ML19275A072

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Final Deficiency Rept Re Electrical Handhole Structural Integrity.Evaluation Indicates That Six Structures in Question Are Adequate for All Design Basis Events
ML19275A072
Person / Time
Site: Sequoyah  Tennessee Valley Authority icon.png
Issue date: 08/16/1979
From:
TENNESSEE VALLEY AUTHORITY
To:
Shared Package
ML19275A063 List:
References
NCR-CDB-79-4, NUDOCS 7908300707
Download: ML19275A072 (1)


Text

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ENCLOSURE SEQUOYAH NUCLEAR PLANT UNITS 1 AND 2 ELECTRICAL hANDH0LE STRUCTURAL INTEGRITY NCR CDB 79-4 10 CFR 50.55(e)

FINAL REPORT Description of Deficiency A recent review of the structural design of six handholes in an under-ground electrical conduit run between the Diesel Generator Building and the Auxiliary Building revealed that seismic and flood loads had not been considered in the design. Handholes are similar to manholes, being smaller but large enough for one man to stand in and work. The handhole numbers are 18-S, 19-S, 20-S, 21-S, 22-S, and 23-S.

Seismic and flood loads were not considered in the original design of these structures in 1972. The oversight was not detected during the checking and review conducted at that time.

Safety Implications

' The conduit run carries the emergency power leads to safeguards equip-ment in the Auxiliary Building. Failure of the handhole structures during a seismic event, or floating or other failure during a flood, could result in open or shorted power leads. This could result in at least a reduction in redundant safety equipment trains. However, the existing design was proven to be adequate, as discussed under " Corrective Action" below.

This nonconformance has no known generic 1 aplications. Seismic and flood loads were considered in the design of the manholes in the same conduit run. The similar Watts Bar Nuclear Plant design was carried out much later than the Sequoyah one and by different employees.

Corrective Action The existing handholes design has been evaluated by including design basis seismic and flood loads in the appropriate loading combinations.

The six structures in question were all found to be adequate for all design basis events.

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