ML20132C102
| ML20132C102 | |
| Person / Time | |
|---|---|
| Site: | Limerick, 05000000 |
| Issue date: | 04/23/1984 |
| From: | Rolonda Jackson Office of Nuclear Reactor Regulation |
| To: | Vollmer R Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20132B198 | List:
|
| References | |
| FOIA-85-363 NUDOCS 8405180313 | |
| Download: ML20132C102 (2) | |
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APR 2 31984 MEMORANDUM FOR:
Richard H. Vollmer, Director Division of Engineering THRU:
ilames P. Knight, Assistant Director for
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Robert E. Jackson, Chief
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SUBJECT:
4.1 MAGNITUDE EARTHQUAKE NEAR L ANCASTER, PENNSYLVANIA
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An earthquake of magnitude
= 4.1 and focal depth of 6 km occurred at 08:36:00.2 P.M. EST on A i22,1984 The epicenter of the earthquake was located at 39.85N - 76.27W.
Personnel at Peach Bottom (10 km from the epicenter) and Three Mile Island (63 km from the epicenter) felt the earthquake but none of the strong motion instruments in the plants triggered.
Personnel at Calvert Cliffs, Surry, Susquehanna, Beaver Valley, Indian Point, Oyster Creek and Salem did not feel the earthquake.
Very minor damage occurred near the epicenter of the earthquake. This earthquake occurred in the same area as the magnitude 3.0 earthquake which occurred on April 18, 1984.
Attached is a map from the Limerick FSAR showing historical seismicity (1755-1980) within 50 miles of the Limerick site.
Indicated on this map are the April 18, 1984 earthquake epicenter and the Peach Bottom and TMI Nuclear Power Plants.
As shown in the figure, the earthquake occurred in a region which has experienced moderate seismic activity '
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/D Robert E. Jackson, Chief Geosciences Branch Division of Engineering
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May 11,1984 Docket No. 50-277 50-278 Dr. Tharas E. Murley Office of Inspection ard Enforcement U.S. Nuclear Regulatory Ccnmission Region I 631 Park Avenue King of Prussia, PA 19406 SUST2Cr: Seismic Event in the Area of Peach Bottcm Atcmic Power Station
Dear Dr. Murley:
The purpose of this letter is to provide you with information relative to the April 22, 1984, seismic activity which ocx:urred in the area of Peach Bottm. This activity did not cause ground motion sufficient to be reportable under facility Technical Specification; how/er, due to the cirewstances of the occurrence, it is prudent to provide you with this information.
On April 22, 1984, at approximately 8:35 p.m., seismic activity was noted by Peach Bottcm personnel. Although no alarms were received and the plant continued to operate normally, the Special Event Procedure for earthquakes (SE-5) was performed.
This procedure involves testing of all emergency diesels, surveying rotating equipt.ent and storage tanks, inspection of the plant for water leaks and testing of the fire pumps. No defects or malfunctions were observed.
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.- >,;, r 's This seismic event was reported by ecologists frcm the states of Pennsylvania and Delaware to be 4.0 on the Richter scale. Table 19-2 of " Nuclear Energy Techrology",provides a correlation of Richter scale vs. grcund acceleration. This correlation indicates that for a Richter magnitude 4.0 event the correspcnding g force is approximately 0.01g at the epicenter.
Since the epicenter was determined by the authcrities to be N
several miles from Peach Bottom, the expected level of ground acceleration should be less at the plant. The trigger threshold for the installed seismic monitoring system activation is 0.019
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Dr. Thanas E. Murley May 11, 1984 Page 2 Due to the fact that the absolute magnitude and exact epicenter of the event were unknown, the appropr.iate surveillance testing was undertaken to verify the operability of the seismic mcnitoring system. These tests revealed that the system would not have responded to any event due to a malfunction of the Strong motion detector which serves as a trigger for the system.
The system had last been demmstrated to be operable during surveillance testing on April 19, 1984. The cause of the failure of the active system trigger was traced to a defective circuit board. This board was replaced ard the system was successfully retested and returned to service on April 27, 1984.
Information frcm the passive recording system which consists of triaxial peak acceleration recorders (etch plate acceleregraphs) was also analyzed. The minimum sensitivity of these devices is 0.01g (or 0.02 mm displacement on the recording). The analysis of the etch plates provided unreasorubly high event levels (0.5 to 1.8g) which have been i
attributed to work activities which had taken place in the areas in which these recorders are located.
The passive system was tested and calibrated in accordance with the acpropriate surveillance test ard the devices were re urned to service. The purp:se of the system is such that the sensitivity of these devices is a;propriate for the application as described on pages 7.21-1 and 2 of the Updated FSAR. No further action is anticipated in this area.
The significance of this event is minimal. In the worst case, assuming t?.c epicenter had been en-site, the grcend acceleration woui? have been 0.01g or 20 percent of the Operating Basis Earthquake level. This level also corresponds to the setpoint of the strong tretion sensor trigger.
If you require further information in this matter, do not hesitate to contact us.
Very truly yours, W. T. Ullrich Superintendent Nuclear Generation Division JCN:vdw cc:
A. R. Blough, Site Inspector
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