Information Notice 1998-19, Shaft Binding in General Electric Type Sbm Control Switches

Shaft Binding in General Electric Type Sbm Control Switches

ML031050156
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, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant
Issue date:	06/03/1998
From:	Roe J W Office of Nuclear Reactor Regulation
To:
References
IN-98-019, NUDOCS 9805280259
Download: ML031050156 (7)

REVISED -TO ADD ATTA JENT 1' June 3,1998NRC INFORMATION NOTICE 98-19: SHAFT BINDING IN GENERAL ELECTRIC TYPE St[ XCONTROL SWITCHESdX

Addressees

All holders of operating licenses for nuclear power reactors.

Purpose

The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice (IN) to alertaddressees to the potential for some General Electric (GE) Type SBM control switches withspring return function to fail to return to the normal position because the manufacturer failed toaccount for shrinkage of the phenolic material as a result of post-mold curing. It is expected thatrecipients will review the information for applicability to their facilities and consider actions, asappropriate, to avoid similar problems. However, suggestions contained in this informationnotice are not NRC requirements; therefore, no specific action or written response is required.

Description of Circumstances

In December 1997, the licensee for LaSalle County Station, Commonwealth Edison Company(ComEd), was replacing the GE Type SBM control switches at both units during a prolongeddual-unit maintenance outage. The licensee was replacing more than 1,100 SBM switchesbecause the switches were reaching the end of service life and because of concerns aboutcracking of the Lexan cam followers, which was originally described In NRC IN 80-13, "GeneralElectric Type SBM Control Switches Defective Cam Followers" (Accession #8002280650).During the replacement effort, the licensee discovered that some of the new switches that hadbeen installed for about a year would not spring return to the reset (normal) position. Thelicensee found that 21 out of the 246 Installed replacement switches exhibited the binding. 0In early January 1998, two of the failed switches were sent to GE-Nuclear Energy (NE) forevaluation to determine the cause of the switch binding. On January 23, 1998, GE-NE issued atransfer of information letter to affected customers In accordance with 10 CFR 21.21(b) to alertthem to the possible failure of the SBM switches to return to the normal position after operation(Accession #9801280338). Subsequently, ComEd determined that the reported deviationrepresented a substantial safety hazard because various equipment important to plant safetyff ected, and submitted a 10 CFR Part 21 notification to the NRC on March, 16, 1998.*8.'052ll IN 98-19June 3.1998 DiscussionThe SBM control switch Is manufactured as a commercial item by GE-Electrical Distribution andControl (GE-ED&C), Power Management Division, In Malvem, Pennsylvania. GE-NE dedicatesthe switches for nuclear safety applications. The switches are used extensively throughout thenuclear power Industry as control board switches to actuate safety-related pump motors, motor-operated valves, and circuit breakers. Although GE-NE has informed Its customers of recordabout the binding of the SBM switches, some licensees may have procured the switches fromthird-party dedicating enUties that purchased the switches as commercial-grade components.This Information notice Is intended to alert all licensees to the potential binding Issue.The failure mode has been Identified as binding caused by Interference between the rear brassbearing and the phenolic rear bearing support. The exploded view of an SBM switch in theattached Figure 1 shows the rear bearing support plate (Item 30, also called the barrier) and therear bearing (Item 32) on the switch shaft. The Interference Is caused by post-mold cureshrinkage of the phenolic material, which takes place for up to 2 years after the phenolicmaterial Is molded Into the bearing support. GE-ED&C found that the mold used to make thebearing support had worn over the years to the point that the diameter of the opening for thebrass rear bearing was still within specifications but near the minimum allowable value. Theoriginal GE design did not account for the post-mold cure shrinkage of the phenolic material.The second contributing factor to switch failure Is a brass rear bearing at Its maximum allowablediameter. Only switches with both the undersized hole In the bearing supports and bearings atthe maximum tolerance have experienced failures. Testing confirmed that switches withbearings of nominal size functioned properly, even with undersized holes In the phenolicbearing support.The failed switches were manufactured between November 1996 and February 1997. Althoughmost of the post-mold cure shrinkage occurs within the first 12 to 18 months, GE conservativelyassumed that switches manufactured after March 1996 may be susceptible. These switchescan be Identified by the last two characters on the green quality control acceptance sticker. Theaffected date codes are PL, RL, SL, TL, UL, VL, WL, XL, YL, ZL, NM, OM, PM, RM, SM, TM,UM, VM, WM, XM, YM, ZM, NN, and ON. The manufacturer has improved the SBM switchmanufacturing process to allow for phenolic post-mold cure shrinkage, and switchesmanufactured as of March 1, 1998, should no longer be susceptible to the failure mode.There are two safety concerns regarding the switch binding: (1) possible control circuit damagecaused by energizing the momentary circuit for a prolonged period and (2) possible preventionof control circuits from performing their function because of the failure of the switch contacts toreturn to the normal position. GE recommends that licensees with SBM switches manufacturedafter March 1996 advise operators to return the switch to the normal position after operation topreclude any circuit malfunctions. Ucensees should also note that susceptible switches mostlikely will fall after about 12 to 18 months after the date of manufacture. Switches more than 2years old are not thought to be susceptible to binding caused by post-mold cure shrinkag IN 98-19June 3, 1998Page 3 eT 3This IN requires no specific action .or written response. However, recipients are reminded thatthey are required to consider industry-wide operating experience (including NRC INs) wherepractical, when setting goals and performing periodic evaluations under Section 50.65,Requirements for Monitoring the Effectiveness of Maintenance at Nuclear Power Plants," ofPart 50 of Title 10 of the Code of Federal Regulations. If you have any questions about theinformation In this notice, please contact one of the technical contacts listed below or theappropriate Office of Nuclear Reactor Regulation (NRR) project manager.\N /s/tdJack W. Roe, Acting DirectorDivision of Reactor Program ManagementOffice of Nuclear Reactor RegulationTechnical contacts: Stephen Alexander, NRR301-415-2995E-mail: sda~nrc.govDavid Skeen, NRR301-415-1174E-mail:dls@nrc.gov

