ML20085G753

AO BFAO-7312W:on 730912,suppression Chamber Vacuum Breakers Failed.Caused by Isolation of Switches When Inadvertently Ommited from Valve Checklists.Switches Valved In,Calibr Checked & New Instrument Checklists Prepared

ML20085G753
Person / Time
Site:	Browns Ferry
Issue date:	09/21/1973
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 8308290334
Download: ML20085G753 (2)

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TENNESSEE VALLEYTENNESSEE CHATTANOOGA, AUTHORI'TY  ; C~7 - 17IjJ -

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1n e WLaTk_%d L September 21, 1973

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".. I h g3 q, g 4 l,' [G- N 4h Mr. John F. O'1cary, Director

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Directorate of Licensing

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Dear Mr. O' Leary:

TE! LESSEE VALIEY AUTHORITY - EROWIIS FERRY NUCI2AR PLA:S UNIT 1 -

DOCKET NO. 50-259 - F/.CILITY OPERATING LICENSE DPR IIII0f01AL OCCURRE1CE REPOITf EFAO-7312U The purpoce of this report la to provide details concerning the failure of Erowns Ferry unit 1 reactor building to cuppreccion >

chamber vacuum breakers to operate. This occurrence was reported on September 12, 1973, to W. S. Littic, AEC-DRO inspector, who was on site, and by tele 6 ram on September 12, 1973, to the Region II Directorate of Regulatory Operations in Atlantr., Georgia.

Deceription of the Incident During reactor cooldown on September 12, 1973, the dryvell precsure decreaced to lecc than atmospheric. At about 1:00 4 a.m. on thic date the operator noticed the dryvell pressure approaching '-0 5 inches H20.

It continued to decrease to -0.6 inches H20 at which time the operator

• manually opened the reactor building to suppression chamber vacuum breakers. The vacuum breakers should have opened automatically at f.

-0 5 inches H2O as sensed by PdIS-&-20 and PdIS-M-21 but failed to do so.

Investication and Corrective Action PdIS-@-20 and PdIS-@-21' cence the difference in pressure betteen the reactor buildin6 and suppression chamber and initiate-logic circuitry to open the vacuum breakers when the suppression chamber ic > 0 5 inches H2 O lower than the reactor building.

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Mr. John F. O'Inary TEII:iESSEE VALLEY NJTHORI"Y - ERC'.l::S FERRY NUCLEAR PLANT U!i1T 1 -

DOCKET IIO. 50-259 - FACILITY OPEP2TI"G LICE:iSE DPR AENOPSIAL OCCURRE:!CE REPCXf EFAC-7312W An investigatica cubsequent to the incident revealed that the prescure differential cvitenes were isolated. A check of operating instructions showed there inctrwnent root valves were not included in the valve checklicto. They were inadvertently omitted from the checklists becauce drawings from which the check 11sto vere made did not chov these valvec.

The evitches were valved in and a calibratica check was made which found then to te cet at the proper ret point.

Operating instruction checklists vere reviewed against the drawingc and the as-built ecndition to dete. ine if icolctica valves for other similar instrtncats were omitted fro:n checklistc. Scme casec were found, primarily on the ventilation cyctem, where instrument valves were not shown on valve checkliets.

To eliminate thin type of oversi ht, G instrunent checklists which include all instrumentation in critical plant cycte:r.c have been prepared nad are nou included in nomal operutirg inctructienc. Thece instrument checklists vill be used to verify that all instrumento are in cervice. Ilo other instrumentation required to be ir. cervice by tcchnical specificationc was found to be icolated. Additionally,

" System Status Report" procedures have been broadened to include documentation when inctInmentation lo removed from service.

Very truly yours, TEIIESSEE VALU2 NJTEORITY

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g D irector of Power Production

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CC: fir. Noman C. Moseley, Director '

Region II Regulatory Operationc Office, USAEC 230 Peachtree Street, I3 f y

Atlanta, Georgia 30303  !

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