ML20043H509

LER 90-009-00:on 900527,automatic Start of Auxiliary Feedwater Pumps Occurred When Both Main Feedwater Pumps Placed in Tripped Condition.Caused by Personnel Error.Trip Circuitry Reset & Operators counseled.W/900621 Ltr

ML20043H509
Person / Time
Site:	Sequoyah
Issue date:	06/21/1990
From:	Bynum J, Whittemore C TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-90-009-01, LER-90-9-1, NUDOCS 9006260038
Download: ML20043H509 (5)

Text

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n . . TENNESSEE VALLEY AUTHORITY 6N 38A Lookout Place Chattanooga, Tennessee 37402-2801 l

(. June-21',_1990 I

R U.S. Nuclear Regulatory Commission  ;

f ATTN: Document Control Desk  !

Washington, D.C. 20555 j l j

q. p l' g a Gentlemen:

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TENNESSEE VALLEY AUTHORITY - SEQUOYAH NUCLEAR PLANT UNIT 1 - DOCKET NO. j 50-327 - FACILITY OPERATING LICENSE DPR LICENSEE EVENT REPORT (LER) l

[ 50-327/90009 j i'r s The enclosed LER provides details concerning the automatic start of the i "y , auxiliary feedwater pumps due to both main feedwater pumps in a tripped ,

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condition on May 27, 1990. This event is being reported in accordance with  !

10 CFR 50.73(a)(2)(iv) as a condition that resulted in an automatic actuation.  !

of an engineered safety feature. -

Very truly yours, .l TENNESSEE VALLEY AUTHORITY c

' W (J.R.Bynum, ice President i 3

Nuclear Power Production Edclosure dk[M4

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INPO Records Center .

!1 Institute of Nuclear Power Operations  !

1100 Circle 75 Parkway, Suite 1500 i

. _ Atlanta, Georgia 30339 m

NRC Resident Inspector i Sequoyah Nuclear Plant i 2600 Igou Ferry Road Soddy Daisy, Tennessee 37379 Regional Administration U.S. Nuclear Regulatory Commission Office of Inspection and Enforcement Region II 101 Marietta Street, Suite 2900 Atlanta, Georgia 30323

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An Equal Opportumty Employer

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• Automatic Start of the Auxiliary Feedwater System as a Result of a linit Operator Failing to Adhere to Procedure Precautions eve =, oavi i i sim=vu .ii u >on oats m ovain eac.6nies wvo6vec esi

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SUPPLlWlh1 AL htPORT O R94CYtD ltei MDNim Dav Vl&R l vis o,, . ,4. t vescr,o avavuo= o.rti T] wo l l l auva.C,u,e, ..m. , ,,,,.. , .., .u,.. o on, On May 27, 1990, at 1756 Eastern daylight time with Unit 1 in Mode 3 (0 percent power, 2.220 psig, and 547 degrees F), an automatic start of the Unit I auxiliary feedwater pumps occurred. Testing of the Unit 1 B main feedeater puniip (MFP) was in progress with the trip circuit energized when the A MFP trip circuit was energized in preparation for putting the A MFP on tuming gear in anticipation of changing modes. The combination of tro MFP trip signals completes a logic to start the auxiliary feedwater pumps, which is

n ESF. Once the trip signal is energized on a MFP, it has to be manually reset to be cleared. Immediate corrective action was taken by resetting the B MFP trip circuit, stopping the auxiliary feed pumps and returning them to their normal configuration. The systeits and components required to actua';e as a result of the ESF f unctioned as required. The root cause of the event has been attributed to personnel error and inattention to detail in that the unit operator failed to adhere to the precautious as outlined in plant procedures.

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O!O 0l 2 oF 0l3 su,w e-.a,m . .eme. .ne.aw w m an m On May 27, 1990, at 1756 Eastern daylight time (EDT) with Unit 1 in Mode 3 (0 percent p;wer, 2,200 psig, and 547 degrees F), an automatic start of the Unit 1 auxiliary icedwater pumps (EIIS Code BA) occurred when both main feedwater pumps (MTPs) were placed in the tripped condition with the trip circuit energized.

