ML20085G621
| 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: |
| References | |
| BFAO-734W, NUDOCS 8308290227 | |
| Download: ML20085G621 (2) | |
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TENNESSEE VALLEY AUTHO AITY M], j CHATTANOOGA, TENNESSEE
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j' Mr. John F. O'Icary, Director Directorate of Licensing g
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Dear Mr. O'Ieary:
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
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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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