ML19208A713

Final Rept Re Flexible Bellows Penetrations of Steel Containment Vessel Misaligned During Installation.Caused by Faulty Installation Sequence.Bellows Reinstalled.Technical Supervisor Appointed to Monitor Further Installation

ML19208A713
Person / Time
Site:	Sequoyah
Issue date:	09/11/1979
From:	TENNESSEE VALLEY AUTHORITY
To:
Shared Package
ML19208A712	List: ML19208A711 ML19208A713
References
NCR-1666, NUDOCS 7909170329
Download: ML19208A713 (2)

Text

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. ENCLOSURE SEQUOYAH NUCLEAR PLANT UNIT 1 FLEXIBLE BELLOWS PENETRATIONS OF STEEL CONTAINMEAT VESSEL MISALIGNED DURING INSTALLATION NCR 1666 10 CFR 50.55(e)

FINAL REPORT Description of Deficiencv During hot functional preoperational testing at unit 1 of Sequoyah Nuclear Plant, removal of the bellows restraints on 32 bellows penetrations o.f the steel containment vessel (SCV). revealed that those bellows restraints

,4ere misaligned. This deficiency is considered reportable because three of

[the bellows penetrations might have leaked containment atmosphere to the

'/ annulus region (between the SCV and concrete containment) when subj ected to the deflections associated with a postulated safe shutdown earth-quake (SSC) or design basis accident (DBA). The balance of the 32 bellows penetrations were analyzed by the manufacturer (Tube Turns, Louisville, Kentucky) and found to be acceptable with the present misalignment to operate when subjected to the deflections associated with an SSE or DBA without containment leakage.

The apparent cause of this deficiency is a taulty installation sequenc'c that permitted the containment-to-bellows weld to be completed before making process -

pipe closure welds. Hence, slight misalignment of the piping resulted in misalignment of the bellows.

Safety Implications If this deficiency had remained uncorrected, it is possible that 3 of 32 bellows penetrations might possibly have failed when subjected to the deflec-tions associated with a postulated SSE or DBA. In this context, a failure would be a small split in the bellows which would permit leakage of the containment atmosr iere into the annulus area. .

Corrective Actions TVA inspected all bellows penetration assemblies in the SCV and took align-ment data. The alignment data was analyzed by the bellows manufacturer.

Following analysis, the bellows manufacturer placed the bellows in three categories.

1. Those bellows (three in number) that analysis could not ensure would survive their misalignment plus the deflections associated with a postulated SSE or DBA without the possibility of a leakage

2. Those bellows (15 in number) that analyses showed would survive their misalignment plus the deflections associated with a pcstulated SSE or DBA, but would require inspection before continued operation

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3. Those bellows (14 in number) that analyses showed would be completely satisfactory for 40 years life with their installed misalignment plus the deflections associated with a postulated SSE or DBA The three bellows which were not c pable of surviving the deflections associated with a postulated SSE or DBA without possible leakage as installed were reinstalled. During the teinstallation process, no problem other than the misalignment was found. The proper installation sequence was strictly followed during reinstallation of these three bellows.

heasurements made following reinstallation of two of these three bellows (X-33 and X-108) ensured that they would be corpietely satisf actor- over 40 years of plant life. Measurements made on the other bellows (X-109) were analyzed as being satisfactory with its misalignment to survive the deflections associated with a postulated SSE or DBA with a required inspection before continued operation.

Means Taken to Prevent Recurrence Sites where TVA has nuclear plants under construction have been requested to reemphasize to craft employees installing bellows that construction efficiency requires proper alf nment of piping and bellows nozzles before installation welding. The Seq yah Nuclear Plant construction forces have appointed a technical supervisor to monitor the installation of all remaining bellows penetrations.

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