Information Notice 1995-19, Failure of Reactor Trip Breaker to Open Because of Cutoff Switch Material Lodged in the Trip Latch Mechanism

Failure of Reactor Trip Breaker to Open Because of Cutoff Switch Material Lodged in the Trip Latch Mechanism
	ML031060244
Person / Time
Site:	Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, Mcguire, 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:	03/22/1995
From:	Grimes B; Office of Nuclear Reactor Regulation
To:	;
References
	IN-95-019, NUDOCS 9503160374
	Download: ML031060244 (12)
	v • d • e

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UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 March 22, 1995 NRC INFORMATION NOTICE 95-19: FAILURE OF REACTOR TRIP BREAKER TO OPEN BECAUSE

OF CUTOFF SWITCH MATERIAL LODGED IN THE TRIP

LATCH MECHANISM

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 possible failure of a circuit breaker to

open because of obstruction by material from a subcomponent switch. It is

expected that recipients will review this 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.

Description of Circumstances

On July 14, 1994, during the monthly testing of the logic matrix of the

reactor protection system at St. Lucie, Unit 2, a General Electric (GE)

Model AK 2-25 circuit breaker failed to open after operating correctly on

three previous steps of the surveillance procedure. This circuit breaker is

one of eight reactor trip circuit breakers in a one-out-of-two taken twice

reactor trip coincidence logic. Several unsuccessful attempts were made to

open the breaker both electrically and mechanically before the licensee

isolated the breaker as required by the Technical Specifications and shut down

the Unit 2 reactor.

The investigation of the problem revealed that a 6-mm-square [1/4-inch-square]

piece of phenolic material had jammed the circuit breaker trip latch

mechanism, preventing its operation. This piece of phenolic material had

broken off from the breaker cutoff switch (p/n 622 C 505 GI), which is part of

the breaker antipump circuitry. The cutoff switch is mounted in the breaker

assembly above the trip latch mechanism (Figure 1). A screw holding the

cutoff switch had come loose, allowing two halves of the switch to separate, become misaligned, and break during the previous circuit breaker operation.

The licensee inspected the remaining Unit 2 trip circuit breakers as well as

the similar motor generator set output breakers. No additional loose screws

were found on the cutoff switch mountings. The licensee has incorporated the

inspection of the cutoff switch phenolic block and screw into the maintenance

procedures for Units I and 2. a ' 6sb

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IN 95-19 March 22, 1995 Discussion

On April 6, 1989, GE Switchgear Operation issued service advisory letter (SAL)

303.0, which dealt with the possibility that the cutoff switch actuator could

crack and break and lead to breaker coil burnout. The text of SAL 303.0 is

shown in Attachment 2. Although these cutoff switches had a different

failure mode and were installed on different breaker models (Models AKR(U) 30s

and AK(U) 25-1), the cutoff switch in question was the same part (p/n 622 C

505 GI) as the one that caused the AK2-25 breaker failure at St. Lucie, Unit 2.

The majority of the reactor trip breaker failures at power reactors have been

caused by problems with relatively small electrical subcomponents in the

breaker assembly, rather that the malfunction of the main breaker mechanism

itself. The failure of the cutoff switch in the trip breaker at St Lucie is

another example of a subcomponent failure resulting in the failure of a trip

breaker. The frequency of reactor trip breaker failures could be reduced if

these small component problems were made less likely by appropriate inspection

and maintenance.

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 (NRP) project manager.

Brian K. Grimes, Director

Division of Project Support

Office of Nuclear Reactor Regulation

Technical contacts: S. Rudisail, Region II S. K. Mitra, NRR

(404) 331-5582 (301) 415-2783 M. B. Shymlock, Region II

(404) 331-5596 Attachments:

1. Figure 1

2. GE SAL 303.0

3. List of Recently Issued NRC Information Notices

KJi

Attachment 1 IN 95-19 March 22, 1995 FIGURE 1 AK-2 BREAKER FRONT VIEW

f CUTOFF SWITCH

TX

CONTACT

OR>

PIECE OF CUTOFF SWITCH

(CUTOFF SWITCH PIN 622 C 505 Gl) DROPPED DOWN TO BOlTOM OF

THE TRIP LATCH PREVENTING

THE LATCH FROM ACTUATING

vJ

Attachment 2 IN 95-19 March 22, 1995 SUBJECT ELECTRICALLY OPERATED

SWITCHGEAR AKR 30S AND AKRU 30S BREAKERS

OPERATION AK 25-1 AND AKU 25-1 BREAKERS

SERVICE ADVICE CUT OF SWITCH BREAKAGE

-- I Ce MAn jnIV n

TAB uIjsu ba A1U . JUJ . U

SWGR OPER O.

_ _ _ _ I _ _ _ _ _ _ _ _ _ _ _ _ _ I _ _ _ _ _ _ _ _ _

_ __ _ __ _ _ _ _ _ _

Backqround

The function of the Cut Off Switch is to interrupt the

closing coil when the breaker is closed.

Problem

On electrically operated AKR(U) 30S and AK(U) 25-1 breakers

manufactured between July 1986 and November 1987 there is a

possibility that the cut off switch actuator may crack and break.

If this occurs, the closing coil may be overheated and burn up

when the breaker is closed.

Recommended Action

GE recommends that the cut off switch actuator on all

affected breakers be visually checked for cracks at the next

regular breaker maintenance / inspection. This includes all

AKR(U) 30S breakers with a Breaker Code Date less than P747+ and

all AK(U) 25-1 breakers with a Breaker Date Code P548+ through

P747+. The Breaker Code Date is on the control voltage nameplate

located to the right of the escutcheon on the breaker frame.

Corrective Action

If a broken or cracked cut off switch is found, contact

Customer Service for a no-charge replacement cut off switch [Part

No. 622C505G1] at:

Mary Hockett Phone: (319) 753-8475 Customer Service 8*673-6475 General Electric Telecopier: (319) 753-5479 PO Box 488 8*673-6479 Burlington, IA 52601 Please have Breaker Serial Numbers and Date Codes when

you contact us.

,

I

PREPARED BY

_ _ _ _ .

.

II ISSUED BY

. z p x

II DATE I bUFtURtULb 1 II II IISSUE DATED IIOF

GARY SCHULE II DON LESNET II 4-06-89 0 (NEW)

Attachment 3 IN 95-19 March 22, 1995 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

95-18 Potential Pressure-Locking 03/15/95 All holders of OLs or CPs

of Safety-Related Power- for nuclear power reactors.

Operated Gate Valves

95-17 Reactor Vessel Top Guide 03/10/95 All holders of OLs or CPs

and Core Plate Cracking

95-16 Vibration Caused by 03/09/95 All holders of OLs or CPs

Increased Recirculation for boiling water reactors.

Flow in a Boiling Water

Reactor

95-15 Inadequate Logic Testing 03/07/95 All holders of OLs or CPs

of Safety-Related Circuits for nuclear power reactors.

95-14 Susceptibility of Con- 02/28/95 All holders of OLs or CPs

tainment Sump Recircula- for nuclear power reactors.

tion Gate Valves to

Pressure Locking

95-13 Potential for Data 02/24/95 All holders of OLs or CPs

Collection Equipment to for nuclear power reactors.

Affect Protection System

Performance

95-12 Potentially Nonconforming 02/21/95 All holders of OLs or CPs

Fasteners Supplied by for nuclear power reactors.

A&G Engineering II, Inc.

95-11 Failure of Condensate 02/24/95 All holders of OLs or CPs

Piping Because of Erosion/ for nuclear power reactors.

Corrosion at a Flow- Straightening Device

95-10 Potential for Loss of 02/10/95 All holders of OLs or CPs

Supp. 1 Automatic Engineered for nuclear power reactors.

