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 Office of Nuclear Reactor Regulation
To:
References
IN-98-019, NUDOCS 9805280259
Download: ML031050156 (7)

REVISED - TO ADD ATTA JENT 1

'

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555-0001 June 3,1998 NRC INFORMATION NOTICE 98-19: SHAFT BINDING IN GENERAL ELECTRIC TYPE St[ X

CONTROL SWITCHES

dX

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 alert

addressees to the potential for some General Electric (GE) Type SBM control switches with

spring return function to fail to return to the normal position because the manufacturer failed to

account for shrinkage of the phenolic material as a result of post-mold curing. It is expected that

recipients will review the information for applicability to their facilities and consider actions, as

appropriate, to avoid similar problems. However, suggestions contained in this information

notice 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 prolonged

dual-unit maintenance outage. The licensee was replacing more than 1,100 SBM switches

because the switches were reaching the end of service life and because of concerns about

cracking of the Lexan cam followers, which was originally described In NRC IN 80-13, "General

Electric Type SBM Control Switches Defective Cam Followers" (Accession #8002280650).

During the replacement effort, the licensee discovered that some of the new switches that had

been installed for about a year would not spring return to the reset (normal) position. The

licensee found that 21 out of the 246 Installed replacement switches exhibited the binding. 0

In early January 1998, two of the failed switches were sent to GE-Nuclear Energy (NE) for

evaluation to determine the cause of the switch binding. On January 23, 1998, GE-NE issued a

transfer of information letter to affected customers In accordance with 10 CFR 21.21(b) to alert

them to the possible failure of the SBM switches to return to the normal position after operation

(Accession #9801280338). Subsequently, ComEd determined that the reported deviation

represented a substantial safety hazard because various equipment important to plant safety

ff ected, and submitted a 10 CFR Part 21 notification to the NRC on March, 16, 1998.

• 8.'052ll

IN 98-19 June 3.1998 Discussion

The SBM control switch Is manufactured as a commercial item by GE-Electrical Distribution and

Control (GE-ED&C), Power Management Division, In Malvem, Pennsylvania. GE-NE dedicates

the switches for nuclear safety applications. The switches are used extensively throughout the

nuclear 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 record

about the binding of the SBM switches, some licensees may have procured the switches from

third-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 brass

bearing and the phenolic rear bearing support. The exploded view of an SBM switch in the

attached Figure 1 shows the rear bearing support plate (Item 30, also called the barrier) and the

rear bearing (Item 32) on the switch shaft. The Interference Is caused by post-mold cure

shrinkage of the phenolic material, which takes place for up to 2 years after the phenolic

material Is molded Into the bearing support. GE-ED&C found that the mold used to make the

bearing support had worn over the years to the point that the diameter of the opening for the

brass rear bearing was still within specifications but near the minimum allowable value. The

original 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 allowable

diameter. Only switches with both the undersized hole In the bearing supports and bearings at

the maximum tolerance have experienced failures. Testing confirmed that switches with

bearings of nominal size functioned properly, even with undersized holes In the phenolic

bearing support.

The failed switches were manufactured between November 1996 and February 1997. Although

most of the post-mold cure shrinkage occurs within the first 12 to 18 months, GE conservatively

assumed that switches manufactured after March 1996 may be susceptible. These switches

can be Identified by the last two characters on the green quality control acceptance sticker. The

affected 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 switch

manufacturing process to allow for phenolic post-mold cure shrinkage, and switches

manufactured 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 damage

caused by energizing the momentary circuit for a prolonged period and (2) possible prevention

of control circuits from performing their function because of the failure of the switch contacts to

return to the normal position. GE recommends that licensees with SBM switches manufactured

after March 1996 advise operators to return the switch to the normal position after operation to

preclude any circuit malfunctions. Ucensees should also note that susceptible switches most

likely will fall after about 12 to 18 months after the date of manufacture. Switches more than 2 years old are not thought to be susceptible to binding caused by post-mold cure shrinkage.

