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

1. 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

1. 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

To receive a copy of this document, indicate In the box C=Copy wlo attachmentlenclosure

E=Copy with attachmentlenclosure

N = No copy*See previous concurrence

OFFICE PECB:DRPM

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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 98-16 98-15 98-14 Federal Bureau of Investigations (FBI) Awareness

of National Security Issues and Responses (ANSIR) Program Inadequate

Operational

Checks of Alarm Ratemeters

Intergrity

of Operator Licensing Examinations

Undocumented

Changes to Non-Power

Reactor Safety System Wiring Post-Refueling

Outage Reactor Pressure Vessel Leak Testing Before Core Criticality

5/7/98 4/30198 4120/98 4/20/98 4/20/98 All U.S. Nuclear Regulatory

Commission

fuel cycle and power and non-power

reactor licensees All Industrial

Radiography

Licensees All holder of operating

licenses for nuclear power reactors except those that have permanently

ceased operations

and have certified

that fuel has been permanently

removed from the reactor vessel All holders of operating

licenses or construction

permits for test research reactors All holders of operating

licenses for nuclear power reactors except those that have permanently

ceased operations

and have certified

that fuel has been permanently

removed from the reactor vessel 98-13 OL = Operating

License CP = Construction

Permit

IN 98WXX MayXX, 1998 Wth information

notice requires no specific action or written response.

However, recipients

are reminded that they are required to consider Industry-wide

operating

experience (including

NRC Information

notices) where practical, when setting goats and performing

periodic evaluations

under Section 50.65, Requirements

for Monitoring

th 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 ts notice, please contact one of the technical

contacts listed below or the appropriate

Office of Nuclear Reactor Regulation (NRR) 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 FICE PECB:DRPM

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D:DRCH _ C:PECBJP ME D. SkeAI r R. Spessard J. Stolz J. Roe rE 05//98 Om$ 05/ /98 05/98 05/ /98 OFFICIAL RECORD COPY

IN 08,X I MayXX, 1 8ai This IN requires no specific action or written response.

However, recipients

are reminded that they uo required to consider Industrywlde

operating

experience (Including

NRC INs) where practical, when setting goals and performing

periodic evaluations

4nder Section 60.65, aRequirements

for Monitoring

tho Effectiveness

of Maintenance

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

.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.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 hI to box CzCopy W/o 8fcnw~cdobw

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