ML19210D646

Forwards LER 79-027/03L-0

ML19210D646
Person / Time
Site:	Cooper
Issue date:	10/29/1979
From:	Lessor L NEBRASKA PUBLIC POWER DISTRICT
To:	Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML19210D647	List: ML19210D646 ML19210D656
References
CNSS790520, NUDOCS 7911270424
Download: ML19210D646 (2)

Text

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CooWER NUCLEAR STATtoN P.o. Box 98, BRoWNVILLE, NEBR ASKA 68321 Nebraska Publ.ic Power Distr.ic t 1ELEmo~E m . m .n CNSS790520 October 29, 1979 Mr. K. V. Seyfrit U.S. Nuclear Regulatory Commission Office of Inspection and Enforcement Region IV 611 Ryan Plaza Suite 1000 Arlington, Texas 76011

Dear Sir:

This report is submitted in accordance with Section 6.7.2.B.1 of the Technical Specifications for Cooper Nuclear Station and discusses a reportable occurrence that was discovered on October 1, 1979. A li-censee event report form is also enclosed.

Report No.: 50-298-79-27 Report Date: October 29, 1979 Occurrence Date: October 1, 1979 Facility: Cooper Nuclear Station Brownville, Nebraska 68321 Identification of Occurrence:

Operation with an engineered safety feature instrument setting less conservative than those established in Table 3.2. A of the Technical Specifications.

Conditions Prior to Occurrence:

The reactor was operating at a ' steady state power level of approk-imately 94% of rated thermal power.

Description of Occurrence:

While performing routine surveillance test procedure 6.2.1.4.2, differential pressure indicating switch MS-DPIS-119B was found set at a setpoint higher than allowed by Technical Specifications.

Designation of Apparent Cause of Occurrence:

The apparent cause of this occurrence was setpoint drift.

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Mr. K. V. Seyfrit October 29, 1979 Page 2.

Analysis of Cccurrence:

The function of MS-DPIS-119B is to monitor the steam flow in the "D" main steam line and initiate a main steam line isolation at 1407. rated steam flow. There are three other differential pressure indicating switches on "D" main steam line, MS-DPIS-119A, 119C, and 119D. These three instruments were oper .ing properly and would have provided the isolation if it had been required.

The subject switch was installed about one month previous to this occurrence. The event occurred the first time the setpoint was checked following initial installation. Discussion with the vendor indicates that the setpoint may drift slightly after initial in-stallation, but this drift can generally be eliminated if the new switch is exercised sufficiently during installation. The switch setpoint was found at 119.5 psid. The required setpoint is less than or equal to 118 psid. This occurrence presented no adverse consequences to public health and safety.

Corrective Action:

The switch was readjusted to the correct setpoint at the time of-the occurrence. The switch was retested a week later and again two weeks after that and found to be operating satisfactorily. The Instrument Shop guide for the subject switch installation procedure has been revised to include fully exercising a new switch from 10 to 15 times during installation, to minimize the set taken by the bellows, before performing the instrument calibration. This event will be reviewed by the Instrument Department.

Sincerely, m

L. C. Lessor Station Superintendent .

Cooper Nuclear Station LCL:cg Attach.

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