ML20064G970

RO 50-338-78-100:on 781108,investigation of in-core Instru Tubes Found 2 to 6 May Yield in Worst Case Seismic Event,But No Tubes Will Rupture

ML20064G970
Person / Time
Site:	North Anna
Issue date:	11/09/1978
From:	VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:
References
NUDOCS 7812150094
Download: ML20064G970 (1)

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N ectric'and Power Company Virginia Eg. 48 North Ann Pcwer Station Unit #1 jg gDV 9 Docket No. 50-338 Report Nol LER 78-1 Event Dat 11-8-78 Repor+. nat G O -78 On August 3.1978, a report was made under the provisions of 10 CF

's 50.55 (e) concerning a deficiency in seismic analysis of the re insulation Unit for North 2 on August Anna Unit 8.1978, 2. encompassed part 21 reporting requiremnt which for Unit No. 1.

A field r%dification was made to the insulation of the in-core mentation r.ozzles, but the inodification was not seismically analyzed.

An investigation was perforred and it was found that 2 to 6 incore It instrunentation tube: may yield in the worse case of a seismic event.

was also found that noFurther tubes will rupture; therefore, the safety of t plant is not endangered.

will be forwarded in a later report.

There is no effect upon the safe operation of the plant at this time i

and power production will continue.

Modifications to the insulation supports will be installed at the next refueling at North Anna Unit 1 in order to rneet the seis.mic criteria.

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781215009I _S