ML19350A680
| ML19350A680 | |
| Person / Time | |
|---|---|
| Site: | Crystal River  |
| Issue date: | 03/02/1981 |
| From: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | Hancock J FLORIDA POWER CORP. |
| References | |
| NUDOCS 8103160645 | |
| Download: ML19350A680 (1) | |
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UNITED STATES
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6'6 Florida Power Corporation ATTN:
J. A. Hancock, Assistant Vice President Nuclear Operations P. O. Box 14C42, Mail Stop C-4 St. Petersburg, CL 33733 Gentlemen:
The enclosed IE Circular No. 81-03 is forwarded for your information. No written response to this Circular is required. If you have any questions related to this matter, please contact this of fice.
Sincerely, s.c wse as
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James P. O'Reilly Director
Enclosures:
1.
IE Circular No. 81-03 2.
List of Recently issued IE Circulars cc w/ encl:
D. C. Poole, Nuclear Plant Manage-8103160 @ %
SSINS No.: 6830 Accession No.:
8008220271 IEC 81-03 i
UNITED STATES NUCLEAR REGULATORY COMMISSION 0FFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 i
March 2, 1981 IE Circular No. 81-03: INOPERABLE SEISMIC MONITORING INSTRUMENTATION Description of Circumstances:
On November 8, 1980, 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 facility.
There were 12 separate seismic events above a magnitude of 3.5 that occurred within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of */ne earthcuake, the largest event measuring 5.2.
Reported damage to structures included several houses that were moved off supporting posts, various chimneys that were knocked down, 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 instruments indicated the following: the magnetic tape triaxial recorders did not produce useful records due 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 set of triaxial recorders); the triaxial response spectrum recorder was the only instrument believed to produce reliable data.
On January 24, 1980, an earthquake measuring 5.5 on the Richter Scale occurred about 10 miles north of Lawrence Livermore Laboratory (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.
Rancho'Seco was shutdown for refueling during these earthquakes.
During this period, the electrical seismic instrumentation system was inoperable because portions of the system were out for calibration.
For the other instruments, power was not being supplied due to electrical cabl roblems.
Whether the seismic instrumentation would have a U.S. Geological Survey equipment clo from a passive recorder showed peak
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