ML20084U609

Interim Deficiency Rept Re Failure of Channel a Traveling Incore Probe Cable & Detector.Initially Reported on 730503. Util & GE Are Determining Safety Implications of Failure & Corrective Measures Required

ML20084U609
Person / Time
Site:	Browns Ferry
Issue date:	06/01/1973
From:	Gerald Williams TENNESSEE VALLEY AUTHORITY
To:	Kruesi F US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084U431	List: ML20084U446 ML20084U462 ML20084U499 ML20084U519 ML20084U551 ML20084U609 ML20084U662 ML20084U689 ML20084U853 ML20084U869
References
10CFR-050.55E, 10CFR-50.55E, NUDOCS 8306290141
Download: ML20084U609 (2)

Text

f OTENNESSEE n VALLEY A\_4HOAITY CHATTANOOGA, TENNESSEE 37401 l 40~

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PARTNE ASHIP June 1,1973 Mr. F. E. Krueci, Director Directorate of Regulatory Operations U.S. Atomic Energy Comission Washington, DC 205h5

Dear Mr. Kruesi:

On May 3, 1973, TVA made initial report to AEC-DRO Inspector l W. S. Little of the failure of a channel A Traveling Incore Probe (TIP) cable and detector at Browns Ferry Nuclear Plant unit 1. In accordance with paragraph 50.55(e) of 10 CFR 50, we are submitting the enclosed formal interim report of the failure. We expect to submit the final report by July 10, 1973.

Very truly yours,

(~L LILW Godwin Williams, Jr. '/ f 1

Assistant Manager of Power' Enclosure CC (Enclosure):

Mr. Norman C. Moseley, Director Directorate of Regulatory Operations U.S. Atomic Energy Comission f Region II - Suite 818 230 Peachtree Street, NW.

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o Browns Ferry Nuclear Plant Unit 1 Deficiency Report j l

CHANNEL A TIP FAILURE

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On the morning of May 2,1973, TIP machine A drive cable and detector wem found damaged. The detector had been severed from the cable. -

It is believed that operation of channel A and B of the TIP system was I

initiated manually from the unit 1 control room. At that time the containment was pressurized to 49 psig during GE No.14 test of the

- integrated leakage rate then in progress. Operation of a TIP channel requires that a ball valve be open in the guide tube to the drywell.

.Apparently the containment pressure was applied down the guide tube containing the probe through the open ball valve to the operating mechanism t'

of the chamber shield limit switch. This limit switch normally stops further withdrawal when the detector on the end of the TIP cable is withdrawn past the switch operating mechanism and through the shield. Design of the limit switch operating mechanism, however, would allow the pressure to hold the 4 mechanism against the switch actuator button and prevent detection of turther withdrawal. Failure of the shield liuit switch to stop the drive mechanism appears to have allowed the channel A detector to be pulled into the drive mechanism where the drive gear probably severed the cable. The channel B detector was pulled past its shield limit switch but did not enter its

, drive unit.

TVA and GE are in the process of determining the safety implications of this failure and the corrective measures required. A final report on this failure is expected to be submitted by July 10, 1973. ,

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