ML20005E852

LER 89-043-00:on 891201.two Outboard MSIVs Inoperable Due to Failure of Corresponding Fast Closure solenoid-operated Valve.Caused by Incomplete Removal of Silicone Lubricant. Lubricant Removed by Application of Acetone.W/900102 Ltr

ML20005E852
Person / Time
Site:	River Bend
Issue date:	01/02/1990
From:	Booker J, England L GULF STATES UTILITIES CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-89-043, LER-89-43, RBG-32045, NUDOCS 9001110179
Download: ML20005E852 (5)

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GULF STATES UTILITIES COMPANY fliVER BEND ST ATlDN PO$1 OFFICE BOX 270 ST FRANC

Sv1LLE LOUIStANA 70716 ,

. ARE A CODE f.04 C35 6094 3464651 L-g-

January 2 , 1990 '

~RBG- ' 32045 '

. File Nos. G9.5,' G9.25.1.3 U.S. Nuclear Regulatory Cm mission s H Document Control-Desk

-. Washington, D.C. 20555 ,

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Gentlemen: .

River Bend Station - Unit 1 '

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Docket No.- 50-458 Please-find enclosed Licensee Event Report tio. 89 043'for River Bend Station - Unit 1. This report is being subnitted pursuant  ;

to 10CFR50.73.

' Sincerely,

/M

. E. Booker Manager-River Bend Oversight River Bend Nuclear Ccoup cc: U.S. Nuclear Regulatory Cmmission -

611 Ryan Plaza Drive, Suite 1000 Arlington, TX 76011 NRC Resident Inspector P.O. Box 1051 St. Francisville, IA 70775 INPO Records Center 1100 Circle 75 Parkway Atlanta, GA 30339-3064 R II -

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LICENSEE EVENT REPORT (LER)

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RIVER BEND STATION 0 l 5 l 0 l 0 l 0 la lc; lg 1 lOFl0 la TITLE te Failure of'Two Outboard Main Steam Isolation Valves EVENT DATE 15) LER NUnasER ts) REPORT DATE 176 OTHER f ACILITIES INVOLVED (0)

MONTH DAY YEAR YEAR saav .As geys, MONTH DAY YEAR ' AciLitv NAuss DOCK E T, NUMBE RISI O15lololog l l 1l2 0l 1 89 8l 9 0l 4l 3 o l0 O! 1 0l2 9l 0 0'l5 0l0l0 l l OPE R ATING THis REPORT IS SUSMITTED PURSUANT TO THE RbOUIREMENTS OF 10 CFR l ICneca ene or more re ene fonew aps till asODE m 4 20 40216) to 4061st 50.73 eH2ibel 73.71thi 20 4064eH11bl 50.381el(1) S0.736 ell 2Het 73.711st

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_ gMER i,sg g,ue 20 406deH1Hesel 60 734eH2H6l 50.73ieH2HveniHA) MAI 20 406tell1Hwi 60.73te H2Hiil 60.73teH21tvia(86 2d 40Hel41Hvl 50.73 eH2H66el 50 734eH211st LICENSEE CONT ACT FOR TMi$ LER {12l NAME TELEPHONE NUMBER ARE A CODE L. A. England - Director, Nuclear Licensing 51 01 4 31 RI 11 -1 41 11 41 c COMPLETE ONE LINE FOR E ACM COMPONENT f ALLURE DESCR10ED IN THl$ REPORT {13) ygOn,Ta man AC- OR?A E CAUSE SYSTEM COMPONE NT MA%AC. q 5 CAUSE SYSTEM COMPONENT g g qpp D stb IIISIV At6l019 Y l l 1 i t i i D SB I lIISIV Al6l0l9 Y l l l l l l l SUPPLEMENT AL REPORT EXPECTED 1141 l MONTH DAY YEAR SU6 MIS $10N YES til pas con.poete gM9fCTfD $U0%dISSION DA TEI NO l l l AS$ TRACT (toner to idOO speces # e escrosemery Mrse* seap<e space typewirefea haest (It' At.2135 on 12/01/89, with the unit in Mode 4 (cold shutdown), main steam isolation valves (MSIVs) 1821*AOVF028A and IB21*AOVP028D were found to be inoperable due to failure of the corresponding fast closure solenoid operated valve (SOV). All remaining MSIVs were closed and each remained in the full closed position indicating proper operation of the fast closure solenoid operated valve (SOV) and the capability of the MSIVs to close on a valid isolation signal. This event is similar to that previously reported in LER 88-023.

In order to preclude recurrence of the failure of the SOVs, all eight (8) MSIV fast closure SOVs were replaced with new SOVs. Prior to installation, the Dow-Corning 550 lubricant was removed from all components within the SOVs. The cause of this event was incomplete removal of the silicone lubricant subsequent to the previously reported event. Gelling of the lubricant has been determined to be the cause of the failure for the fast closure SOVs.

Only two of the eight MSIVs failed to close with the remaining six functioning properly. The closure of a minimum of one MSIV in each of the four main steam lines demonstrated that had a valid isolation been required, each main steam line would have been isolated thereby ensuring adequate protection of the health and safety of the public.

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l 012 0F 0h ww .. m ranc a onawnn REPORTED CONDITION At 2135 on 12/01/89, with the unit in Mode 4 (cold shutdown), outboard main steam isolation valves (MSIVs) (*ISV*) 1B21*AOVF028A and

.lB21*AOVF028D were found to be inoperable due to failure of the corresponding fast' closure solenoid operated valve (SOV). Because i reactor power was at 0 percent, and the inboard isolation valves had. '

previously been closed, no immediate actions relative to plant operating conditions were taken.

