ML20029C210

LER 91-002-01:on 901009,inadvertent Start of Auxiliary Feedwater Pump Occurred.Caused by Inadequate Test Procedures.Auxiliary Feedwater Pump Secured & Maint Work Request Mwr 904517 initiated.W/910320 Ltr

ML20029C210
Person / Time
Site:	Point Beach
Issue date:	03/20/1991
From:	Fay C WISCONSIN ELECTRIC POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
CON-NRC-91-029, CON-NRC-91-29 LER-90-002, LER-90-2, VPNPD-91-101, NUDOCS 9103260442
Download: ML20029C210 (6)

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VPNPD-91-101 10 CFR 50.73 NRC-91-029 March 20, 1991 U. S. NUCLEAR REGULATORY COMMISSION Document Control Desk Mail Station F1-137 Washington, D. C. 20555 Gentlemen DOCKET 50-301 LICENSEE EVENT REPORT 90-002-01 I

INADVERTENT START OF AUXILIARY PEEDWATER PUMP POINT BEACH NUCLEAR PLANT. UNIT 2 Enclosed is Licensee Event Report 90-002-01 for Point Beach  ;

Nuclear Plant, Unit 2. This report is provided in accordance with 10 CFR 50.73 (a) (2) (iv) , "The licensee shall report...any event or condition that resulted in manual or automatic actuation of any engineering safety feature...."

This is a supplement to the report submitted on November 8,-1990, which described the inadvertent start of' motor-driven auxiliary foodwater pump P38A during a ten-year hydrostatic test of the steam generators and associated systems. This report includes..

the results of our root cause evaluation'and corrective actions.

If'further information is required, please contact us.

Very truly yours, (4

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.C. W. Fay' Vice President Nuclear Power Enclosure

' Copies to NRC Regional Administrator, Region III NRC Resident Inspector

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ABSTRACT:

On October 9, 1990, during a 10-year hydrostatic test of the steam generators and steam lines, and simultaneous performance of maintenance on the Unit 2 "B" train safeguards relays, both motor-driven auxiliary foodwater (AFW) pumps roccived automatic start signals. When the "A" main food pump was started in accordance with the test proceduro, the 2/3 steam generator low-low level automatic start logic for the motor-driven APW pumps was fulfilled. The "A" motor-driven AFW pump automatically started. The "B" motor-driven APW pump was aircady running as required-by the hydrostatic test, with the steam generators filled and pressurized.

All systems functioned as designed. A small amount of water was injected into the Unit 1 "A" steam generator; however, an operator took immediato action to secure the injection. The "A" motor-driven AFW pump was secured. Upon releano of its control switch, the switch returned to the auto position and the pump restarted and then tripped. An investigation revealed the pump's breaker pneumatic overload devico had failed to completely roset following initial activation.

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On October 9, 1990, at 1346 hours0.0156 days <br />0.374 hours <br />0.00223 weeks <br />5.12153e-4 months <br /> the "A" motor-driven auxiliary feedwater pump (P38A) received an automatic start signal. At the timo of the event, operating personnel wo*e in the process of performing'a hydrostatic test of the Unit 2 steam generators and steam lines in accordance with inservice test procedure, IT-1025.

The Unit.2 steam generators.were filled and prossurized. In accordance with the procedure's requirements, the "D" motor-driven auxiliary feeduater pump (P38B) was running, and the main feed pump control switchen were in pullout.in order to block the signal for the auxiliary feedwater pump automatic start circuit.

Simultaneous with this test condition, the Unit 2 "B" train safeguards had been removed from service for maintenance.

Removal of the "B"' train safeguards included the disconnection and tagout:of'the low-low steam generator level bistable output cables. This fulfilled the logic requirements for 2/3 low-low level even though the steam generators woro full of water. The start circuitry was blocked as long as the main foodwater pump switches were in pullout.

In accordance with the test procedure, the "A" main food pump control switch was passed through the neutral position to start the pump to increase the pressure to greator than that which the auxiliary feedwater pump supplies. This unblocked the steam generator low-low level automatic actuation signal to auxiliary feodwater resulting in: automatic actuation of both motor-driven auxiliary feedwater pumps. The "B" motor-driven auxiliary .

feedwater pump was already running. The "A" pump started in accordance with system design.

Some. water was injected into the Unit 1 "A" steam generator because of that unit's lower pressure (as compared to the hydrostatic test pressure of Unit 2). The Unit 1 control operator immediately closed the auxiliary food discharge valve to the Unit 1 "A" steam generator. The operator attempted to securo the "A" motor-driven auxiliary feedwater pump by moving its control _ switch to the trip position. Upon roloasing the control switch, however, the pump restarted. On the second automatic start, the pump tripped on overload.

