ML20085G621

AO BFAO-731W:on 730808,refueling Zone Vacuum Increased to Approx 0.8 Inch of Water.Caused by Slow Response of Refueling Zone Static Pressure Control Modulating Dampers. Setting of Switches Decreased

ML20085G621
Person / Time
Site:	Browns Ferry
Issue date:	08/17/1973
From:	Eric Thomas TENNESSEE VALLEY AUTHORITY
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20085G594	List: ML20085G601 ML20085G621
References
BFAO-734W, NUDOCS 8308290227
Download: ML20085G621 (2)

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O TENNESSEE CHATTANOOGA, VALLEY AUTHO AITY M], ,e TENNESSEE j 3740'1 L _em tog 1 %~ !s k

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x Mr. John F. O'Icary, Director g MG211973: j' y

Directorate of Licensing g L3 f,*:1pua U. D. Atomic Energy Commission , u.m 2./ J Washington, DC 20545 s Ed 4:::aa ('

Dear Mr. O'Ieary:

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Subject:

TENIESSEE VALIEY AU1'HORITY - BROWNS FERRY NUCIEAR PIANT

, UNIT 1 - DOCKET NO 50-259 - FACILITY OPERATING LICENSE DPR ABNORMAL OCCURRENCE REPORT BFAO-734W The purpose of this report is to provide details concerning an incident which occurred on August 8,1973, when the refueling zone vacuum increased to approximately 0.8 inch of water.

Description of Incident I

While conducting a surveillance test on unit 1 to verify the capability

! of the standby gas treatment system to maintain at least 1/4 inch of i water vacuum on the secondary containment after modification to secondary containment boundary doors, the modulating dampers failed tolimittherefuelingfloorvacuumto1/2inchofwater. The reactor was in the refueling mode, and new fuel was being removed to permit inspection of control rods. Fuel-handling operations were immediately

suspended.

Invcatigation and Corrective Action The trouble was traced to the slow response of the refueling zone static pressure control modulating dampers. When the refueling zone static j pressure control modulating dampers actuated to maintain the 1/2-inch-water vacuum, their response time to changing vacuum conditions was too slow to prevent closure of the in-series isolation dampers set at 3/8-inch-water vacuum. Closure of the isolation dampers caused the con-trolling relays to deenergize, resulting in lockout which prevents further operation of the isolation dampers and static pressure control modulating dampers.

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. . 2 Mr. John F. O' Leary August 17, 1973 TENNESSEE VALLEY AUTHORITY - BROWNS FERRY NUCLEAR PIANT .

UNIT 1 - DOCKET NO. 50-259 - FACILITY OPERATING LICENSE DPR ABNORMAL OCCURRENCE REPORI BFAO-734W The setting of the pressure differential switches controlling the isolationdampershasbeenchangedfrom3/8-inch-watervacuumto 1/4-inch-watervacuum. This allows the isolation dampers and static pressure control modulating dampers to operate and maintain secondary containment pressure limits. Concurrence with the setpoint change was obtained from the dcsign engineering department. A surveillance test was satisfactorily performed following these changes, and fuel-handling operations were resumed.

Very truly yours, TENNESSEE VA Y AUTHORITY c .

E. F. Thomas Director of Power Production .

( CC: Mr. Normen C. Mcseley, Director I

Region II Regulatory Operations Office, USAEC

! 230 Peachtree Street, NW.

i Atlanta, Georgia 30303 l

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