ML19332E624

LER 89-019-00:on 891031 & 891103,HPCI Sys Declared Inoperable Due to Electrical Ground in Speed Control Circuit.Caused by Buildup of Conductive Corrosion Products. Connector Cleaned & Sys Returned to svc.W/891130 Ltr

ML19332E624
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-89-0851, JAFP-89-851, LER-89-019, LER-89-19, NUDOCS 8912080100
Download: ML19332E624 (6)

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[/ Jesum A. MhPeMak

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P. . D M 41 h N.' 6 LY00mino. New York 13093

.- ' 316 342-3640 William Femander 11 Resident Manager November 30, 1989 b JAFP-89-0851 i.

t United States Nuclear Regulatory Commission Document Control Desk Mail Station PI-137

. Washington, D.C. 20555 l

REFERENCE:

DOCKET NO. 50-333 LICENSEE EVENT REPORT: 89-019-00

, High Pressure Coolant Injection Turbine - Electrical Ground Dear-Sir f This Licensee Event Report is submitted in accordance with 10 CFR 50.73 (a)(2)(v).

-Questions concerning this report may be addressed to L Mr. Hamilton Fish at (315) 349-6013.

..Very truly yours,

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Enclosure cci '.USNRC, Region I INPO Re' cords Center American Nuclear Insurers NRC Resident Inspector f

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l 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 i in the speed control circuit. A buildup of conductive corrosion  ;

' products between an Amphenol type connector, which was in an oil environment, and its mounting plate was contributed to by moisture in the oil, a change in the connector mounting grommet configuration, and inadequate shrink tube insulation over the conductor connection to the +

Amphenol pins. The connector was cleaned and HPCI restored to service at 9:10 p.m the same day. Two and one half days later, on November 3, ,

1989, at 3:00 a.m. HPCI was again declared inoperable for the same reason. The connector was removed, cicaned, and a silicone resin conformable coating was applied to continuously seal the pins, e insulation, and the mounting plate. The shaft seal leak-off drain piping was modified to improve the moisture removal capability of the gland seal exhauster. Two subsequent and unrelated scrams during plant start-uo delayed completion of surveillance testing until November 14, 1989, wien HPCI was returned to service.

Related LERs include:

LER-89-005 - HPCI INOPERABLE DUE TO ELECTRICAL GROUND LER-89-014 - HPCI INOPERABLE DUE TO MOISTURE IN LUBE OIL

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Description The plant was operating at 100 percent of rated power. At 3:25 a.m.

on October 31, 1989, the annunciator for the B side 125 volt DC station battery [EJ) ground detection circuit activated. The p associated volt meter indicated a negative 65 volt potential difference to ground. Following the ground isolation procedure, the ground was traced to-the speed control circuit of the High Pressure Coolant Injection System-(HFCI) [BJ) turbine at.6:25 a.m.

< HPCI was then declared to be inoperable to allow the grounded circuit i

to be de-energized for continued trouble shooting. This placed the plant in a seven day limiting' condition for operation (LCO). As

' required by Technical Specif1 cation 3.5.C, testing of Reactor Core

, , Isolation Cooling (RCIC) [BN), Residual Heat Removal (RHR)/ Low

,. Pressure-Coolant Injection (LPCI) [BO), Low Pressure Core Spray (LPCS)

[BM), and the actuation logic for Automatic Depressurization System

-(ADS) [AD) was performed to demonstrate that tnese systems were operable as required by Technical Specification 4.5.C.1.a. At 11:49 a.m. RCIC failed the surveillance test due to burn up of the injection valve operator motor (LER-89-021). This 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 /> LCO because both HPCI and RCIC were inoperable simultaneously. RCIC was returned to~ service at 6:29 p.m. ending the 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> LCO.

~The Local HPCI speed contrc;. enclosure was opened for trouble shooting

-and inspection; The ground was systematically traced to the i

electrical three pin receptacle on the Woodward EGR actuator. Upon L

-inspection of the receptacle it was determined that the ground path resulted from a build up of corrosion products from one of the three pins, across the insulating ring, to the grounded receatacle mounting l

plate. This receptacle is submerged in oil during turbine operation.

