Information Notice 1993-09, Failure of Undervoltage Trip Attachment on Westinghouse Model DB-50 Reactor Trip Breaker

Failure of Undervoltage Trip Attachment on Westinghouse Model DB-50 Reactor Trip Breaker
	ML031080169
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:	02/02/1993
From:	Grimes B; Office of Nuclear Reactor Regulation
To:	;
References
	IN-93-009, NUDOCS 9301260286
	Download: ML031080169 (8)
	v • d • e

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 February 2, 1993 NRC INFORMATION NOTICE 93-09: FAILURE OF UNDERVOLTAGE TRIP ATTACHMENT ON

WESTINGHOUSE MODEL DB-50 REACTOR TRIP BREAKER

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 failure of an undervoltage trip attachment

on a reactor trip breaker at the Salem Nuclear Generating Station, Unit 1.

The failure occurred during surveillance testing. 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.

Description of Circumstances

On July 25, 1991, Public Service Electric and Gas Company, the licensee for

Salem, Unit 1, was conducting the monthly surveillance tests of the

undervoltage trip attachment and the shunt trip attachment associated with

reactor trip circuit breakers. Licensee personnel successfully completed the

shunt trip attachment surveillance tests. However, when the undervoltage trip

attachment trip test was attempted on the "A" reactor trip breaker

(Westinghouse model DB-50), the circuit breaker required approximately

16 cycles (0.267 seconds) to open. For the function to be considered

operable, technical specifications require that the breaker open in 10 cycles

(0.167 seconds) or less. A second attempt to open the breaker using the

undervoltage attachment was unsuccessful; the breaker remained closed.

Discussion

On July 26, 1991, a Westinghouse representative and licensee personnel

performed various bench tests on the "A" reactor trip breaker. The tests

indicated that the breaker had been properly maintained and that the breaker

trip bar was functioning normally. However, when the undervoltage trip

attachment was tested, it again failed to open the breaker. The undervoltage

trip attachment was not striking the circuit breaker trip bar with sufficient

force to lift the bar. When the undervoltage trip attachment was lubricated

and retested, the undervoltage trip attachment armature successfully lifted

the circuit breaker trip bar, opening the breaker within the required

10 cycles. The licensee re-lubricated and tested the undervoltage trip

9301260286 PatI If past 9l3-0

4 EC

IN 93-09 February 2, 1993 attachment with 300 grams of weight added to the trip bar as required

monthly surveillance test procedure. The test was again performed by the

satisfactorily. The trip attachment also lifted the trip bar with an

460 grams, the amount of additional weight required by the licensee semi-added

annual surveillance test procedure.

Initially, the cause of the failure appeared to have been inadequate

lubrication; however, the undervoltage trip attachment was returned

Westinghouse for further evaluation. Westinghouse later concluded to

that the

root cause of the failure'of the device was abnormal frictional forces

resulted primarily from the unpolished outside latch contact surfaces which

undervoltage trip attachment. Westinghouse representatives stated thatof the

areas had not been properly finished during the manufacturing process. these

outside contact surface of the latch was "bright" on only one edge ratherThe

on the entire surface. The "bright" edge also appeared to be burred than

serrated. or

Westinghouse representatives also found excessive wear and grooving

on

undervoltage trip attachment latch spring at a location where the latch the

latch spring were making'contact. Contact between the latch and the and

spring occurred because the latch spring was somewhat deformed and did latch

flat as designed. The latch spring deformation, grooving, and wear not lie

in

combination with the improperly finished latch contact surfaces created

additional internal frictional forces such that the undervoltage trip

attachment armature-was unable to apply sufficient-force-to lift the-breaker

trip bar.

During the evaluation, Westinghouse personnel reassembled and cycled

the

undervoltage trip attachment 250 times. The undervoltage trip attachment

then tested, lubricated, and retested. Each time the undervoltage trip was

attachment was tested, it provided sufficient force to operate the breaker

trip bar. However, the force applied by the device appeared to decrease

250 cycles but increase at 500 cycles. 'The force then appeared to decrease at

somewhat after 750 cycles, although this may be attributed to testing

inaccuracies. While the testing was not considered conclusive, the

performance of the undervoltage trip attachment apparently degrades

improves to some plateau. Westinghouse concluded that this change and then

from, first, increasing friction as the latch cuts into the latch results

spring; and

later, decreasing friction as the parts wear and as pressure from the

spring decreases as it permanently deforms. latch

The undervoltage trip attachments equipped with improperly finished

latches

were provided to various utilities by the Replacement Component Services

Department of the Westinghouse Nuclear Services Division (NSD). These (RCS)

