Information Notice No. 88-54:Failure of Circuit Breaker following Installation of Amptector Direct Trip Attachment
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555
July 28, 1988
Information Notice No. 88-54: FAILURE OF CIRCUIT BREAKER FOLLOWING
INSTALLATION OF AMPTECTOR DIRECT TRIP
ATTACHMENT
Addressees:
All holders of operating licenses or construction permits for nuclear power
reactors.
Purpose:
This information notice is being provided to alert addressees to potential
problems resulting from the installation of Amptector direct trip attachments
on Westinghouse Electric Corporation (W) and General Electric Company (GE)
circuit breakers. 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 do not constitute NRC requirements; therefore, no specific action or
written response is required.
Description of Circumstances:
On December 21, 1987, the "B" train residual heat removal (RHR) pump at the
R.E. Ginna Nuclear Power Plant failed to start during a required surveillance
test. The cause of the failure was attributed to a power supply circuit
breaker that failed to remain closed on a valid close signal. The spurious
opening of this circuit breaker interrupted power to the RHR pump because the
circuit breaker Amptector direct trip attachment (DTA) was improperly
installed. Inadequate clearance existed between the circuit breaker trip bar
and the DTA's actuating arm. Therefore, the mechanical vibration that
generally accompanies the closing of a circuit breaker was sufficient to cause
the DTA's actuating arm to actuate the circuit breaker trip bar and resulted
in the reopening of the breaker.
During the failure, a battery equalizing charge was in progress, which the
licensee feels also contributed to the opening of the breaker. The higher
than normal operating voltage of 140V dc (as opposed to the normal 130V dc)
applied to the breaker likely increased the vibration generated during the
closing of the breaker.
Discussion:
As a result of the RHR pump breaker failure, the licensee conducted
operational tests on all Class 1E circuit breakers that had undergone the
Amptector modification. The "B" train safety injection pump breaker failed on
the seventh
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July 28, 1988
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actuation. Additional checks of the RHR pump circuit breaker did not result
in a failure until the 14th actuation. No other failures were observed and
the problem was determined to be intermittent.
The licensee, in consultation with W representatives determined that there was
a direct correlation between the circuit breaker failure and the procedure
used by the licensee in mounting the Amptector DTA. The procedures supplied
by W for installing the trip attachment did not specifically indicate a
minimum clearance that was to be maintained between the DTA's actuating arm
and the circuit breaker trip bar. W representatives orally informed the
licensee that the clearance should measure between 1/32 and 1/16 of an inch
which is the gap used by W in establishing the seismic adequacy of the DTA on
W circuit breakers.
W representatives stated that this minimum clearance is recommended to ensure
that there is no contact between the actuating arm and the trip bar during
pre-trip steady-state operating conditions to reduce the possibility of
inadvertent actuation. It is our understanding that W will be issuing a
technical bulletin addressing the DTA.
The circuit breakers for which this modification is designed are the W Model
DB series and the GE Model AK 2A series. The Amptector DTA is manufactured
and supplied by W. The operating plants that are known to have the
attachments in place are H. B. Robinson, Indian Point 2, Connecticut Yankee,
Three Mile Island 1, Cooper, Fitzpatrick, Monticello and San Onofre, but this
list may not be complete.
No specific action or written response is required by this information notice.
If you have any questions about this matter, please contact the technical con-
tact listed below or the Regional Administrator of the appropriate regional
office.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contact: N. Fields, NRR
(301) 492-1173
Attachment: List of Recently Issued NRC Information Notices
. Attachment
IN 88-54
July 28, 1988
Page 1 of 1
LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
_____________________________________________________________________________
Information Date of
Notice No._____Subject_______________________Issuance_______Issued to________
88-53 Licensee Violations of NRC 7/28/88 All manufacturers
Regulations, Which Led to and distributors
Medical Diagnostic of radio-
Misadministrations pharmaceuticals
for human use,
nuclear
pharmacies, and
medical licensees.
88-52 Failure of Intrauterine 7/27/88 Medical licensees.
Tandem of Fletcher
Applicator Brachytherapy
Devices During Patient
Treatment
88-46, Licensee Report of 7/26/88 All holders of OLs
Supplement 1 Defective Refurbished or CPs for nuclear
Circuit Breakers power reactors.
88-51 Failures of Main Steam 7/21/88 All holders of OLs
Isolation Valves or CPs for nuclear
power reactors.
88-50 Effect of Circuit 7/18/88 All holders of OLs
Breaker Capacitance or CPs for nuclear
on Availability of power reactors.
Emergency Power
88-49 Marking, Handling, 7/18/88 All holders of OLs
Control, Storage and or CPs for nuclear
Destruction of Safe- power reactors and
guards Information all other licensed
activities
involving a
formula quantity
of special nuclear
material.
88-48 Licensee Report of 7/12/88 All holders of OLs
Defective Refurbished or CPs for nuclear
Valves power reactors.
88-47 Slower-Than-Expected 7/14/88 All holders of OLs
Rod-Drop Times or CPs for PWRs.
_____________________________________________________________________________
OL = Operating License
CP = Construction Permit
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