ML19261B646

Forwards First Interim Rept on Potential Excessive Water Hammer Forces in Main Feedwater Sys Initially Reported 790115.Will Submit Next Rept by 790313

ML19261B646
Person / Time
Site:	Sequoyah
Issue date:	02/14/1979
From:	Gilleland J TENNESSEE VALLEY AUTHORITY
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
NUDOCS 7902280326
Download: ML19261B646 (2)

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Dear lir. O'Reilly:

SEQUOYAH NUCLEAR FI. ANT UNITS 1 AND 2 - POTENTIAL EXCESSIVE WATER liA!CiER FORCES IN THE MAIN FEEDWATER SYSTEM - NCR MEB 79 FIRST INTERIII REPORT The subject deficiency was initially reported to NRC-0IE Inspector C. R. McFarland on January 15, 1979. Enclosed is our first interim report. We expect to submit our next report by 'farch . 13, 1979.

If you have any questions concerning this matter, please get in touch with M. R. Wisenburg at FTS 854-2581.

Very truly yours, J. E. Gilleland Assistant Manager of Power Enclosure cc: Mr. John G. Davis, Acting Director (Enclosure)

Office of Inspection and Enforcenent U.S. Nuclear Regulatory Commission Washington, DC 20555

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ENCLOSURE SEQUOYAh NUCLEAR PLANT UNITS 1 AND 2 POTENTIAL EXCESSIVE WATER ham!ER FORCES IN THE MAIN FEEDWATER SYSTEM FIRST INTERIM REPORT Description of Deficiency Westinghouse informed TVA of the potential for excessively high water hammer forces associated with the main feedwater line check valves.

This deficiency involves excessively high water hammer forces generated by slamming of the three main feedwater line check valves as a result of a postulated pipe rupture in the other main feedwater line. The water-hammer forces caused by slamming of the three check valves might be high enough to adversely affect the integrity of those three check valves and hence lead to a multiple steam generator blowdown.

The failure of TVA to evaluate in detail at the design stage the capability of the main feedwater check valves to absorb the water hammer forces associated with a closure of those valves following a postulated break in one leg of the main feedwater system piping resulted in this deficiency.

Corrective Actions TVA is presently evaluating the capability of the main feedwater check valves to absorb the energy of closure of the disc without failure following a worst-case pipe rupture in the main feedwater system. In the final report on this deficiency, TVA will provide a comparison of the results of the study of the check valve loads following a postulated main feedwater line rupture with the hydrodynamic analysis values for the main feedwater system check valves. Also, details of the fix, if required, to the main feedwater check valves will be provided at that time. -

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