ML19257C634

Forwards LER 79-040/03L-0

ML19257C634
Person / Time
Site:	Cooper
Issue date:	01/02/1980
From:	Lessor L NEBRASKA PUBLIC POWER DISTRICT
To:	Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML19257C635	List: ML19257C634 ML19257C640
References
CNSS800002, NUDOCS 8001290524
Download: ML19257C634 (2)

Text

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, COOPER NUCLEAR ST ATioN Nebraska Public Power District

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CNSS800002 January 2, 1980 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 6.7.2.3.2 of the Technical Specifications for Cooper Nuclear Station and discusses a reportable occurrence that was discovered on December 3,1979. A li-censee event report form is also enclosed.

Report No.: 50-298-79-40 Report Date: January 2, 1980 Occurrence Date: December 3, 1979 Facility: Cooper Nuclear Station Brownville, Nebraska 68321 Identification of Occurrence:

Conditions which may have led to operation in a degraded mode permitted by a limiting condition for operation as delineated in Section 3.12.C.2 of the Technical Specifications.

Conditions Prior to Occurrence:

Steady state power operation at approximately 98% reactor power.

Description of Occurrence:

During maintenance on rFe Service Water pump strainer backwath line, it was noted that .e wall thickness of this line was less than normal.

Designation of Apparent Cause of Occurrence:

The apparent cause of the occurrence is excessive erosion of the backwash system piping.

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Mr. K. V. Seyfrit January 2, 1980 Page 2.

Analysis of Occurrence:

The Service Water System provides cooling water for critical plant equipment. The system takes a suction on the Missouri River. The backwash line carries silt and debris from the strainer back to the river. The velocity of water in the backwash line is not in itself excessive, however, it is greater than in the rest of the system.

The concentration of silt in this line is greater than in the rest of the Service Water System. The increased velocity and silt concentration accelerated erosion in this line. If the line would have failed, the strainer could have been bypassed and the leak isolated. The redundant Service Water loop was also operable.

This occurrence presented no adverse consequences from the stand-point of public health and safety.

Corrective Action:

The defective piping and fittings were replaced and the system was returned to its normal lineup. The wall thickness of the backwash line on the redundant loop was inspected and is satisfactory. The wall thickness of the backwash lines will be periodically evaluated to determine whether a change in design is warranted.

Sincerely, AfL. C. Lessor m

Station Superintendent Cooper Nuclear Station LCL:cg Attach.

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