ML20084U415

AO BFAO-731W:on 730628,refueling Interlock Failed.Caused by Switch Being Loosened or Misaligned When Switch Actuating Arm Passed Over Power Cable Which Had Caught Under Platform Frame.Switch Readjusted

ML20084U415
Person / Time
Site:	Browns Ferry
Issue date:	07/06/1973
From:	Eric Thomas TENNESSEE VALLEY AUTHORITY
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084U373	List: ML20084U415 ML20084U427
References
AO-BFAO-731W, NUDOCS 8306290025
Download: ML20084U415 (2)

Text

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O O TENNESSEE CHATTANOOGA, VALLEY TENNESSEE AUTHORITY M]\ , /r 3740'l L LlA

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July 6, 1973 //

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Mr. John F. O' Leary, Director 4 Directorate of Licensing g N4 p U. S. Atomic Energy Ccemiscion * ,,

Washington, DC 20545

Subject:

TENNESSEE VALLEY AUTHORITY - BROWNS FERRY NUCLEAR PIANT UNIT 1 - DOCKET NO. 50-259 - FACILITY OPERATIHG LICENSE DPR ABNOR!'AL OCCURRENCE REPORT BFAO-731W The purpose of this report is to provide details concerning the failure of a refueling interlock at Browns Ferry Nuclear Plant Unit 1 on June 28, 1973 Description of Incident During initial fuel loading of unit 1, the reactor operator and a General Electric Ccepany representative in the control room noted that the control rod permissive light remained lit when the fuel grapple on the refueling platform was moved over the reactor pressure vessel to load the 43rd fuel element into the core. A limit switch which had failed to actuate properly was manually actuated to obtain a rod block, and the suspended fuel element was properly positioned in the core. Further fuel loading operations were suspended.

Investigation and Corrective Action The cause of the trouble was immediately traced to a limit switch adjustment on the refueling platform. The function of the switch is to prohibit control rod withdrawal when the loaded refueling platform is over the core. The limit switch had functioned correctly when loading the previous (42nd) fuel assembly.

Before loading the 42nd fuel assembly, the power supply cable to the refueling platform had caught under the platform frame and had been freed. A visual inspection and functional check at the time did not reveal any derangement. In retrospect, it appears the refueling

' interlock switch had loosened or misaligned slightly when the switch i actuating arm passed over the captured power cable.

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Mr. John F. O' Leary July 6, 1973 TENNESSEE VALLEY AUTHORITY - BROWNS FERRY NUCLEAR PIANT UNIT 1 - DOChTf NO. 50-259 - FACILITY CPERATING LICENSE DPR ABNORTAL OCCURRENCE REPORT BFAO-731W The interlock switch was read. justed to properly perform by repositioning the actuating arm. The~ tension on the power supply cable reel was increased to prevent entanglement with the moving platform.

This switch, identified as " refueling interlock, switch No.1," was subsequently surveillance-tested. An adjacent mounted interlock switch, identified as " refueling interlock, switch No. 2," which also passed over the power cable was also visually inspected and surveillance-tested. Upon satisfactory ccmpletion of these surveillance tests and review by the Plant Operations Review Committee, fuel loading was resumed.

Very truly yours, TENNESSEE VALLEY AUTHORITY

• k *f B.F. Thomas]

Director of Power Production CC: Mr. Norman C. Moseley, Director Region II Regulatory Operations Office Atomic Energ'/ Ccmmission 230 Peachtree Street, IM.

Atlanta, Georgia 30303 9

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