ML19241A681

LER 79-083/01T-0 on 790621:station Personnel Informed by Westinghouse That Main Feedline Rupture Can Cause Delay in Protection Signals Initiated by low-low Steam Generator Level.Caused by Incomplete Previous Westinghouse Analysis

ML19241A681
Person / Time
Site:	North Anna
Issue date:	07/03/1979
From:	Cartwright W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19241A670	List: ML19241A669 ML19241A681
References
LER-79-083-01T, LER-79-83-1T, NUDOCS 7907090285
Download: ML19241A681 (2)

Text

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,, 5 L1 w-1 w steam generator level. This event is reportable pursuant to T.S. 6.9.1.8.i. l i o i c, ; l The health and safety of the general public were not affected by this event. l 0 / l l PRI 7 8 ')

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44 41 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS i l o 1 l The cause of this event is that heatup of reference legs followinq high energy line

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Virginia Electric and Power Company North Anna Power Station, Unit -11

Attachment:

Page 1 of 1 Docket No. 50-338 Report No. LER 79-083/0lT-0 Description of Event On 6/21/79, Westinghouse informed Vepco that if high energy line breaks occurred within the containment, causing containment temperature to increase, heatup of the steam generator level reference legs would result. This heatup would cauce steam generator level indication to be higher than actually exists, possibly delaying the protection signals that are initiated by a low-low steam generator level. This event is reportable per T.S. 6.9.1.8.i.

Probable Consequences of Occurrence Comment 6.105 of the FSAR, which analyzes a main steamline break (similar to a main feedline break), shows that if a rupture in a main feedline should occur, safety injection, reactor trip and auxiliary feedwater actuation will be initiated by a containment high pressure signal before any significant error in steam generator level indication could occur due to reference leg heatup, therefore the health and safety of the general public were nat jeopardized.

Unit 2 has the same derign and is similarly affected.

Cause of Occurrence The cause of this occurrence is that the heatup of steam generator level reference legs following a main feedline break within containment was not taken into account during the previous analyses by Westinghouse.

Immediate Corrective Action Westinghouse has provided the necessary data to determine reference leg heatup effects following a high energy line rupture. Station operating personnel will be made aware of this problem.

Schedol-d Corrective Action Further discussions with Westinghouse are required to determine future corrective actions.

Action Taken to Prevent Recurrence No further action required.

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