ML20085G746

Rev 1 to AO BFAO-7312W:on 730912:suppression Chamber Vacuum Breakers Failed to Open at 0.5 Psid.Caused by Isolation of Pressure Differential Switches Valved in

ML20085G746
Person / Time
Site:	Browns Ferry
Issue date:	06/03/1974
From:	Eric Thomas TENNESSEE VALLEY AUTHORITY
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20085G751	List: ML20085G746 ML20085G753 ML20085G762
References
AO-BFAO-7312W, NUDOCS 8308290327
Download: ML20085G746 (2)

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Mr. John F. O' Leary, Director Directorate of Licencind 50-2:;9 Office of Eeculation U.S. Atomic Energy Cc~niccion Wachington, DC 20545 Decr 10'. O' Leary:

TEIII!E3SEE VALL9. Y ALCHCRITY - BROWI!S FERFY I;UCLEAR PLit:T U'IIT 1 -

DOCKET I!O. 50-259 - SACILITY OPER'TIIIG LICE::SE DPR ABI:LR?%L s OCCURREI!CE REPORT EFAO-7312W, REVISIO'! 1 The enclosed reviced report in to correct the error concerning unit of preccure in EFAO-7312W submitted September 21, 1973 Very truly ycuro, ,/ \ -

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Mr. I:cr.~an C. ::cceley, Director Region II Regulator;. Operatienc Office, USAEC 230 Peachtree S;rcet, IT4. , Suite 818 Atlanta, Georgia 30303 1

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heport Co.- BFAO-7312W (Revision 1) l Peport Late:

Occurrence Date: Ocptember 12, lcI/3 Facility: Drownc Ferry nuclear Plent - Unit 1 The purpose of thic report is to provide detalle concerning the failure of l Erownc Ferry unit 1 reactor buildin:; to cuppreccion chamber vacuum breakers l to opernte. Thic occurrence wac reported on Septerter 12, 1973, to W. G. Little, AEC-Dh0 Incpector, ,no vac on cite, and by telegran on Ceptember 12, 1973, to the Region II Directorate of Regulatorj Operations in Atlanta, Georgia.

Decerintion of the Incident I

During reactor cooldown on Septen.ber 12, 1973, the dr/well precsure decreaced to lecc than atmocpheric. At about 1+:00 a.m. on thic date, the operator noticed the drivell preccure approaching -0 5 psi. It cortinued to decrease to -0.6 pci

! at which time the operator manually opened the reactor building to suppreccion  !

chan.ber vacuum breakers. The vacuum treakers chould have opened automatically  !

at 0.5 paid, as senced by PdIS-61-20 4 and FdIG-61-21, but failed to do no.

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lnventir; ition and Corretive Action l PdI3-61-20 and PdIS-6b 21 cence the difference in pressure between the reactor 4

building and cupprecsion chamber and initiate logic circuitry to open the vacuu.c breakers when the cuppreccion che-ber is 0 5 psi lcuer than the reactor building.

An investigation cubcecuent to the incident revealed that the pressure differential switchen were icolated. A check of operatin j; instructions showed these instrument root valves were not included in the valve checklicts. They were inaavertently omitted from the checklicts becauce drawings from which the checklists were l

mnde did not chow thece vslvec.

The ;witchen were valved in and a calibration check was cade which found then to be set at the proper setpoint.

Operating instruction checklicts were reviewed against the drawings and the as-built condition to determine if icolation valves for other sinilar instrr.cnts were omitted frca checklicts. Some esses were found, primarily on the ventilation cyctem, where inctreront valvec were not chown on valve checklictc.

To eliminute thin type of overcicht, instrument checklists which include all inntrumentation in critical plant cystecc have been prepared and are now included in normal operatind instructions. These instrument checklists will be uced to verify tnat a'l inctruments are in service. Ho other instrumentation recuired l to be in cervice by technical specificationc us found to be icolated. Additionally, i " System Status Eeport" procecurec have ccen trondened to include documentation

, when instrumentation is rec.oved from service, k

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