ML19331E037

Forwards LER 80-031/01T-0

ML19331E037
Person / Time
Site:	Cooper
Issue date:	08/18/1980
From:	Lessor L NEBRASKA PUBLIC POWER DISTRICT
To:	Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML19331E038	List: ML19331E037 ML19331E040
References
CNSS800499, NUDOCS 8009050252
Download: ML19331E037 (2)

Text

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Ys COOPER NUCLEAR STATION gi 'N i Nebraska Public Power District " '"

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CNSS800499 tust 18, 1980 Mr. K. V. Seyfrit, Director U.S. Nuclear Regulatory Commission Office of Inspection 2nd Enforcement R- ion IV 67, Ryan Plaza Drive Suite 1000 Arlington, Texas 76011

Dear Sir:

This report is submitted la accordance with Section 6.7.2.A.7 of the Technical Specifications for Cooper Nuclear Station and discusses a repertable occurrence that was discovered on August 4, 1980. A licensee event report form is also enclosed.

Report No.: 50-298-80-31 Report Date: August 18, 1980 Occurrence Date: August 4, 1980 Facility: Cooper Nuclear Station Brownville, hbraska 68321 Identification of Occurrence:

Conditions arising from a natural phonomenon that, as a direct  ;

result of the event, caused the reactor to shutdown, Conditions Prior to Occurrence:

Steady state power operation at 86% of rated thermal power.

Description of Occurre :ce:

During normal operation, a severe weather storm caused a line fault on the 345 KV distribution system which initiated a voltage trans-l ient that induced erroneous signals into the turbine control digital electric hydraulic (DEH) System computer. These erroneous signals caused the DER Syster, to indirectly initiate a reactor shutdcwn.

Designation of Apparent C. rise of Occurrence:

The 345 KV distribution system line fault induced voltage trans-ients into the plant's electrical ~ system.

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, V Mr. K. V. Seyfrit August 18, 1980 Page 2.

Analysis of Occurrence:

It is believed that the 345 KV distribution system line fauie induced voltage transients which were sensed by the DEH System.

This resulted in a chain of events that caused the main turbine bypass valves to open. The governor valvea did not control reactor pressure and a Group I isolation due to low pressure closed the MSIV's resulting in a reactor scram. All systems that scram the reactor functioned as designed. There were no significant oc-currences as a result of this scram and there were no adverse affects to the public health and safety.

Corrective Action:

No corrective action is planned at this time, but evaluation of the electrical circuitry to prevent transients from affecting the plant's eperation is being studied.

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

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