Information Notice 1998-19, Shaft Binding in General Electric Type Sbm Control Switches: Difference between revisions

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| issue date = 06/03/1998
| issue date = 06/03/1998
| title = Shaft Binding in General Electric Type Sbm Control Switches
| title = Shaft Binding in General Electric Type Sbm Control Switches
| author name = Roe J W
| author name = Roe J
| author affiliation = NRC/NRR
| author affiliation = NRC/NRR
| addressee name =  
| addressee name =  
Line 14: Line 14:
| page count = 7
| page count = 7
}}
}}
{{#Wiki_filter:REVISED -TO ADD ATTA JENT 1'UNITED STATES NUCLEAR REGULATORY
{{#Wiki_filter:REVISED - TO ADD ATTA JENT 1
'
                                            UNITED STATES


COMMISSION
NUCLEAR REGULATORY COMMISSION


===OFFICE OF NUCLEAR REACTOR REGULATION===
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
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==
==Addressees==
All holders of operating
All holders of operating licenses for nuclear power reactors.
 
licenses for nuclear power reactors.


==Purpose==
==Purpose==
The U.S. Nuclear Regulatory
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice (IN) to alert
 
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
addressees to the potential for some General Electric (GE) Type SBM control switches with


that some of the new switches that had been installed
spring return function to fail to return to the normal position because the manufacturer failed to


for about a year would not spring return to the reset (normal) position.
account for shrinkage of the phenolic material as a result of post-mold curing. It is expected that


The licensee found that 21 out of the 246 Installed
recipients will review the information for applicability to their facilities and consider actions, as


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


switches exhibited
notice are not NRC requirements; therefore, no specific action or written response is required.


the binding. 0 In early January 1998, two of the failed switches were sent to GE-Nuclear
==Description of Circumstances==
In December 1997, the licensee for LaSalle County Station, Commonwealth Edison Company


Energy (NE) for evaluation
(ComEd), was replacing the GE Type SBM control switches at both units during a prolonged


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


the cause of the switch binding. On January 23, 1998, GE-NE issued a transfer of information
because the switches were reaching the end of service life and because of concerns about


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


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


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


#9801280338).
been installed for about a year would not spring return to the reset (normal) position. The


Subsequently, ComEd determined
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


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


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


safety hazard because various equipment
them to the possible failure of the SBM switches to return to the normal position after operation


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


to plant safety ff ected, and submitted
represented a substantial safety hazard because various equipment important to plant safety


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


to the NRC on March, 16, 1998.*8.'052ll
*8.'052ll


IN 98-19 June 3.1998 Discussion
IN 98-19 June 3.1998 Discussion


The SBM control switch Is manufactured
The SBM control switch Is manufactured as a commercial item by GE-Electrical Distribution and
 
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
Control (GE-ED&C), Power Management Division, In Malvem, Pennsylvania. GE-NE dedicates


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


the nuclear power Industry as control board switches to actuate safety-related
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


pump motors, motor-operated valves, and circuit breakers.
about the binding of the SBM switches, some licensees may have procured the switches from


Although GE-NE has informed Its customers
third-party dedicating enUties that purchased the switches as commercial-grade components.


of record about the binding of the SBM switches, some licensees
This Information notice Is intended to alert all licensees to the potential binding Issue.


may have procured the switches from third-party
The failure mode has been Identified as binding caused by Interference between the rear brass


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


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


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


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


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


notice Is intended to alert all licensees
bearing support had worn over the years to the point that the diameter of the opening for the


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


binding Issue.The failure mode has been Identified
original GE design did not account for the post-mold cure shrinkage of the phenolic material.


as binding caused by Interference
The second contributing factor to switch failure Is a brass rear bearing at Its maximum allowable


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


Is caused by post-mold
the maximum tolerance have experienced failures. Testing confirmed that switches with


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


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
bearing support.


but near the minimum allowable
The failed switches were manufactured between November 1996 and February 1997. Although


value. The original GE design did not account for the post-mold
most of the post-mold cure shrinkage occurs within the first 12 to 18 months, GE conservatively


