Information Notice 1998-38, Metal-Clad Circuit Breaker Maintenance Issues Identified by NRC Inspections
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555-0001
October 15, 1998
NRC INFORMATION NOTICE 98-38: METAL-CLAD CIRCUIT BREAKER MAINTENANCE
ISSUES IDENTIFIED BY NRC INSPECTIONS
Addressees
All holders of operating licenses for nuclear power reactors.
Purpose
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice to alert
addressees to inspection findings concerning inadequate preventive and corrective
maintenance programs and corrective actions. 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.
Background
In 1997, failures of safety-related circuit breakers at nuclear power facilities prompted reactive
inspections by the NRC. The staff is concerned about these failures because a common failure
mode of safety-related circuit breakers could significantly hamper a plant's ability to deal with a
transient. This information notice will offer some insights gained from the findings of the
In response to these recent events, the NRC is now conducting a series of inspections at some
nuclear power plants, original equipment manufacturer (OEM) facilities, and third-party overhaul
contractor shops to determine the present state of medium-voltage and low-voltage metal clad
circuit breaker maintenance and overhaul programs. At the conclusion of these Inspections, the
staff will evaluate the results, along with the progress made by the Electric Power Research
Institute's Nuclear Maintenance Applications Center (EPRI/NMAC) circuit breaker users groups
and the Nuclear Energy Institute (NEI) task force, to determine whether further regulatory
actions are needed.
The staff recognizes that the industry Is working to Improve the reliability of medium and low- voltage circuit breakers, as evidenced by the activities of the EPRIINMAC circuit breaker users
groups and the NEI Circuit Breaker Task Force. Those groups are working to Issue preventive
maintenance and overhaul guidance for breakers made by General Electric, Westinghouse, and
Asea Brown Boveri (ABB).
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IN 98-38 October 15, 1998
Description of Circumstances
In 1997, three nuclear power plants were either forced to shut down or to extend an outage, and one plant considered shutting down because a potential common failure mode called into
question the operability of safety-related circuit breakers. The NRC sent Inspection teams to
the four sites to review and evaluate licensee maintenance practices and corrective actions. All
of the breakers in the discussions that follow were manufactured by Westinghouse or General
Electric, but ABB product lines have also experienced similar problems over the last few years.
Issues involving circuit breaker maintenance and overhaul are germane to all manufacturers.
CLINTON POWER STATION
On August 5, 1997, Clinton Power Station was preparing to return to power after an outage
when the A-train residual heat removal (RHR) pump supply breaker did not open on demand
when operators attempted to swap RHR pumps In the shutdown cooling mode. Only two
weeks before this event, on July 22, 1997, the reserve auxiliary transformer (RAT) feeder
breaker to the 4-kV bus for Division 1 failed to open when operators attempted to swap the bus
feed to the emergency reserve auxiliary transformer. The failed breakers In both instances
were Westinghouse Type DHP 4-kV metal clad circuit breakers. Because (1) there appeared to
be a common failure mode, (2) the licensee corrective action for the first breaker failure did not
prevent the second failure, and (3) there was a poor maintenance history, the NRC dispatched
an augmented inspection team (AIT) to the site and issued a demand for information (DFI)
letter concerning the licensee's corrective action program and its effectiveness in ensuring the
operability and reliability of safety-related systems, and informing the licensee that a response
was required before the NRC would authorize a plant restart. The plant remains shut down at
this time.
The AIT concluded that both of the circuit breaker failures were caused by inadequate and
inappropriate preventive maintenance activities, and deficiencies in Clinton's corrective action
program. The preventive maintenance program did not include lubrication of all vendor- recommended areas, most notably in the main and arcing contacts. The licensee also used
unapproved cleaning agents, which inadvertently removed vendor-applied lubricant, and then
did not relubricate the affected areas. The licensee also did not effectively evaluate the July 22 breaker failure. These combined deficiencies resulted in the introduction of a common failure
mode for all of the safety-related 4-kV Westinghouse breakers at the plant. The licensee's
investigation of the August 5 breaker failure was significantly more rigorous than the
investigation Into the July 22 failure had been. However, NRC prompting was necessary at
times to ensure a thorough licensee Investigation. For example, Initially the licensee
Investigation focused on the lack of lubrication, and did not consider that the opening springs
could have contributed to the failure. Subsequent review determined that although the lack of
lubrication was the main contributor to the RHR breaker failure, a bent and shortened kick-out
spring also played a significant role. Refer to NRC Inspection Report 50-461/97018 (Accession
- 9712040128) for further details.
