ML19242D338
| ML19242D338 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 07/26/1979 |
| From: | TENNESSEE VALLEY AUTHORITY |
| To: | |
| Shared Package | |
| ML19242D323 | List: |
| 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 coluun external to the SG but The col mn tas a condensate reservoir at 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 thus provides a ref erence the column and the SG water space.
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 of a main feedwater line break, this erroneously high.
In the event would delay actuation of the SG low-low level signal which initiates A timely reactor trip is assumed in the plant safety a reactor trip.
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 The Westinghouse letters on this subject importance for TVA plants.
are generic to all Westinghouse plants.
It appears, based on cursory the TVA plants which are of ice condenser containment
- analyses, tnat design may have minimal problems introduced by the water column error.
is assumed in the safety analyses of a main feedwater line break it Also, the reactor trip by low-low steam generator water level is coincident that with safety injection actuation signals from the unaffected steam generators.
Westinghouse is to perform detailed analyses for Sequoyah and Watts Bar if any, are necessary.
Nuclear Plants to determine what corrective actions, The analyses and any necessary hardware and/or procedural changes will be completed before fuel loading for each plant.
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