Information Notice 1996-24, Preconditioning of Molded-Case Circuit Breakers Before Surveillance Testing
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C.
20555-0001
April 25, 1996
NRC INFORMATION NOTICE 96-24: PRECONDITIONING OF MOLDED-CASE CIRCUIT BREAKERS
BEFORE SURVEILLANCE TESTING
Addressees
All holders of operating licenses or construction permits for nuclear power
reactors.
Purpose
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information
notice to alert addressees to the detrimental effect that preconditioning of
molded-case circuit breakers could have on the diagnostic validity of
surveillance tests.
It is expected that recipients will review this
information for applicability to their facilities and consider actions, as
appropriate, to avoid similar problbms.
However, suggestions contained in
this information notice are not NRC requirements; therefore, no specific
action or written response is required.
DescriDtion of Circumstances
During an inspection at the Diablo Canyon Nuclear Power Plant (IR 50-275,
323/94-27 dated December 21, 1994), NRC inspectors noted that the licensee
preconditioned circuit breakers before performing surveillance testing.
Before the overcurrent trip testing, Diablo Canyon staff exercised the circuit
breakers by manually opening and closing them three times. The plant staff
'did not record the as-found condition of the breakers in terms of unexercised
trip currents and times.
During another inspection at the South Texas Project (IR 50-498, 499/94-35 dated January 19, 1995), NRC inspectors noted that the licensee exercised
similar circuit breakers manually at least five times before testing the
overcurrent trip unit.
Discussion
A molded-case circuit breaker is one of the most widely used protective
devices for electrical circuits at nuclear power plants.
Its proper operation
is essential for the protection and safe operation of plant electrical
equipment. Many circuit breakers are continuously energized for long periods.
Often they are in service for years and are rarely, if ever, called upon to
perform a protective function.
Nevertheless, when needed, they must rapidly
isolate a faulted or overloaded circuit to prevent equipment damage.
Therefore, for the safe operation of the electrical distribution system
equipment of a nuclear power plant, it is important to periodically verify
their continued reliability.
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IN 96-24 April 25, 1996 Periodic inspection and testing of circuit breakers in their as-found
condition is an appropriate way of demonstrating the functional operability of
the breaker and of detecting any degradation. However, the practice of
preconditioning before testing (e.g., lubricating pivot points and manually
cycling the breaker) defeats the purpose of the periodic test. Such
preconditioning does not confirm continued operability between tests nor does
it provide information on the condition of the circuit breaker for trending
purposes.
Testing some circuit breakers in the as-found condition can provide
useful data on which to base decisions on surveillance intervals and the
ability of the untested circuit breakers to perform their intended function.
Since only a fraction of the circuit breakers are tested each refueling outage
to justify the operability of the remaining circuit breakers, preconditioning
before testing does not provide the expected assurance of the operability of
remaining breakers which are not tested.
By preconditioning circuit breakers, useful information may be lost because the breaker may not have been capable
of performing its intended function without preconditioning.
To correct this situation, Diablo Canyon Power Plant plans to revise the
electrical maintenance procedure before the next surveillance test has to be
performed.
The revised procedures will state that electrical testing should
be performed before any intentional manual exercising of the breakers, and to
ensure that electrical testing on breakers with removable trip units is
performed before removing the trip unit.
Some plants have older technical specification bases that cite National
Electrical Manufacturers Association (NEMA) Standard AB 2-1980. This version
of the standard specifies mechanical cycling of circuit breakers prior to
electrical testing.
In later versions of this standard, this procedure was
deleted. There appears to be no valid technical need for mechanical cycling
prior to electrical surveillance testing.
The NRC has issued other generic communications on molded-case circuit breaker
applications and testing:
NRC Information Notice (IN) 92-51, and its
Supplement 1, "Misapplication and Inadequate Testing of Molded-Case Circuit
Breakers;" IN 93-26, "Grease Solidification Causes Molded Case Circuit Breaker
Failure to Close;" and IN 93-64, "Periodic Testing and Preventive Maintenance
of Molded-Case Circuit Breakers."
If I
IN 96-24 April 25, 1996 This information notice requires no specific action or written response. 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.
/a
L.."