October 15, 1998 INDIAN POINT 2 NUCLEAR POWER PLANT
On October 14, 1997, Consolidated Edison Company of New York voluntarily shutdown its
Indian Point 2 Nuclear Power Plant (IP2) because of concerns about the operability and
reliability of its safety-related 480-V Westinghouse Type DB-50 circuit breakers. The action
was taken after experiencing recurring problems with these breakers to either close on demand
or to remain closed.
An NRC inspection Identified several weaknesses associated with the licensee's corrective
maintenance, preventive maintenance, and other corrective actions concerning circuit breakers.
In June 1997, the licensee hired a contractor to perform a root-cause analysis. The contractor's
report did not discuss all the possible failure modes and erroneously concluded that the DB-50
breaker failures were caused by malfunctioning solid-state trip devices (Amptectors) and
operating mechanism binding caused by accumulated dust ant dirt contaminating the
mechanism's lubricant. The inadequate root-cause analysis led to the occurrence of more
failures, which eventually prompted the October shutdown. B fore the plant shutdown, the
licensee did not vigorously pursue a root cause after experiene)ng a breaker failure. Typically, a failed breaker would be removed from service and the preventive maintenance procedure
would be performed to restore it to an operable status without i1entifying the cause of the
problem.
Following the plant shutdown, the IP2 licensee conducted an i. dtensive testing program to
determine the root cause of the breaker failures. High-speed video, static and dynamic dosing
coil current measurements, component displacements, and foi ce measurements were made, which identified several contributors to breaker failures. Refer to NRC Inspection Report 50-
247/97-13 (Accession #9802250110) for further details. The licensee has developed useful
diagnostic tools that could help in revealing or predicting breaker performance problems.
COOPER NUCLEAR STATION
On October 5, 1997, failure of a non-safety-related General Electric 4-kV (Magne-Blast) circuit
breaker prompted the Cooper licensee to review its breaker maintenance and overhaul
program. The review identified 6 of 24 safety-related 4-kV breakers that had not been
overhauled during the 23 years of plant operation. The affected breakers included two
emergency diesel output breakers, two residual heat removso pump breakers, a service water
pump breaker, and a 4-kV/480-V transformer supply breaker. The licensee initially considered
shutting the plant down if the six safety-related breakers we e judged to be inoperable.
Subsequent discussions with GE about the condition of these breakers determined that the
breakers were in a degraded but operable condition. The licensee Implemented an accelerated
program to overhaul the six breakers.
The NRC sent an Inspection team to the site on October 20, 1997, to review the causes and
circumstances associated with this issue. The team found that the licensee experienced
several problems with the GE Magne-Blast breakers In the late 1980's and implemented a
program to overhaul Its safety-related 4-kV breakers, but for reasons unknown, the program
was terminated in 1994 with 6 of the breakers not being overhauled. The licensee's operating
experience review program did not include review of the vendor's service advice letters (SALs),
IN 98-38 October 15, 1998 which are issued to alert customers to changes In maintenance recommendations or physical
design changes made in subcomponent piece parts to address a specific identified problem. In
addition, licensee review of NRC information notices was narrowly focused and sometimes did
not consider the information provided in a specific notice as applicable to Cooper because'of
minor differences between the model numbers discussed in the notice and the components
used at Cooper. Several inconsistencies were identified between licensee maintenance
procedures and vendor recommendations. The licensee did not have adequate justification for
many of the identified inconsistencies. Refer to NRC Inspection Report 50-298/97018 (Accession #9712220092) for further details.
INDIAN POINT 3 NUCLEAR POWER PLANT
On December 18, 1997, at Indian Point 3 Nuclear Power Plant (IP3), an RHR pump breaker
(Westinghouse Type DS-416) failed to open to disconnect the pump motor from its 480-V
emergency electrical bus at the end of a surveillance run. The electrical bus was declared
inoperable, which forced a plant shutdown. The NRC sent a special inspection team to the site
because of the potential generic implications. On December 22, 1997, during testing of
additional breakers, another safety-related breaker was found to be potentially degraded.
