TXX-4457, Significant Deficiency Rept SDAR-173 Re Undetectable Failure in Safety Features Actuation Sys.Test Procedures Will Be Revised to Incorporate Previously Furnished Specific Testing Requirements,Per Westinghouse Recommendations

Significant Deficiency Rept SDAR-173 Re Undetectable Failure in Safety Features Actuation Sys.Test Procedures Will Be Revised to Incorporate Previously Furnished Specific Testing Requirements,Per Westinghouse Recommendations

ML20204K070
Person / Time
Site:	Comanche Peak
Issue date:	04/15/1985
From:	Clements B TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC)
To:	Hunter D NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
References
@EFR-850415, SDAR-173, TXX-4457, NUDOCS 8504250304
Download: ML20204K070 (2)

Text

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TEXAS UTILITIES GENERATING COMPANY MKYWAY TOWER . 400 NORTH OLIVE MTREET. L.B. St . DALLAN. TEXAM 75201

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g Q , 1985 Mr. D.R. Hunter, Chief Reactor Project Branch 2 U.S. Nuclear Regulatory Commission Office of Inspection & Enforcement 611 Ryan Plaza Drive, Suite 1000 Docket Nos.: 50-445 Arlington, TX 76012 50-446 COMANCHE PEAK STEAM ELECTRIC STATION UNDETECTABLE FAILURE IN SAFETY FEATURES ACTUATION SYSTEM QA FILE: CP-85-13, SDAR-173 FILE NO.: 10110

Dear Mr. Hunter:

In accordance with 10CFR50.55(e), we are submitting the enclosed report of actions taken to correct a deficiency regarding failures that exist in the safety features actuation system.

Supporting documentation is available at the CPSES site for your Inspector's review.

Very truly yours,

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Director, Inspection & Enforcement (15 copies) APR I 61985 i

U.S. Nuclear Regulatory Commission y Washington, DC 20555 i

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UNDETECTABLE FAILURE IN SAFETY -

FEATURES ACTUATION SYSTEM _a- N Description TheNSSSsupplierhasadvisedTUGCoofaniteminvolvingthepossibilithfor certain failures in engineered safety' features actuation systems to remain undetected. .,

As a result of earlier concerns, specifically 10CFR50.55(e) report, SDAR CP-82-09, the supplier recommended corrective actions which were adopted by TUGCo. These measures consisted of special plant specific tests to make previously undetectable failures of the P-4 Permissive detectable.

The P-4 Permissive is provided by electrical contacts in the reactor trip breakers. When the breaker is open (reactor tripped), P-4 permits the operator to block actuation of the Safety Injection System and to enter the recirculation mode. The design did not provide for on-line testing of the P-4 contacts and failure of.those contacts to perform properly was undetectable.

The recommended tests resolved this by entering the switchgear cabinets and using a meter to measure the condition of the P-4 contacts.

The NRC and several utilities requested Westinghouse to give consideration to a hardware change to permit verification of P-4 without the need to enter the switchgear cabinets with portable test' equipment. A change was developed and offered by Westinghouse as an option. This change consisted of mounting a .

meter and a_multiposition switch on each cabinet door. It was accepted for use in fifteen plants (including CPSES) then in various stages of construction.

It has been recently determined, after evaluating an earlier identified concern as to the overall effectiveness of the change, that the possibility of undetect-able failures remained under certain circumstances.

Safety Implications In the event the deficiency had remained undetected, the potential exists for an undetectable loss of safeguards actuation devices.

Corrective Action In accordance with Westinghouse recommendations, CPSES test procedures will be revised to incorporate the previously furnished CPSES specific testing requirements.

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