Information Notice 1987-35, Reactor Trip Breaker, Westinghouse Model DS-416, Failed to Open on Manual Initiation from the Control Room

Reactor Trip Breaker, Westinghouse Model DS-416, Failed to Open on Manual Initiation from the Control Room

ML031130528
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, 05000000, Zimmer, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant, Skagit, Marble Hill
Issue date:	07/30/1987
From:	Rossi C Office of Nuclear Reactor Regulation
To:
References
IN-87-035, NUDOCS 8707270073
Download: ML031130528 (9)

SSINS No.: 6835 TN 87-35 UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 July 30, 1987 NRC INFORMATION NOTICE NO. 87-35: REACTOR TRIP BREAKER, WESTINGHOUSE MODEL

DS-416, FAILED TO OPEN ON MANUAL

INITIATION FROM THE CONTROL ROOM

Addressees

All nuclear power reactor facilities holding an operating license (OL) or

construction permit (CP) employing Westinghouse DS-416 reactor trip breakers.

Purpose

This notice is provided to alert recipients to a potentially significant safety

problem associated with a reactor trip breaker (RTB). The NRC expects that

recipients will review this notice for applicability to their facilities and

consider actions, if appropriate, to preclude a similar problem. However, suggestions contained in this notice do not constitute ARC requirements;

therefore, no specific action or written response is required.

Description of Circumstances

On July 2, 1987, McGuire Nuclear Station Unit 2 was performing control rod drop

tests after its recent refueling outage. This test was in progress with the

plant in mode 3 (hot shutdown). With all control rods inserted and the RTBs

closed for testing the next bank of control rods, station personnel smelled

smoke in the vicinity of the RTBs. A manual trip of A and B train RTBs was

Initiated from the control room. Only the A train RTB opened. The B train RTB

was eventually tripped manually at the breaker panel. The smoke had come from

the 8 train breaker shunt trip coil, which had burned and shorted while trying

to open the breaker. The coil is designed for intermittent duty and to carry

current only until the breaker opens. Failure of the breaker to open resulted

in a prolonged and damaging current. Operators in the control room stated that

open indications for both the A and B train redundant RTBs were observed for

all attempted breaker opening evolutions during the control rod drop testing

process. However, the event recorder indicated that the B train RTB failed to

open on a previous manual trip attempt (approximately 4 minutes before) when

operators were setting up for the control rod drop test on the last bank of

rods.

2D7-l

87077007

/t

6-I

h11,' Ido (C Y

IN 87-35 July 30, 1987 An NRC Augmented Inspection Team (AIT) evaluated the licensee's Investigation

into the reactor trip breaker problem. Abnormal wear and a broken weld

were

found in this early vintage of Westinghouse DS-416 breaker (see Westinghouse

Figure, Attachment 1). The broken weld was on the main drive link between

center pole lever and the pole shaft. Except for the shunt trip coil the

that had

burned and shorted while trying to open the breaker, the breaker's electrical

controls and auxiliary contacts were verified to be properly wired and

ing as designed. The cause for the anomalous breaker status Indicationoperat- still under investigation. is

Attempts to repeat the condition, where the breaker was mechanically

binding in

the closed position, were minimally successful. Preliminary conclusions

AlT are that the breaker's mechanical binding was caused by a combination of the

wear (greater than 2000 cycles of operation), manufacturing tolerances of

early vintage breaker, and the broken weld. These factors may have in this

combined

allow sufficient lateral movement of the main linkage to cause it to Jam to

at or

near full breaker closure and thus prevent the breaker from opening.

control room operating personnel stated that they observed the open Since the

on the closed B train RTB, the field wiring is being verified by the indication

to ensure that wiring is as designed. The shorted shunt trip coil hadlicensee

125 volts dc between the positive terminal and the chassis; a "sneak" allowed

circuit

is possible.

Discussion:

Final conclusions for the cause of this event have not been reached.

