05000280/LER-1980-059-01, Util Informed of Potential for Loss of Auxiliary Feedwater Flow Following Steamline Rupture.Caused by Original Design Allowing Pump Runout & Subsequent Tripping of Sys Pump Motors

Util Informed of Potential for Loss of Auxiliary Feedwater Flow Following Steamline Rupture.Caused by Original Design Allowing Pump Runout & Subsequent Tripping of Sys Pump Motors

ML20055B724
Person / Time
Site:	Surry
Issue date:	07/15/1982
From:	Joshua Wilson VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20055B719	List: 05000280/LER-1979-045-01, Air Would Not Flow Through Filters If Consequence Limiting Safeguards hi-hi Signal Removed from Control Circuit of Safeguards Area Exhaust Ventilation Dampers.Caused by Design Deficiency 05000280/LER-1980-059-01, Util Informed of Potential for Loss of Auxiliary Feedwater Flow Following Steamline Rupture.Caused by Original Design Allowing Pump Runout & Subsequent Tripping of Sys Pump Motors ML20055B718
References
LER-80-059-01X, LER-80-59-1X, NUDOCS 8207230193
Download: ML20055B724 (3)

LER-1980-059, Util Informed of Potential for Loss of Auxiliary Feedwater Flow Following Steamline Rupture.Caused by Original Design Allowing Pump Runout & Subsequent Tripping of Sys Pump Motors

Event date:
Report date:
2801980059R01 - NRC Website

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4 UPDATE REPORT - PREVIOUS REPORT DATL-10-30-80*

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CAUsE DESCRIPTION AND CCRRECTIVE AO"*1CNS gJThe original AFW System design did not preclude pump runout and the subsequent i

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UPDATE REPORT - PREVIOUS REPORT DATE 10-30-80 ATTACHMENT 1 SURRY. POWER STATION, UNIT NO. 1 DOCKET No:

50-280/281 REPORT NO:

80-059/OlX-1 EVENT DATE:

10-16-80 TITLE OF THE EVENT: Potential Loss of Auxiliarv Feedwater 1.

DESCRIPTION OF EVENT

While Unit No. 1 was shutdown for steam generator replacement and Unit No. 2 was at steady state operation at full power, the licensee was notified by USSS Vendor of a potential for a loss of Auxiliary Feedwater flow following a rupture of a small steamline. The location of the postulated rupture can be either in the decay heat removal (DHR) system header or the steam supply header for the turbine driven auxiliary feedwater (AFW) pucp.

An evaluation of this event, using " Balance of Plant" design information has been performed.

It was concluded that the potential for pump runout and subsequent loss of AFU flow with the existing AFW system configuration existed.

This condition is reportable per Technical Specification 6.6.2.a.(9).

2.

PROBABLE CONSEQUENCES and STATUS of REDUNDANT SYSTEMS :

Auxiliary feedwater (AFW) pumps remove decay heat via the steam generators following the loss of main feed water system. The rupture of DER system header or the steam supply header for the turbine driven AFW pump would initiate an uncontrolled blowdown of all the three steam generators, causing a reduced steam generator back pressure. In the limiting case, motor driven AFW pump flow rate would increase to pump runout value.

Extended operation of the pump at runout conditions could lead to a trip of the AFW pump on high motor current, thereby causing a loss in the capability to remove decay heat via the steam generators.

3.

CAUSE

The original auxiliary feed water system design did not preclude pump runout and subsequent tripping of AFW pump motors.

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IM"EDIATE CORRECTIVE ACTIONS:

The operators were inforned of this postulated transient and the possibility of a loss of AFW flow due to pump runout.

They were also provided instructions on how to prevent pump runout.

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SI'ESE0ENT CORRECTIVE ACTION:

The Emergency Procedure for a loss of secondary coolant was revised to provide l

the necessary instruction to prevent pump runout.

6.

ACTION TAKEN TO PREVENT RECURRENCE:

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Flow restricting orifices were installed in each AFL' line (Desi gn Change 80-75) which will provide AFW puep runcut protection.

This assures adequate heat sink i

l capabilities following any postulated steamline rupture.

UPDATE REPORT - PREVIOUS REPORT DATE 10-30-80 Page 2 Report !;o. 80-059/0lX 7.

GENERIC IMPLICATIONS:

The !!SSS Vendor notification of this potential problem indicates that other plants with similar balance of plant design may be affected.

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