05000395/LER-1984-024, Revised LER 84-024-01:on 840422 & 29,reactor Tripped Due to Low Main Turbine Shaft Oil Pump Discharge Pressure.Caused by Conservative Switch Settings & Loss of Suction on Motor Suction Pump.Switch Setpoint Will Be Changed

Revised LER 84-024-01:on 840422 & 29,reactor Tripped Due to Low Main Turbine Shaft Oil Pump Discharge Pressure.Caused by Conservative Switch Settings & Loss of Suction on Motor Suction Pump.Switch Setpoint Will Be Changed

ML20093A117
Person / Time
Site:	Summer
Issue date:	07/02/1984
From:	Dixon O, Koon A SOUTH CAROLINA ELECTRIC & GAS CO.
To:	NRC OFFICE OF ADMINISTRATION (ADM)
References
LER-84-024, LER-84-24, NUDOCS 8407100122
Download: ML20093A117 (4)

LER-2084-024, Revised LER 84-024-01:on 840422 & 29,reactor Tripped Due to Low Main Turbine Shaft Oil Pump Discharge Pressure.Caused by Conservative Switch Settings & Loss of Suction on Motor Suction Pump.Switch Setpoint Will Be Changed

Event date:
Report date:
3952084024R00 - NRC Website

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71TLE 448 Main Turbine Trip - Reactor Trip EVENT DATE 151 LOR NURGER ($1 RSPORT DATE 17) OTMER PACILITIE9 INVOLVEO ISI MONTM OAY YEAR YEAR

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@O  ;  ; l A TRACT <v,,,R,,Am - ,.. nei On April 22, 1984, with reactor power at 12%, and on April 29, 1984, with reactor power at 11%, the reactor tripped due to a main turbine trip. Both main turbine trips occurred as a result of main turbine ,

l shaft oil pump low discharge pressure while rolling the main turbine up to 1800 rpm. The Reactor Protection System functioned properly on both events, and Engineering Safety Feature actuated as designed (i.e., ,

Emergency Feedwater Pump start on Low-Low Steam Generator Level). The l causes of these events were attributed to conservative switch settings  ;

and loss of suction on the motor suction pump. l t

I Inspection of the motor suction pump and' check valve will be performed during the First Refueling outage. The procedure has been changed to delete the head correction on the pressure switch, and the pressure ,

switch setpoint will be changed during the First Refueling Outage.

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i NAC Ferse 3esA U S. NUCLEAR KEGULATO7Y COMMISSION LICENSEE EVENT REPORT (LER) TEXT CONTlWUATION mRovEo oMe No 3 iso-w f MPIRE5 8/31115 F ACILITY NAmet tu OOCKET NUMSER (21 LER NUMgER d6) PAGE(31

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At approximately 0903, April 22, 1984, the reactor tripped fran 12% power due to a main turbine trip. While rolling the main turbine to 1800 rpu, the main turbine shaft oil pump discharge low pressure switch actuated causing the main turbine to trip. NCffE: First Out Annunciator was Turbine Trip and P-7 Fermissive. The Reactor Protection System functioned properly, and there was nc actuation of any safety or Power Operated Relief valves. he Steam Dump Valves functioned properly and no Safety Limits nor Limiting Safety Setting were exceeded.

Subsequent investigation revealed actual lube oil pressure to be normal when checked locally with the turbine rolling between 1600 and 1700 rpm. Maintenance personnel manually actuated the switch several times, verified calibration, and found it to be satisfactory. Inadvertent switch operation was attributed to the cause of the reactor trip.

The unit was placed in a stable condition after the trip; the cause of the reactor ,

trip was adequately evaluated, ard a restart was autlurized in accorcance with Emergency Operating Procedure (EOP) 5, " Recovery fran Reactor Trip."

On April 29, 1984, at approximately 0855 hours0.0099 days <br />0.238 hours <br />0.00141 weeks <br />3.253275e-4 months <br />, the reactor tripped from 11% power due to a main turbine trip. The main turbine tripped while rolling up to 1800 rpm on main turbine shaft pump discharge low pressure. 'lhis aggin was verified by First Out Annunciator. Local readings taken immediately following the c'eactor trip showed the discharge pressure of the main turbine motor suction pump arri the shaft driven lube oil pump to be zero. 'Ihe Reactor Protection System functioned properly, and there was no actuation of arly safety or Power Operated Relief Valves.

