 61727, is the

          responsible officer notifying the Nuclear Regulatory Commission

          of a condition reportable under the provisions of 10CFR, Part

          21.



(ii)      The basic component involved in this condition is a model

          50DHP350, 1200-amp, 4160-volt circuit breaker.  The breaker is

          the Division 1 RAT main feed breaker and is required to close

          to the supply the Division 1 4160-volt safety-related bus.



          The motor cut-off switch and spring coil (closing coil)

          circuitry of both DHP and DVP type breakers.  Therefore, all

          type DHP and DVP breakers could be susceptible to the failure

          mechanism described in this report.



(iii)     The DHP and DVP circuit breakers are manufactured and supplied

          by Westinghouse.



(iv)      The breaker failed to close on demand during surveillance

          testing due to a dirty and binding motor cut-off switch charge

          indicator mechanism.  The dirty and binding condition of the

          mechanism was a result of not performing periodic maintenance

          to inspect, clean, adjust, and lubricate this mechanism.  A

          periodic maintenance activity was not scheduled because the

          vendor's maintenance literature did not indicate that periodic

          maintenance was necessary for continuous proper operation of

          the motor cut-off switch and spring charge indicator mechanism.



          The principle function of the motor cut-off switch and spring

          charge indicator mechanism is to shut off the spring charging

          motor after the springs are charged, and to provide a close

          permissive to the closing coil.  Linkage in the mechanism rides

          on a cam that follows breaker spring operation.  The

          mechanism's linkage was found to be dirty and binding, and that

          condition prevented the linkage from operating properly.  As a

          result, the cut-off switch (limit switch) did not allow the

          close signal to get to the close coil.



          Failure of the breaker to complete its safety function and

          close on demand during a LOCA could prevent safety-related

          equipment from performing its intended function.



(v)       The failure of the circuit breaker to close on demand during

          surveillance testing was identified and determined to be a

          potentially reportable condition under the provisions of 10CFR,

          Part 21, on October 27, 1996.



(vi)      Clinton Power Station (CPS) has twenty-one other DHP type and

          four DVP type breakers in installed and spare locations of

          various safety-related circuits.  None of these breakers are

          known to have previous failures similar to the Division 1 RAT

          main feed breaker.





          Westinghouse has indicated that another purchaser experienced a

          similar deficiency.



(vii)     After IP notified Westinghouse about the dirty and binding

          motor cut-off switch and spring charge indicator mechanism,

          Westinghouse provided instructions to IP for inspecting,

          cleaning, adjusting, and lubricating the mechanism.



          IP inspected, cleaned, adjusted, and lubricated the motor cut-

          off switch and spring charge indicator mechanism in the breaker

          that failed to close.  IP retested the breaker with

          satisfactory results and restored it to service.



          IP has incorporated instructions for maintaining the motor cut-

          off switch and spring charge indicator mechanism into

          maintenance procedures, and will incorporate that information

          into applicable vendor manuals.



(viii)    IP advises other purchasers or licensees to contact

          Westinghouse to obtain information about maintenance of the

          mechanism.  Additionally, per discussion with Westinghouse

          personnel, a technical bulletin will likely be issued to inform

          customers about this potential problem.



          Additional information about this issue may be obtained by

contacting D. G. [Illegible], system engineer, at (217) 935-8881,

extension 3952.



                                        Sincerely yours,



                                        Wilfred Connell

                                        Vice President



WC/krk



cc:  NRC Clinton Licensing Project Manager

     NRC Resident Office, V-690

     Regional Administrator, Region III, USNRC

     Illinois Department of Nuclear Safety

     INPO Records Center

     Westinghouse





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