Further

investigation and dismantling of the breaker will be conducted in Westinghouse

laboratory facilities. The licensee and NRC will participate in this

investi- gation. If the results indicate findings different than the above preliminary

conclusions, a supplement to this notice will be issued.

The licensee is inspecting all of the RTBs for signs of abnormal wear, cracks

in welds, and excessive lateral play (greater than 1/8 inch) in the roller

of the main drive link where it contacts the close cam. This measurement end

not previously been part of the periodic preventive maintenance for the had

Moreover, following any reactor trip, the licensee is ensuring the open RTB.

tion of both RTBs by inspecting the breaker before reclosure. These are posi- short-term corrective actions until the detailed analysis of the deficiencies

is completed.

A significant number of generic communications have been issued with regard

reactor trip breakers (RTBs) and similar circuit breakers used in safety- to

related systems. Such communications that may be related to the matter

in this

information notice are listed in Attachment 2.

IN 87-35 July 30, 1987 No specific action or written response is required by this information notice.

If you have any questions about this matter, please contact the Regional

Administrator of the appropriate NRC regional office or this office.

harl E.Ros Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contacts: C. Vernon Hodge, NRR

(301) 492-8196 T. Peebles, R11

(404) 331-4196 A. Ruff, R11

(404) 331-5540

Attachments:

1. Power-Operated (Stored-Energy) Mechanism Graphic Details

2. Generic Comunications on Reactor Trip Breakers and Similar Circuit

Breakers

3. List of Recently Issued NRC Information Notices

I

(

1. SHUNT TRIP DEVICE 10. RATCHET WHEEL 19. RESET SPRING

2. TRIP SHAFT 11. HOLD PAWL 20. CLOSING SPRING ANCHOR

3. ROLLER CONSTRAINING LINK 12. DRIVE PLATE 21. POLE SHAFT

4. TRIP LATCH 13. EMERGENCY CHARGE PAWL 22. MOTOR

5. CLOSE CAM 14. OSCILLATOR 23. EMERGENCY CHARGE HANDLE

6. STOP ROLLER 15. CRANK SHAFT 24. MOTOR CRANK AND HANDLE

7. SPRING RELEASE LATCH 16. EMERGENCY CHARGE DEVICE 25. MOVING

CONTACT

ASSEMBLY

8. SPRING RELEASE DEVICE 17. CRANK ARM 26. INSULATING LINK

,9. OSCILLATOR PAWL 18. CLOSING SPRING 27. MAIN DRIVE LINK

ft

ft

Figure 2-16. Power-Operated (Stored-Energy) Mechanism Graphic Details

(Close Spring Shown in the Charged Position)

=I-

Broken weld from center pole lever to pole shaft (21). Another lever not shown in diagram

had an intact weld. The combination of broken weld, manufacturing tolerance, and high

cycle wear are considered to be factors in the mechanical binding of the breaker.

(Figure from Maintenance Program Manual MPM-WOGRTSDS 416-01 for W type DS-416 reactor trip

circuit breakers.)

Attachment 2 IN 87-35 July 30, 1987 GENERIC COMMUNICATIONS ON REACTOR TRIP BREAKERS

AND SIMILAR CIRCUIT BREAKERS

Information Notice 86-62, "Potential Problems in Westinghouse Molded Case

Circuit Breakers Equipped With a Shunt Trip," July 31, 1986.

Information Notice 85-93, "Westinghouse Type DS Circuit Breakers, Potential

Failure of Electric Closing Feature Because of Broken Spring Release Latch

Lever," December 6, 1985.

Bulletin 85-02, 'Undervoltage Trip Attachments of Westinghouse DB-50 Type

Reactor Trip Breakers," November 5, 1985.

Information Notice 85-58, "Failure of a General Electric Type AK-2-25 Reactor

Trip Breaker," July 17, 1985.

---

Supplement 1, November 19, 1985.

Information Notice No. 83-76, "Reactor Trip Breaker Malfunctions (Undervoltage

Trip Devices on GE Type AK-2-25 Breakers)," November 2, 1983.

