ML20099F630
| ML20099F630 | |
| Person / Time | |
|---|---|
| Site: | Fort Saint Vrain  |
| Issue date: | 11/07/1984 |
| From: | Brey H PUBLIC SERVICE CO. OF COLORADO |
| To: | Johnson E NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| References | |
| P-84478, NUDOCS 8411260526 | |
| Download: ML20099F630 (2) | |
Text
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'4 public Service Company CfOdenda s
November 7, 1984 Fort St. Vrain Unit No. 1 P-84478
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Regional Administrator Region IV l NOV l 3W
-l Nuclear Regulatory Commission i
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611 Ryan Plaza Drive, Suite 1000 A J Arlington Texas 76011 Attn: Mr. E. H. Johnson
SUBJECT:
Southeastern Wyoming Earthquake on October 18, 1984
Dear Mr. Johnson:
In response to a phone conversation of October 24, 1984 between Messrs. Wagner, Johnson, and Powers of the Nuclear Regulatory Commission and Messrs. Burchfield and Holmes of Public Service Company of Colorado, the following information is offered concerning the effects of the October 18, 1984 earthquake in Southeastern Wyoming on the Fort St. Vrain plant site:
1)
The six seismic instruments at Fort St. Vrain, three smoked glass motion detectors and three accelerometers, were all operable on October 18, 1984.
The Fort St. Vrain accelerometers are set to operate at a ground acceleration of
.01g.
The accelerometers did not begin operation, and the smoked glass motion detectors had no marks which could be attributed to the earthquake.
Surveillances performed on October 24, 1984 to test and calibrate these devices confirmed that they were operable.
2)
Section G.1 of the Fort St. Vrain FSAR includes information on a 1967 earthquake that was rated VI on the Modified Mercalli Scale twenty-five miles frem Fort St. Vrain.
It was determined that ground accelerations of.002g +.001g were felt at the Fort St. Vrain site during that earthquake.
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-e Preliminary-in'dications are that the October 18, 1984
' Southeastern Wyoming earthquake was rated only IV on the modified Mercalli. Scale at the Fort St. Vrain site. - Based-on the above information, it can be concluded that the grcund accelerations from the recent earthquake were substantially below the
.01g trigger ~ point on the accelerometers at Fort St. Vrain.
Nine accelerometers with a trigger setpoint of.019 located on ' dams in the Denver area did not trigger.
3)
There were no reports of damage to residences or-farm buildings near the Fort St. Vrain Station, and there was no-indication of any damage to buildings or facilities on the Fort.St. Vrain site.
In fact, many people at Fort St. Vrain did not feel the earthquake.
Arrangements' are being made to send an accelerometer from Fort St. Vrain to be completely tested by the manufacturer.
An "as found" report on the instrument trigger point will be produced, any appropriate refurbishing will be done, and an "as left" report will be produced as a result of this-testing.
We will inform you of the results of this accelerometer testing.
If you have questions regarding this material, please contact Mr. M. H. Holmes on (303) 571-8409.
Very truly yours, Me i H. L. Brey l
Executive Stcff Assistant Electric Production HLB /JW:pa 1
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