Brian K. Grimes, Acting Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts:
Sikhindra Mitra, NRR
(301) 415-2783 Internet:skml@nrc.gov
Steve Alexander, NRR
(301) 415-2995 Internet:sda@nrc.gov
Christopher Myers, RIV
(817) 860-8144 Internet:cjm@nrc.gov
Attachment:
List of Recently Issued NRC Information Notices
-tw@ / "Y
K
Attachment
April 25, 1996 LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
Information
Date of
Notice No.
Subject
Issuance
Issued to
96-23
96-22
96-21
96-20
Fires in Emergency Diesel
Generator Exciters During
Operation Following Unde- tected Fuse Blowing
Improper Equipment Set- tings Due to the Use of
Nontemperature-Compensated
Test Equipment
Safety Concerns Related
to the Design of the Door
Interlock Circuit on
Nucletron High-Dose Rate
and Pulsed Dose Rate
Remote Afterloading
Brachytherapy Devices
Demonstration of Associ- ated Equipment Compliance
with 10 CFR 34.20
Failure of Tone Alert
Radios to Activate When
Receiving a Shortened
Activation Signal
Compliance with 10 CFR
Part 20 for Airborne
Loss of Reactor Coolant
Inventory and Potential
Loss of Emergency Mitiga- tion Functions While in a
Shutdown Condition
04/22/96
04/11/96
04/10/96
04/04/96
04/02/96
03/25/96
03/25/96
All holders of OLs or CPs
for nuclear power reactors
All holders of OLs or CPs
for nuclear power reactors
All U.S. NRC Medical to the
Licensees authorized to use
brachytherapy sources in
high- and pulsed-dose-rate
remote afterloaders
All industrial radiography
licensees and radiography
equipment manufacturers
All holders of OLs or CPs
for nuclear power reactors
All material licensees
authorized to possess and
use thorium in unsealed
form
All holders of OLs or CPs
for PWR power plants
96-19
96-18
95-03 Supp. 1 OL = Operating License
CP - Construction Permit
K2
2 IN 96-24 April 25, 1996 This information notice requires no specific action or written response.
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.
original signed by
Brian K. Grimes, Acting Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts:
Sikhindra Mitra, NRR
(301) 415-2783 Internet:skml@nrc.gov
Steve Alexander, NRR
(301) 415-2995 Internet:sda@nrc.gov
Christopher Myers, RIV
(817) 860-8144 Internet:cjm@nrc.gov
Attachment:
List of Recently Issued NRC Information Notices
DOCUMENT NAME:
96-24.IN
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IN 96-XX
April XX, 1996 This information notice requires no specific action or written response.
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.
Dennis M. Crutchfield, Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts: Sikhindra Mitra, NRR
(301) 415-2783 Internet: skmlnrc.gov
Christopher Myers, RIV
(817) 860-8144 Internet: cjm@nrc.gov
Steve Alexander, NRR
(301) 415-2995 Internet: sda@nrc.gov
Attachment:
List of Recently Issued NRC Information Notices
DOCUMENT NAME:
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DATE
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IN 96-XX
April XX, 1996 This information notice requires no specific action or written response.
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.
Dennis M. Crutchfield, Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts: Sikhindra Mitra, NRR
(301) 415-2783 Internet: skmlnrc.gov
Christopher Myers, RIV
(817) 860-8144 Internet: cjm~nrc.gov
Attachment:
List of Recently Issued NRC Information Notices
DOCUMENT NAME: 95-XX.IN
Tech Editor reviewed 9/21/95 To receive a copy of this document, Indicate In the box: 'C' - Copy without enclosures 'E' - Copy with enclosures 'No = No copy
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IN 96-XX
April XX, 1996 This information notice requires no specific action or written response. 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.
Dennis M. Crutchfield, Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts:
Christopher Myers, RIV
(817) 860-8144
Sikhindra Mitra, NRR
(301) 415-2783 Attachment:
List of Recently Issued NRC Information Notices
DOCUMENT NAME:
95-XX.IN
Tech Editor reviewed 9/21/95 To receive a copy of this document. Indicate In the box: wCw = Copy without enclosures 'E" - Copy with enclosures 'N'= No copy
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OFFICIAL RECORD COPY
IN 96-XX
April xx, 1996 This information notice requires no specific action or written response. 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.
