ML20207E872

Special Rept 86-011:on 861201,failure of Emergency Diesel Generator a Occurred.Caused by Faulty Speed Switch.Switch Replaced.Faulty Switch Returned to Vendor for Failure Analysis & Repair

ML20207E872
Person / Time
Site:	Wolf Creek
Issue date:	12/24/1986
From:	Koester G KANSAS GAS & ELECTRIC CO.
To:	Martin R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
References
86-011, 86-11, KMLNRC-86-242, NUDOCS 8701050174
Download: ML20207E872 (3)

Text

_ _ _ _ _

> y- ;

KANSAS GAS AND ELECTRIC COMPANY THE ELECTAC COMPANY GLENN L MOESTER vettpets.oggy.hucLeam December 24, 1986 BON $

Mr. R. D. Martin, Regional Administrator g lj U.S. Nuclear Regulatory Commission DEC 2 91986 L .

Region IV g j 611 Ryan Plaza Drive, Suite 1000 '-

/))

Arlington, Texas 76011 KMLNRC 86-242 Re: Docket No. 50-482 Subj: Special Report 86-011 D;sr Mr. Martin:

The enclosed Special Report is submitted pursuant to Technical Specifications 4.8.1.1.3 and 6.9.2.

Yours very truly, 6 51 44.

Glenn L. Koester Vice President - Nuclear GLK:see cc: P0'Connor (2)

JCummins 8701050174 DR 861224 ADOCK 05000492 ' '

PDR ,

-\Y O l I 201 N. Market -Wichota, Kansas - Mail Address: PO. Box 208 I Wichita, Kansas 67201.- Telephone: Area Code (316) 261-6451

F 2 SPDCIAL REPORT 86-911 DIESEL GENERA'IOR 'A' FAILURE On December 1 1986, a failure of Emergency Diesel Generator 'A' occurred when an attempt was made to start the engine to allow transfer of Engineered Safety Features bus NB01 back to its normal power supply. % is Special Report is being subnitted in accordance with Technical Specifications 4.8.1.1.3 and 6.9.2.

At approximately 2028 CST, when the start pushbutton on the Control Room Main Control Board was depressed, the engine failed to start. Operations personnel stationed locally in the diesel generator room reported that the engine did not rotate, indicating that starting air was not admitted to the engine. When this event occurred, the unit was in Mode 6, Refueling. The engine was declared inoperable, and an entry was made into the appropriate Technical Specification Action Statement.

During suosequent troubleshooting, the starting air shut off relay associated with the Syncro Start Electric Speed Switch was found energized.

With this relay energized, the starting air solenoid valves remained closed, inhibiting starting air for the diesel cranking cycle.

The Synchro Start Electric Speed Switch has five internal contacts used for functional control as the diesel engine speed increases to rated speed.

Normally when the engine start pushbutton is depressed, the starting air solenoid valves are energized and opened, admitting starting air to the engine. The engine speed is sensed by a mechanically driven signal generator which feeds the Synchro Start Electric Speed Switch. When it is sensed that the engine has reached approximately 85 revolutions per minute, one of the internal contacts in the Speed Switch close to energize the starting air shut off relay. The normally closed contacts off the starting air shut off relay then open, causing the starting air solenoid valves to de-energize, thus completing the engine cranking cycle.

A new Synchro Start Electric Speed Switch was calibrated and installed at approximately 0518 CST on December 2. The engine was then successfully started and run loaded for approximately one hour, thus completing a valid successful test and restoring the engine to operable status. Subsequently, it was used to transfer bus NB01 to its normal power supply. At approximately 0641 CST, the engine was secured. Diesel Generator 'A' was out of service for approximately ten hours, from the time of the initial unsuccessful start attempt until verification of correction of the problem.

%e faulty Speed Switch has been returned to the vendor for failure analysis and repair.

We unsuccessful start attempt discussed in this report is considered to be a valid test and failure in accordance with Regulatory Position C.2.e(l) of Regulatory Guide 1.108, Revision 1.

1

c g* .D

. As of December 2,1986, there have been thirty (30) valid successful tests and ten- (10) invalid failures of Diesel Generator.'A'. There have been twenty-eight valid successful tests and seven (7) invalid failures of Diesel Generator B'. The valid test failure described in this report is the first-valid failure that has occurred on either diesel unit. '(Previous diesel generator failures are discussed in Special Reports85-001, 85-002,85-003, 85-004,85-005, 85-006,85-010 Supplement 1,85-012, 85-013,85-015, and 86-002.)

'Ite valid failure discussed in this report had no effect on the diesel generator testing frequency of once per thirty-one days. This is in conformance with the schedule presented in Regulatory Position C.2.d. (1) of Regulatory Guide 1.108 and with Technical Specification Table 4.8-1, which require the testing interval to be not more than thirty-one days if the number of valid failures in the last 100 valid tests is one or zero.

%,