ML20236E501

Ro:On 870318 & 0417,diesel Generator 1A Failed to Reach Rated Speed,Voltage & Frequency within Required Time Set by Tech Specs.Caused by Inadequate Prime in Fuel Oil Supply Line & Ruptured Diaphragm,Respectively

ML20236E501
Person / Time
Site:	Byron
Issue date:	06/25/1987
From:	Querio R COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
BYRON-87-0576, BYRON-87-576, NUDOCS 8707310396
Download: ML20236E501 (2)

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Commcnwdith Edison - PRIOMTY ROUTId Syron Nuclear Station rst I mi

, ~iVfaM ~ 4450 North German Church Road ,

3 g Byron, Illinois 61010 . oy n n$ L 7

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June 25,1987 g[

LTR: ' BYRON 87-0576 g/[d - f[

Mr. A. Bert Davis Regional Administrator /

Region 3 U.S. Nuclear Regulatory Commission

-799 Roosevelt Road Glen Ellyn, Illinois G0137 l .f'

Dear Sir:

This report is submitted in accordance with Byron St'ation Unit 1 Operating License ~ f NPF-37 Appendix A, Technical Specification 4.8.1.1.3, reporting of Diesel Generator Failures. .g This report addresses two valid tests and failures experienced on the 1 A Diesel Generator. The criteria to detcrmine valid tests and '

failures is in accordance 7

. with Section C.2.e of Regulatory Guide 1.108I f 1

qu On March 18,1987 the 1 A Diesel Generator was started per the monthly operability a surveillance,1BOS 8.1.1.2.a-1. Per Technical Specification 4.8.1.1.2 the Diesel Generators are required to reach rated speed, voltage, and frequency.within

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l ten seconds of the start signal. The 1 A Diesel Generator required 15 seconds  !

to reach rated conditions. At the time that tysurveillance was performed, j, no requirement existed for an emergency A.C. power source. Following the + .

failure, the 1 A diesel generator was taken out'of service in preparation for the '/.

18 month inspection. Additionally, on April 17,1987 the .1 A diesel generator was started per the 18 month operability emergency start test,'1BVS 8.1.1.2.f-7. 7 Per Technical Specification 4.8.1.1.2.f.5 the diesel generator is required to reach rated speed, voltage, and frequency within ten seconds of the start signal. The 1 1 A diesel generator required 13 seconds to reach rated conditions. The 1 A diesel generator was not required for operation at the time of this event.

The root cause for this failure has been attributed to two separate problems,-

both contributing to the slow starts. Following the first failure the cause was attributed solely to an inadequate prime in the fuel oil supply line. This problem occurs when the fuel oil check valve, located between the engine mounted day tank and the supply day tank, fails to seat properly. Due to the elevation of -

the engine mounted day 3nnk, fuel oil can gravity feed back to the supply day tank if the check valve fails to sest. Several corrective actions were taken during the.18 month inspection to alh'vkte this problem. The failed check valve was disassembled and cleaned, and'the valve seating surfaces were lapped. An additional soft seat check valve was also installed between the engine mounted day tank and the supply day tank.-

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Following the second failure,'another contributing factor.'was discovered. This -

problem involved a ruptured diaphragm on the fuel oil pressure ratio relay. The j function of this relay is to convert fuel oil pressure into' air pressure at a ratio l of one to one. Fuel oil pressure acts on one side of the diaphragm which in turn pilots the correct amount of supplied air to the local control panel for fuel pressure i indication. Due to the ruptured diaphragm, supply air was leaking into the fuel j oil system causing the fuel system to be pressurized. Byron Station believes i that this condition, in conjunction with the previously described condition, caused the slow starts on the 1 A diesel generator. Corrective action for this failure involved isolating the fuel pressure relay from the fuel system. Parts have been ordered to replace the failed diaphram.

As stated earlier the'1 A Diesel Generator was not required for operation durmg these events, therefore the 1 A' diesel generator was not considered unavailable for any length of time. These failures are the second and third failures within the last twenty valid tests. The testing frequency will be increased to'a weekly basis until twenty valid tests are completed with less than two failures during i, the testing period.

l' l A.  ?

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l R. E. Querio Station Manager j

-Byron Nuclear Power Station .!

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cc: P. Brochman, NRC Acting Senior Resident Inspector U. S. NRC Document Control Desk, Washington,' D.C.

INPO Record Center CECO Distribution List M. Robert l J. Cook

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