IN 98-19 June 3, 1998 Page 3 eT 3 This IN requires no specific action .or written response. However, recipients are reminded that

they are required to consider industry-wide operating experience (including NRC INs) where

practical, when setting goals and performing periodic evaluations under Section 50.65, Requirements for Monitoring the Effectiveness of Maintenance at Nuclear Power Plants," of

Part 50 of Title 10 of the Code of Federal Regulations. If you have any questions about the

information In this notice, please contact one of the technical contacts listed below or the

appropriate Office of Nuclear Reactor Regulation (NRR) project manager.

\N /s/ t d

Jack W. Roe, Acting Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts: Stephen Alexander, NRR

301-415-2995 E-mail: sda~nrc.gov

David Skeen, NRR

301-415-1174 E-mail:dls@nrc.gov

Attachment: Figure 1 - Exploded View of Type SBM Switch

List of Recently Issued NRC Information Notices

DOCUMENT NAME: G:\DLS\IN97-XX.SBM

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KjAttachment 2 IN 98-19 June 3, 1998 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

98-18 Recent Contamination Incidences 5113/98 Part 35 Medical Licensees

Resulting from Failure to Perform

Adequate Surveys

98-17 Federal Bureau of Investigations 5/7/98 All U.S. Nuclear Regulatory

(FBI) Awareness of National Commission fuel cycle and power

Security Issues and Responses and non-power reactor licensees

(ANSIR) Program

98-16 Inadequate Operational Checks 4/30198 All Industrial Radiography

of Alarm Ratemeters Licensees

98-15 Intergrity of Operator Licensing 4120/98 All holder of operating licenses

Examinations for nuclear power reactors except

those that have permanently

ceased operations and have

certified that fuel has been

permanently removed from the

reactor vessel

98-14 Undocumented Changes to 4/20/98 All holders of operating licenses

Non-Power Reactor Safety or construction permits for test

System Wiring research reactors

98-13 Post-Refueling Outage Reactor 4/20/98 All holders of operating licenses

Pressure Vessel Leak Testing for nuclear power reactors except

Before Core Criticality those that have permanently

ceased operations and have

certified that fuel has been

permanently removed from the

reactor vessel

OL = Operating License

CP = Construction Permit

IN 98WXX

MayXX, 1998 Wth information notice requires no specific action or written response.

reminded that they are required to consider Industry-wide operating experience However, recipients are

Information notices) where practical, when setting goats and performing (including NRC

under Section 50.65, Requirements for Monitoring th Effectiveness of periodic evaluations

Maintenance at Nuclear

Power Plants.' of Part 50 of Title 10 of the Code of Federal Regulations.

questions about the Information Ints notice, please contact one of the If you have any

below or the appropriate Office of Nuclear Reactor Regulation (NRR) technical contacts listed

project manager.

Jack W. Roe, Acting Dfrector

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts: Stephen Alexander, NRR

301-415-2995 E-mall: sda~nrc.gov

David Skeen, NRR

301-415-1174 E-mail:disenrc.gov

Attachment: Ust of Recently Issued NRC Information Notices

DOCUMENT NAME: G:\DLSUN97-XX.SBM

ohro a copy of NIs docwnmnt Indicste In ft box CxCopy wo attachmoentnclosure

E=Copy with attacelntendcosure N u No copy

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IN08,X I

MayXX, 1 8ai This IN requires no specific action or written response. However, they uo required to consider Industrywlde operating experience recipients are reminded that

practical, when setting goals and performing periodic evaluations (Including NRC INs) where

4nder Section 60.65, aRequirements for Monitoring tho Effectiveness of Maintenance

Part 50 of Title 10 of te Code of Federat Reguation . If you have at Nuclear Power Planta. of

Information Inthis notice, please contact one of the technical contacts any questions about the

appropriate Office of Nuclear Reactor Regulation (NRR) project listed below or the.

manager.

Jack W. Roe, Acting Director

Dvislon of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts: Stephen Alexander, NRR

301-415-2995 E-mail: sdaenrc.gov

David Skeen, NRR

301-416-1174 E-mail:dlsonrc.gov

Atachment: Figure 1 - Exploded View of Type SBM Switch

List of Recently Issued NRC Information Notices

DOCUMENT NAME: G:%DLSIN97XXS6BM

gv a wpy of efl documwt kxat hIto box CzCopy W/o 8fcnw~cdobw

E-Copy wMlatowhmn/doune N a No copy

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