ML20006E210

LER 89-019-01:on 891031,HPCI Turbine Declared Inoperable Due to Electrical Ground in Speed Control Circuit.Caused by Conductive Corrosion Products Between Amphenol Type Connector & Mounting Plate.Connector cleaned.W/900212 Ltr

ML20006E210
Person / Time
Site:	FitzPatrick
Issue date:	02/12/1990
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-90-0128, JAFP-90-128, LER-89-019, LER-89-19, NUDOCS 9002220303
Download: ML20006E210 (7)

Text

g@9Q,

3) James A.(Mupatflok.

($kg.

-b #.-

. Shselaer Power Plant '.

P.O. Box 41- 0

.g"'- A Lycoming. New York 13093 fP ' 316 342-3840' h

William Femander il Resident Manager February 12, 1990-JAFP-90-0128 United. States Nuclear' Regulatory Commission Document Control Desk Mail Station P1-137 Washington, D.C. 20555 DOCKET NO. 50-333.

LICENSEE EVENT RF. PORT: 89-019-01 High Pressure Coolant Injection' System Electrical Ground-

Dear Sir:

~

This~is a revision to the Licensee Event Report.which as submitted in'accordance with 10 CFR 50.73(a)(2)(v) on

. November 30,L1989. This revision reclassifies the.LER as "Other" (voluntary).

This-revision, reports an additional-recurrence of an identical electrical ground on December.5, 1989 and the results-of.an' engineering analysis completed on February 5,'1990. The analysis.

indicates that the HPCI system would have performed its intended-function even with.the existence of the electrical ground in the control circuit.

Questio.ns concerning this report may be addressed to

-Mr. Hamilton Fish at (315) 349-6013.

~Very.tru -yours, c

ILLI FERNAN EZ Mt$wO WF:HCF:lar Enclosure q

'c'c : USNRC, Region I lp A

d hp INPO Records Center American Nuclear Insurers 1

50 "$U NRC Resident Inspector p assunsaPDb, 3 o h j

.. %)

f } _

IIRC Po,e M UA fouCLSAR AsOubATORY 0 EAISIsh Appm0VOD Dee es0 at a-0100 8'*a **'**

UCEN8EE EVE di REPORT (LER)

.AmuTv mAme ni acca:T mumen m a.

J AllEl A Fli2PATRICE HCLE AR POWER PL Alli o is lo io iol3 is i3 il0Pl016

"'* High Pressure Coolant Injection Turbine Inoperable Due to Electrical Ground In Soeed Control Circuit Due to corrosion Product Build-Up tweeff DAT9 401 LeR 9eussen te REPORT Daft til OTMSA P ActLITies serv 0Lygo el 4808ftM DAY YEAR VSAR .

'8UTa $$ ns04 Tee Dav vtAR ' AC'6st, naases DOCKET seuesotatti 015l01010 1 t l

- ~~

1l0 3l1 89 8l9 0 l1 [9 0 l1 0 l2 1l2 9l0 o,g,o,o,o, , ,

,,,,,,,,,, T== no 0.T e euemrfe0,uneuA=T 70 tMe neavinemsoe 0, ie Cea i to c a, m n.i asa m nem mw m im. aH=: ruine a Os.4EBeeH1H4 e0 asteH1l es.?stetGHet 73,71tes ne, 1 i 001 . wmm _

m.m m _

a w en. g g,j;.,g.

3 g 4 'y y ,,_

suaemmHe su m.iuHu se.rmiseH.=HAe meas g t;C.q g ' somemHm m.rswmm es w eH.*'*8 Voluntary

's t < '

se.4eswmm es.rsesHaHet so.tseeHeHas LIC88dBE0 CONTACT POR That L8R 113)

TRLEPMoelt NyheseR Hamilton C. Fish '"**

3 115 3 4191-160 11 1 3 00HPL879 0006 LHet MA SACM CondP00000ff F AILUAt DGeCReseo see TMS Repo#T tia CAvee OYSY848 Cot #0segnT

"(88QO R

d'y8 '

CAust SYtfEM ConsPONeest

""A yy "O R Ays E s

X BU 651 W2 9 0 Y .w'b'3 q l I I i i i i i i i l i i Aa?%e'5 l t I i l l 1 l l i i l l l M' N' k'5 f supetsa4NTAL R$80Rf GKPSCT90 He 400NTM DAY YBAR sue..esio.

