ML20204J843

Deficiency Rept SDAR-173 Re Undetectable Failures in Safety Features Actuation Sys.Test Procedures Revised Per Westinghouse Recommendations

ML20204J843
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
SDAR-173, TXX-4457, NUDOCS 8504250178
Download: ML20204J843 (2)

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TEXAS UTILITIES GENERATING COMPANY BKYWAY TOWER . 400 NORTH OLIVE STREET, L.B. 31

• DALLAS,TEXAB 75901 m..".'.h!,,"'15'O,..

g g , 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 N0.: 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, M

BRC:tig Attachment .

cc: NRC Region IV - (0 + 1 copy)

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Director, Inspection & Enforcement (15 copies) APR I 61985 U.S. Nuclear Regulatory Commission

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Washington, DC 20555 -

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. TXX-4457 4/15/85 Page 2 ATTACHMENT UNDETECTABLE FAILURE IN SAFETY FEATURES ACTUATION SYSTEM Description

-The NSSS supplier has advised TUGCc of an item involving the possibility for 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 pennits 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.

l Safety Implications l

l 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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