ML20080G472

Ro:On 941223,invalid Failure Experienced on 2A DG During Normal Start of Engine to Support Transformer Maint Activities.Speed Module Which Initiates Various Control & Support Features as Function of Engine Speed Replaced

ML20080G472
Person / Time
Site:	Byron
Issue date:	01/18/1995
From:	Schwartz G COMMONWEALTH EDISON CO.
To:	Martin J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
BYRON-95-0023, BYRON-95-23, NUDOCS 9502070366
Download: ML20080G472 (2)

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Byron Nucteer annon V 4450 Norm German Church Road PRIORITY ROUTING  :

Byron, Hhnois 61010 RMt Smd E RA RC Janua'ry 18, 1995 TIC DRA DRP _S .C. .A. _

LT: BIRON 95-0023 DF $l . , _. [

FILE: 2.07.400 [gRSS P40 }

OFIMA .

Mr. John Martin Regional Administrator flLE M5 ret i on III U.S. Nuclear Regulatory Commission 001 Warrenville Road Lisle, Illinois 60532-4351 >

SUBJECT:

Byron Unit 2 Operating License NPF-66, Docket No. 50-455 Reporting of Emergency Diesel Generator Failures ,

Dear Mr. Martin:

This report is submitted in accordance with Byron Station Unit-2 Operating License NPF-66 Appendix A, Technical Specification 4.8.1.1.3, Reporting of Diesel Generator Failures.

The attached report addresses an invalid failure experienced on the 2A Diesel i Generator during a normal start of the engine to support transformer maintenance activities. The criteria to determine valid and invalid tests and failures is in accordance with Section C.2.e of Regulatory Guide 1.108, and as such does not affect the testing requirements established in the Byron

• Technical Specifications. ,

If you have any questions, feel free to contact Dave Baran (ext. 2050) of the Systems Engineering Department.

Sincerely, 4

J .  !

.b i.bb)e G.K. Schwartz -'

Station Manag Byron Nuclear er Station GKS/ DAB /cib Attachments cc: Byron Station NRC Senior Resident Inspector U.S. NRC Document Control Desk, Washington, D.C INPO Record Center /

Comed Distribution List J 2 5 1995

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• DIESEL GENERATOR 2A INVALID FAILURE DECEMBER 23, 1994 On December 23, 1994 the 2A Diesel Generator (DG) was started in support of a System Auxiliary Transformer outage on Unit 2. The engine started and achieved rated speed, but, immediately after the start, a loud blowing noise was detected in the vicinity of the right bank starting air valve. A starting air system problem was originally suspected, but after observing all indications at the DG local control panel, it was apparent that the starting system control logic had malfunctioned. The Essential Service Water (SX) supply valve to the Jacket Water Heat Exchanger failed to open and the Fuel Oil Transfer Pumps did not start at 280 rpm during the engine startup. After approximately a minute following the engine start, the right bank starting air receiver had completely blown down because a starting air solenoid failed to drop out at 280 rpm. The Nuclear Station Operator in the Control Room responded immediately to his indications and annunciators by opening the SX supply valve. The selected Fuel Oil Transfer Pump started on low day tank level and the Equipment Operator at the 2A DG responded by manually starting both pumps.

A review of the DG electrical schematics narrowed down the source of the problem to a single device, a speed module whicn initiates various centrol and support features as a function of engine speed. After approximately an hour, the speed module internal relays changed state and automatically initiated the control features that were manur.lly actuated after startup. In addition, the device operated properly during engine shutdown. Since the ability of the speed module to perform reliably during future starts was suspect, the device was replaced. A successful start during the post maintenance run confirmed the operability of the replaced device. A bench test of the removed speed module was performed in an attempt ';o pinpoint the fault within the module.

The testing simulated several engine startups and shutdowns, however, the problem previously experienced could not be repeated. Since the condition corrected itself in the field and could not be repeated on the bench, this component problem is considered spurious.

This failuce is classified as invalid because the component malfunction required minimal problem diagnosis and operator response. The design characteristics and bases of the affected support systems, as described ir. the ,

Byron Station UFSAR, justify this failure classification. With respect to the 1 SX supply to the engine, UFSAR Section 8.3.1.2 states that lack of essential service water flow at the time the diesel generator starts will not prevent the accomplishment of its safety function. In addition, the UFSAR states that the engine was tested under load at 4000 KW for 20 minutes without service water and without exceeding temperature alarm setpoints. During the failure event, the selected Fuel Oil Transfer Pump started on low level. The design bases for the Fuel Oil Transfer System, as described in UFSAR Section 9.5.4.1, states "each pump is capable of transferring oil from the diesel oil storage tank to its corresponding day tank at sufficient pressure and flow to exceed the maximum demand rate." The Diesel-Generator Starting System description, l' UFSAR Section 9.5.6.1, states "This is a dual system with either half capaole of starting the engine." The component malfunction disabled the right bank starting air system, but the left bank was available and did start the engine as designed.

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