05000327/LER-1980-151-03, /03L-0:on 800811,turbine Driven Auxiliary Feedwater Pump Failed to Start After Loss of Both Main Feedwater Pumps.Caused by Torque Switch Failure,Causing Valve FCV-1-51 Motor Operator to Short

/03L-0:on 800811,turbine Driven Auxiliary Feedwater Pump Failed to Start After Loss of Both Main Feedwater Pumps.Caused by Torque Switch Failure,Causing Valve FCV-1-51 Motor Operator to Short

ML19332A559
Person / Time
Site:	Sequoyah
Issue date:	09/10/1980
From:	Gelston A TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19332A553	List: 05000327/LER-1980-151, Forwards LER 80-151/03L-0 05000327/LER-1980-151-03, /03L-0:on 800811,turbine Driven Auxiliary Feedwater Pump Failed to Start After Loss of Both Main Feedwater Pumps.Caused by Torque Switch Failure,Causing Valve FCV-1-51 Motor Operator to Short
References
LER-80-151-03L, LER-80-151-3L, NUDOCS 8009160398
Download: ML19332A559 (3)

LER-1980-151, /03L-0:on 800811,turbine Driven Auxiliary Feedwater Pump Failed to Start After Loss of Both Main Feedwater Pumps.Caused by Torque Switch Failure,Causing Valve FCV-1-51 Motor Operator to Short

Event date:
Report date:
3271980151R03 - NRC Website

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TENNESSEE VALLEY AUTHORITY Sequoyah Nuclear Plant LER SUPPLEMENTAL INFORMATION SQRO-50-327/80151 Technical Specification Involved 3.7.1.2

. Reported Under Technical Specification 6.9.1.13.b Date of Occurrence 8/11/80 Time of Occurrence 0911 CDST Unit 1 Identification and Description of Occurrence:

During the perfor=ence of preoperational test TVA-22 the stea= generator level exceeded the high level set point and, tripped both main feedwater pumps.

The two motor driven auxiliary feedvater pumps worked properly but the turbine driven pump did not start. The turbine driven auxiliary feedwater pu=p was declared inoperable per L.C.O. 3.7.1.2.

Investigation indicated the thermal overloads had melted for the trip and throttle motor operated valve FCV 51, to the steam driven auxiliary feedwater pu=p.

The motor operator for the valve was meggered and found to be within the acceptance criteria. The thermal overloads were replaced. A check of the motor operator indicated the valve was still inoperable. The valve operator motor was bridge tested and found to be shorted. The valve operator motor was repicced. A check of the motor operator indicated the valve was still inoperable. Futher investigation indicated the torque switch was not opening properly. The torque switches were replaced. The torque switches and the limit switches were adjusted. The vendor of the valve operator has been contacted to supply infor=ation regarding these' torque switches.

Condition Prior to Occurrence:

Mode 2 Reactor Power 4%

Reactor Pressure 2230 PSIG Reactor Temperature 549 Degrees F Action specified in the Technical Specifications Surveillance Requirements met due to Inoperable Equipment.

l Accarent Cause of Occurrence:

Motor and operator are mismatched. The motor maximum torgue is 24 in-pounds, the minimum cperator torque setting is 28 in-pounds.

Analysis of Occurrence:

Torque switch failed to stop motor operator at proper setting causing motor to fail and thermal overloads to melt.

Corrective Action

1.

Thermal overloads replaced.

2.

Valve operator motor replaced.

2 TENNESSEE VALLEY AUTliORITY Sequoyah Nuclear Plant LER Supplemental Information 3.

Torque switches replaced.

4 Adjustments have been prescribed by the vendor which allows the maximum motor torque to overlap with the minicus setting of the operator torque switch.

Failure Data:

N/A 1

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