The pin connections were cleaned. After completion of required testing, HPCI was restored to service at 9:10 p.m the same day ending  ;

the seven day LCO.

Less than:three days later, on November 3, 1989, the ennunciator for the B side 125 volt DC battery ground was again activated. The source

! 7 of the ground was again traced to the HPCI speed control circuit.

HPCI was declared to be inoperable at 3:00 a.m. This placed the plant in a new seven day limiting condition for continued operation.

Inspection of the internal surface of the actuator three pin receptacle again showed evidence of a corrosion product conductive path to ground. The shrink tubing seals over the wire insulation and

.the receptacle pins were removed and all surfaces again thoroughly cleaned. A minor modification was approved to apply two layers of a silicone resin conformable coating as an oil resistant, moisture proof, insulating barrier on the electrical receptacle back plate at ggp~ ~- ,

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g g 8I the interface-between the actuator coil lead wires and the receptacle L pins'. The total cure time for this two layer coating was

approximately two days.

t l On November 5, before the coatings were cured, an automatic plant

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shutdown-(scram) (LER-89-020) occurred for reasons not related to this event. The shutdown and subsecuent cooldown of the plant effectively

. nullified the seven day LCO'by placing the plant in a condition which

. did not require HPCI to be operable. The time needed to investigate b the cause-of the scram was used to modify the pipe arrangement from the HPCI shaft gland seal drain to improve the moisture removal capability of the HPCI gland seal exhauster. This in turn reduced a postulated source of entry for water into the turbine lubricating oil and the possible contribution of this moisture to the potential corrosion'and grounding of the speed control circuit. The modification was completed on November 8, 1989, 1

During plant start-up on November 12, 1989, surveillance testing of L

HPCI was completed satisfactorily at less than 150 psig reactor pressure. Before HPCI could be tested at normal reactor pressure a scram was initiated (LER-89-023) during testing of the safety relief

valves.- Surveillance testing of HPCI at normal reactor operating pressure was subsequently completed satisfactorily on November 14 during plant start-up.

Cause Moisture in the turbine-lubricating and control oil system contributed to corrosion product formation and increased electrical conductivity of the oil providing a conductive path to ground. The use of shrink tubing to cover the connection of the speed control circuit to the Amphenol pins was not adequate to prevent contact between the oil and the conductor. A change (from the previous design) in the configuration of the insulating and sealing grommet between the Amphenol ains and the metal mounting alate provided a shorter distance between tae conductor and ground. T:le simultaneous conditions of

. moisture and corrosion products in the oil, oil in contact with the I conductors, and shortened distance to ground and continuously l energized. conductors is believed to have led to the rapid build up of l Ja conductive corrosion product path to ground.

l In 1985 the manufacturer of the speed control had found excessive i accumulation of iron oxides inside the governor actuators of both HPCI I

and the Reactor Core Isolation Cooling (RCIC) [BN) turbines. The actuators were replaced with modified units in March 1985. Four years

, later in April 1989 the HPCI became inoperable (LER-89-005) due to an L electrical ground under circumstances almost identical to the two grounds which are the subject of this LER. At that time the electrical receptacle was removed, cleaned, and reinstalled in the gg,u. mu

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actuator. Although no problems occurred-during the next six months,  ;

.the entire actuctor, including the receptacle was replaced as a 1 a

precautionary measure during the scheduled fall 1989 maintenance

outage. There is a difference in the configuration of the insulating

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and sealing grommet between the original receptacle and the receptacle

-installed during the outage. The grommet of the original connector was a disc of insulating material covering most of the surface area of the mounting plate, with three penetrations for the three pins of the h

-Amphenol connector. The replacement connector consisted of three individual grommeted seals in an exposed metal mounting plate, one

. penetration for each pin. Thus, the distance netween each of the three ains and the grounded surface of the mounting plate was shorter

.than the original connector. Therefore, a reduced quantity of

! corrosion product build-up was sufficient to create a conductive path to ground. .The existence of this shorter path to ground was a contributing factor to the quicker build-up of a ground path (three days instead of three weeks).

