ML19210D069

LER 79-149/01T-0:on 791031,discovered That Safeguards Area Exhaust Sys Providing post-LOCA Ambient Cooling for Recirculation Spray & Low Head Safety Injection Pumps Not Entirely Seismically Designed.Cause Unknown

ML19210D069
Person / Time
Site:	North Anna
Issue date:	11/14/1979
From:	Cartwright W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19210D066	List: ML19210D065 ML19210D069
References
LER-79-149-01T, LER-79-149-1T, NUDOCS 7911200493
Download: ML19210D069 (2)

Text

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DAT L LveNT oEcCnierlON AND PROBAP_E CONSEQUENCES h lo l7i lIt was discovered on October 26, 1979 and determined reportable on October 31. 19 79 .  !

g g gthat the Safeguards Area Exhaust System which provides post LOCA ambient coolinn for 1 o 4 lthe recirculation spray and low head safety injection pumps is not entirely seismigally]

o ,, [ designed as stated in FSAR Section 9.4.6.1. The health and safety of the general I o c lpublic uere not affectEd by this event. Reportable pursuant to T.S. 6.9 .1. 8.1. 1 I

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43 lZ l9 [9 l9 [g 44 47 CAUSE DESCRIPTION AND CORRCCTIVE ACTIONS h i O [The cause for the entire system not being seismically designed is unknown at this time.l

, , gA n evaluation is presently underway to determine what modifications, if any are  !

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Virgiuta Electric and Power Conpany North Anna Power Station

Attachment:

Page 1 of 1 Docket No. 50-338 Repart No. LER 79-149/01T-0 Description of Event On October 26, 1979, with the unit in a refueling shutdown mode, it was discovered that only the ductuork on the suction side of the Safeguards Area Exhaust fans is Seismic Catenary 1. This is contrary to FSAR which states that the entire Saf eguards Area Exhaust Systen is seismically designed.

This event was deterair.ed to be reportable on October 31, 1979.

Probable Consequences of Occurrence Since the fan discharge ductwork up to and including the ventilation stack is not designed as Seismic Category 1, a seismic event coincident with a LOCA could cause the non-seismic discharge portion to fall in such a nanner as to prevent the exhaust system from perforning its intended function.

This could in turn jeopardize the ability of the ECCS Systen and the Containment Depressurization System to perform their required design function following an carthquake. The health and safety of the general public were not affected by this event. Unit 2 has the same design and is similarly af fected.

Cause of Occurrence The cause for the entire Safeguards Area Exhaust System not being seismically designed is unknown at this time.

Immediate Corrective Action An evaluation is presently underway to determine what nodifications, if any, are required to correct the possible design problem.

Scheduled Correct ive Action If required, nodifications to the Safeguards Area Exhaust System will be made as deternined necessary.

Actions Taken to Prevent Recurrence No further actions are required.

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