ML19242D338

First Interim Deficiency Rept Re Steam Generator Water Level Ref Column Error.Caused by Westinghouse Design Oversight. Vendor to Perform Detailed Analyses to Determine Necessary Corrective Action

ML19242D338
Person / Time
Site:	Sequoyah
Issue date:	07/26/1979
From:	TENNESSEE VALLEY AUTHORITY
To:
Shared Package
ML19242D323	List: ML19242D319 ML19242D338
References
NCR-MEB-79-32, NRC-MEB-79-32, NUDOCS 7908140808
Download: ML19242D338 (2)

Text

ENCLOSURE SEQUOYAH NUCLEAR PLANT UNITS 1 AND 2 STEAM GENERATOR WATER LEVEL REFERENCE COLUMN ERFOR NCR MEB 79-32 10 CFR 50.55(e)

FIRST INTERIM REPORT Description of Deficiency The steam generator (SG) secondary side water level instrumentation inside the utilizes a reference water The col mncoluun external to reservoir tas a condensate the SG butat the top with SG enclosure. A the top portion of the reservoir connected to the SG steam space.

differential pressure transmitter is connected between the bottom of the column and the SG water space.

The column thus provides a ref erence water column of constant height to which the water depth in the SG is In the event of a high energy line co= pared through the transmitter.the reference column could become heated and break in the containment, the reduced water density could cause the SG water level to be indicated erroneously high. In the event of a main feedwater line break, this would delay actuation of the SG low-low level signal which initiates a reactor trip. A timely reactor trip is assumed in the plant safety ane.ysis of a main feedwater line break.

Westinghouse The deficiency results from a Westinghouse design oversight.

reported the deficiency to TVA and other Westinghouse plant owners and has also reported it to NRC under 10 CFR 21.

Corrective Action It is not clear at this time that the deficiency is of significant importance for TVA plants. The Westinghouse It letters on this subject appears, based on cursory are generic to all Westinghouse plants.

analyses, tnat the TVA plants which are of ice condenser containment design may have minimal problems introduced by the water column error.

Also, it is assumed in the safety analyses of a main feedwater line break that the reactor trip by low-low steam generator water level is coincident with safety injection actuation signals from the unaffected steam generators.

Westinghouse is to perform detailed analyses for Sequoyah and Watts Bar Nuclear Plants to determine what corrective actions, if any, are necessary.

The analyses and any necessary hardware and/or procedural changes will be completed before fuel loading for each plant.

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