Two months prior to this event, in August 1989, the presence of moisture in the turbine oil was identified as a problem when HPCI was declared inoperable (LER-89-014). At that time the principal source o of entry for the moisture was identified as a leaking steam supply valve and turbine seals. The valve and seals were repaired during the scheduled fall 1989 maintenance outage. The lubricating oil was also replaced during that outage. Still undesirable moisture was found in the oil three weeks after start-up. Another contributing source of moisture. build-up was identified as a problem in the turbine shaft seal gland drain piping. The shaft gland seal drain would typically

.be expected to continuously slope, downward directly to a drain u collection tank vented by the gland-seal exhaust fan. However, it was l found that an unintended eleven' inch loop seal was created by the I drain configuration which had existsd since the original plant construction. This in turn reduced the moisture removal capability of

, the gland seal exhauster.

l h Analysis The HPCI system is an engineered safety feature designed to inject a highly-reliable source of water into the reactor at rated pressure and Jin sufficient volume to maintain core coverage through a broad spectrum of hypothetical accident conditions. The principal component ,

is a turbine-driven high pressure, high volume multi-stage centrifugal pump. The steam supply to the turbine comes directly from the reactor vessel thus ensuring availability regardless of the condition of AC electric power supplies.

Because the HPCI system was inoperable due to an electrical ground in the speed control circuit, it qualifies as an event reportable under 10 CFR 50.73 (a)(2)(v) as a condition that alone could have prevented the fulfillment of the safety function of a system needed to remove residual heat or mitigate the consequences of an accident, g ,1.

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[ Although the surveillanca tests of back-up emergency core cooling systems were successfully completed, the motor for the RCIC injection valve failed during testing making RCIC inoperable at 11:49 a.m.

On October 31 while both the HPCI and RCIC systems were unavailable, core cooling would still have been assured by the automatic

'depressurization system [AD) together with low pressure emergency core cooling systems including the two core spray systems [BM) and two Low Pressure Coolant Injection subsystems (BO).

I' RCIC was inoperable for 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and 39 minutes and was restored to service at 6:28 a.m. on October 31, 1989, ending the 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> LCO.

HPCI was inoperable for 14 hours1.62037e-4 days <br />0.00389 hours <br />2.314815e-5 weeks <br />5.327e-6 months <br />, 45 minutes on October 31. HPCI was subsequently inoperable again during power operations from 3:00 p.m.

on November.3 through 5:34 p.m. on November 5 for a total of 2 days, 2 o hours, 34 minutes at which time the plant was shut down by a scram and HPCI'was no longer required to be operable.

Corrective Action

1. The connector was removed, cleaned, and reinstalled following the first grounding (OR-89-200) on October 31, 1989,

2. Following-the occurrence of the second ground (OR-89-205) on November 3, 1989, the three pin Amphenol receptacle was removed, cleaned, and an oil resistant, moisture proof, insulating silicone resin coating was applied to provide a continuous seal of the back mounting plate'and the conductor to pin connections.

L 3. ,The HPCI shaft seal gland dra'in piping was modified to reduce the loop seal from 11 inches to 5 inches to improve the moisture removal capacity of the gland e'xhaust system. Complete

. elimination of the seal was not possible due to the physical l arrangement of other HPCI system piping.

P Additional Information:

1 Failed component data:

JComponent: Governor Actuator, Part Number 9903-026 Manufacturer: Woodward Governor Co.

-NPRD Code: W290 Related LERs:

LER-89-005 of 4/12/89, HPCI Inoperable due to Electrical Ground LER-89-014 of 8/17/89, HPCI Inoperable due to Moisture in Lube Oil g .2.. .

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