ML20085M021

AO BFAO-749W:on 740212,during Blowdown Following Main Steam Line Isolation Valve Closure,Pressure Relief Valve PCV 1-41 on Main Steam Header Failed to Reseat.Cause Unknown.Valve Replaced

ML20085M021
Person / Time
Site:	Browns Ferry
Issue date:	02/22/1974
From:	Eric Thomas TENNESSEE VALLEY AUTHORITY
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20085M020	List: ML20085M021 ML20085M025
References
AO-BFAO-749W, NUDOCS 8311070093
Download: ML20085M021 (3)

Text

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• TENNECSEE VALL AUTHO AITY MB CHATTANOOGA, TENNESSEE *: L

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@[c5 February 22, 1974 ,, s

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Mr. John F. O' Leary, Director cm a. ')lp,Q ~' ,2 Directorate of Licensing t .:ro ^

Office of Regulation

')Q L d "l** M U.S. Atomic Energy Co ::nission i g .p Washington, DC 20545

Dear Mr. O' Leary:

tem 1ESSEE VALLEY AUTHORITY - BROWNS FERRY NUCLEAR PLANT UNIT 1 -

DOCKET NO. 50-259 - FACILITY OFFJATING LICENSE DPR ABNORMAL OCCURRENCE REPORT BFAO-749W The enclosed report is to provide details concerning =ain steam pressure relief valve PCV 1-41 that failed to resent after having lifted at approxi=ately 1,080 psig which occurred on Browns Ferry Nuclear Plant unit 1 on February 12, 1974, and is submitted in accordance with Ippendix A to Regulatory Guide 1.16, Revision 1, October 1973 Very truly yours, TENNESSEE VALLEY MJTHORITY f4.4A<A

. CCas lirector of Power Production Enclosure CC (Enclosure):

Mz. Nor=an C. Moseley, Director Region II Regulatory Operations Office, USAEC 230 Peachtree Street, NW., Suite 818 Atlanta, Georgia 30303

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I i C 1 l 8311070093 740306

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ABNORMAL OCCURRENCE REPORT r

Report No.: BFAO-749W ReIorti Date: February 22, 1974 (f

• Occurrence Date: February 12,1774 Facility: Browns Ferry Nuclear Plant unit 1 .

Identification of Occurrence Main steam pressure relief valve PCV 141 fai?ed to resent after having lifted at approxir.ately 1,080 psig.

Conditions Prior to Occurrence The reactor was in the shutdown condition following reactor isolation as a result of high temperature in the main steam pipe tunnel. High tunnel temperature occurred because of reduced ventilation flow. The reduced flow resulted from shutting down ventilation fans to calibrate a reactor building ventilation controller.

Descript' ion of Occurrence During . blowdown of reactor pressure following main steamline isolation valve closure, pressure relief valve PCV 1-41 on the main steam header failed to reseat.

Designation of Annarent Cause of Occurrence PCV 1-41 actuated a number of times during the pressure blowdown following isolation. The exact cause of failure to reseat is not known at this time.

The valve will be disassembled and inspected with the manufacturer's representative present to determine cause of failure to reclose. Before its failure to reclose, this relief valve had been manually operated at least

! two times during startup testing and eleven times during torus testing. Since i

}thisreliefvalvehasthelowestsetpointofallthereliefvalves,ithas operated in all of the automatic pressure actuation situations. Only one other valve has been operated automatically by pressure actuation.

Analysis of Occurrence All plant systems performed their intended functions in t,he expected manner after the relief valve failed to reclose. The average rate of change of the

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[freactog of 100 vessel and coolant did not greatly exceed the normal'cooldow

,; . Preliminary calculations indicate that the blowdown did not contribute significantly to the' vessel usage factor. The preliminary esiculations show the following: ,

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Vessel flange and studs--No effect on usage factor

' Vessel shell-- Usage factor = 0.00003 Feedwater nozzle--Usage factor = 0.00017 All other plants operating parameters were within satisfactory limits, and no safety limits were exceeded.

Corrective Action The failed valve was replaced with a new relief valve. Disassembly of the failed valve when perfor=ad will supply information for use in detemining preventive ceasures if needed. After fully determining the cause of the valve failure, we will supply this information by amending this report.

Failure Data TargetRockCorporation,Model67F, safety /reliefvalve Size: 6 inch inlet; 10 inch outlet 1,200 psi design pressure Setpoint 1,080 psig + 11 psi c Capacity 800,000 lb/hr saturated steam Serial No. 55 O

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