Generic Letter 83-28, "Required Actions Based on Generic Implications of Salem

ATWS Events," July 8, 1983.

Information Notice 83-18, "Failures of the Undervoltage Trip Function of

Reactor Trip System Breakers," April 1, 1983.

Bulletin 83-04, "Failure of the Undervoltage Trip Function of Reactor Trip

Breakers," March 11, 1983.

Bulletin 83-01, "Failure of Reactor Trip Breakers (Westinghouse DR-50) to Open

on Automatic Trip Signal," February 25, 1983.

Circular 81-12, "Inadequate Periodic Test Procedure of PWR Protection System,"

July 22, 1981.

Bulletin 79-09, "Failures of GE Type Circuit Breaker in Safety Related System,"

April 17, 1979.

Attachment 3 IN 87-35 July 30, 1987 LIST OF RECENTLY ISSUED

INFORMATION NOTICES 1987 Information Date of

Notice No. Subject Issuance Issued to

87-34 Single Failures in Auxiliary 7/24/87 All holders of an

Feedwater Systems OL or a CP for

pressurized water

reactor facilities.

87-33 Applicability of 10 CFR 7/24/87 All NRC licensees.

Part 21 to Nonlicensees

87-3? Deficiencies in the Testing 7/10/87 All nuclear power

of Nuclear-Grade Activated reactor facilities

Charcoal. holding an OL or CP.

87-31 Blocking, Bracing, and 7/10/87 All NRC licensees.

Securing of Radioactive

Materials Packages in

Transportation.

87-30 Cracking of Surge Ring 7/2/87 All nuclear power

Brackets in Large General reactor facilities

Electric Company Electric holding an OL or CP.

Motors.

87-29 Recent Safety-Related. 6/26/87 All NRC licensees

Incidents at Large authorized to possess

Irradiators. and use sealed sources

in large irradiators.

87-28 Air Systems Problems at 6/22/87 All nuclear power

U.S. Light Water Reactors. reactor facilities

holding an OL or CP.

87-27 Iranian Official Implies 6/10/87 All nuclear power

Vague Threat to U.S. reactor facilities

Resources. holding an OL or CP,

research and nonpower

reactor facilities, and fuel fabrication

and processing

facilities using or

possessing formula

quantities of special

nuclear material.

OL = Operating License

CP = Construction Permit

• IN 87-35 July 30, 1987 No specific action or written response is required by this information notice.

If you have any questions about this matter, please contact the Regional

Administrator of the appropriate NRC regional office or this office.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contacts: C. Vernon Hodge, NRR

(301) 492-8196 T. Peebles, RII

(404) 331-4196 A. Ruff, RII

(404) 331-5540

Attachments:

1. Power-Operated (Stored-Energy) Mechanism Graphic Details

2. Generic Comnunications on Reactor Trip Breakers

3. List of Recently Issued NRC Information Notices

• SEE PREVIOUS CONCUI

• OGCB:DOEA:NRR *RII *PPMB:ARM *C/OGCB:DOEA:NRR

CVHodge

07/17/87 TPeet

07/1l

TechEd CHBerlinger

07/17/87 07/17/87 df1 O7i2787

IN 87-XX

July xx, 1987 No specific action or written response is required by this information notice.

If you have any questions about this matter, please contact the Regional

Administrator of the appropriate NRC regional office or this office.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contacts: C. Vernon Hodge, NRR

(301) 492-8196 T. Peebles, RII

(404) 331-4196 A. Ruff, RII

(404) 331-5540

Attachments:

1. Generic Communications on Reactor Trip Breakers

2. Figure 2-16, Power-Operated (Stored-Energy) Mechanism

Graphic Details

3. List of Recently Issued NRC Information Notices

freL 6f t A

OGCB:DOEA:NRR RII P PPMB:ARM C/OGCB:DOEA:NRR D/DOEA:NRR

CVHodge TPeebles TechEd CHBerlinger CERossi

07/11/87 07/r7/87 07/t1/87 07/tq/87 07/ /87