An investigation by operating personnel showed that the "A" auxiliary food pump breaker pneumatic overload device had actuated to trip the breaker. At 1411 hours0.0163 days <br />0.392 hours <br />0.00233 weeks <br />5.368855e-4 months <br />, the braaker was reset. When restored to the auto position, the breaker and pump operated normally. At 1425 hours0.0165 days <br />0.396 hours <br />0.00236 weeks <br />5.422125e-4 months <br />, the simulated steam generator low-low level signals were reset and the motor-driven auxiliary feedwater pumps were secured. During the period of timo, the "A" 1

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SYSTEM-QESCRIPTION At Point Beach, there are two motor driven auxiliary foodwater pumps shared betwoon the two units and two turbine-driven auxiliary foodwater pumps, one for each unit. The motor-driven auxiliary fortdwater pumps recolve a start signal on (1) low-low water level in any stonm generator, (2) trip or shutdown of both main foodwater pumps in one unit, or (3) safeguards sequence signal.

I CAUSE The causes of this event were as follows:

1. The starting of the main foodwater pump concurront with "B" train safeguards service work fulfilled the logic required to automatically start both motor-driven auxiliary foodwater pumps. The two procedures, completed indopondently of each other, would have resulted in no consequence. The inservice test proceduro war loss than adequato in recognizing the potential for contributing to an inadvertent start of the auxiliary foodwater pump.

2. The subsequent trip after the second automatic start of the "A" motor-driven auxiliary foodwater pump WaE' due to the failure of the pump breaker overload device to completely roset following the first automatic actuation.

REPORTABILITl This event is being reported under the requirements of 10 CFR50.73 (a) (2 ) (iv) , "The licensco shall report...any event or condition that resulted in a manuni or automatic actuation of an engineered safety featuro...."

SAFETY ASSESSMENT The auxiliary foodwater system operated as designed. Thoroforo, the safety of the plant and the health and safety of the public and plant employees woro not jeopardized.

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1. The auxiliary feedwater pump was immediately secured.

2.- A maintenance work request (MWR 904517) was initiated to determine the cause of the "A" auxiliary foodwater pump ,

breaker overload trip. The breaker was removed and overload tested. Testing of the "C" phase (C$) revealed resistanco inconsistencies.- Accordingly, the overload was disassembled,

-inspected, cleaned, and its pick-up current adjusted. post-  :

maintenance testing was successfully completed with the auxiliary feedwater pump running in the recirculation modo.

long Termt

1. A ten-year pressure test of the main steam and main food systems will-bo conducted during the upcoming Unit 1 Refueling

-18. Becauss this procedure will be conducted concurrently with Instrument and Control maintenance, a procedure chango

- shall be made. The change will " caution" the reactor operator of potential engineered safeguards actuations when operating '

the main feed pump control switch.

2. A-root =cause evaluation was performed on this event and similar occurrences of ESF actuations to determine what corrective actions could minimize the potential for recurrence. A specific precursor condition, common to each event, could not be identiflod. Based on this finding, no further corrective action is planned.

3. Modification Request 67-034, "Amptoctor Overload Upgrado of 480 V:DB Breakers", had been initiated previously to replace all existing 400 V DB breakers overcurrent trip devices. Our schedule for this modification is.for completion by the end of

-1992. The auxiliary feedwater pump breakers are included-within the scope s.,f this modification request. This will improve the reliability and repeatability of the sottings of-the'overcurrent trip devices and eliminato the timo delay for the overload-reset.

4. The original revision of this Licensco Event Report (301-90-002) was required reading for each operating crow.

This revision will also be reviewed by each operating crow, un , ma m

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5. Operations outage planning is an area in which Point Beach management has been increasingly sensitivo. Previous to this event, considerable timo was spent integrating the Instrument and Control maintenance work with the Operations Unit 2, l Refueling 16 activities. Operations plannors analyzed the 1 potential impacts of each instrument refurbishment on plant i systems and assisted in the scheduling of the maintenance to limit overall exposure to safoguards actuations. Savoral potential events were avoided. Outage planning activition will continue with increased emphasis on proventing inadvertent safeguards actuations.

GENERIC IMPLICATIONS A generic problem with the pnoumatic overload devices was previously identified. This identification and ovaluation concluded with the initiation of a modification request to chango out 480 V breaker trip devices.

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