05000298/LER-1982-020, Forwards LER 82-020/03L-0.Detailed Event Analysis Submitted

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Forwards LER 82-020/03L-0.Detailed Event Analysis Submitted
ML20065S291
Person / Time
Site: Cooper Entergy icon.png
Issue date: 10/22/1982
From: Lessor L
NEBRASKA PUBLIC POWER DISTRICT
To: Jay Collins
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML20065S296 List:
References
CNSS820598, NUDOCS 8211010170
Download: ML20065S291 (2)


LER-2082-020, Forwards LER 82-020/03L-0.Detailed Event Analysis Submitted
Event date:
Report date:
2982082020R00 - NRC Website

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9 CouPER NUCLEAR STATION Nebraska Public Power District " "

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CNSS820598 October 22, 1982 g - ~:-- ~~1 4l % .

y!i' OCT 2 61982 Mr. John T. Collins, Regional Administrator )  !

U. S. Nuclear Regulatory Commission "' ~~

i 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 4, 1982. A licensee event report form is also enclosed.

Report No.: 50-298-82-20

( Report Date: October 22, 1982 Occurrence Date: October 4, 1982 Facility: Cooper Nuclear Station Brownville, Nebraska 68321 Identification of Occurrence:

A condition which resulted in operation in a degraded mode permitted by a limiting condition for operation established in Section 3.9.B.3 of the Technical Specifications.

Conditions Prior to Occurrence:

The reactor was at a steady state power level of approximately 96% of rated thermal power.

Description of Occurrence:

During performance of Surveillance Procedure 6.3.12.1, #2 Diesel Generator (DG) tripped with no attendant alarm. Inspection revealed water in the lube oil system and #2 DG was declared inoperable.

Designation of Apparent Cause of Occurrence:

Rupture of #8 left cylinder liner expansion seal was the source of water in the lube oil system.

Analysis of Occurrence:

The station's emergency power system consists of two emergency diesel generators, each capable of supplying power for post accident safety system operation and safe reactor cooldown.

}b B211010170 821022 PDR ADOCK 05000 S

Mr. John T. Collins October 22, 1982 Page 2 During an operability test, #2 DG shut down with no attendant alarms. An air fitting leak was found at the 80 psig port "A" of the Amot safety ,

trip valve in the control air system. The fitting was repaired but the diesel would not start on subsequent trials and #2 DC was declared inoperable.

Further examination found a high oil level and water in the lube oil system which was traced to a rupture of #8 left cylinder liner expansion seal. Splashing due to the high crankcase level had tripped several vent valve trip levers associated with the connecting rod bearing temperature detectors. This allowed 30 psig control air to vent off and trip the diesel.

The metal expansion seal provides the lower water jacket seal between the liner and engine main frame. The seal expands and contracts with engine temperature variations.

The high bearing temperature vent valve trip levers are normally activated by a spring loaded fuse rod which strikes the trip lever on a high bearing temperature which releases the control air pressure. The fuse rods were not activated and no attendant alarm with the DG shutdown sounded.

During this event the redundant Diesel Generator, normal, startup and emergency transformers were operable. This occurrence presented no adverse consequences to the public health and safety.

Corrective Action:

The #8 left liner expansion seal was replaced. No. I left liner expansion seal was also replaced after inspection revealed several dents in the bellows. The lube oil system was completely drained and cleaned.

Various portions of the DG annual inspection were performed to ensure no damage was done to any bearings or cylinders due to lube oil delusion.

This included a boroscope inspection of all power cylinders, a crankcase inspection of all cylinders and liners, crank shaf t web deflection readings and jacking clearances of all rod bearings. The DG was tested satisfactorily and returned to service on October 7, 1982.

The ruptured liner expansion seal will be returned to Cooper Energy Services for inspection. Our conversation with Cooper Energy Services reveals there have been other failures with other engines, but the failure rate was not excessive.

Sincerely, L. C. Lessor Station Superintendent Cooper Nuclear Station LCL:cg Attach.

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