Information Notice 1995-53, Failures of Main Steam Isolation Valves As a Result of Sticking Solenoid Pilot Valves

Failures of Main Steam Isolation Valves As a Result of Sticking Solenoid Pilot Valves

ML031060246
Person / Time
Site:	Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, Mcguire, Nine Mile Point, Palisades, Palo Verde, Perry, Indian Point, Fermi, Kewaunee, Catawba, Harris, Wolf Creek, Saint Lucie, Point Beach, Oyster Creek, Watts Bar, Hope Creek, Grand Gulf, Cooper, Sequoyah, Byron, Pilgrim, Arkansas Nuclear, Three Mile Island, Braidwood, Susquehanna, Summer, Prairie Island, Columbia, Seabrook, Brunswick, Surry, Limerick, North Anna, Turkey Point, River Bend, Vermont Yankee, Crystal River, Haddam Neck, Ginna, Diablo Canyon, Callaway, Vogtle, Waterford, Duane Arnold, Farley, Robinson, Clinton, South Texas, San Onofre, Cook, Comanche Peak, Yankee Rowe, Maine Yankee, Quad Cities, Humboldt Bay, La Crosse, Big Rock Point, Rancho Seco, Zion, Midland, Bellefonte, Fort Calhoun, FitzPatrick, McGuire, LaSalle, 05003411, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant
Issue date:	12/01/1995
Revision:	0
From:	Crutchfield D M Office of Nuclear Reactor Regulation
To:
References
IN-95-053, NUDOCS 9511270087
Download: ML031060246 (9)

a- --Z- ;,\-,:v> December 1, 1995NRC INFORMATION NOTICE 95-53:FAILURES OF MAIN STEAM ISOLATION VALVES AS ARESULT OF STICKING SOLENOID PILOT VALVES

Addressees

All holders of operating licenses or construction permits for nuclear powerreactors.PurDoseThe U.S. Nuclear Regulatory Commission (NRC) is issuing this informationnotice to alert addressees to a potential problem involving the failure ofmain steam isolation valves (MSIVs) to close because of sticking solenoidpilot valves. It is expected that recipients will review the information forapplicability to their facilities and consider actions, as appropriate, toavoid similar problems. However, suggestions contained in this informationnotice are not NRC requirements; therefore, no specific action or writtenresponse is required.

