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 L NRC/IE
To:
References
IN-85-058, NUDOCS 8507120303
Download: ML031180184 (3)

SSINS NO.: 6835IN 85-58UNITED STATESNUCLEAR REGULATORY COMMISSIONOFFICE OF INSPECTION AND ENFORCEMENTWASHINGTON, D.C. 20555July 17, 1985IE INFORMATION NOTICE NO. 85-58: FAILURE OF A GENERAL ELECTRIC TYPE AK-2-25REACTOR 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) orconstruction permit (CP).

Purpose

This information notice is to alert recipients of a potentially significantproblem pertaining to the failure of a General Electric (GE) -type AK-2-25reactor trip breaker. It is expected that recipients will review the informationfor applicability to their facilities and consider actions, if appropriate, topreclude a similar problem occurring at their facilities. However, suggestionscontained 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 refuelingoutage and preparing to restart. During the outage, the licensee installedrefurbished reactor trip breakers (RTBs). On June 5, 1985, one of the dc RTBsfailed to trip open when its undervoltage trip attachment (UVTA) was actuatedduring a test. Although the UVTA had de-energized, its armature had not movedout of the energized position (a sketch of an RTB with all components in theirnormal positions is shown in Attachment 1). Investigation revealed that thetrip paddle, which is the mechanical interface between the armature and thetrip shaft of the RTB, had jammed against the armature, and as a result the RTBwould not trip. Subsequently, when the shunt trip coil was actuated, the trippaddle associated with the UVTA rotated about 450 clockwise to a position abovethe armature (See Attachment 1). In-this position the armature cannot engagethe trip paddle when the UVTA is de-energized, and the RTB would not trip.Further investigation revealed that the clearance between the roller rivet andarmature within the UVTA was significantly greater than the specified allowablerange. This increased downward displacement was sufficient to allow the trippaddle to interfere with the armature. Preliminary information also indicatesthat the UVTA rivet-armature clearances may have been excessive for all five ofthe other RTBs installed at the plant.The RTBs used at B&W- and CE-designed reactor facilities are the GE-typeAK-2-25 breaker. The licensee had sent the Rancho Seco RTBs to GE-Atlanta for8507120303 IN 85-58July 17, 1985 refurbishment, which included installing a new lubricant in critical bearingsin the front frame of the RTB. Subsequent to their refurbishment, the RTBswere tested at B&W-Lynchburg and certified as acceptable for service as safety-related reactor trip breakers. Incoming receipt inspection of the RTBs atRancho 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 checksof the critical parameters of the breakers, as required for safety-relatedequipment. These procedures are based on guidance recently provided by B&W toits 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 inprevious vendor information, the measurement should be made with the UVTAarmature down in the energized position. The manufacturer's representative isproviding onsite assistance to the licensee. A B&W engineer also is assistingat the site. The licensee has identified the failure mechanism, completedappropriate corrective action, and satisfactorily tested all RTBs beforewithdrawing control rods and resuming power operations.The refurbishment of the RTBs is one of the major items of the long-termprogram developed by the B&W Owners Group and the CE Owners Group to assurethat 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 isof a different failure mechanism than previously experienced. The NRC iscurrently 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 RegionalAdministrator of the appropriate regional office or this office.Edward kil Jordan, DirectorDivisi of Emergency Preparednessand igineering Response-Office of Inspection and Enforcement

Technical Contact:

J. T. Beard, NRR(301) 492-7465R. N. Singh, IE(301) 492-8985Attachments:1. Undervoltage Trip Device Coil De-energized2. List of Recently Issued Information Notices

Attachment 2IN 85-58July 17, 1985LIST OF RECENTLY ISSUEDIE INFORMATION NOTICESInformation Date ofNotice No. Subject Issue Issued to85-5785-56Lost Iridium-192 SourceResulting In The Death OfEight Persons In MoroccoInadequate EnvironmentControl For Components AndSystems In Extended StorageOr LayupRevised Emergency ExerciseFrequency Rule7/16/857/15/857/15/8585-5585-54Teletheraphy Unit Malfunction 7/15/8585-5385-52Performance Of NRC-LicensedIndividuals While On DutyErrors In Dose AssessmentComputer Codes And ReportingRequirements Under 10 CFRPart 21Inadvertent Loss Or ImproperActuation Of Safety-RelatedEquipmentComplete Loss Of Main AndAuxiliary Feedwater At A PWRDesigned By Babcock & WilcoxRelay Calibration Problem7/12/857/10/857/10/857/8/857/1/85All power reactorfacilities holdingan OL or CP; fuelfacilities; andmaterial licenseesAll power reactorfacilities holdingan OL or CPAll power reactorfacilities holdingan OL or CPAll NRC licenseesauthorized to useteletheraphy unitsAll power reactorfacilities holdingan OL or CPAll power reactorfacilities holdingan OL or CPAll power reactorfacilities holdingan OL or CPAll power reactorfacilities holdingan OL or CPAll power reactorfacilities holdingan OL or CP85-5185-5085-49OL = Operating LicenseCP = Construction Permit