Safety Features

Actuation

OL = Operating License

CP = Construction Permit

IN 95-19 March 22, 1995 Discussion

On April 6, 1989, GE Switchgear Operation issued service advisory letter (SAL)

303.0, which dealt with the possibility that the cutoff switch actuator could

crack and break and lead to breaker coil burnout. The text of SAL 303.0 is

shown in Attachment 2. Although these cutoff switches had a different

failure mode and were installed on different breaker models (Models AKR(U) 30s

and AK(U) 25-1), the cutoff switch in question was the same part (p/n 622 C

505 Gi) as the one that caused the AK2-25 breaker failure at St. Lucie, Unit 2.

The majority of the reactor trip breaker failures at power reactors have been

caused by problems with relatively small electrical subcomponents in the

breaker assembly, rather that the malfunction of the main breaker mechanism

itself. The failure of the cutoff switch in the trip breaker at St Lucie is

another example of a subcomponent failure resulting in the failure of a trip

breaker. The frequency of reactor trip breaker failures could be reduced if

these small component problems were made less likely by appropriate inspection

and maintenance.

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. Gri fbyiatlI K. rmes

Division of Project Support

Office of Nuclear Reactor Regulation

Technical contacts: S. Rudisail, Region II S. K. Mitra, NRR

(404) 331-5582 (301) 415-2783 M. B. Shymlock, Region II

(404) 331-5596 Attachments:

1. Figure 1

2. GE SAL 303.0

3. List of Recently Issued NRC Information Notices

DOCUMENT NAME: S:\DOPS SEC\95-19.IN *See previous concurrence

OECB:DOPS:NRR* RPB:ADM EELB:DE C/EELB:DE

DCKirkpatrick l BCalure, Tech Ed* SKMitra* CEBerlinger*

12/22/94 l 12/28/94 01/23/95 01/23/95 RII (via e-mail) RII (via e-mail) SC/OECB:DOPS:NRR OECB:DOPS:NRR

SRudisail* MBShymlok* EFGoodwin* RJKiessel*

01/25/95 01/25/95 Z 01/26/95 02/01/95 C/OECB:DOPS:NRR D/J4* 7 =

AEChaffee*

03/11/95 03// /95 OFFICIAL RECORD COPY

v~~

IN 95-XX

March xx, 1995 Discussion

On April 6, 1989, GE Switchgear Operation issued service advisory letter (SAL)

303.0, which dealt with the possibility that the cutoff switch actuator could

crack and break and lead to breaker coil burnout. The text of SAL 303.0 is

shown in Attachment 2. Although these cutoff switches had a different

failure mode and were installed on different breaker models (Models AKR(U) 30s

and AK(U) 25-1), the cutoff switch in question was the same part (p/n 622 C

505 Gl) as the one that caused the AK2-25 breaker failure at St. Lucie, Unit 2.

The majority of the reactor trip breaker failures at power reactors have been

caused by problems with relatively small electrical subcomponents in the

breaker assembly, rather that the malfunction of the main breaker mechanism

itself. The failure of the cutoff switch in the trip breaker at St Lucie is

another example of a subcomponent failure resulting in the failure of a trip

breaker. It follows that the frequency of reactor trip breaker failures could

be significantly reduced if these small component problems could be eliminated

by careful inspection and maintenance.

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, Director

Division of Project Support

Office of Nuclear Reactor Regulation

Technical contacts: S. Rudisail, Region II S. K. Mitra, NRR

(404) 331-5582 (301) 504-2783 M. B. Shymlock, Region II

(404) 331-5596 Attachments:

1. Figure 1

2. GE SAL 303.0

3. List of Recently Issued NRC Information Notices

DOCUMENT NAMF: s!\nlfPS SFC\RRFAKER *See nrev'ious concurrence

OECB:DOPS:NRR* RPB:ADM EELB:DE C/EELB:DE

DCKirkpatrick BCalure, Tech Ed* SKMitra* CEBerlinger*

12/22/94 12/28/94 01/23/95 01/23/95 RII (via e-mail) RII (via e-mail) SC/OECB:DOPS:NRR OECB:DOPS:NRR

SRudisail* MBShymlok* EFGoodwin* RJKiessel*

01/25/95 01/25/95 01/26/95 02/01/95 C/OECB:DOPS:NRR D/DOPS:NRR

AEChaffee* BKGrimes

03/11/95 0 / j95_

OFF ICIAL RECORD COPY

IN 95-xx