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


of the phenolic material.The second contributing
can be Identified by the last two characters on the green quality control acceptance sticker. The


factor to switch failure Is a brass rear bearing at Its maximum allowable diameter.
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


Only switches with both the undersized
manufacturing process to allow for phenolic post-mold cure shrinkage, and switches


hole In the bearing supports and bearings at the maximum tolerance
manufactured as of March 1, 1998, should no longer be susceptible to the failure mode.


have experienced
There are two safety concerns regarding the switch binding: (1) possible control circuit damage


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


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


that switches with bearings of nominal size functioned
return to the normal position. GE recommends that licensees with SBM switches manufactured


properly, even with undersized
after March 1996 advise operators to return the switch to the normal position after operation to


holes In the phenolic bearing support.The failed switches were manufactured
preclude any circuit malfunctions. Ucensees should also note that susceptible switches most


between November 1996 and February 1997. Although most of the post-mold
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.


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


occurs within the first 12 to 18 months, GE conservatively
they are required to consider industry-wide operating experience (including NRC INs) where


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


after March 1996 may be susceptible.
Part 50 of Title 10 of the Code of Federal Regulations. If you have any questions about the


These switches can be Identified
information In this notice, please contact one of the technical contacts listed below or the


by the last two characters
appropriate Office of Nuclear Reactor Regulation (NRR) project manager.


on the green quality control acceptance
\N /s/ t d


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
Jack W. Roe, Acting Director


has improved the SBM switch manufacturing
Division of Reactor Program Management


process to allow for phenolic post-mold
Office of Nuclear Reactor Regulation


cure shrinkage, and switches manufactured
Technical contacts:        Stephen Alexander, NRR


as of March 1, 1998, should no longer be susceptible
301-415-2995 E-mail: sda~nrc.gov


to the failure mode.There are two safety concerns regarding
David Skeen, NRR


the switch binding: (1) possible control circuit damage caused by energizing
301-415-1174 E-mail:dls@nrc.gov


the momentary
Attachment: Figure 1 - Exploded View of Type SBM Switch


circuit for a prolonged
List of Recently Issued NRC Information Notices


period and (2) possible prevention
DOCUMENT NAME: G:\DLS\IN97-XX.SBM


of control circuits from performing
To receive a copy of this document, indicate Inthe box C=Copy wlo attachmentlenclosure E=Copy with attachmentlenclosure N = No copy


their function because of the failure of the switch contacts to return to the normal position.
*See previous concurrence


GE recommends
OFFICE        PECB:DRPM            E HQMB/:DRCH _            D:DRCH                C:PECBDRPM          _D:DRPM


that licensees
NAME          D. Skeen*                S. Alexander*          R. Spessard*          J. Stolz*                  J. Roe*
  DATE          05/14/98                05/12/98              05/19/98              05/21/98                  05/26/98 OFFICIAL RECORD COPY


with SBM switches manufactured
I


after March 1996 advise operators
4311MS WSS edAj lo ma!A popoldx3 -I OJnflq!
    udnS BumM J)
              je9e et


to return the switch to the normal position after operation
11 A?


to preclude any circuit malfunctions.
ft


Ucensees should also note that susceptible
uotlo8 wnaej ID00
                                                                                            03      '0
                                                                                                        rt


switches most likely will fall after about 12 to 18 months after the date of manufacture.
03
                          ,N                                -Supds aiM S"tmi!MS joi POsn


Switches more than 2 years old are not thought to be susceptible
o        '%O


to binding caused by post-mold
AN  _/*
                                      I-
                                                                                              I-h%a


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


IN 98-19 June 3, 1998 Page 3 eT 3 This IN requires no specific action .or written response.
NRC INFORMATION NOTICES


However, recipients
Information                                        Date of


are reminded that they are required to consider industry-wide
Notice No.            Subject                      Issuance    Issued to


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


experience (including
Resulting from Failure to Perform


NRC INs) where practical, when setting goals and performing
Adequate Surveys


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


under Section 50.65, Requirements
(FBI) Awareness of National                  Commission fuel cycle and power


for Monitoring
Security Issues and Responses                and non-power reactor licensees


the Effectiveness
(ANSIR) Program


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


at Nuclear Power Plants," of Part 50 of Title 10 of the Code of Federal Regulations.
of Alarm Ratemeters                          Licensees