Unit I was in hot standby (Mode 3) and in the process of being brought into criticality cnd minimum load (Mode 2). One MFP is needed for operation in Mode 28 prior to operating the MFP, it must be put on the turning gear for approximately one hour to cvoid any thermal damage to the shaft. The turning gear activity is accomplished while the unit is in Mode 3, and the pump must have the trip circuitry energized (i.e., MFP tripped) before it can be put in turning gear. This activity is procedurally controlled by Section F of System Operating Instruction (SOI) 2.1 and 3.1, " Condensate and Fcedwater System." The B MFP was being prepared for an overspeed test, which is procedurally controlled by Section M of S01-2.1 and 3.1, and was already in the tripped '

condition. The A MFP was being prepared for placement on turning gear in accordance with S01-2.1 and 3.1. Dif ficulty was encountered when the A MFP was attec'pted to be j placed on turning gear, and the unit operator (UO) instructed the control room auxiliary unit operator to energize the trip circuit to facilitate the operation. The logic was then complete (i.e., both MFPs tripped) for the turbine-driven and motor-driven cuxiliary feedwater pumps to automatically start. S01-2.1 and 3.1 contain precautions to ensure at least one MFP trip bus is deenergized if below Mode 2 to ensure an inadvertent engineered safety feature (ESP) actuation does not occur while in Modes 3, 4, 5. or 6.

Cause nL1helunt The root cause of this event has been attributed to personnel error ud inattention to detail in that the UO failed to adhere to the precaution as outlined in SOI-2.1 and 3.1.  !

SOI-2.1 and 3.1 states in Section F, paragraph IV.C.17, to ensure at least one main j feedwater pump trip bus is deenergized if below Mode 2 to ensure an inadvertent ESF cctuation does not occur while in Modes 3, 4, 5, or 6. The checklist for the MFP turbine startup has a checkoff step to ensure at least one MFP turbine trip bus is deenergized if below Mode 2. These precautions are also repeated in Section M of the S01-2.1 and 3.1. Section M is the overspeed test for the MFPs. The unit operator involved was aware of the precaution and had just reviewed the procedure. However, in the preparations to enter Mode 2 and go critical, the tripped condition of the second MFP in the overspeed test was overlooked.

Analysis _oflYcnt This event is being reported in accordance with 10 CFR 50.73(a)(2)(iv) as an event or condition that resulted in an automatic actuation of an ESF.

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010 0 l3 0F 0 13 tat. . - ==c.- m4.,nn Th3 MFPs' tripped condition simulated loss of normal feedwater to the steam generators tnd generated auxiliary feedwater pump start signals as designed. The auxiliary f0:dwater pumps are designed to start upon loss of normal feedwater to steam generators tnd maintain water level in the steam generator to remove residual heat from the reactor coolant system (RCS) to prevent overpressurization of RCS or loss of water from the r::ctor core. If loss of main feedwater to steam generators occurred during power cperations, the ESF actuation would have initiated as designed.

Th2 starting of the auxiliary feedwater pumps did not adversely affect or degrade any s,fety systems or components. All systems functioned as designed. There was no adverse cffect nor danger to the health and safety of the plant or public.

Corrective._Acilon Tha B MFP trip circuitry was reset, and the auxiliary feedwater pumps were stopped and roturned to their normal position. The operators involved were counselled on the 1 portance of being aware of ongoing activities that could affect operations and the inportance of following procedures.

Additional 1ntormation A review of LERs has revealed several instances where an ESF actuation resulted from MFP trips. No instances were id-ntified with identical or similar circumstances as this EST cetuation (i.e., operator failed to recognize one MFP tripped for testing while ottempting to put the second MFP on turning gear).

Conuitmenta ,

None.

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