Dennis M. Crutchfield, Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts:
Tom Westerman, RIV
(817) 860-8145
Christopher Myers, RIV
(817) 860-8144
Stephen Alexander, NRR
(301) 415-2995
Sikhindra Mitra, NRR
(301) 415-2783 Attachment:
List of Recently Issued NRC Information Notices
DOCUMENT NAME: 95-XX.IN
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IN 96-XX
January xx, 1995 This information notice requires no specific action or written response.
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.
Dennis M. Crutchfield, Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts:
Tom Westerman, RIV
(817) 860-8145
Christopher Myers, RIV
(817) 860-8144
Stephen Alexander, NRR
(301) 415-2995 Sikhindra Mitra,
(301) 415-2783 NRR
Attachment:
List of Recently Issued NRC Information Notices
DOCUMENT NAME:
95-XX.IN
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IK
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IN 95-XX
September xx, 1995
This information notice requires no specific action or written response. 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.
Dennis M. Crutchfield, Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts:
Tom Westerman, RIV
(817) 860-8145 Christopher Myers,
(817) 860-8144 RIV
Stephen Alexander, NRR
(301) 415-2995
Sikhindra Mitra, NRR
(301) 415-2783 Attachment:
List of Recently Issued NRC Information Notices
DOCUMENT NAME: 95-XX.IN
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EFGoodwin
RJK
AChaffee
DMCrutchfield
DATE
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OFFICIAL RECORD COPY
IN 95-XX
September xx, 1995 This information notice requires no specific action or written response. 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.
Brian K. Grimes, Deputy Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical Contacts: Tom Westerman, RIV
(817) 860-8145
Christopher Myers, RIV
(817) 860-8144
Stephen Alexander, NRR
(301) 415-2995
Sikhindra Mitra, NRR
(301) 415-2783 Attachment:
List of Recently Issued NRC Information Notices
DOCUMENT NAME: 95-XX.IN
- , See previous concurrence
To receive a copy of this document. Indicate In the box: 'C'
Copy without enclosures
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CMyers
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SAlexander
DATE
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TECH ED
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DATE
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09/20/95
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DD:DRPM
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BKGrimes
DATE
I /95
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/95 l//
OFFICIAL RECORD COPY
i
IN 95-XX
August XX, 1995 one of the technical contacts listed below or the appropriate Office of
Nuclear Reactor Regulation (NRR) project manager.
Brian K. Grimes, Deputy Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical Contacts:
Tom Westerman, RIV
(817) 860-8145
Christopher Myers, RIV
(817) 860-8144
Stephen Alexander, NRR
(301) 415-2995
Sikhindra Mitra, NRR
(301) 415-2783 Attachment:
List of Recently Issued NRC Information Notices
DOCUMENT NAME:
95-XX.IN
a
nv
Cf
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donument. indicate In the box:
- . See previous concurrence
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Coov without enclosures 'E' - Copy with enclosures 'N'
. No copy
To rAceivA
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RIV
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NAME
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CMyers
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DATE
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/ /95
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/95 OFFICE
TECH ED
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DATE
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PECB:DRPM
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NAME
AChaffee
BKGrimes
DATE
I /95
/ /95
/ /95
OFFICIAL RECORD COPY
K-/
IN 95-XX
August XX, 1995 one of the technical contacts listed below or the
Nuclear Reactor Regulation (NRR) project manager.
appropriate Office of
Brian K. Grimes, Deputy Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical Contacts:
Tom Westerman, RIV
(817) 860-8145
Christopher Myers, RIV
(817) 860-8144
Stephen Alexander, NRR
(301). 415-2995
Sikhindra Mitra, NRR
(301) 415-2783 Attachment:
List of Recently Issued NRC Information Notices
DOCUMENT NAME:
95-XX.IN
To receive a copy of this document. Indicate In the box:
- = See previous concurrence
wEd - Copy with oncosurss
rW - No copy
NCR - Copy without endosurms
OFFICE
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I E RIY
E RIV
E RIV
I E PSIB:DISP I E
NAME
TWesterman
CMyers
I
jSAlexander
DATE
/ /95
/ /95
1/. /95
/95
/ /95 OFFICE
TECH ED
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NAME
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1SKMitra
ASGill
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DATE
08/03/95* gf(g
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/ /95
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/ /95 OFFICE
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C:PECB:DRPM
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DATE/
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OFFICIAL RECORD COPY