ML19254E999

Interim Deficiency Rept Re Failure of Modulating Control Valves to Revert to Safe Position Upon Loss of Air Following Seismic Event.Final Rept Will Be Filed by 791007

ML19254E999
Person / Time
Site:	Catawba
Issue date:	09/07/1979
From:	DUKE POWER CO.
To:
Shared Package
ML19254E997	List: ML19254E996 ML19254E999
References
NUDOCS 7911050318
Download: ML19254E999 (2)

Text

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DUKE POWER COMPANY Catawba Nuclear Station Units 1 & 2 Report Number: IE-79/03-SDD-413/414 Report Date: September 7,1979 Facility: Catawba Nuclear Statica, Units 1 & 2 Descriptions of Deficiencv:

The present design criterion is to provide air operators for modulating control valves in Engineered Safeguards Systems which are designed to fail the valves in the safe position upon loss of air.

Recent review of the modulating control valves indicates that the application of control grade positioners, solenoids, and instumentation could result in failure of these valves to go to the safe position upon loss of air or to control properly if air is available f ollowing a seismic event.

The problems identified to date are categorized as follows:

Category 1: Potential Failure of Cooling Water Flow Control Valves for Engineered Safeguards Heat Exchangers and Motor Coolers.

Category 2: Potential Failure of Main Steam Power Operated Relief Valves.

Category 3: Potential Failure of Auxiliary Feedwater Flow Control Valves.

Analysis of Safety Implications:

Category 1:

A. Loss or impairment of function of control grade instrumentation and controls following a seismic event may cause unacceptable reduction in ecoling water flow to the Nuclear Service Water, Component Cooling, Safety Injection, Centrif ugal Charging, and Auxiliary Feedwater pump motor coolers.

B. Loss or impairment of function of control grade temperature instrumentation and controls following a seismic event may cause an unacceptable reduction in cooling water flow to the Component Cooling Heat Exchangers.

C. Loss or impairment of function of control grade flow instrumentation and con-trols following a seismic event may cause unacceptable reduction in cooling flow to the Residual Heat Removal Heat Exchangers.

Category 2:

Loss of function of control grade instrumentation and controls for the main steam power operated relief valves following a seismic event which causes loss of normal 1269 310 -

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feedwater could result in opening of the relief valves with subsequent failure of one or more of these valves to close af ter main steam pressure has dropped below the closure setpoint. This would result in an uncontrolled loss of steam or the equivalent of a main steam break caused by a seismic event.

Category 3:

Loss or impairment of function of control grade instrumentation and controls for auxiliary feedwater flow control valves, following a seismic event which causes loss of normal feedwater, may result in inadequate feedwater flow.

Corrective Action:

Class IE solenoid valves will be added to the instrumentation air lines immediately upstream of the affected valve operators and downstream of all control grade components to vent the operator on the appropriate signal thus allowing it to fail the valve in the safe position.

Our review of this matter is not complete at this time. A followup report will be filed by October 7, 1979.

Consideration will be given to the potential impact of failure of centrol grade instrumentation and controls on the performance of Engineered Safeguards Systems for all future plant designs.

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