PNO-V-85-051, on 850804,two Earthquakes Measuring 4.6 & 5.5 on Richter Scale Occurred 70 Miles from Facility.Primary Seismic Recording Equipment Failed to Trigger as Setpoint Higher than Acceleration Experienced at Site

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PNO-V-85-051:on 850804,two Earthquakes Measuring 4.6 & 5.5 on Richter Scale Occurred 70 Miles from Facility.Primary Seismic Recording Equipment Failed to Trigger as Setpoint Higher than Acceleration Experienced at Site
ML20133K691
Person / Time
Site: Diablo Canyon  Pacific Gas & Electric icon.png
Issue date: 08/05/1985
From: Mendonca M, Pereira D
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
To:
References
PNO-V-85-051, PNO-V-85-51, NUDOCS 8508120329
Download: ML20133K691 (1)


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((j PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE--PNO-V-85-51 Dste: 08/05/85 Thio preliminary notification constitutes EARLY notice of events of POSSIBLE safety or public int: rest significance. The information presented is as initially received without verification cr cvaluation and is basically all that is known by Region V staff on this date.

FACILITY: Diablo Canyon Unit 1&2 Emergency Classification San Luis Obispo County, California X Notification of Unusual Event Docket Nos. 50-275/323 Alert Site Area Emergency General Emergency Not Applicable

SUBJECT:

EARTHQUAKES Two earthquakes occurred 70 miles Northeast of Diablo Canyon Nuclear Generating Station on August 4, 1985. The first earthquake measuring 4.6 on the Richter scale occurred at 4:29 a.m. (PDT) and the second, registering 5.5 on the Richter scale, occurred at 5:02 am (PDT). The epicenter was 10 miles southeast of Coalinga, California.

Pri ary seismic recording equipment at the Diablo Canyon site did not trigger in that the trigger set point was higher than the acceleration experienced at the site. More sensitive

a
ctndary seismic recording equipment located at the site actuated as expected and results f cra now being evaluated. No damage occurred at the site; however, some control room I

parconnel onsite reported feeling the earthquake. The plant was operating at 60% of full pow:r at the time of the earthquake.

Thi= information is current as of 9:00 am (PDT) on August 5, 1985.

CONTACT: David B. Pereira, RV M. Mendonca FTS 463-3788 (805) 595-2353 DISTRIBUTION 11 St. ll. 37 MNBBN.*/[ Phillipslf'l7 E/WlI h ulste/f b r RightsM#I/ Ma n -

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ACRS Licensee: J: Y2 CA (Reactor Licensecs) REGION V: FORM 211 PDR Resident Inspector,f 3 7 (Revised 3/14/83) 8508120329 850805 Ol PDR I&E PNO-V-85-051 PDR ,

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