ML19256G535

Forwards LER 79-036/03L-0

ML19256G535
Person / Time
Site:	Cooper
Issue date:	12/10/1979
From:	Lessor L NEBRASKA PUBLIC POWER DISTRICT
To:	Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML19256G536	List: ML19256G535 ML19256G537
References
CNSS790649, NUDOCS 7912310442
Download: ML19256G535 (2)

Text

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COOPER NUCLEAR STATION p.O. Box 98. BRoWNVILLE, NEBR ASKA 6832:

Nebraska Publ.ic Power D. is tr.

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_=m CNSS790649 December 10, 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.2 of the Technical Specifications for Cooper Nuclear Station and discusses a reportable occurrence that was discovered on November 10, 1979. A licensee event report form is also enclosed.

Report No.: 50-298-79-36 Report Date: December 10, 1979 Occurrence Date: November 10, 1979 Facility: Cooper Nuclear Station Brownville, Nebraska 68321 Identification of Occurrence:

Conditions leading to operation in a degraded mode permitted by a limiting condition for operation as delineated in Secticn 3.9.B.3 of the Technical Specifications.

Conditions Prior to Occurrence:

Steady state power operation at approximately 987. reactor power.

Description of Occurrence:

During surveillance testing of the #2 diesel generator, four cylinder sleeves were damaged.

Designation of Apparent Cause of Occurrence:

The cause of the occurrence is related to metal movement between the cylinder sleeves and pistons. The exact cause of this occur-rence is being investigated by Cooper Energy Services and an updated licensee event report will be submitted if an exact cause can be determined. Y 4494,'\

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4 Mr. K. V. Seyfrit December 10, 1979 Page 2.

Analysis of Occurrence:

The purpose of the two diesel generators is to provide e=ergency power during a less of offsite power event.

An analysis of this occurrance does not lend itself to a straight forward conclusion based on the events that led up to this occur-rence. There is some evidence that would indicate the diesel engine jacket cooling water pump was airlocked at one time, pos-sibly overheating the engine, causing some incremental damage.

Examination of the piston and sleeves revealed that four (4) pistons had loose piston pin caps which created wear marks on the cylinder walls that may have aggravated the problem. On the day of the occurrence, the diesel engine had been started several times without allowing the diesel engine to come to operating temper-ature. This type of cperation could have led to abnormal piston ring and cylinder wall wear.

Other inspections during the course of our investigation revealed portions of several turbocharger blades were missing. The cause of this is attributed to debris removed from the inlet piping. This

=ay have caused the engine to run slightly hotter than normal and may have attributed to the event.

In the event the diesel generator was needed, the #1 diesel gen-erator was operable. Since repairs would take longer than seven (7) days, the reactor was shutdown until #2 diesel generator was returned to service.

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

Corrective Action:

New cylinder sleeves and pistons were installed in three cylinders.

One cylinder sleeve was reconditioned. The turbocharger rotating assembly was replaced. New piston pin caps which have a greater interference fit were installed in all pistons which were removed.

All cylinders on both engines were inspected with a borescope and no other cylinders indicated abnormal wear. One additional piston was removed and the piston and cylinder sleeve directly inspected after the borescope inspection. The applicable operating procedure was changed at the time the water pump was airlocked to preclude recurrence. As previously discussed, Cooper Energy Services is investigating this occurrence and will submit their report along with any recommendations.

Sincerely, r 4 ,e fT L CWm L. C. Lessor Station Superintendent Cooper Nuclear Station 1657' [65 LCL:cg Attach.