If you have any questions
98-15            Intergrity of Operator Licensing  4120/98    All holder of operating licenses


about the information
Examinations                                  for nuclear power reactors except


In this notice, please contact one of the technical
those that have permanently


contacts listed below or the appropriate
ceased operations and have


Office of Nuclear Reactor Regulation (NRR) project manager.\N /s/t d Jack W. Roe, Acting Director Division of Reactor Program Management
certified that fuel has been


===Office of Nuclear Reactor Regulation===
permanently removed from the
Technical


contacts:
reactor vessel
Stephen Alexander, NRR 301-415-2995 E-mail: sda~nrc.gov


David Skeen, NRR 301-415-1174 E-mail:dls@nrc.gov
98-14            Undocumented Changes to          4/20/98    All holders of operating licenses


Attachment:
Non-Power Reactor Safety                      or construction permits for test
Figure 1 -Exploded View of Type SBM Switch List of Recently Issued NRC Information


Notices DOCUMENT NAME: G:\DLS\IN97-XX.SBM
System Wiring                                  research reactors


To receive a copy of this document, indicate In the box C=Copy wlo attachmentlenclosure
98-13            Post-Refueling Outage Reactor      4/20/98    All holders of operating licenses


E=Copy with attachmentlenclosure
Pressure Vessel Leak Testing                  for nuclear power reactors except


N = No copy*See previous concurrence
Before Core Criticality                      those that have permanently


OFFICE PECB:DRPM
ceased operations and have


E HQMB/:DRCH
certified that fuel has been


_ D:DRCH C:PECBDRPM
permanently removed from the


_D:DRPM NAME D. Skeen* S. Alexander*
reactor vessel
R. Spessard*
J. Stolz* J. Roe*DATE 05/14/98 05/12/98 05/19/98 05/21/98 05/26/98 OFFICIAL RECORD COPY


I 4311MS WSS edAj lo ma!A popoldx3 -I OJnflq!udnS BumM J)je9e et 11 ID00 rt 03 '0 03 o %O 'I-h %a A?ft ,N uotlo8 wnaej-Supds aiM S"tmi!MS joi POsn AN _/* I-
OL = Operating License
KjAttachment


2 IN 98-19 June 3, 1998 LIST OF RECENTLY ISSUED NRC INFORMATION
CP = Construction Permit


NOTICES Information
IN 98WXX


Date of Notice No. Subject Issuance Issued to 98-18 Recent Contamination
MayXX, 1998 Wth information notice requires no specific action or written response.


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


5113/98 Part 35 Medical Licensees Resulting
Information notices) where practical, when setting goats and performing                  (including NRC


from Failure to Perform Adequate Surveys 98-17 98-16 98-15 98-14 Federal Bureau of Investigations (FBI) Awareness
under Section 50.65, Requirements for Monitoring th Effectiveness of             periodic  evaluations


of National Security Issues and Responses (ANSIR) Program Inadequate
Maintenance at Nuclear


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


===Checks of Alarm Ratemeters===
questions about the Information Ints notice, please contact one of the If you have any
Intergrity


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


Undocumented
project manager.


Changes to Non-Power
Jack W. Roe, Acting Dfrector


Reactor Safety System Wiring Post-Refueling
Division of Reactor Program Management


Outage Reactor Pressure Vessel Leak Testing Before Core Criticality
Office of Nuclear Reactor Regulation


5/7/98 4/30198 4120/98 4/20/98 4/20/98 All U.S. Nuclear Regulatory
Technical contacts:      Stephen Alexander, NRR


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


fuel cycle and power and non-power
David Skeen, NRR


reactor licensees All Industrial
301-415-1174 E-mail:disenrc.gov


Radiography
Attachment: Ust of Recently Issued NRC Information Notices


Licensees All holder of operating
DOCUMENT NAME: G:\DLSUN97-XX.SBM
 
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
ohro a copy of NIs docwnmnt Indicste In ft box CxCopy wo attachmoentnclosure


