05000251/LER-1981-004-03, /03L-0:on 810322,reactor Trip Resulted from Steam Flow/Feedwater Flow Mismatch Coincident W/Steam Generator a Low Level.Caused by Failed Solenoid Coil on Feedwater Regulator Valve.Evaluation Continuing

/03L-0:on 810322,reactor Trip Resulted from Steam Flow/Feedwater Flow Mismatch Coincident W/Steam Generator a Low Level.Caused by Failed Solenoid Coil on Feedwater Regulator Valve.Evaluation Continuing

ML17340B177
Person / Time
Site:	Turkey Point
Issue date:	04/21/1981
From:	Pace P FLORIDA POWER & LIGHT CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML17340B173	List: 05000251/LER-1981-004, Forwards LER 81-004/03L-0 05000251/LER-1981-004-03, /03L-0:on 810322,reactor Trip Resulted from Steam Flow/Feedwater Flow Mismatch Coincident W/Steam Generator a Low Level.Caused by Failed Solenoid Coil on Feedwater Regulator Valve.Evaluation Continuing
References
LER-81-004-03L, LER-81-4-3L, NUDOCS 8105120415
Download: ML17340B177 (5)

LER-1981-004, /03L-0:on 810322,reactor Trip Resulted from Steam Flow/Feedwater Flow Mismatch Coincident W/Steam Generator a Low Level.Caused by Failed Solenoid Coil on Feedwater Regulator Valve.Evaluation Continuing

Event date:
Report date:
2511981004R03 - NRC Website

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ASPQATOAia 6 IBNTOBSCRIPTlON ANO PRCBABI,S CCNSBCUBNCcS QIO During power operation, a reactor trip resulted from steam flow/feedwater flow mismatch coincident with 'A'team generator low level.

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This is reportable pursuant to TS 6.9.2.b.2.

Both Emergency Diesel Generators were operable and available-during this occurrence.

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The cause of the tri was a failed solenoid coil on the 'A'eedwater regulator valve which caused the valve to fail closed.

Testing of the automatic transfer between the auxiliar and startu transformers could not replicate the failure.

The evaluation is continuing, and pending the results an update report will be issued.

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REPORTABLE OCCURRENCE 251-04 LICENSEE EVENT REPORT PAGE TWO Additional Event Descri tion and Probable Conse uences:

During power operation on both March 22,

1981, and April 11,

1981, the 4A 4160 V bus did not energize on transfer from the auxiliary to startup transformer following a reactor trip.

This is reportable pursuant to TS 6.9.2.b.2.

The USNRC was notified following each occurrence pursuant to 10 CFR 50.72.

Both Emergency Diesel Generators were operable and available during these occurrences.'n March 22,

1981, the reactor trip resulted from steam flow/feedwater flow mismatch coincident with 'A'team generator low level.

The reactor coolant pumps tripped on underfrequency following the failure of the 4A 4160 V bus to transfer.

The unit was in hot shutdown condition on natural circulation for approximately three minutes until a reactor coolant pump could be restarted.

On April 11,

1981, the reactor trip from full power resulted from over temperature delta-T on loop 'A'ue to a loss of load when the auxiliary governor operated with a resultant closing of the turbine control and, intercept valves.

The reactor coolant pumps tripped on underfrequency following the failure of the 4A 4160 V bus to transfer.

The unit was in hot shutdown on natural circulation for approximately four minutes until a reactor coolant pump could be restarted.

Additional Cause Descri tion and Corrective Actions:

The cause of the trip on Maich 22,

1981, was a solenoid coil which failed open on SV-4-478C.

The failure of this coil caused FCV-4-478, Steam Generator

'A'eedwater Flow Control valve, to fail closed.

The cause of the coil failure appeared to be due to long term low level mechanical vibration which caused the lead to separate from the coil.

The solenoid valve was replaced.

On March 24,

1981, a channel functional test was performed four times to simulate automatic transfer between the auxiliary and startup transformer.

The automatic transfer tests were all successful'dditionally, a

functional test was performed by manually tripping the turbine-generator from approximately 60 HWe.

This transfer test was also successful.

The cause of the trip on April 11,

1981, was due to operation of the auxiliary governor which caused the turbine-generator to trip.

The cause of the inadvertent operation of the auxiliary governor could not be determined.

The automatic transfer between the auxiliary and startup transformer is designed to operate within 10 cycles after the generator main breakers have opened.

This timing was established via the implementation of Plant Change/Modification 78-14, Replace 15 Cycle T.D.D.O. Relays with 10 Cycle T.D.D.O. Relays in Close Circuits of Breakers 3AA02, 4AA02, 3AB02, and 4AB02.

The cause of the failure of the 4A 4160 V bus to transfer from the auxiliary to the startup transformer has not been determined,

however, evaluation and testing are in progress.

It is currently felt that the relay drop out time varied intermittently.

REPORTABLE OCCURRENCE 251-8 -04 LlCENSEE EVENT REPORT PAGE THREE An u date report will be submitted upon conclusion of the testing and evaluation.

An evaluation pursuant to the requirements of 10CFR w

nupae 21 will be performed as part of the update report preparation.

Com onent Data:

ASCO Solenoid Valve Model WPLB 8300B72F GE Relay Model 12HGA17C52