ML19208A099

LER 79-104/01T-0:on 790823,feeder Breakers to Several Electrical Penetrations Found Not Set to Protect Penetration Integrity for Range of Faults.Caused by Design Problem

ML19208A099
Person / Time
Site:	North Anna
Issue date:	09/06/1979
From:	Cartwright W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19208A098	List: ML19208A097 ML19208A099
References
LER-79-104-01T, LER-79-104-1T, NUDOCS 7909120560
Download: ML19208A099 (2)

Text

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- LICENSEE EVENT REPORT (PLE ASE PRINT OR TYPE ALL REQUIRED INFORMATION)

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discovered that the feeder breakers to rany of tha electric,1 nono+v,+1nne ,ra nn* l o 3 l properly set to protect the pentration's intoerity for n enmnloro r,nua nf f,n1 + c .rf e d o 4 O s in its design. The vendor infomed Vepco that leakaee would be ninor if a sent or 1 Thorofnro tbo bool th ,na 1 0 6 l penetration failed due to an overcurrant condition.

0 7 safety of the gcneral public were not affected bv this event. Penortnblo nursuant I I

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J3 J4 33 36 31 40 41 42 44 47 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS i O ] Reanalysis revealed that a number of containment nonetrations are not orotectoA for l I i I i l I intemediate faults or overloads slightly, bevond the continuous vntino nf ru -nnn- 1 3 7 tration. An investigation is presently being performed to determine the corrective I 1

i 3 3 l actions to be taken to resolve the problem.

l i 4 l 80 7 8 9 OTHER ST ATUS ISCO PY DISCOVEHY DESCRIPTION SfA 5  % POWER i 5 lE l@ l1 l0 0 h NA j lC l@l46 Review requested by NRC l 10 12 13 44 45 80 7 8 9 ACTIVITY CON TE NT RELEASED OF RELE ASE AMOUNT OF ACTIVITY J LOC ATION OF F.ELEASE i c l7, l@& l@ to NA 44 l lNA 45 80 l

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W. R. Cartwright (703)894-5151 o N A'.iE OF PRE PAR ER PHONE: S

Virginia Electric and Power Company North Anaa Power Station, Unit 1

Attachment:

Page 1 of 1 Dockat No. 50-338 Report No. LER 79-104/01T-0 Description of Event During a review of containment penetration breaker protection, prompted by NRC letter "Staf f Position on Electrical Protection of Containment Penetrations for North Anna Unit 2", Vepco discovered that the feeder breakers to many of the penetrations are improperly set to protect the penetration's integrity for overloads beyond the continuous rating of the penetration.

Probable Consequences of Occurrence Consequences of this event were minimal because Icakage would be minor if a seal or penetration failed as a result of an overcurrent condition. Also, due to the existing protection scheme, an overcurrent condition beyond the rating of the penetration will result in a breaker trip. No breaker trip related to this problem has occurred to date. Therefore, the public health and safety were not affected by this event. The electrical penetrations for Unit 2 are similarly af fected.

Cause The cause of this problem is that intermediate faults or overloads slightly beyond the continuous rating of the penetration were overlooked and not considered in the original design analysis.

Immediate Corrective Action Further investigation is being performed to determine the exact breakers that are affected and the corrective actions necessary to modify each one of them.

Scheduled Corrective Actions To be determined by the investigation.

Actions Taken to Prevent Recurrence No further actions required.

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