E=Copy with attacelntendcosure
E=Copy with attacelntendcosure N u No copy
 
N u No copy FICE PECB:DRPM
 
L HQMB/:DRCH
 
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
FICE      PECB:DRPM L HQMB/:DRCH                      D:DRCH          _ C:PECBJP


operating
ME        D. SkeAI                            r      R. Spessard          J. Stolz                  J. Roe


experience (Including
rE        05//98                Om$                  05/ /98              05/98                    05/ /98 OFFICIAL RECORD COPY


NRC INs) where practical, when setting goals and performing
IN08,X      I


periodic evaluations
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


4nder Section 60.65, aRequirements
practical, when setting goals and performing periodic evaluations (Including NRC INs) where


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


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


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


at Nuclear Power Planta. of Part 50 of Title 10 of te Code of Federat Reguation
appropriate Office of Nuclear Reactor Regulation (NRR) project            listed below or the.


.If you have any questions
manager.


about the Information
Jack W. Roe, Acting Director


In this notice, please contact one of the technical
Dvislon of Reactor Program Management


contacts listed below or the.appropriate
Office of Nuclear Reactor Regulation


Office of Nuclear Reactor Regulation (NRR) project manager.Jack W. Roe, Acting Director Dvislon of Reactor Program Management
Technical contacts:    Stephen Alexander, NRR


===Office of Nuclear Reactor Regulation===
301-415-2995 E-mail: sdaenrc.gov
Technical


contacts:
David Skeen, NRR
Stephen Alexander, NRR 301-415-2995 E-mail: sdaenrc.gov


David Skeen, NRR 301-416-1174 E-mail:dlsonrc.gov
301-416-1174 E-mail:dlsonrc.gov


Atachment:  
Atachment: Figure 1 - Exploded View of Type SBM Switch
Figure 1 -Exploded View of Type SBM Switch List of Recently Issued NRC Information


Notices DOCUMENT NAME: G:%DLSIN97XXS6BM
List of Recently Issued NRC Information Notices


gv a wpy of efl documwt kxat hI to box CzCopy W/o 8fcnw~cdobw
DOCUMENT NAME: G:%DLSIN97XXS6BM


E-Copy wMl atowhmn/doune
gv a wpy of efl documwt kxat hIto box CzCopy W/o 8fcnw~cdobw


N a No copy FICE PECB:DRPM
E-Copy wMlatowhmn/doune N a No copy


HQMS:DRCH
FICE    PECB:DRPM            HQMS:DRCH             D:DRC              C:F        RPM          D:RP


D:DRC D:RP C:F RPM VIE D. S S .Ahxae R. tSpmard J. 8U -rE ._5i%8 05P418 0&8 05P198 051 198 OFFICIAL RECORD COPY}}
VIE     D. S               S . Ahxae             R. tSpmard         J. 8U             -
rE   ._5i%8                 05P418               0&8                 05P198                 051 198 OFFICIAL RECORD COPY}}


{{Information notice-Nav}}
{{Information notice-Nav}}

Latest revision as of 04:45, 24 November 2019

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  Entergy icon.png
Issue date: 06/03/1998
From: Roe J
Office of Nuclear Reactor Regulation
To:
References
IN-98-019, NUDOCS 9805280259
Download: ML031050156 (7)
v • d • e


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

To receive a copy of this document, indicate Inthe box C=Copy wlo attachmentlenclosure E=Copy with attachmentlenclosure N = No copy

  • See previous concurrence

OFFICE PECB:DRPM E HQMB/:DRCH _ D:DRCH C:PECBDRPM _D:DRPM

NAME D. Skeen* S. Alexander* R. Spessard* J. Stolz* J. Roe*

DATE 05/14/98 05/12/98 05/19/98 05/21/98 05/26/98 OFFICIAL RECORD COPY

I

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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

FICE PECB:DRPM L HQMB/:DRCH 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

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

FICE PECB:DRPM HQMS:DRCH D:DRC C:F RPM D:RP

VIE D. S S . Ahxae R. tSpmard J. 8U -

rE ._5i%8 05P418 0&8 05P198 051 198 OFFICIAL RECORD COPY


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