] V88 fit res. eengsmus fxptCTfD suseness0Ar DA rt; U I'

[ ae0 l l g Asernacton. <.._. __...-.e.,n.,

Update Report - Original Report Date 11/30/89 EIIS Codes are in []

On 10/31/89 at 0625, the High Pressure Coolant Injection (HPCI) [BJ system was declared inoperable due to an electrical ground in the speed cc,ntrol circuit. Build-up of conductive corrosion products between an amphenol type connector in an oil environment and its mounting plate was contributed tc by moisture in the oil, a change in the connector mounting grommet configurrtion, and inadequate shrink tube insulation over the conductor connection to the amphenol pins. The connector was cleaned and HPCI restored to service at 2110. On 11/3/89 at 0300 HPCI was declared inoperable for the same reason. The connector was removed, cleaned, and a silicone resin coating was applied to seal the pins, 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 unrelated scrams delayed completion of surveillance testing until 11/1t/89 wben HPCI was returned to service.

On 12/5/89 HPCI was declared inoperable for an electrical ground. The actuator was replaced and HPCI restored to service 12/12/89. Analysis completed 2/5/90 concluded that HPCI would have performed its safety function and therefore it was not, in fact, ir.o p e rab l e during those time intervals when the ground was present.

Related LERs: 89-005 and 89-014.

1 1

p l'e n

• I. g, en vs muca ...vutoa, ca UCENSEE EVENT REPORY (LER) TEXT CONTINUATION **aovio oue no >=-cio.

iamii se

.asyrv m ooc.ii momea a, n.... ...,,,,

JAbfl A, fli!PAf tlCR . . . "tM,N l'nt; ggCitAt POWit PL ANT o is lo lo lo l3 l: p 8l9 -

0 l1l9 -

0l1 8l2 or 8 l6 rent -. . mc ,n Update Report - Original Report Date 11/30/89 EIIS Codes are in []

Description The olant was operating at 100 percent of rated power. At 3:25 A.M. on Octo'aer 31, 1989, the annunciator for the B side 125 volt DC station battery [EJ) ground detection circuit activated. The 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 (HPCI) [BJ) turbine at 6:25 A.M.

HPCI was then declared to be inoperable to allow the grounded circuit to be deenergized for continued troubleshooting. This placed the plant in a 7-day Limiting Condition for Operation.(LCO). As required by Technical Specification 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 aerformed to demonstrate that these systems were operable as required ay 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-hour LCO because both HPCI and RCIC were inoperable simultaneously. RCIC was returned to service at 6:29 P.M., ending the 24-hour LCO.

The local HPCI speed control enclosure was opened for troubleshooting and inspection. The ground was systematically traced to the electrical

, three-pin _ receptacle on the Woodward EGR actuator. Upon 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 receptacle mounting 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 7-day LCO.

Less than three days later, on November 3, 1989, the annunciator for the B side 125 volt DC battery ground was again activated. The source 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 7-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 g ... .

n L' -  ;

ua vea.. 4.vuvo., . , .

"" i UCENSEE EVENT REPORT (LER) TEXT CONTINUATON **aovio owe =o sinom noen emn VAC6Livt04A15 m pocast wueet.44' Lt. Wune.4 A tel

• A DS 13)

JAufl A.Fl12 PATRICK pa " W," "'ut; NgCLE AR POW [R PL Ahi o ooo 8l9 ._ 0 p [9 _

0 [1 0l3 o' 01 6 venv. . m cs am.mm 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 backplate at the interface between '

the actuator coil lead wires and the receptacle pine. The total cure  :

time for this two-layer coating was approximately two days.  :

On November 5, 1989, before the coatings were cured, an automatic plant shutdown (scram) (LER 02.0 ) occurred for reasons not related to this i event. The shutdown and subsequent cooldown of the plant effectively  :

nullified the 7-day LCO by placing the plant in a condition which did not require HPCI to be operable. The time needed to investigate the i 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 i on November 8, 1989.

During plant start-up on November 12, 1989, surveillance testing of 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 HPCl at normal reactor operating pressure was subsequently completed satisfactorily on November 14, 1989 during plant start-up.

On December 5, 1989, while the HPCI system was out of service (LER-89-025) due to unrelated problems with high steam flow isolation signals, a fluctuating 3) volt DC ground was traced to the HPCI electro-hydraulic (EGR) actuator. The ground again involved the three-pin connector which had been previously insulated with a silicone resin coating. The complete actuator mechanism was replaced with an actuator of the original design. Continued investigation of concerns with the turbine ramp speed control circuit and high steam flow isolation setpoint delayed a declaration of operability until December 12, 1989 (LER-89-025).

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 actuator coil wirea to the amphenol ains and the metal mounting plate provided a shorter distance between the conductor and ground. The simultaneous conditions of moisture and corrosion products in the oil, oil in contact with the conductors, and shortened distance to ground and continuously energized conductors is believed to have led to the rapid build-up of a conductive corrosion products path to ground, g,o= =..

e .

