ML19253C888

LER 79-141/01X-1:on 791106,sys Operation Review Revealed Design Deficiencies in Engineered Safety Feature Equipment. Deficiencies Could Result in Less Conservative Operation than Assumed in Fsar.Cause Unknown

ML19253C888
Person / Time
Site:	North Anna
Issue date:	12/10/1979
From:	Cartwright W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19253C882	List: ML19253C881 ML19253C888
References
LER-79-141-01X, LER-79-141-1X, NUDOCS 7912120311
Download: ML19253C888 (3)

Text

U. S. NUCLEAR REGULATORY C N NRC FORM 366 (7 77)

LICENSEE EVENT REPORT (PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION)

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EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h o 2 l During a review of system operation, it was discovered that do< f on doffeloncfoc e n.1 A I

[O l3 ) [ result in ESF equipment operating less conservatively than assuned in the F9AR.

o 4 i Specifically: systems returning to non-safety mode following reset nf F9F nnA tino l lolsl l delay start systems not going to completion following reset of ESF. SV. HV. RS and W l lo is l Isystems are affected. The safety of the public was not affected. Renorenble nurcnnnt l l o l 7 l l to T.S. 6.9.1.8.1.

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CAUSE DESCRIPTION AND CORRECTIVE ACTIONS h o lThe exact cause for the nonconservative operation of these ESF Systems is unknown ne I i

i i [this time, however, a design deficiency by the architect eneineer is cusnected. m I

,, ;7; l problem is being evaluated to determine the corrective actions required . I 1 3

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% pot.E R OTHER STATUS IS O RY DISCOVERY DESCRIPTION A S Review of System Operation l1 l5 l [H Jg l 0 l 0 l 0 l@l NA l W @l ACTIVITY CO TENT AYOUNT OF ACTIVITY LOCATION OF RELEASE RELEASE NA l l NA l l i l 8c9 l C @D OF RELE ASEU@l 7 10 tt 44 45 80 PERSONNEL EXPOSURES NU"8ER TYPE DESCRIPTION NA l li l 71 l0 l010 l@lz l@l PERSONNEL INJuR ES i s 0'l3"'l"0igi

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NAME OF PREPARER V D. Cneturfoht PHONE: 703 37' 5151

Updated Report

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Virginia Electric and Power Company North Anna Power Station #1

Attachment:

Page 1 of 2 Docket No. 50-338 Report No. LER 79-141/01X-1 Description of Event On November 6,1979, during a review of system operation following a review of system performance during a recent unit trip and subsequent safety injection, it was discovered that the control room air-operated dampers which isolate the control room from outside air on an SI signal return to their non-safety mode when the SI signal is reset. This is contrary to FSAR comment 7.4 which states that two actions are required to return ESF equipment to a non-safety mode. Specifically, it is accom-plished by resetting the appropriate actuation signal and subsequently operating the control switch for the device.

A review was immediately initiated to determine if any other deficiencies existed.

The following is a list of potential design deficiencies that were discovered.

The following systems return to their non-safety mode following reset of an ESF signal:

Control Room Habitability System (HV)

Supply Air Damper A0D-HV-160-1 Exhaust Air Damper A0D-HV-161-1 Dampers reopen af ter the SI signal is reset.

Safeguards Area Ventilation System (HV)

Exhaus t Air Dampers A0D-HV-128-1,2,-3,-4 Filter Bank Dampers A0D-HV-107A-1,A-2,A-3,A-4,B-1,B-2,B-3,B-4 Dampers re-position to bypass filters af ter Containment Depressurization Actuation (CDA) signal is reset.

Containment Ventilation System (HV)

Containment Recirculation Cooler Fan, 1-HV-F-1 A,-B Control Rod Drive Cooling Fan, 1- HV- F-37 A , B , C , D , E , F Fans restart af ter CDA signal is reset.

Service Water System (SW)

Supply to Air Cooling Coils, MOV-SW-110A,B,-114A,B Supply to Air Cooling Coils, TV-SW-101 A,B Valves reopen to provide service water to the containment air coolers af ter CDA signal is reset. This occurs only when the control switch for cooling had previously been placed in the service water position. Normal cooling of the recirculation air coolers is with chilled water.

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Updated Report

Attachment:

Page 2 of 2 Secondary Vents System (SV)

Air Ejector Air Discharge Valve TV-SV102-1 Air Ejector Air Discharge Valve TV-SV103 With a Hi-Hi radiation signal present, valves reopen to divert air to the containment after Phase A Containment Isolation signal is reset.

The following systems do not go to completion if the CDA signal is reset prior to expiration of the starting time delay relay:

Recirculation Spray System (RS)

Outside Recirculation Spray Pump, 1-RS-P-2 A, B Inside Recirculation Spray Pump, 1-RS-P-1A,B Service Water System (SW)

RS Heat Exchanger Radiation Monitoring Sample Pumps, 1-SW-P-5,6,7,8 Probable Consequences of Occurrence The reset capability of ESF signals is required to permit action in the post accident period. With the present design, the protective actions of the af fected systems could be prevented or cancelled once the associated actuation signal is reset which is in noncompliance with IEEE Standards.

The health and safety of the general public were not af fected by this event.

Unit 2 systems have the same reset design and are similarly af fected.

Cause of Occurrence The cause of these discrepancies is not known at this time. However, it appears that they may have resulted from a possible design deficiency by Stone and Webster.

Immediate Corrective Action The problem is being evaluated by Engineering Services to determine what corrective actions are required.

Scheduled Corrective Action The reset circuitry for tha affected ESF equipment will be modified or redesigned, as required.

Actions Taken to Prevent Recurr?nce No further actions are required.

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