Information Notice 2002-34, Failure of Safety-Related Circuit Breaker External Auxiliary Switches at Columbia Generating Station
| ML023300015 | |
| Person / Time | |
|---|---|
| Site: | Columbia  |
| Issue date: | 11/25/2002 |
| From: | Beckner W NRC/NRR/DRIP/RORP |
| To: | |
| Hodge, CV, NRR/DRIP/RORP, (415-1861) | |
| References | |
| IN-02-034 | |
| Download: ML023300015 (7) | |
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, DC 20555-0001 November 25, 2002 NRC INFORMATION NOTICE 2002-34: FAILURE OF SAFETY-RELATED CIRCUIT
BREAKER EXTERNAL AUXILIARY SWITCHES
AT COLUMBIA GENERATING STATION
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 inform
addressees of failures of circuit breaker external auxiliary switches because of inadequate
maintenance of the associated switchgear. 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 in this information notice are not NRC requirements;
therefore, no specific action or written response is required.
Description of Circumstances
On February 14, 2002, at the Columbia Generating Station, the licensee initiated a required
plant shutdown because of a mechanical problem in an emergency diesel generator (EDG)
output circuit breaker. Although the breaker was capable of closing and connecting the EDG to
its safety bus, its cubicle-mounted auxiliary contacts, called mechanism-operated cell (MOC)
switches, failed to change state as designed. The licensee determined that the MOC switch
failures associated with this breaker and other breakers of this type resulted in failure of various
electrical distribution system control functions, including some non-safety loads not being
removed from the EDG bus following an accident signal.
On June 29, 2001, during a refueling outage at the same plant, after breaker replacement, a
standby service water pump breaker MOC switch failed to reposition during breaker closure.
This failure recurred on November 19, 2001. A MOC switch contact prevented the pump
discharge valve from opening after a pump start, rendering the service water system and
supported systems, such as EDGs, inoperable.
Discussion
The licensee believes the failure was caused by excessive resistance in the linkage between
the breaker and the MOC switches. The licensee had not performed periodic maintenance on
this linkage in the breaker cell housing. Over time, dirt and dust accumulated and grease
hardened to increase the resistance in the linkage mechanism.
During the preceding refueling outage, ending in July 2001, the licensee replaced 22 safety- related 4160-volt circuit breakers, exchanging older design Westinghouse Type DHP-350 (air- magnetic) breakers with newer design, Westinghouse-dedicated, Cutler Hammer Type
DHP-VR (vacuum replacement) breakers using Sure-CloseTM mechanisms to operate the MOC
switches.
In the DHP-VR, the Sure-CloseTM mechanism operates the MOC switches independently of the
breakers main contacts so that the MOC switches can be operated at a slower speed to avoid
excessive kinetic energy and wear. In addition, the external MOC switch linkage drag wont
stall the main contacts, even if the linkage is poorly maintained. However, because the design
of the Sure-CloseTM mechanism intentionally limits the force on the linkage, it does not have
sufficient force margin to overcome the excessive drag of poorly maintained MOC switch
linkages (for an explanation of Sure-CloseTM operation, see DHP -VR SURE CLOSE
Mechanism: A Kinematic System Solution for Medium Voltage Circuit Breaker MOC Auxiliaries
Operation, U. S. Patent 5,856,643, Ronald E. Vaill, available from Cutler-Hammer Nuclear
Programs).
The Columbia Generating Station experience illustrates that the newer design breakers with the
Sure-CloseTM mechanisms operating the MOC switches depend more heavily on the state of
maintenance of the linkage than do the older design breakers coupled directly to the MOC
switches. Older design breakers will eventually cause damage to poorly maintained MOC
switches and linkages. In severe cases, poorly maintained MOC switches and linkages could
stall the older design breaker main contacts with potentially serious results.
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 project manager from the NRCs Office of Nuclear Reactor
Regulation (NRR).
/RA/
William D. Beckner, Program Director
Operating Reactor Improvements Program
Division of Regulatory Improvement Programs
Office of Nuclear Reactor Regulation
Technical contacts: V. Hodge, NRR Steven Alexander, NRR
301-415-1861 301-415-2995 E-mail: cvh@nrc.gov E-mail: sda@nrc.gov
Attachment: List of Recently Issued NRC Information Notices
ML023300015 DOCUMENT NAME: G:\RORP\OES\STAFF FOLDERS\Hodge\event reviews\col_brkr\21016 short col_brkr inf.wpd
OFFICE OES:RORP:DRIP Tech Editor IQMB:DIPM EEIB:DE
NAME CVHodge PKleene* SDAlexander* ASGill
DATE 11/07/2002 05/072002 11/07/2002 11/19/2002 OFFICE C:EEIB:DE SC:RORP:DRIP PD:RORP:DRIP
NAME JACalvo TReis WDBeckner
DATE 11/20/2002 11/22/2002 11/25/2002
Attachment 1 LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
_____________________________________________________________________________________
Information Date of
Notice No. Subject Issuance Issued to
_____________________________________________________________________________________
2002-33 Notification of Permanent 11/21/2002 All teletherapy and radiation
Injunction Against Neutron processing licensees.
Products Incorporated of
Dickerson, Maryland
2002-29 Recent Design Problems in 11/06/2002 All holders of operating licenses
(Errata) Safety Functions of Pneumatic or construction permits for
Systems nuclear power reactors.
2002-32 Electromigration on 10/31/2002 All holders of operating licenses
Semiconductor Integrated for nuclear power reactors except
Circuits those who have ceased
operations and have certified that
fuel has been permanently
removed from the reactor vessel.
2002-31 Potentially Defective UF6 10/31/2002 All licensees authorized to
Cylinder Valves (1-inch) possess and use source material
and/or special nuclear material for
the heating, emptying, filling, or
shipping of uranium hexafluoride
(UF6) in 30- and 48-inch
cylinders.
2002-30 Control and Surveillance of 10/30/2002 All NRC licensees authorized to
Portable Gauges During Field possess, use, transport, and store
Operations portable gauges.
2002-29 Recent Design Problems in 10/15/2002 All holders of operating licenses
Safety Functions of Pneumatic or construction permits for
Systems nuclear power reactors.
2002-28 Appointment of Radiation 09/27/2002 All medical licensees.
Safety Officers and Authorized
Users Under 10 CFR Part 35 Note: NRC generic communications may be received in electronic format shortly after they are
issued by subscribing to the NRC listserver as follows:
To subscribe send an e-mail to <listproc@nrc.gov >, no subject, and the following
command in the message portion:
subscribe gc-nrr firstname lastname
______________________________________________________________________________________
OL = Operating License
CP = Construction Permit