undervoltage trip attachments were supplied either individually or as

remanufactured or overhauled Westinghouse Model DB-50 circuit breakers part of

installed undervoltage trip attachments. Westinghouse determined that with

improperly finished undervoltage trip attachment parts were from one all the

parts that was made exclusively for RCS by a subcontractor. The same lot of

subcontractor made a second lot of undervoltage trip attachment parts;

second lot contained no improperly finished parts. Westinghouse this

IN 93-09 February 2, 1993 representatives stated that none of the defective parts have been used in

undervoltage trip attachments or DB-50 circuit breakers available on the open

market as commercial 'grade items. Westinghouse informed the NRC that it has

notified all customers of record who have purchased undervoltage trip

attachments or Model DB-50 circuit-breakers with parts from the affected lot.

Westinghouse personnel recommended that the Salem licensee visually inspect, for proper finish, the undervoltage trip attachment latches on all other Model

DB-50 circuit breakers at the Salem facility. They also recommended that the

licensee develop criteria for replacing the undervoltage trip attachment when

the difference in the force generated before and after lubrication exceeds a

predetermined value.

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 Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contacts: N. Fields, NRR

(301) 504-1173 S. Alexander, NRR

(301) 504-2995 Attachment: List of Recently Issued NRC Information Notices

Attachment

IN 93-09 February 2, 1993 Page I of i

Q0 e?

LIST OF RECENTLY ISSUED 4 NRC INFORNATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

93-08 Failure of Residual 02/01/93 All holders of OLs or CPs Sa.

Neat Removal Pump for nuclear power reactors. 0

Bearings due to High 0. N

Thrust Loading

93-07 Classification of Trans- 02/01/93 All Licensees required to

portation Emergencies have an emergency plan.

93-06 Potential Bypass Leak- 01/22/93 All holders of OLs or CPs

age Paths Around Filters for nuclear power reactors.

Installed in Ventilation

Systems

93-05 Locking of Radiography 01/14/93 All Nuclear Regulatory

Exposure Devices Commission industrial

radiography licensees.

93-04 Investigation and Re- 01/07/93 All U.S. Nuclear Regulatory '0'

porting of Misadministra- Commission medical

tions by the Radiation licensees.

Safety Officer

93-03 Recent Revision to 01/05/93 All byproduct, source, and

10 CFR Part 20 and special nuclear material

Change of Implementa- licensees.

tion Date to

January 1, 1994

93-02 Nalfunction of A Pres- 01/04/93 All holders of OLs or CPs

surizer Code Safety for nuclear power reactors.

Valve

93-01 Accuracy of Notor- 01/04/93 All holders of OLs or CPs

Operated Valve Diagnostic for nuclear power reactors.

Equipment Nanufactures

l by Liberty Technologies

92-86 Unexpected Restriction 12/24/92 All holders of OLs or CPs W Uj

to Thermal Growth of for nuclear power reactors.

Reactor Coolant Piping

2.

IL-

co

m_J

2 OL - Operating License 2ZL g

CP

Construction Permit

0t

z

ot

I

IN 93-09 February 2, 1993 representatives stated that none of the defective parts have been used in

undervoltage trip attachments or DB-50 circuit breakers available on the open

market as commercial grade items. Westinghouse informed the NRC that it has

notified all customers of record who have purchased undervoltage trip

attachments or Model DB-50 circuit breakers with parts from the affected lot.

Westinghouse personnel recommended that the Salem licensee visually inspect, for proper finish, the undervoltage trip attachment latches on all other Model

DB-50 circuit breakers at the Salem facility. They also recommended that the

licensee develop criteria for replacing the undervoltage trip attachment when

the difference in the force generated before and after lubrication exceeds a

predetermined value.

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.

Orig /s/'d by BKGrimes

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contacts: N. Fields, NRR

(301) 504-1173 S. Alexander, NRR

(301) 504-2995 Attachment: List of Recently Issued N C Information Notices

SEE PREVIOUS CONCURRENCE

OEAB:DORS ADM:RPB EELB:DE ASC/OEAB:DORS

NFields* JMain* SAlexander* EGoodwin *

01/25/93 09/06/92 10/22/92 01/13/93 F C/EELB:DE

CBerlinger*

01/15/93 C/OEAB:DORS

AChaffee*

01/19/93 C/OGCB:DORS

GMarcus*

01/25/93 e

1/2a/93 OFFICIAL RECORD COPY

DOCUMENT NAME: 93-09.IN

IN 93-XX

January xx, 1993 representatives stated that none of the defective parts have been used in