ML20062C152
| ML20062C152 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 11/02/1978 |
| From: | Crews E SOUTH CAROLINA ELECTRIC & GAS CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 7811070128 | |
| Download: ML20062C152 (1) | |
Text
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November 2, 1978 l
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i Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D. C. 20555
Subject:
Virgil C. Summer Nuclear Station l
Docket No. 50-395 Seismic Monitoring
Dear Mr. Denton:
I This letter is to confirm our oral discussion with members of the NRC Staff concerning two recent seismic events recorded by the seismic networks of the Applicant and the United States Geological Survey.
l 1
l On August 27, 1978, seismometers recorded an event with a Richter magni-tude of approximately 2.7.
In October, after analysis by USGS of data from its strong motion accelerometer installed as part of its monitoring system, the Applicant was informed that the August 27, 1978, event had produced a ground acceleration value of 0.25g for approximately 0.030 second.
While such a peak acceleration is usually not associated with an event of Richter magnitude 2.7, the USGS has informed the Applicant that the relatively high, but brief, acceleration is not unusual, where the instrument was located less than one mile from the epicenter of the seismic event. As was initially discussed with your Projects Licensing Staff on October 10 and 11, 1978, and
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further discussed in detail on October 13, 1978, with the geoscience technical branch, such an event is well within the seismic design parameters of the fa-cility and has no significance as far as the seismic design of the facility is concerned.
l On October 27, 1978, the monitoring network recorded an event of Richter magnitude of approximately 2.8.
The corresponding ground acceleration value as recorded by the USGS strong motion accelerometer has not yet been determined.
This information will be made available to the Applicant after its determination by USGS.
We will contiaue to keep the Staf inf ed of developments with regard to this matter.
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g E. H.
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