The River Bend Station Technical Specifications require the MSIVs to  ;

be operable in Modes 1, 2, and 3. The River Bend Technical Specifications allow continued operation with one or more MSIVs inoperable provided that the affected steam line is isolated by use of '

a deactivated MSIV within 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />. The SOVs that failed were both on

' outboard MSIVs, and therefore would not have' prevented isolation of the affected main steam lines. This event is being reported pursuant to 10CFR50.73 (a) (2) (v) because even though six of the eight MSIVs functioned properly, discovery of some evidence of hardened lubricant inside an unfailed inboard SOV raised the question of the potential for a common mode failure.

INVESTIGATION-

. After shutdown of the reactor, the MSIVs are closed.using System Operating Procedure (SOP)-0011, " Main Steam System". Specifically, the MSIVs are closed by transferring the MSIV control switch (*HS*)

from the " auto" position to the "open-test" position and then the test pushbutton is depressed. The test pushbutton activates the slow-closure SOV allowing the MSIV to close. When the indicating lamps (*IL*) show that the MSIV has reached the full closed position, the control switch is transferred to the "close" position, de-energizing both coils on the fast closure SOV. If the MSIV remains  ;

in the closed position, the fast closure SOV vented properly. If the MSIV returns to the open position, the ammeters (*II*) and isolation indication lamps on a control room back panel are checked to verify that power has been removed from both coils of the fast closure SOV.

If all indications are that both coils of the fast closure SOV are de-energized and the MSIV is still open, failure of the fast closure SOV to vent is indicated because all other components functioned properly to allow slow closure of the MSIV. Closure of the MSIVs is performed in this manner to minimize the potential for inducing a plant transient while at power, and to preclude unnecessary wear to the MSIV seating sucfaces during shutdowns.

Prior to removal of the failed SOVs from the MSIV, Engineering personnel inspected the MSIVs in-situ to determine if any physical evidence of degradation existed. The MSIVs were inspected for discoloration, rust, and other types of deposits that would indicate the occurrence of steam impingement or high humidity. In addition, NICF0mm3esa e u 8 G,01966 0 424 634,466 SW

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l 0 13 M Ok van. . ane a muw nn the exhaust ports were checked for particulate matter which may have blocked.the exhaust pilot area of the SOVs. No evidence of steam impingement or other adverse environmental factors were apparent on the external surfaces of the MSIV actuator or SOV, and no particulate-matter.was found in or around'the exhaust ports. The failed SOVs were then removed from service for disassembly and internal inspection.

Valve 1B21*AOVF028YD (SOV) was disassembled and subjected to internal inspection using an approved plan that had been developed for the previous event (LER 88-023). O-rings and gaskets (EPDM) had taken-varying degrees of compression set, and one 0-ring had flowed slightly, but all gaskets and 0-rings were intact and no evidence that the elastcairs had contributed to the observed failures was found.

The EPDM disc holder cubassembly seat (exhaust seat) was inspected for degradation - (reference NRC Information Notice 89-66) and while a compression set was noted, no evidence of bonding to the exhaust pilot orifice (brass mating surface) was found. Examination of the "B" core assembly revealed an amber colored ring on the surface that mates with the plugnut assembly when energized. The amber colored ring was hardened and had some darkened areas observable. Inspection of the plugnut assembly revealed similar material deposits. From these observations, it was determined that the failures had occurred as a result of gelling of the silicone lubricant contained within the SOVs similar to that reported in LER 88-023.

As a result of the previous event at RBS, the silicone lubricant (Dow-Corning 550) had been removed from the metallic portions of the SOVs prior to their return to service. Removal of the lubricant was performed using a modified version of the vendor's manual with Engineering review and approval. The modification to the vendor's manual only removed the lubricant from the metallic portions of the SOVs and failed to delete a step which called for application of the lubricant to all internal 0-rings. It is surmised that reintroduction of the lubricant contaminated the "B" core assembly and the plugnut resulting in the observed failure. To validate the failure mechanism, SOV 1B21*AOVF022YA (inboard) was removed from service and subjected to disassembly and internal inspection. Similar compression set was found on all internal 0-rings and gaskets, and a more severe compression set was found on the disc holder subassembly (exhaust seat) than that observed for the failed SOV. An amber colored ring was found on the mating surfaces of the "B" core assembly and the plugnut although much smaller in quantity thun that observed on the failed SOV. The findings indicated that residual lubricant had existed in other SOVs as well.

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l 0 l4 W D l4 i n. . ne w meawim CORRECTIVE ACTION In order to preclude recurrence of'the failure of the SOVs, all eight *

.(8) SOVs were replaced. Prior to their installation, the Dow-Corning 550 lubricant was removed from the SOVs by placing all metallic components in an ultrasonic bath using Acetone, and wiping all non-metallic components (except coil assemblies) with Acetone. (Note:

ASCO has provided GSJ with a statement that silicone lubricant is no longer used in the manufacture of the NP8323 SOV). Interim corrective action includes monthly cycling of the' fast closure SOVs intil the long term corrective actions (replacement of the dual coil SOVs with a single coil design) are implemented.

SAFETY ASSESSMENT The MSIVs are not required to be operable in Mode 4 Icold shutdown).

Only two of the eight MSIVs failed to close with the remaining six functioning properly. The closure of one MSIV in each affected steam line demonstrated that had a valid isolation signal occurred, each main steam line would have been isolated thereby ensuring that the health and safety of-the public was adequately protected at all times.

NOTE: Energy Industry Identification System Codes are identified in

. the text as -(*XX*).

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