ML20203F602

Special Rept:On 860223 & 0313,diesel Generator 1B Experienced Two Nonvalid Tests & Failures Due to Isochronous Relay Failure.Caused by Intermittent Continuity Between Contacts in Isochronous Relay While in Test Mode

ML20203F602
Person / Time
Site:	Byron
Issue date:	03/20/1986
From:	Querio R COMMONWEALTH EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
#33-014, #33-14, BYRON-86-0273, BYRON-86-273, NUDOCS 8604250190
Download: ML20203F602 (2)

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BYRON 86-0273 i i FILE: 2.4.700 flLW Mr. James G. Keppler Regional Administrator Region 111 U. S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, Illinois 60137

Dear Sir:

This special report is submitted in accordance with Byron Station Unit 1 Operating License NPF-37 Appendix A, Technical Specification 4.8.1.1.3, reporting of Diesel Generator Failures.

This report addresses two nonvalid tests and failures experienced on the IB Diesel Generator. Both of these failures were classified as nonvalid tests and failures, occurring in the testing mode and not affecting the ability of the Diesel Generator to perform its intended safety function.

The criteria to determine valid tests and failures versus nonvalid tests and failures is in accordance with Regulatory Guide 1.108 Section C.2.e which states in part:

Valid tests and failures should be based on the following criteria:

C.2.e "(2) Unsuccessful start and load attempts that can definitely be attributed to operating error, to spurious operation of a trip that is bypassed in the emergency operating mode, to malfunction of equis, ment that is not operative in the emergency operating mode (e.g., synchronizing circuitry) or is not part of the defined diesel generator unit design should not be con-sidered valid tests or failures."

The IB Diesel Generator has experienced two nonvalid tests and failures due to isochronous relay failure. The first failure occurred on 2/23/86 following a Manual Safety injection Initiation surveillance. The Diesel Generator was run at idle for one hour during this surveillance, allowing fluid temperatures to drop. It was then decided to load the generator to the system grid for one hour to bring fluid tempera-8604250190 860320 "

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BYRON 86-0273 g Page 2 B

tures back to normal. The generator was loaded to 5500 KW where it stablized tem- '

4 porarily. The Kilowatt output then began to fluctuate. The Unit 1 Operator could not gain control of Kilowatt output so the output breaker was opened and the Diesel Generator was tripped from the Main Control Board (MCB). Limiting Condition =

for Operation Action Requirement (LCOAR) 8.1.1-la was entered immediately. -

The second failure occurred on 3/13/86 during the monthly operability surveillance. -

During the loading sequence, at approximately 3000 KW, the generator lost all of _

its load causing the Diesel Generator to trip on reverse power. LCOAR 8.1.1-la was entered immediately. _

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Both failures have been attributed to intermittent continuity between contacts in the isochrt nous relay while in the test mode. In this mode, the relay deenergizes _

making up two sets of contacts, putting the governor in the speed drop mode. The _

two failures experienced by the IB Diesel Generator occurred in the test mode, j resulting from intermittent continuity between one set of contacts that is closed when the relay is deenergized. Without proper continuity across these contacts a the governor has no load compensation input, and thus operates on speed compensation only. This condition significantly impairs governor control, and will eventually cause  ;

the Diesel Generator to trip in the testing mode. In the emergency mode, the relay's I solenoid energizes making up a different set of contacts. This places the governor '

in the isochronous mode. Consequently,1B Diesel Generator operability in the emergency a mode was not affected. j Following the first failure the relay was removed and the contacts were cleaned to improve continuity. The relay was then placed back in service. The IB Diesel  !

Generator was run at 5500 KW for one hour. No governor control problems were _

experienced during the run. LOCAR 8.1.1-la was exited approximately five hours  ;

after it was initiated. Following the second failure the relay was removed and replaced inkind with a new relay. The IB Diesel Generator was then run at 5500 KW for one 5 hour5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />. LOCAR 8.1.1-la was exited approximately six hours after it was initiated.

Long term corrective action to replace the relay with a more reliable relay is currently h being pursued. Commonwealth Edison's Station Nuclear Engineering Department, and Cooper Bessemer will assist in the investigation. _

These failures will have no impact on the testing frequency of the IB Diesel Generator. _b Nonvalid tests and failures are not included in the criteria used to determine the z testing frequency as stated in Section C.2.d of Regulatory Guide 1.108.  ;

-a R. E. Querio "

Station Manager Byron Nuclear Power Station REQ /JC/bf j a

ec: J.1:inds, NRC Resident inspector ],

U. S. NRC Document Control Desk, Washington, D.C.

INPO Record Center '

CECO Distribution List -

M. Roberts '

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1. 33/014 -