ML20002B933

Forwards LER 80-043/03L-0

ML20002B933
Person / Time
Site:	Cooper
Issue date:	11/20/1980
From:	Lessor L NEBRASKA PUBLIC POWER DISTRICT
To:	Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML20002B934	List: ML20002B933 ML20002B935
References
CNSS800678, NUDOCS 8101070351
Download: ML20002B933 (2)

Text

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} E( COOPER NUCLEAR STATION

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S CNSS800678 -.

Novemoer 20, 1980 e  :

Mr. K. V. Seyfrit, Director i--

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

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2 Region IV 611 Ryan Plaza Drive Suite 1000 Arlington, Texas 76011

Dear Sir:

This report is submitted in accordance with Section 6.7.2.B.2 of the Technical Specifications for Cooper Nuclear Station and discusses a reportable occurrence that was discovered on October 21, 1980. A li-censee event report form is also enclosed.

Report No.: 50-298-80-43 Report Date: November 20, 1980 Occurrence Date: October 21, 1980 Facility: Cooper Nuclear Station Brownville, Nebraska 68321 Identification of Occurrence:

A condition which resulted in operation in a degraded mode per-mitted by a limiting condition for operation specified in Technical Specification 3.5.B.3.

Conditions Prior to Occurrence:

Reactor power was at approximately 97% of rated thermal power.

Description of' Occurrence:

While performing Surveillance Procedure 6.3.20.1 motor operated valve SW-MO-89B failed to open.

Designation of Apparent Cause of Occurrence:

The apparent cause of this occurrence has been attributed to a broken lead on the 1,000 ohm variable resistor. This resistor, mounted inside the valve operator, provides feedback to the valve positioner and without a feedback signal the valve motor operator would not start.

00

Mr. K. V. Seyfrit November 20, 1980 Page 2.

The exact cause as to how the subject lead was broken is not known.

The variable resistor is a sensitive electrical component and is i subject to that type of failure. In this case the variable re-

sistor was installed in a valve motor operator which was seismic-ally qualified and has functioned properly for several years. The failure is considered "one of a kind" and unique at Cooper Nuclear Station.

Analysis of Occurrence:

The RER Service Water System provides cooling to the RHR System and water for emergency core flooding under accident conditions.

The system consists of two independent loops, each rated 4,000 gpm.

It maintains the service water side of the RHR heat exchanger at a higher pressure to prevent leakage of radioactive water in the service water system.

Each RHR service water loop has sufficient capacity with two pumps operating to remove the designed heat load during accident conditions.

Since Loop "A" was operable, the failure of this valve presented no adverse condition to the reactor. Loop "B" was inoperable fo.-

approximately 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br />. This occurrence had no adverse effect on public health and safety.

Corrective Action:

The broken lead on the 1000 ohm variable resistor was resoldered.

The valve was retested and its correct operation verified. The corresponding valve, SW-MO-89A, in Division I loop was also checked and proper connections to the 1000 ohm resistor were verified.

Sincerely, L. C. Lessor ,

Station Superintendent Cooper Nuclear Station LCL:cg l Attach.

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