ML19260A946
| ML19260A946 | |
| Person / Time | |
|---|---|
| Site: | La Crosse File:Dairyland Power Cooperative icon.png |
| Issue date: | 11/26/1979 |
| From: | Wetmore J Office of Nuclear Reactor Regulation |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| TASK-02-04, TASK-2-4, TASK-RR NUDOCS 7912060180 | |
| Download: ML19260A946 (4) | |
Text
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NUCLEAR REGULATORY COMMISSION o
h WASHINGTON, D. C. 20555 k*****/
November 26, 1979 Docket No. 50-409 Licensee: Dairyland Power Cooperative Facility: La Crosse Boiling Water Reactors (LACBWR)
Subject:
Summary of November 2, 1979 Meeting Regarding Liquefaction Potential at LACBWR (SEP Topic II-4)
On November 2,1979, the NRC staff and their consultarts met with Dairyland Power Cooperative (DPC) and their consultants in Bethesda, Maryland, A list of meeting attendees is attached. The meeting was a follow-up meeting to our October 17, 1979 meeting on the same subject (see meeting summary dated Ocuber 29,1979). The purpose of the meetir.g was to allow DPC and their consultants to respond to the staff concerns identified in our October 17 meeting.
A sumary of the important points follows:
1.
DPC stated that they wanted to cooperate with NRC to resolve this issue. Their consultant, Dames and Moore, briefly sumarized the liquefaction studies that have been performed at LACBWR.
The results of the latest study are contained in a report entitled
" Liquefaction Potential at La Crosse Boiling Water Reactor (LACBWR)
Site" dated September 28, 1979. This study was undertaken at the NRC's request to supplement the data base obtained in previous work, using state-of-the-art techniques.
2.
Using the resuits cf laboratory triaxial tests, this study concludes that the minimum factor of safety against liquefaction for a 0,12g SSE is 1.50.
Lower fa: tors of safety were computed using an empirical treatment of Standard Penetration Test (SPT) data.
3.
Dames and Moore indicated that they had more confidence in the results obtained from laboratory testing than in those derived from SPT data; and thus, gave little weight to the SPT results.
4.
The NRC staff has independently compared the SPT data with that at Niigata, Japan, and obtain factors of safety less than 1.
In addition, the staff and its consultant, the U. S. Army Engineer Waterways Experiment Station (WES), believe that the soil samples used for laboratory testing were densified 3 to 4 lbs/cu ft from the in-situ condition. This densification is due to the sampling process itself and in the later consolidation of the samples for lab testing. WES asserted that the increased density was not adequately accounted for in Dames and Moore's analysis; and when properly accounted for, would substantially reduce the factors of safety against liquefaction.
1510 295 7912060lFC
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, 5.
Dames and Moore acknowledged that increases in soil sample density would decrease computed factors of safety, but stated that they believed a more realistic estimate of the density increase was 2 lbs/cu ft. According to their rough calculations, such a density increase would yield a minimum factor of safety of 1.2 instead of the 1.50 given in their report.
6.
The NRC staff and WES disagreed with Dames and Moore's judgement that 2 lbs/cu ft was an appropriate density increase to assume. They cited past experience with this type of sampling, and the data in the Dames and Moore report, to support their contention that the probable increase in density was 3 to 4 lbs/cu ft. With this increase, and their analysis of the SPT data, the staff concluded that if sustained strong ground motion with peak accelerations of 0.12g or higher occurs, liquefaction can occur at the LACBWR site.
7.
The IJ'C staff has concluded based on its evaluations to date that there is a relatively low seismic hazard at this site because of the earthquake history and initial estimates of the long return periods in this region for the size event that would have to occur to generate a.12g.
The staff indicated that it was proceeding with its evaluation of the SEP seismic methodology and the establishment of the seismic design basis for La Crosse.
It will take approximately three months to complete this evaluation.
The NP.C staff concluded that operation during this limited period will not pose a hazard to the public health and safety from potential liquefaction at the site.
In the interim, DpC agreed to consider modifying the site soils to preclude liquefaction.
8.
DPC agreed to submit a detailed plan for precluding liquefaction to the NRC by Novmber 30, 1979. The approach they will use may involve a dewatering system, but '. hey could use other methods depending upon costs and ease of implcun io. [}4 7
ck S. Wetmore, SEPM erating Reactors Branch #2 ivision of Operating Reactors
Attachment:
List of Attendees cc w/ attachment:
See next page 1510 296
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< cc w/ attachment:
Fritz Schubert, Esquire Staff Attorney Dairyland Power Cooperative 2615 East Avenue South La Crosse, Wisconsin 54601
- 0. S. Heistand, Jr., Esquire Morgan, Lewis & Bockius 1800 M Street, N. W.
Washington, D. C.
20036 Mr. R. E. Shimshak La Crosse Boiling Water Reactor Dairyland Power Cooperative P. O. Box 135 Genoa, Wisconsin 54632 Coulee Region Energy Coalition ATTN: George R. Nygaard P. O. Box 1583 La Crosse, Wisconsin 54601 Charles Bechhoafer, Esq., Chairman Atomic Safety and Licensing Board U. S. Nuclear Regulatory Commission Washington, D. C.
20555 Dr. George C. Anderson Department of Oceanography University of Washington Seattle, Washington 98195 Mr. Ralph S. Decker Route 4, Box 190D Cambridge, Maryland 21613 La Crosse Public Library 800 Main Street La Crosse, Wisconsin 54601 Mr. Frank Linder General Manager Dairyland Power Cooperative 2615 East Avenue South La Crosse, Wisconsin 54601 1510 297
LIST OF ATTENDEES NOVEMBER 2. 1979 LIQUEFACTION POTENTIAL AT LACBWR DPC E. Trercmel J. Parkyn Dames and Moore M. Nataraja H. Singh R. Fox NRC J. Wetmore C. Hofmayer J. Greeves L. Heller J. Shea C. Woodhead D. Crutchfield P. DiBenedetto T. Cheng P. Sobel J. Harbour L. Reiter H. Levin H. Lee R. Jackson WES W. Marcuson NES R. Milos I. Husain 1510 298