ML19259C233

Final Deficiency Rept:Bistable Contacts in Auxiliary Room Loops of Pressurizer Power Relief Valves Failed in Undersirable Position.Valve Wiring Corrected.No Other Discrepancies Found

ML19259C233
Person / Time
Site:	Sequoyah
Issue date:	05/10/1979
From:	TENNESSEE VALLEY AUTHORITY
To:
References
NCR-MEB-79-40, NUDOCS 7906140442
Download: ML19259C233 (1)

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ENCLOSURE ,

SEQUOYAH NUCLEAR PLANT UNITS 1 AND 2 ,'

CONTROL LOOP BISTABLES FAIL TO

UNDESlRABLE POSITION ON LOSS 0F CONTROL POWER NCR ME3 79-10 FINAL REPORT Description of Deficiency .

Bistable contacts in the auxiliary control loops of the pressurizer power relief valves were found to fail in an undesirable position on loss of control power. The problem was found during preoperational testing of the unit 1 f acility auxiliary control room controls and was due to an error in the wiring of the bistable. The problem does not exist in the main control room instrumentation.

The wiring of the pressurizer auxiliary spray valves and the pressurizer backup heater bistables was also in question.

Safety Implications Had the deficiency gone uncorrected, the air operated pressurizer power relief valve, given loss of control power to the valve bistables, would fail open.

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The control loop wiring for the pressurizer auxiliary spray valve and the pressurizer backup heater bistables was evaluated and has been determined to be correct.

Corrective Action The wiring to the pressurizer relief valve bistables has been corrected This such that the bistables will f ail open on loss of control power.

assures that the valves will fail in their preferred closed position.

Upon examination of all other control loops in the auxiliary control room controls for similar configurations, I no discrepancies were found.

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3-Mr. James P. O'Reilly, Director -- y N

Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission -

Region II - Suite 3100 101 Marietta Street ~

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Atlanta, Georgia 30303

Dear Mr. O'Reilly:

SEQUOYAH NUCLEAR PLANT UNITS 1 AND 2 - CONTROL LOOP BISTABLES FAIL TO UNDESIRABLE POSITION ON LOSS OF CONTROL POWER - NCR MEB 79 FINAL REPORT The subject deficiency was initially reported to NRC-0IE Inspector Mike Gouge on February 14, 1979. An interim report was submitted on March 14, 1979. Enclosed is our final report.

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

Very truly yours,

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<I A . E. Gillel nd Assistant Manager of Power Enclosure ec: Mr. John G. Davis, Acting Director (Enclosure)

Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission Washington, DC 20555 s 2284 174 6,

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