ML19209A533

First Interim Deficiency Rept Re Excessive Output Fluctuations of Foxboro Instrumentation.Corrective Action May Involve Mod to Instruments to Comply W/Specs.Next Rept Will Be Submitted Before Fuel Loading in Unit 1

ML19209A533
Person / Time
Site:	Sequoyah
Issue date:	09/26/1979
From:	TENNESSEE VALLEY AUTHORITY
To:
Shared Package
ML19209A526	List: ML19209A525 ML19209A533
References
NCR-SWP-79-S-5, NUDOCS 7910040289
Download: ML19209A533 (1)

Text

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ENCLOSURE SEQUOYAH NUCLEAR PLANT UNITS 1 AND 2 WATTS BAR NUCLEAR PLANT UNITS 1 AND 2 EXCESSIVE OUTPUT FLUCTUATIONS OF FOXBOR0 INSTRUMENTATION SEQUOYAH NCR SWP 79-S-5 WATTS BAR NCR'S 1778R AND 1779R 10 CFR 50.55(e)

FIRST INTERIM REPORT Description of Condition Personnel at Sequoyah and Watts Bar Nuclear Plants have noted erroneous output signals coming from Foxboro equipment containing magnetic amplifiers (current / current repeaters and square root converters). This instrumentation was supplied by Westinghouse on the NSSS contract. The equipment is not performing according to the specifications in the Foxboro Equipment Manual which specifies this equipment to have an accuracy of 11/2 percent with input voltage variations of 110 percent. Tests have shown that a 1.5 and 4.J percent input variation resulted in a 5.0 and 15.5 percent output current change. These excessive output variations have caused spurious operations of plant equipment by producing erroneous safety injection signals. Some of the Foxboro units are used to actuate safeguards equip-ment and to initiate reactor trip signals. There are 168 modules per unit containing magnetic ampl.fiers at Sequoyah Nuclear Plant and approximately 250 modules per unit at Watts Bar Nuclear Plant.

Corrective Action TVA and Westinghouse are working on possible solutione this problem.

The corrective action may involve modification to the Foxboro instruments to bring them into accordance with the specifications.

1090 23i V

70100$0 3