ML19345G184
| ML19345G184 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 03/02/1981 |
| From: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| References | |
| NUDOCS 8103170001 | |
| Download: ML19345G184 (1) | |
Text
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- / >2 UCgo UNITED STATES 8
k NUCLEAR REGULATORY COMMISSION REGION V 1990 N. CALIFORNI A BOULEVARD e,
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SUI *E 202, WALNUT CREEK PLAZA e,,,*
WAL9 UT CR E E K, CALIFORNI A 94596 March 2, 1981 Docket No. 50-312 o
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L.U Sacramento Municipal Utility District P. O. Box.15830 f.MR 0 6198N. 8 Sacramento, California 95813 J
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Attention: Mr. John J. Mattimoe o
Assistant General Manager D
Gentlemen:
The enclosed circular is fwwarded for your information. No written response.
to this circular is required.
If you have any questions related to this matter, please contact this office.
Sincerely, R. H. Engelken Director 1
Enclosure:
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IE Circular No. 81-03 2.
List of IE Information Notice.Recently Issued cc w/ enclosures:
l R. J.. Rodriguez,-SMUD l
L. G. Schwieger,~SMUD I
810817000l N
SSINS No.: 6830 Accession No.:
8008220271 IEC 81-03 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 fiarch 2,1981 IE Circular No. 81-03: IN0PERABLE SEISMIC MONITORING INSTRUMENTATION Description of Circumstances:
On November 8, 1080, an earthquake occurred off the coast near Eureka, California.
The earthquake was reported to have a magnitude of 7.0 on the Richter Scale at the epicenter, approximately 25 to 75 miles from the Humboldt Bay Power Plant f acili'cy.
There were 12 separate seismic events above a magnitude of 3.5 that occuned within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of the earthquake, the largest event measuring 5.2.
Reported damage to structures included several houses that were moved off supporting posts, various chimneys that were knocked iown, one highway overpass that collapsed, and unspecified damage that occurred at two pulp mills.
There were three potentially different sources of plant response data: three sets of magnetic tape triaxial accelograph recorders; three sets of triaxial film recorders (passive device); and one set of triaxial response spectrum recorders (passive device). A review of the records from these instrumer.ts indicated the following: the magnetic tape triaxial recorders did not produce useful records ue to a degraded low-voltage power supply in the recording system (previously scheduled for routine servicing one week after the earthquake);
a buildup of dirt and dust appeared to make inoperable six of the nine film recorders (the readings from the other three are considered highly unreliable and were not obtained from the same si:t of triaxial recorders); the triaxial response spectrum recorder was the only instrument believed to produce reliable da ta.
On January 24, 1980, an earthquake measuring 5.5 on the Richter Scale occurred about 10 miles north of Lawrence Livermore Lacoratory (near San Francisco, California). Numerous aftershocks also occurred with one measuring 5.2 on January 26. The damage to civil structures was considered minor.
Rancho Seco Nuclear Plant, located approximately 45 miles northeast of the earth-quake area, reported no physical damage, although plant personnel felt slight building motion.
F 1 these earthquakes. During this Mgge
-er an system was inoperable because
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