Steam Dump Valves functioned properly, and there were no Safety Limits nor Limiting Safety Setting exceeded. Steam Generator "B" Feedwater Isolation Valve XVG-1611B failed to auto close on reactor trip; however, the Feedwater Control Valve gcVided Feedwater Isolation. Valve XVG-1611B wes manually closed anormiste.y seven (7) minutes into the event. The operator also received an urgent failure alann on rod control, and NI-31, Source Range Detector "B", developad excessive spikirg before failing low. Maintenance work requests were initiated to investigate and repair XVG-1611B, NI-31, ard the urgent failure alann in rof. control. The air motor on the hydraulic pump for the operation of XVG-1611B was found to be defective and was replaced. The valve was tested satisfactorily ard declared operable April 30.

Blown fuses were found in the rod control power cabilets. 'Ihe fuses were replaced ard the rod control returned to service April 29 Investigation into the spiking of NI-31 attributed the cause to a defective detecto'. The detector was replaced, calibrated, and declared operable May 3, 1984.

As noted previously, local reading on the nnin turbire notor suction pump discharge pressure indicated zero. When the motor suction pump was manually stopped ard restarted, oil pressure indications were obtained. D_scussion with General Electric Corporation (G.E.) revealed that other planti had experienced similar problems because of the notor suction pump discharge check valve sticking closed.

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NRC Form 3ssa U S NUOLE&2 REGULATOXY COMMISSION LICENSEE EVENT REPORT (LER) TEXT CONTINUATION AreROvEo cus NO atso-oio4 empires 8/3115 P ACILIM NAME (M DOCKET NUMeER (2) LER NUMSER 161 PAGE(31 l

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Ol1 01 3 OF 0l3 l TEXT IJF mee space e recured, use adseenaf hMC Fomo JIM'sJ tlh Preventive Test Procedure (PTP) 102.006, " Main Turbine Lube Oil Suction Pressure Monitoring," was written to be implemented on the next turbine roll up. The PTP was initiated to gather information to help determine the root cause of the trips because of low lube oil pressure. The PTP was conducted on May 3 and May 7,1984.

Fran the test data results, the turbine would have tripped in both roll ups because of low shaft driven pump discharge pressure at 1300 rpm. The main turbine mctor suction pump, on occasions appeared to lose prime causing the discharge pressure to decrease. The dischargp pressure of the shaft driven pump did not increase linear with pump speed, but there appeared to be a droop in the discharge pressure. l G.E. was also questioned concernirs the set points of the pressure switch. The schematics show the pressure setpoints in relation to the centerline of the turbine. The Licensee, therefore, applied a " head correction" of 23.5 psig due to the location of the switch in respect to the centerline of the turbine.

Confirmation was received fran G.E. on May 16, 1984, that the value shown at centerline should be the value at the pressure switch. As such, the setting has been conservative. A procedure change has been issued to delete the head correction from the setpoint.

Inspection of the pump and check valve has been scheduled during the First Refueling Outage.

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SOUTH CAROLINA ELECTRIC & GAS COMPANY post OFFICE 784 CotuusiA. South CAROLINA 29218 O W. Druom. Ja.

Vict PatsDENT NuCLEan Optmatio~S July 2, 1984 i

U.S. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555

SUBJECT:

Virgil C. Summer Nuclear Station .

Docket No. 50/395 I Operating License No. NPF-12 LER 84-024, Revision 1

Dear Sir:

Please find attached Revision 1 to Licensee Event Report #84-024 for the Virgil C. Summer Nuclear Station. The changes are denoted by the bar lines in the right hand margin on pages 1, 2 and 3.

This Report was previously submitted on May 22, 1984, in accordance with the requirements of 10 CFR 50.73(a)(2)(iv).

Should there be any questions, please call us at your convenience.

Very truly yours, y- m O. W. , ixon, Jr.

ARK:RJB:OWD/dwf Attachment cc: V. C. Summer J. F. Heilman T. C. Nichols, Jr./O. W. Dixon, Jr. C. L. Ligon (NSRC)

E. H. Crews, Jr. K. E. Nodland E. C. Roberts R. A. Stough W. A. Williams, Jr. G. Percival D. A. Nauman C. W. Hehl J. B. Knotts, Jr.

J. P. O'Reilly Group Managers INPO Records Center ANI Library O. S. Bradham NPCF C. A. Price  ;

D. A. Lavigne File h,,

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