ML19322C152

Unusual Event Rept 287/75-04:on 750419,condenser Circulating Water Valves 3CCW21,22 & 23 Failed to Operate Properly During Test.Caused by Switches in Open Position.Operating Procedure for Sys Modified

ML19322C152
Person / Time
Site:	Oconee
Issue date:	05/30/1975
From:	DUKE POWER CO.
To:
Shared Package
ML19322C138	List: ML19322C137 ML19322C152
References
RO-287-75-04, RO-287-75-4, NUDOCS 8001090563
Download: ML19322C152 (2)

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O DUKE POWER COMPANY OCONEE UNIT 3 Report No.: UE-287/75-4 Report Date: May 30, 1975 Event Date: April 19, 1975 Facility: Oconee Unit 3, Seneca, South Carolina Identification of Event: Failure of condenser circulating water valves to operate properly during test Conditions Prior to Event: Unit in cold shutdown Description of Event:

On April 19, 1975, the condenser circulating water (CCW) system gravity and recirculation flow test was performed on Oconee Unit 3. The test automatically shuts the six condenser discharge valves and opens the condenser emergency discharge valves to establish flow to the Keowee Hydro tailrace. In the performance of the test, three of the six condenser discharge valves, 3CCW 21, 22, and 23 did not close. The condenser emergency discharge valves did not open as they are interlocked to the condenser discharge valves.

Designation of Apparent Cause of Event:

The CCW condenser discharge valves control switches have three positions:

open-remote-close. The switches for valves 3CCW 21, 22, and 23 were found in the open position. This will not allow the valves to shut upon loss of power to all CCW pumps. The position of the switch is not designated in the operating procedures.

Analysis of Event:

The purpose of the periodic test is to assure that following a loss of power i

! to the CCW pumps, cooling water flow is maintained by gravity and siphon effect to the Keowee Hydro Plant tailrace and to verify that recirculation flow can be maintained from the intake canal back to the intake canal via the unit condenser, should a dam break accident occur. In this incident, I the failure of the condenser discharge valves occurred during the time the  !

unit was in cold shutdown and thus the function of the valves was not )

necessary. I 1

In the event that the unit had been at power when all CCW pumps were lost, condenser vacuum would have decreased resulting in a turbine trip and then a high RC pressure reactor trip. Adequate heat removal capacity would have been available by the use of the main steam relief valves. In addition, the condenser discharge valves could have been manually operated to obtain l

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the gravity flow of condenser water. It is concluded that the health and safety of the public was not affected.

Corrective Action:

The operating procedure fcr the condenser circulating water system has been modified such that the CCW discharge valve control switches are specified to be in the remote position. It is considered that this action will prevent future occurrences of this nature.

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