Information Notice 1985-58, Failure of a General Electric Type AK-2-25 Reactor Trip Breaker

Failure of a General Electric Type AK-2-25 Reactor Trip Breaker

ML031180184
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, 05000258, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant, Skagit, Marble Hill
Issue date:	07/17/1985
From:	Jordan E NRC/IE
To:
References
IN-85-058, NUDOCS 8507120303
Download: ML031180184 (3)

SSINS NO.: 6835 IN 85-58 UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF INSPECTION AND ENFORCEMENT

WASHINGTON, D.C. 20555 July 17, 1985 IE INFORMATION NOTICE NO. 85-58: FAILURE OF A GENERAL ELECTRIC TYPE AK-2-25 REACTOR TRIP BREAKER

Addressees

All nuclear power reactor facilities designed by Babcock and Wilcox Company

(B&W) and Combustion Engineering (CE) and holding an operating license (OL) or

construction permit (CP).

Purpose

This information notice is to alert recipients of a potentially significant

problem pertaining to the failure of a General Electric (GE) - type AK-2-25 reactor trip breaker. It is expected that recipients will review the information

for applicability to their facilities and consider actions, if appropriate, to

preclude a similar problem occurring at their facilities. However, suggestions

contained in this information notice do not constitute NRC requirements; there- fore, no specific action or written response is required.

Description of Circumstances

The Rancho Seco Nuclear Power Generating Station was completing a refueling

outage and preparing to restart. During the outage, the licensee installed

refurbished reactor trip breakers (RTBs). On June 5, 1985, one of the dc RTBs

failed to trip open when its undervoltage trip attachment (UVTA) was actuated

during a test. Although the UVTA had de-energized, its armature had not moved

out of the energized position (a sketch of an RTB with all components in their

normal positions is shown in Attachment 1). Investigation revealed that the

trip paddle, which is the mechanical interface between the armature and the

trip shaft of the RTB, had jammed against the armature, and as a result the RTB

would not trip. Subsequently, when the shunt trip coil was actuated, the trip

paddle associated with the UVTA rotated about 450 clockwise to a position above

the armature (See Attachment 1). In-this position the armature cannot engage

the trip paddle when the UVTA is de-energized, and the RTB would not trip.

Further investigation revealed that the clearance between the roller rivet and

armature within the UVTA was significantly greater than the specified allowable

range. This increased downward displacement was sufficient to allow the trip

paddle to interfere with the armature. Preliminary information also indicates

that the UVTA rivet-armature clearances may have been excessive for all five of

the other RTBs installed at the plant.

The RTBs used at B&W- and CE-designed reactor facilities are the GE-type

AK-2-25 breaker. The licensee had sent the Rancho Seco RTBs to GE-Atlanta for

8507120303

IN 85-58 July 17, 1985 refurbishment, which included installing a new lubricant in critical bearings

in the front frame of the RTB. Subsequent to their refurbishment, the RTBs

were tested at B&W-Lynchburg and certified as acceptable for service as safety- related reactor trip breakers. Incoming receipt inspection of the RTBs at

Rancho Seco consisted of only a visual review; no functional test nor verifi- cation of critical parameters was conducted before installation.

At Rancho Seco, the licensee has now developed procedures to perform checks

of the critical parameters of the breakers, as required for safety-related

equipment. These procedures are based on guidance recently provided by B&W to

its customers. It is our understanding that CE has not issued similar guidance.

The UVTA rivet-armature clearance is a difficult measurement to perform pro- perly and may require a special tool. Further, although not mentioned in

previous vendor information, the measurement should be made with the UVTA

armature down in the energized position. The manufacturer's representative is

providing onsite assistance to the licensee. A B&W engineer also is assisting

at the site. The licensee has identified the failure mechanism, completed

appropriate corrective action, and satisfactorily tested all RTBs before

withdrawing control rods and resuming power operations.

The refurbishment of the RTBs is one of the major items of the long-term

program developed by the B&W Owners Group and the CE Owners Group to assure

that the RTBs will function in a highly reliable manner. The failure experi- enced at Rancho Seco is the first repotted-failurb of a refurbished RTB and is

of a different failure mechanism than previously experienced. The NRC is

currently assessing the generic applicability of this failure.

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 regional office or this office.

Edward kil Jordan, Director

Divisi of Emergency Preparedness

and igineering Response

- Office of Inspection and Enforcement

J. T. Beard, NRR

(301) 492-7465 R. N. Singh, IE

(301) 492-8985 Attachments:

1. Undervoltage Trip Device Coil De-energized

2. List of Recently Issued Information Notices

Attachment 2 IN 85-58 July 17, 1985 LIST OF RECENTLY ISSUED

IE INFORMATION NOTICES

Information Date of

Notice No. Subject Issue Issued to

85-57 Lost Iridium-192 Source 7/16/85 All power reactor

Resulting In The Death Of facilities holding

Eight Persons In Morocco an OL or CP; fuel

facilities; and

material licensees

85-56 Inadequate Environment 7/15/85 All power reactor

Control For Components And facilities holding

Systems In Extended Storage an OL or CP

Or Layup

85-55 Revised Emergency Exercise 7/15/85 All power reactor

Frequency Rule facilities holding

an OL or CP

85-54 Teletheraphy Unit Malfunction 7/15/85 All NRC licensees

authorized to use

teletheraphy units

85-53 Performance Of NRC-Licensed 7/12/85 All power reactor

Individuals While On Duty facilities holding

an OL or CP

85-52 Errors In Dose Assessment 7/10/85 All power reactor

Computer Codes And Reporting facilities holding

Requirements Under 10 CFR an OL or CP

Part 21

85-51 Inadvertent Loss Or Improper 7/10/85 All power reactor

Actuation Of Safety-Related facilities holding

Equipment an OL or CP

85-50 Complete Loss Of Main And 7/8/85 All power reactor

Auxiliary Feedwater At A PWR facilities holding

Designed By Babcock & Wilcox an OL or CP

85-49 Relay Calibration Problem 7/1/85 All power reactor

facilities holding

an OL or CP

OL = Operating License

CP = Construction Permit