Description of Circumstances

On February 18-19, 1995, while LaSalle County Station, Unit 2, was enteringinto a refueling outage, the control room was unable to close two outboardMSIVs. The MSIVs at LaSalle use Ralph A. Hiller electrically operatedpneumatic actuators. The actuator has a pneumatic control assembly, which wasdesigned to use an Automatic Switch Company (ASCO) Model NP8323 solenoid-operated valve (SOV) as the pilot valve to control the opening and closing ofthe MSIVs. The ASCO NP8323 SOV (see Figure 1) is a dual-coil, 3-way solenoidvalve, which is commonly used in both foreign and domestic MSIV applications.The testing interval for the MSIVs that failed had been extended to 118 daysfrom the usual period of 92 days.On June 11, 1995, LaSalle Unit 1 experienced a similar failure in that one ofthe outboard MSIVs failed its 30-day surveillance test. Two internal parts ofthe SOV (the core and the plugnut) stuck together for approximately15 seconds.DiscussionCommonwealth Edison (ComEd), the licensee for LaSalle County Station,initiated an investigation and determined that the ASCO solenoid valves hadfailed to oper:a: because the core (item 9 in Figure 1) and the plugnut(item 8) had stuLk together. The root cause of the sticking of the two piecesappeared to be the presence of a lubricant (Nyogel 775A) and a thread sealant(Loctite PST 550 or Neolube 100), which had formed an adhesive film betweenfr). jet,'-'I9511270087,,,, 4 0 ol 1;/ /fr9S.0's-.3z1tIa IIIu Ao--'IN 95-53December 1, 1995 the core and the plugnut (see NRC Inspection Reports 50-373 & 50-374/95003, 4,5, and 9 covering inspections at LaSalle between February and July 1995, and99900369/95-01 which provides details of an NRC vendor inspection at ASCO onMarch 13-14, 1995).Neither ComEd, ASCO, General Electric (GE), nor the NRC inspectors were ableto conclusively determine how the lubricant or thread sealant got on the coreand the plugnut. The thread sealant cures only under anaerobic conditions.If the thread sealant was improperly installed on any of the connecting pipefittings, or not allowed to cure for 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> before air was blown through thepneumatic actuator, some of the uncured thread sealant could migrate throughthe system. Additionally, on the basis of NRC staff observations of the ASCOassembly techniques and discussions with ASCO personnel, it was concluded thatthe ASCO NP8323 assembly and testing methods could have allowed inadvertentlyapplied lubricant (Nyogel 775A) to be transferred to the core and/or plugnutduring fabrication or operational testing activities.Extensive testing was performed by both ComEd and ASCO in an attempt todetermine the root cause of the sticking SOVs. ComEd concluded that theNyogel 775A lubricant used during assembly at the factory was applied insufficient quantity to deposit a film on the core and plugnut interface.Although the Nyogel 775A alone would not cause the SOV to stick, the licenseebelieves that the Nyogel film acted as a collection point for microscopicamounts of uncured thread sealant that migrated through the pneumaticactuators, and over time enough thread sealant accumulated to cause the SOVsto stick. The licensee noted that all three of the installed valves thatfailed were found to have Nyogel present at the core and plugnut interface.GE and ASCO determined from their testing that Nyogel 775A lubricant would notdevelop sufficient adhesive force between the core and the plugnut to causethem to stick. However, their testing showed that uncured thread sealantapplied to the core and plugnut interface could cause the core and the plugnutto stick together and prevent operation of the SOV.Long-term corrective measures taken by LaSalle personnel included bettercontrol of the use of thread sealant and the replacement of ASCO NP8323solenoid valves with valves made by a different manufacturer (Valcor). Fourof the eight Unit 2 MSIV solenoid valves were replaced with the new valves.The remaining four MSIV solenoid valves had the same model ASCO valvesreinstalled. Before installation, the licensee returned the valves to ASCOfor inspection and cleaning. During inspection at the factory before thevalves were cleaned, some lubricant was found on the plugnut of one of thereturned valves. To ensure only clean valves would be used, new valves wereassembled without using internal lubricants and returned to LaSall IN 95-53December 1, 1995 After the event of June 11, 1995, ComEd did not have enough ASCO valves forthe Unit 1 replacement and obtained four additional valves from an east coastutility. One of the valves from the other utility was found to have amaterial that appeared (and was subsequently analyzed) to be Nyogel 775A onthe core. This utility had 45 valves left in stock. Other utilities also hada supply of the valves.Problems with sticking of model NP8323 valves in MSIV applications were firstidentified in the mid to late 1980s. Some boiling-water reactor (BWR) plantsexperienced failure of the valves as a result of degradation of the ethylenepropylene elastomers and contamination of the valve internals by a foreignmaterial. The foreign material was not present in sufficient amounts to beidentified at the time. ASCO issued a field notification to the industry thatit was discontinuing the NP8323 product line on October 27, 1989, mainlybecause of concerns over the degradation of the elastomers. The vendorrecommended that NP8323 valves be removed from MSIV applications in as timelya manner as possible, and as an interim measure manufactured NP8323 valveswith Viton elastomers (because of its superior performance at hightemperatures) until September 1, 1990.After the LaSalle event in February 1995, the vendor issued a service bulletinrecommending that any plant continuing to use the NP8323 valves for MSIVapplications reconsider such usage.Related Generic CommunicationsProblems with lubricants or thread sealants contaminating solenoid valveinternals are not new. The staff issued Generic Letter 91-15, "OperatingExperience Feedback Report, Solenoid-Operated Valve Problems at U.S.Reactors," to distribute NUREG-1275, Volume 6, to the industry. This documentcontained the NRC staff analysis of recent experience with SOVs at U.S. light-water reactors (primarily 1984-1989). Appendix D to NUREG-1275, Volume 6,listed NRC generic communications on SOYs. Five of the information noticeslisted discuss the sticking of solenoids as a result of contamination of valveinternals from maintenance activity by the licensee or manufacturer assembl IN 95-53December 1, 1995 This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactone of the technical contacts listed below or the appropriate Office ofNuclear Reactor Regulation (NRR) project manager.rutc e- rtg ;Division of Reactor ogram ManagementOffice of Nuclear Reactor RegulationTechnical contacts: Edward R. Schweibinz, RIII(708) 829-9712Joseph J. Petrosino, NRR(301) 415-2979David L. Skeen, NRR(301) 415-1174

Attachments:

1. Figure 1 -ASCO NP8323 3-Way Pilot Solenoid Valve2 List of Recently Issued NRC Information Notices SOLE~i)ID A-Attachment 1IN 95-53December 1, 1995 COILCORE ASSEMBLYSOLENOID BASESUB ASSEMBLYDISC HOLDERASSEMBLYDISC SPRINGPLUG NUT GASKETIG210.13515PLUG NUT ASSEMBLY 8STEM 14CORE ASSEMBLY9SOLENOID BFigure 1 -ASCO NP8323 3-Way Pilot Solenoid Valve Atsvdhment 2IN 95-53December 1, 1995 LIST OF RECENTLY ISSUEDNRC INFORMATION NOTICES..n..es a-InfrM-at i onNotice No.SubjectIsuaeVIIssuanceIssued to...95-47,Rev. 194-13,Supp. 295-13,Supp. 1Unexpected Opening of aSafety/Relief Valve andComplications InvolvingSuppression Pool CoolingStrainer BlockageControl and Oversight ofContractors during Re-fueling Activities andClarificaiton of Applica-bility of Section 50.120 ofTitle 10 of The Code ofFederal Regulations toContractor PersonnelPotential for DataCollection Equipment toAffect Protection SystemPerformanceDeficiencies Identifiedduring ElectricalDistribution SystemFunctional InspectionsLegal Actions AgainstThermal Science, Inc.,Manufacturer of Thermo-Lag11/30/9511/28/9511/22/9511/22/9511/15/95All holders of OLs or CPsfor nuclear power reactors.All holders-of OLs or CPsfor nuclear power reactors.All holders of OLs or CPsfor nuclear power reactors.All holders of OLs or CPsfor nuclear power reactors.All holders of OLs or CPsfor nuclear power reactors.91-29,Supp. 394-86,Supp. 195-52Fire Endurance Test Resultsfor Electrical Raceway FireBarrier Systems Constructedfrom 3M Company Interam FireBarrier Materials11/14/95All holders of OLs or CPsfor nuclear power reactors.95-51Recent Incidents InvolvingPotential Loss of Controlof Licensed Material10/27/95All material and fuelcycle licensees.OL -Operating LicenseCP = Construction Permit IN 95-53December 1, 1995 This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactone of the technical contacts listed below or the appropriate Office ofNuclear Reactor Regulation (NRR) project manager.orig /s/'d by DMIrutchfieldDennis M. Crutchfield, DirectorDivision of Reactor Program ManagementOffice of Nuclear Reactor RegulationTechnical contacts:Edward R. Schweibinz, RIII(708) 829-9712Joseph J. Petrosino, NRR(301) 415-2979David L. Skeen, NRR(301) 415-1174

Attachments:

1. Figure 1 -ASCO NP8323 3-Way Pilot Solenoid Valve2. List of Recently Issued NRC Information Notices'kC~~ qZZ:.TechEd reviewed this document via* Previouslv concurredemail 10/31/95.OFC PECB:DRPM C/PECB:DRPM D t lNAME DSkeen* AChaffee* DCr chfieldDATE 1 10/31/95 111/13/95 1 11-1/95[OFFICIAL RECORD COPY]DOCUMENT NAME: 95-53.IN IN 95-XXNovember XX, 1995 This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactone of the technical contacts listed below or the appropriate Office ofNuclear Reactor Regulation (NRR) project manager.Dennis M. Crutchfield, DirectorDivision of Reactor Program ManagementOffice of Nuclear Reactor RegulationTechnical contacts:Edward R. Schweibinz, Region III(708) 829-9712Internet:ers@nrc.govJoseph J. Petrosino, NRR(301) 415-2979Internet:jjpl~nrc.govDavid L. Skeen, NRR(301) 415-1174Internet:dls~nrc.gov

Attachments:

1. Figure 1 -ASCO NP8323 3-Way Pilot Solenoid Valve2. List of Recently Issued NRC Information Notices*-D 4-atiCnotelu 4nnnAlrr'-f I GV IUUa NJ .UII1UI I GUOFC PECB:DRPM R-III j PSIB:DISP D/DISPNAME DSkeen* ESchweibinz* JPetrosino* FGillespie*DATE 10/31/95 [11/01/95 1 10/31/95 11/03/95I OFC C/PECB:DRPM D/DRPMNAME AChaffee* DCrutchfieldDATE 11/13/95 / /95!-[OFFICIAL RECORD COPY] -4DOCUMENT NAME: G:\DLS\IN95-XX.LAS IN 95-XXNovember XX, 995This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactone of the technical contacts listed below or the appropriate Office ofNuclear Reactor Regulation (NRR) project manager.Dennis M. Crutchfield, DirectorDivision of Reactor Program ManagementOffice of Nuclear Reactor RegulationTechnical contacts:Edward R. Schweibinz, Region III(708) 829-9712Internet:ers@nrc.govJoseph J. Petrosino, NRR(301) 415-2979Internet:jjpl@nrc.govDavid L. Skeen, NRR(301) 415-1174Internet:dls@nrc.gov

Attachment:

List of Recently Issued*DA A^j;A^l-1t#A^lXMNRC Information Notices--rrevOiUSy Lonc.ureu[ OFC PECB:DRPM R-III PSIB:DISP l D/DISPNAME DSkeen* ESchweibinz* JPetrosino* } FGillespie*DATE 110/31/95 11/01/95 110/31/95 111/03/95[OFC CIPECB:DRPM D/DRPMNAME P offee DCrutchfieldDATE 1l/{) /95 / /95'X4 \[OFFICIAL RECORD COPY]DOCUMENT NAME: G:\DLS\IN95-XX.LAS