Information Notice 1998-38, Metal-Clad Circuit Breaker Maintenance Issues Identified by NRC Inspections

Metal-Clad Circuit Breaker Maintenance Issues Identified by NRC Inspections

ML031040554
Person / Time
Site:	Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, 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
Issue date:	10/15/1998
From:	Roe J Office of Nuclear Reactor Regulation
To:
References
IN-98-038, NUDOCS 9810090322
Download: ML031040554 (7)

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

reactive inspections.

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).

9810 0/ j 1b)IqlV P9t rI ,g -foi

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 Inthe 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

1. 9712040128) for further details.

IN 98-38 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 Inthe 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

IN 98-38 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 Inadequate or Poorly Controlled 9/18/98 All holders of operating licenses

Non-Safety-Related Maintenance

for nuclear power reactors

Activities Unnecessarily Challenged

Safety Systems

98-35 Threat Assessments and 9/4/98 All U.S. NRC fuel cycle facilities

Consideration of Heightened

power and non-power reactor

Physical Protection Measures

licencees (Safeguard issues, not

for public disclosure.)

98-34 NRC Configuration Control 8/28/98 All holders of Operating licenses

Errors

for nuclear power reactors, except

for those who have ceased

operations and have certified that

fuel has been permanently

removed from the reactor vessel

98-33 NRC Regulations Prohibit 8/28/98 All holders of a U.S. Nuclear

Agreements that restrict or

Regulatory Commission (NRC)

Discourage an Employee from

license.

Participating In Protected Activities

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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