Attachment:

Figure 1 -Exploded View of Type SBM SwitchList of Recently Issued NRC Information NoticesDOCUMENT NAME: G:\DLS\IN97-XX.SBMTo receive a copy of this document, indicate In the box C=Copy wlo attachmentlenclosure E=Copy with attachmentlenclosure N = No copy*See previous concurrenceOFFICE PECB:DRPM E HQMB/:DRCH _ D:DRCH C:PECBDRPM _D:DRPMNAME D. Skeen* S. Alexander* R. Spessard* J. Stolz* J. Roe*DATE 05/14/98 05/12/98 05/19/98 05/21/98 05/26/98OFFICIAL RECORD COPY I4311MS WSS edAj lo ma!A popoldx3 -I OJnflq!udnS BumM J)je9e et11ID00 rt03 '0 03o %O 'I-h %aA?ft,Nuotlo8 wnaej-Supds aiM S"tmi!MS joi POsnAN _/* I-

KjAttachment 2IN 98-19June 3, 1998 LIST OF RECENTLY ISSUEDNRC INFORMATION NOTICESInformation Date ofNotice No. Subject Issuance Issued to98-18 Recent Contamination Incidences 5113/98 Part 35 Medical LicenseesResulting from Failure to PerformAdequate Surveys98-1798-1698-1598-14Federal Bureau of Investigations(FBI) Awareness of NationalSecurity Issues and Responses(ANSIR) ProgramInadequate Operational Checksof Alarm RatemetersIntergrity of Operator LicensingExaminationsUndocumented Changes toNon-Power Reactor SafetySystem WiringPost-Refueling Outage ReactorPressure Vessel Leak TestingBefore Core Criticality5/7/984/301984120/984/20/984/20/98All U.S. Nuclear RegulatoryCommission fuel cycle and powerand non-power reactor licenseesAll Industrial RadiographyLicenseesAll holder of operating licensesfor nuclear power reactors exceptthose that have permanentlyceased operations and havecertified that fuel has beenpermanently removed from thereactor vesselAll holders of operating licensesor construction permits for testresearch reactorsAll holders of operating licensesfor nuclear power reactors exceptthose that have permanentlyceased operations and havecertified that fuel has beenpermanently removed from thereactor vessel98-13OL = Operating LicenseCP = Construction Permit IN 98WXXMayXX, 1998 Wth information notice requires no specific action or written response. However, recipients arereminded that they are required to consider Industry-wide operating experience (including NRCInformation notices) where practical, when setting goats and performing periodic evaluationsunder Section 50.65, Requirements for Monitoring th Effectiveness of Maintenance at NuclearPower Plants.' of Part 50 of Title 10 of the Code of Federal Regulations. If you have anyquestions about the Information In ts notice, please contact one of the technical contacts listedbelow or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.Jack W. Roe, Acting DfrectorDivision of Reactor Program ManagementOffice of Nuclear Reactor RegulationTechnical contacts: Stephen Alexander, NRR301-415-2995E-mall: sda~nrc.govDavid Skeen, NRR301-415-1174E-mail:disenrc.gov

Attachment:

Ust of Recently Issued NRC Information NoticesDOCUMENT NAME: G:\DLSUN97-XX.SBMohro a copy of NIs docwnmnt Indicste In ft box CxCopy wo attachmoentnclosure E=Copy with attacelntendcosure N u No copyFICE PECB:DRPM L HQMB/:DRCH D:DRCH _ C:PECBJPME D. SkeAI r R. Spessard J. Stolz J. RoerE 05//98 Om$ 05/ /98 05/98 05/ /98OFFICIAL RECORD COPY IN 08,X IMayXX, 1 8ai