ML19332F047

LER 89-021-00:on 891031,circuit Breaker for RCIC Inboard Injection Valve to Feedwater Sys Tripped During Required Valve Testing.Caused by Fault in Motor Winding Insulation. New Motor installed.W/891130 Ltr

ML19332F047
Person / Time
Site:	FitzPatrick
Issue date:	11/30/1989
From:	Fernandez W, Fish H POWER AUTHORITY OF THE STATE OF NEW YORK (NEW YORK
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
JAFP-89-0850, JAFP-89-850, LER-89-021, LER-89-21, NUDOCS 8912130320
Download: ML19332F047 (5)

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C- James A.MtsPetrisk s 'e r Huolent Power Mont

-. PC, Box 41 Lycoming, New York 13093 I

. 315 M24H0 - l i

WrkPbwer William Femandez 11  ;

Resident Manager i Navsber 30, 1989 .

JNPP-894850 I United States Nuclear Regulatory Commission Document Control Desk ,

Mail Station PI-137  :

Washington, D.C. 20555

REFERENCE:

DOCKET No. 50-333 LICENSEE EVENT REPORT: 89-021-00 Reactor Core Isolation Cooling Inboard Injection Valve Motor  :

Failed

Dear Sir:

'This Licensee Event Report is submitted in accordance with 10 CFR 50.73.(a)(2)(v).

Questions concerning this report may be addressed to Mr. Hamilton Fish at (315) 349-6013. l Very tru yours, i

}/hl ,

WILL AM FERNA >EZ WF:HCF:mac U .

Enclosure cc: USNRC, Region I INPO Records Center #

-American Nuclear Insurers NRC Resident Inspector 8912130320 891130 /

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l The plant was operating at 100 percent power. The High Pressure ,

Coolant Injection (HPCI) [BJ) system was inoperable. Following approved procedures, the Reactor Core Isolation Cooling (RCIC) [BN) system was being tested for operability on October 31, 1989. At 12 noon, during the performance of this test, the circuit breaker for the RCIC inboard injection valve to the feedwater system (and ultimately the reactor) tripped during the required valve testing.  ;

The electric motor for the valve operator failed due to a fault in the motor winding insulation. The valve was observed to have ,

closed. The combined inoperability of both RCIC and HPCI placed the plant in a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> Limiting Condition for Operation (LCO). The motor was replaced, testing was completed, and the RCIC system was declared operable at 6:29 p.m., ending the LCO within eight hours.

Testing of the motor circuits, valve actuator and valve ruled out known potential external causes. The motor had been in service for -

14 years. The cause was failure of the electrical insulation believed to have been caused by poor quality control in the winding of the series field over the shunt field winding.

Related LERs: 88-001,86-014, 86-003, 85-025

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Description:

On October 31, 1989, at 6:25 a.m. the High Pressure Coolant Injection (HPCI) [BJ) system was declared inoperable due to an electrical ground in the speed control circuit (LER-89-019).

Because HPCI was inoperable it was required that the Reactor Core Isolation Cooling (RCIC) (BN) system be tested for op-erability. During the performance of an approved surveillance test, "RCIC Flow Rate and Inservico Test", ST-24J, the control switch for the inboard injection valve from the RCIC system to the feedwater line to the reactor was moved to the closed 70sition. The green closed indicator lamp on both the bench 3oard and containment isolation graphic display illuminated.

Approximately five minutes later at 11:49 a.m. (the normal closing time is 11 seconds) the 20 amp Motor Control Center (MCC) circuit breaker for the valve motor operator tripped open. RCIC was declared to be inoperable. An o aerator ver-ified that the valve was in the closed losition by visual observation of the valve stem. The com)ined inoperability of both RCIC and HPCI placed the plant in a Limiting Condition for Operation (LCO) in accordance with Technical Specifications 3.5.C.l.b and 3.5.E.2 which require that the plant be in a cold condition at less than 150 psig reactor pressure within twenty four hours.

Inspection of the motor showed that the internals were burned and melted. The motor was removed. A new motor was installed and tested in accordance with approved procedures. Valve and actuator diagnostic testing was completed at 6:29 p.m. System testing was completed and RCIC was declared operable at 7:58 p.m. ending the LCO.

Cause Testing of the 125 volt DC motor leads at the motor control center demonstrated an open circuit in the motor shunt field.

The 300 percent overload relay was tested and found to be normal. The motor was disconnected, removed, and the valve was

- stroked manually with no problems. The torque switch was tested externally from the motor ainion gear. The "close" torque switch oaerated normally waen a small amount of torque was applied. This ruled out a defective torque switch. The function of the torque switch is to stop the motor when the closing torque matches the value for a fully closed valve. The spring pack cartridge cover was removed and checked for hydraulic locking. Only a small an.ount of grease was detected inside the cover.- A relief groove was present in the housing between the inner and outer ends of the spring pack further ruling out the possibility of a hydraulically locked spring pack.

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It is hypothisized that during the last closing cycle, the torque developed by the motor was sufficient to physically move the valve to the closed position, but not sufficient to move the torque switch contacts to the "stop" or "off" position.

With the valve closed, but the torque switch remaining in the "on" position, current would have continued to flow in the motor windings until sufficient heat was developed to cause massive insulation failure, short circuit currents, and melting of motor internals.

Analysis Technical Specifications require that the RCIC system be operable whenever the reactor pressure is greater than 150 psig. A seven-day LCO is provided for repair if HPCI is operable. When HPCI is also inoperable, as it was during this event, a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> LCO applies. The RCIC was returned to opera-ble status within approximately eight hours. During this time period, when both the HPCI and RCIC were not operable, adequate protection of the reactor core continued to be provided by the availability of the automatic depressurization system [AD]

together with the low pressure Emergency Core Cooling Systems (ECCS) including the two core spray system [BM) and two Low Pressure Coolant Injection subsystems (BO).

Although RCIC is required to be operable by the Technical Specifications, the Final Safety Analysis Report (FSAR) does not take credit for the availability of RCIC for mitigation of l any of the design basis events. However, Title 10 of the Code i

of Federal Regulation (CFR), Section 50.73(a)(2)(v)(B) requires l reporting of an event that alone could have prevented the fulfillment of the safety function of structures or systems l that are needed to remove residual heat. The RCIC system is I designed to remove residual heat. Therefore, although it is L not a part.of the ECCS and is not required for safe shutdown of the reactor, it may be possible to interpret this section of the CFR to require reporting of RCIC inoperability.

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A new motor was installed and motor current traces taken at the MCC during post work testing using an approved procedure. The l actuator motor current traces were reviewed by the mo- )

- tor-operator valve expert and were determined to be normal.  ;

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Other Information:

Component: Electric Motor for Valve Operator for 1 13MOV-21 Manufacturer: Peericas Manufacturing Company Frame: DG56D Size: 0.72 hp, 125 volt DC Full Load Current: 6 amps The-following LERs describe other events in which -

safety-related valve operator motors were destroyed by overcurrent:

88-001 HPCI Steam Supply 23MOV-14 86-014 HPCI Torus Suction 23MOV-58 86-003 HPCI outboard Steam Bypass 23MOV-60 85-025 HPCI Outboard Isolation 23MOV-16 l

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