Investigation of the failed RHR pump breaker found that factory-applied lubrication (poxylube)
had been removed from several locations on the operating mechanism during overhaul by a
third-party contractor during refurbishment activities In 1994. Neither the licensee nor the
contractor knew about the use of poxylube because the information was considered proprietary
by the OEM and, as a result did not appear in any of the vendors literature. The vendor's
manual specifies some preventive maintenance actions to be taken by the customer but
recommends that the breaker be returned to Westinghouse for disassembly and overhaul of the
operating mechanism.
The lack of lubrication was a primary contributor to the breaker failure but the licensee and
Westinghouse discovered another anomaly during the investigation. With the pole shaft reset
spring removed, some breakers could be made to lock up in the closed position. Normal
operation of the breaker calls for the reset spring to be installed, but the spring was removed to
facilitate testing of the failed breaker. The Investigation found that a combination of wear, inadequate lubrication, and clearances In the linkage subcomponents (clevises, pins, and
support points) could allow the pole shaft to overtravel and cause the breaker to lock up in the
closed position when the reset spring was removed. It was discovered that some breakers
overhauled by the OEM would also lock up In the closed position without the reset spring
attached. While this information Is new to both the OEM and the licensee, it Is not considered
to be a defect in the breaker since the reset spring is attached during normal operation. See
NRC Inspection Report 50/285 97-81 (Accession #9804080233) for details.
Related Generic Communications
Numerous information notices have been Issued concerning lubrication of circuit breakers. It
appears that ineffective preventive maintenance, including a lack of lubrication or Inadvertent
removal of factory-applied lubricant, continues to be a major factor in circuit breaker failures.
IN 98-38 October 15, 1998 This 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 goals and performing periodic evaluations
under Section 50.65, "Requirement for monitoring the effectiveness of maintenance at nuclear
power plants," to 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.
W. Roe, Acting Director
Oinsion of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts:
Steve Alexander, NRR
Kamalakar Naidu, NRR
301-415-2995
301-415-2980
E-mail: sda@nrc.gov
E-mail: km@nrc.gov
David Skeen, NRR
301-415-1174 E-mail: dls@nrc.gov
Attachment: List of Recently Issued NRC Information Notices
V2 fttachment I
October 15, 1998
Page 1 of I
LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
Information
Date of
Notice No.
Subject
Issuance
Issued to
98-37 Eligibility of Operator License
10/01/98
All holders of operating licenses
Applicants
for nuclear power reactors, except those who have
permanently ceased operations
and have certified that fuel has
been permanently removed from
the reactor vessel.
98-36
98-35
98-34 Inadequate or Poorly Controlled
9/18/98 Non-Safety-Related Maintenance
Activities Unnecessarily Challenged
Safety Systems
Threat Assessments and
9/4/98
Consideration of Heightened
Physical Protection Measures
NRC Configuration Control
8/28/98 Errors
NRC Regulations Prohibit
8/28/98
Agreements that restrict or
Discourage an Employee from
Participating In Protected Activities
All holders of operating licenses
for nuclear power reactors
All U.S. NRC fuel cycle facilities
power and non-power reactor
licencees (Safeguard issues, not
for public disclosure.)
All holders of Operating licenses
for nuclear power reactors, except
for those who have ceased
operations and have certified that
fuel has been permanently
removed from the reactor vessel
All holders of a U.S. Nuclear
Regulatory Commission (NRC)
license.
98-33 OL = Operating License
CP = Construction Permit
IN 98-XX
October XX, 1998 This 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 goals and performing periodic evaluations
under Section 50.65, "Requirement for mbnito ing the effectiveness of maintenance at nuclear
power plants," to 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.
Jack W. Roe, Acting Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts:
Steve Alexander, NRR
Kamalakar Naidu, NRR
301-415-2995
301-415-2980
E-mail: sda@nrc.gov
E-mail: km@nrc.gov
David Skeen, NRR
301-415-1174 E-mail: dls@nrc.gov
Attachment: List of Recently Issued NRC Information Notices
DOCUMENT NAME: G:\\DLS\\IN98-XX.BKR
To receive a copy of this document, indicate in the box C=Copy wfo attachment/enclosure E=QqpyfN, attachment/enclosure NNo copy
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