U-602163, Special Rept:On 930623,Div I DG (DG1A) Failed to Synchronize W/Associated Safety Bus & Generator Output Breaker Tripped on Reverse Power Signal Due to Faulty Reverse Power Relay. DG1A Reverse Power Relay Replaced W/Newer Model

Special Rept:On 930623,Div I DG (DG1A) Failed to Synchronize W/Associated Safety Bus & Generator Output Breaker Tripped on Reverse Power Signal Due to Faulty Reverse Power Relay. DG1A Reverse Power Relay Replaced W/Newer Model

ML20056C935
Person / Time
Site:	Clinton
Issue date:	07/23/1993
From:	Phares R ILLINOIS POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
U-602163, NUDOCS 9307300107
Download: ML20056C935 (3)

Text

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• Ubnots Power Company ' .'

• Gknton Power StaMn P.O. Box 678 .

Chnton. IL 61727 Tei 217 935-8881 ILLINOIS u.sous3 PfaMR t47-93co723tp 8E.110c July 23, 1993 Docket No. 50-461 10CFR50.36 Document Control Desk

• Nuclear Regulatory Commission Washington, D.C. 20555

Subject:

Special Report: Invalid Test Failure of Division 1 Diesel Generator at Clinton Power Station (CPS) >

Dear Sir:

Clinton Power Station (CPS) Technical Specification 4.8.1.1.3 requires' all diesel generator failures, valid or non-valid, to be reported to the NRC within 30 days pursuant  !

to Specification 6.9.2, SPECIAL REPORTS. Due to a invalid failure of the Division I  !

Diesel Generator (DGIA) during surveillance testing on June 23, 1993 the attached -

Special Report is being submitted in accordance with the CPS Technical Specifications to {

provide the'information required by Regulatory Guide 1.108, Revision 1, " Periodic  ;

Testing of Diesel Generator Units Used as Onsite Electric Power Systems at Nuclear Power Plants," Regulatory Position C.3.b. l Submittal of this letter and its attachment satisfies the requirements of CPS b Technical Specifications 4.8.1.1.3 and 6.9.2 for submitting a Special Report for diesel generator failures.

l Sincerely yours,

.' 7  !

titu Richard F. Phares Director-Licensing CLJE/nis cc. NRC Clinton Licensing Project Manager NRC Resident Office, V-690 Regional Administrator, Region III, USNTC

. Illinois Department ofNuclear Safety 9307300107 930723 /~

ADOCK 05000461 %w_ . 1 i PDR a l S PDR Q -

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. Attachment  !

to U-602163.

Page1 of2 Ilescrintion of Event / Cause of Failure At !118 hours0.00137 days <br />0.0328 hours <br />1.951058e-4 weeks <br />4.4899e-5 months <br /> on June 23, 1993, the Division I Diesel Generator (DG1 A) was j started for routine surveillance per Clinton Power Station (CPS) Procedure 9080.01, j

" Diesel Generator 1 A (IB) Operability - Manual." During this monthly surveillance test, i the generator failed to successfully synchronize with its associated safety bus and the ~

generator output breaker tripped on a reverse power signal. A second attempt to synchronize DGI A was mede but again the generator output breaker tripped on reverse power. The DG1 A was dechred INOPERABLE which placed the plant in a 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />  ;

Limiting Condition of Operation (LCO). The remaining divisional diesel generators were  ;

verified OPERABLE in accordance with Technical Specifications.

Based on Regulatory Guide 1.108 Regulatory Position C.2.e.(2), the trip of the DGl A due to the reverse power relay is not considered a valid failure. Since the reverse power relay is used to prevent motoring the generator during synchronization, it would not be operative during an emergency operating mode. Therefore, this failure has been classified as invalid.

i Maintenance Work Request (MWR) D51957 was initiated to troubleshoot and identify the cause of the output breaker trip. After connecting various test equipment to critical diesel generator parameters and circuits, it was determined that the reverse power relay was the cause of the DGl A reverse power trip. Upon investigation, the reverse power relay was found to be out of calibration. The relay was recalibrated and reinstalled in the system, but again failed when an attempt was made to synchronize the generator with its associated safety bus. A decision was made to replace the original reverse power- i relay. Modification (MOD) DG-073 was initiated to replace the original relay (which no longer is available) with a newer model reverse power relay in stock. Since the model that failed no longer exists, commercial grade dedication of the newer model relay had to be performed to qualify the relay for use in this safety related application. Condition ,

Report (CR) 1-93-06-024 was initiated to document the failure of the DGI A output '

breaker to remain closed.

Following replacement of the reverse power relay, DGI A tested without any problems. Post maintenance testing for the MOD was performed which verified the relay worked in the application. Based on the completion of the operability surveillance and ,

post-maintenance testing of the installed new reverse power relay, DGI A was restored to OPERABLE status at 2225 hours0.0258 days <br />0.618 hours <br />0.00368 weeks <br />8.466125e-4 months <br /> on June 25,1993. i Corrective Actions The cause of the recent failure of DGI A was deterinined to be a faulty reverse '

power relay. As a result, the DGl A reverse power relay was replaced with the newer ,

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Attachment to U-602163 Page 2 of 2  ;

i model. In addition, both Division 2 and 3 Diesel Generators have been replaced with the l newer model relay as part of the corrective action plan.

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The reverse power relay was sent for a root cause evaluation and this evaluation is expected to be completed by August 30, 1993. The information gathered from this ,

investigation will be evaluated and any additional corrective actions will be identified by  ;

September 15,1993.

i IesLIlltelrah i As of June 23, 1993, DGI A had experienced four valid failures in the last 100 valid tests performed. In accordance with CPS Technical Speci0 cations Table 4.8 l .1.2-1, DGl A continues to be tested at least once per 31 days. l i

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