ML19256A412

Deficiency in Essential Raw Cooling Water Sys Supply to Heat Exchangers:W/Loss of Water Through Exchangers,Ercw Sys Will Not Meet Sys Design Basis of LOCA Associated W/Loss of Offsite Power & Loss of Train a

ML19256A412
Person / Time
Site:	Sequoyah
Issue date:	11/16/1978
From:	TENNESSEE VALLEY AUTHORITY
To:
Shared Package
ML19256A410	List: ML19256A409 ML19256A412
References
MEB-78-2, NUDOCS 7901050188
Download: ML19256A412 (1)

Text

, n:.L WaUdb o

SEQUOYAH NUCLEAR Pl. ANT - UNITS 1 AND 2

,, ESSEt;TIAL RAW COOLING WATER SYSTEM FLOW IIALDISTR!!W floN '10 Tl;E CCS HEAT EXCHANGERS NCR Meli 78-2 FINAL REPORT -

Description of Condition The subject deficiency is a problem with the Essential Raw Cooling Water (ERCW) supply to the Component Cooling System (CCS) heat exchangers. The present arrangement of the motor-operated valves and their emergency power train supply would result in a loss of water through an inoperative CCS heat exchanger under a loss of of fsite power and a loss of train A emergency power supply. Upon loss of power train A the CCS heat exchanger A will no longer be receiving CCS flow from the train A loads for unit 1. The valves which are capable of isolating ERCH flow to heat exchanger A are on train A power, while the supply is from ERCW train B pumps. Thus there will be a loss of water through heat exchanger A resulting in insufficient flow through heat exchanger C. With this loss of flow, the ERCW system will not meet the system design basis of a LOCA simultaneous with a loss of offsite power and a loss of train A.

Safety Implications Under a design basis LOCA simultaneous with a loss of offsite power and a loss of train A emergency power supp)y, there would be less than the design basis ERCW flow rate supplied to safety related equipment. This situation could cause safety related equipment to overheat thereby creating an unsafe condition.

Corrective Action A qualified motor operator will be added to the existing manual valve 0-67-546A with power supply from emergency train B so as to provide the operator with the capability to close the valve from the nain control room upon loss of train A power. This valve will naintain the capability to be used as a throttling valve for the purpose of initial balancing of flov through the heat exchanger under nonaccident operational iodes.

This modification will be completed pri< to Unit. 2 fuel loading.

If modi fications are not complete prior ., Unit ] fuel loading, temporary alteration of the normal posimion of the three flou control valves will be made so that t h t. ERCW system will satisfactorily perform under all possib]e modes of Unit 1

• operation. The temporary alteration will change flow control valves 1-FCV-67-223 and 2-FCV-67-223 1 rom normally closed to norma]ly open and 1-FCV-67-424 will be changed from normally open to normally closed. (See FSAR figure 9.2-12.) This would permit supply of ERCW from the same train as the heat exchangern being served.

7?nosw&5' -