L 4 ==c m.* v2 muc6 == nieuuronvca UCENGEE EVENT REPORT (LER) TEXT CONTINUATION maovep o =o sino-eio.

=eass sv *

'ac14sf v tiaast e,s pocaat musstem tal 6te wunasta :si tatt tai J AN[$ A. FITZPATRICK i.. " W .; r W.n NUCl[ AR POW [R PL ANT o ooo 89 --

0l1l9 __

0 l1 014 0F 0 l6 vart n- . a.c w an.mm In 1985 the manufacturer of the speed control had found excessive accumulation of iron oxides inside the governor actuators of both HPCI 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 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 actuator.

Although no problems occurred during the next six months, the entire actuator, including the receptacle, was replaced as a precautionary measure during the scheduled fall 1989 maintenance outage. There is a difference in the configuration of the insulating and sealing grommet between the original receotacle 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 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 between each of the three pins and the grounded surface of the mounting plate was shorter then the ori Final connector. Therefore, a reduced quantity of corrosion products 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 of entry for the moisture was identified as a lerking steam supply valve and turbine seals. The valve and seals were remaired 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 contributin.; 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 gland seal condenser vented by the gland seal exhaust fan. However, it was found that an unintended eleven inch loop seal was created by the drain configuration which had existed since the original plant construction.

This in turn reduced the moisture removal capability of the gland seal exhauster.

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 in sufficient volume to maintain core coverage through a broad spectrum of hypothetical accident conditions. The principal component is a go . .

. _a

P

- anc ana u s aucuan neouc,on, ca ,

UCENSEE EVENT REPORT (LER) TEXT CONTINUATION ***aovto owe =o mo-m.

tatsmil 64196 f acau,, esasst til occant wuasSta tal Ltm humasta to: Pact tai JAut$ A.FlilPATtlCE saa " C'A" 'l'#.?: t NUCLEAR POWit PLANT o lo ojo 3l: 8 l9 -

0 l1 l9 -

0l1 0l5 or 816 turbine-driven high pressure, high volume multi-state 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.

The HPCI system was originally (November 30, 1989) reported in this LER as being inoperable. However, a subsequent engineering analysis (Calculation [[::JAF-90-003|JAF-90-003]]) was completed on February 5, 1990. This analysis concluded that the electrical ground faults which developed in the HPCI EGR actuator circuits would not have affected the operability of this circuit. A single DC pin to ground fault at the HPCI EGR l actuator coil connector would not have adversely affected the safety function of the coil. Therefore, the HPCI system was in fact operable and when the grounds were present.

Because the HPCI system was originally thought to be inoperable due to an electrical ground in the speed control circuit, it qualified 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. Since the engineering analysis concluded that HPCI was in '

fact operable, this LER is reclassified as voluntary with HPCI having -

heen removed from service for planned maintenance.

Although the surveillance 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, 1989 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 [B0].

RCIC was inoperable for 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />, 39 minutes and was restored to service at 6:28 P.M. on October 31, 1989, ending the 24-hour 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, 1989. HPCI was subsequently inoperable again during power operations from 3:00 P.M. on November 3, 1989 through 5:34 P.M. on November 5, 1989 for a total of 2 days, 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />, 34 minutes at which time the plant was shutdown 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. I l

l l

I L

$4N

r 6

• 'anic e asma uJ wucLean neoutitoa, consesses.on UCENSEE EVENT REPORT (LERI TEXT CONTINUATION waovto one =o mo-oio.

tapiate tones pa56LsTV Inhaft n> Docatt Nuestem til Lla wunseem tal Past tas J Aut$ A. FIT!PAf tlCK ia. " t'a" "h?J:

NWCLEAR POWit PL ANT

. a.c w m.w, oislo olol3l313 8 19 -

O lil9 -

0 11 0 16 oF 016 vert .

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

3. Following the occurrence of the third electrical ground on December 5, 1989, the HPCI electro-hydraulic actuator was replaced with an actuator of the original design which was obtained from the inventory of another plant.

, 4. The HPCI shaft seal gland drain piping was modified to reduce the loop seal from 11 inches to 5 inches to improve the moisture removal capacity of the gland exhaust system. Complete elimination of the seal was not possible due to the physical arrangement of other HPCI system piping.

Additional Information:

Failed component data:

Component: Governor Actuator, Part No. 9903-026 Manufacturer: Woodward Governor Co.

NPRD Codet W290 Related LERs:

LER-89-005 of 04/12/89 - HPCI Inoperable Due to Electrical Ground LER-89-014 of 08/17/89 - HPCI Inoperable Due to Moisture in Lube Oil This LER is revised to reflect the reclassification as voluntary based on an analysis that concluded that the presence of the electrical ground did not render the HPCI inoperable.

l l

L l

g,.o. -.

w _  :