ML20138B860

Ro:On 851202,reactor Sys Experienced Unrelated Rod Position Instrumentation Indication Failure.Operators Manually Tripped Reactor.All Sys Returned to Normal Status Following Completion of Safety Functions

ML20138B860
Person / Time
Site:	Diablo Canyon
Issue date:	12/03/1985
From:	Thornberry R PACIFIC GAS & ELECTRIC CO.
To:	Brian W SAN LUIS OBISPO, CA
References
NUDOCS 8512120397
Download: ML20138B860 (3)

Text

, PACIFIC GAS AND E LE C T RIC C O M PANY 4' DIABLO CANYON POWER PLANT RO. Box 56 Avila Beach, Cahfornia 93424 *(805) 595-7351

[gllllllllj R C. THORNBERRY PLANT MANAGER December 3, 1985 Mr. William Briam, Administrator San Luis Obispo County Administrative Office County Government Center San Luis Obispo, CA 93408

Dear Mr Briam:

Pursuant to NUREG-0654, Revision 1, Appendix 1, the following is a summary report concerning the following Unusual Event at the Diablo Canyon Nuclear Power Plant site.

On December 2,1985, while Unit 2 was reducing power because of circulating water system problems caused by kelp at the Intake Structure, the reactor system experienced an unrelated rod position instrumentation indication failure. The operators manually tripped the reactor. A High Steam Flow signal initiated a safety injection, causing the Emergency Core Cooling System to initiate and discharge to the Reactor Coolant System.

An Unusual Event was declared by the Shift Foreman at 2120 PST and emergency notifications were started. After the protection system completed its safety functions, all systems were returned to their normal status.

The Unusual Event was concluded at 2140 PST December 2, 1985, and all response organizations were notified. This event has in no way affected the health ar.d safety of the public ard no discharge of radioactive materials was made to the environment.

G512120397 851203 PDR ADOCK 05000323 S PDR 1

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Mr.yilliamBriam Decemb;r 3, 1985 e

i For your information, on November 28, 1985, while performing the Unit 2 startup testing program, the reactor protection system was activated by a momentary signal causing a reactor trip. At this time, this event was conservatively classified as an Unusual Event. Upon further investigation, it was determined that the reactor protection system functioned as designed and thus this was not considered to be an Unusual Event.

Sincerely, or e V ROBERT C. THORNBERRY RCT:jhr DC0456 PII

_, , Mr. , William Briam December 3, 1985 i

l 4

l cc Mr. Benjamin F. Tong, Chief Nuclear Power Plant Planning P. O. Box 9577.

Sacramento, CA 95823 Mr. John B. Martin, Administrator U. S. Nuclear Regulatory Comission, Region V 1450 Maria Lane, Suite 210 Walnut Creek, CA 94596-5368 Mr. George Whiting, Sheriff San Luis Obispo County P. O. Box 32 San Luis Obispo, CA 93401 Mr. George Licensing W.No.

Branch Knighton, 3 Chief [

Diviv on of Licensing Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Comission Washington, D. C. 20555 Director, Office of Management Information and Program Control U. S. Nuclear Regulatory Comission Washington, D. C. 20555 Drnd% ?T v- -w w y "

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