ML13310A744
| ML13310A744 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 10/18/1982 |
| From: | Crutchfield D Office of Nuclear Reactor Regulation |
| To: | Dietch R Southern California Edison Co |
| References | |
| TASK-02-04.F, TASK-2-4.F, TASK-RR LSO5-82-10-053, LSO5-82-10-53, NUDOCS 8210260229 | |
| Download: ML13310A744 (9) | |
Text
October 18, 1982 Docket No. 50-206 LS05 10-053 Mr. R. Dietch, Vice President Nuclear Engineering and Operations Southern California Edison Company 2244 Walnut Grove Avenue Post Office Box 800 Rosemead, California 91770
Dear Mr. Dietch:
SUBJECT:
SEP TOPICS II-4.F, SETTLEMENT OF FOUNDATIONS AND BURIED EQUIPMENT - REQUEST FOR ADDITIONAL INFORMATION SAN ONOFRE NUCLEAR GENERATING STATION, UNIT 1
Reference:
(1) "Report of Soil Backfill Conditions - San On6ftre Nuclear Generating Station, Unit 1" dated August 12, 1982, sub mitted under cover of K.P. Baskin Southern California E
Edison Company letter to D.M. Crutchfield, NRC, dated August 17, 1982 subject: "In-Situ Soil Conditions SEP Topic 111-6, Seismic Design Considerations, San Onofre Nuclear Generating Station, Unit I'.'.
(2) "Draft Licensee Assessment for SEP Topic II-4.5 - Settle ment of Foundations and Buried Equipment" submitted under dover of W.C. Moody, Southern California Edison Company, letter to D.M. Crutchfield, NRC, dated November 2, 1982, subject: "SEP Tppic II'_4.D and II-4.F San Onofre Nuclear Generating Station Unit 1".
(3) Additional information regarding SEP Topic II-4.F (Sett.l ment of Foundations and Buried Equipment) submitted under cover of R.W. Krieger Southern California Edison Company letter to D.M. Crutchfield, NRC, dated February 1, 1982 subject: "SEP Topics II-4.D and II-4.F, San Onofre Nuclear Generating Station Unit 1".
OFFICE OFFICME 2 12..2 SURNAME) 8210260229 821018 PDR ADOCK 05000206 T pPDR NCRM318(10-80)NMn 0
OFICIAL RECORD COPY
Mr. R. Dietch
-2 Enclosed are our review comments on the information you have submitted in the above References concerning the subject topic.
Comparison of data presented in Reference 1 with data previously submitted in References 2 and 3 has identified significant differences in reported subsurface soil conditions related to the static and dynamic properties of backfill material at many locations 4t the Unit 1 plant site. 'These differences are considered sufficient to question the validity of the conclusions presented in Reference 2.
Because of these discrepancies in docketed information, we request that you reassess SEP Topic II-4.F and submit a revised topic SAR incorporating appropriate revisions related to soil conditions at the site, structural settFment estimates, Seismic Category I pip&lines, ducts and buried equip ment, other settlement estimates, and a oomplete analysis of liquefaction Iotential and its effects on settlement of structures and buried equipment for the site.
You should prepare thediscuss the subject issue in the forthcoming meeting on October 21 and 22, 1982, and submit your response within 30 days after the meeting.
The reporting and/or recordkeeping requirements contained in this letter affect fewer than ten respondents; therefore, OMB clearance is not required under P.L.96-511.
Sincerely, Original. signe'd bif Dennis M. Crutchfield, Chief Operating Reactors Branch No. 5 Division of Licensing
Enclosure:
As stated cc w/enclosure:
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NCFORM 318 (10-80) NRCM 020OFFICIAL RE CORD CO PY USGPO: 1981-335-960
Mr. R. Dietch
-2 Enclosed is our review comments on the information you have submitted in the above Reference concerning the subject topic.
Comparison of data presented in Reference 1 with data previously submitted in Reference 2 and 3 has identified significant differences in reported subsurface soil conditions related to the static and dynamic properties of backfill meterial at many locations at the Unit 1 plant site. These differences are considered sufficient to question the validity of the conclusions presented in Reference 2.
Because of these discrepancies in docketed information, we request that you reassess SEP Topic II-4.F and submit a revised topic SAR incorporating appropriate revisions related to soil conditions at the site, structural settlement estimates, Seismic Category I pipplines, ducts and buried equip ment, other settlement estimates, and a complete analysis of liquefaction potential and its effects on settlement of structures and buried equipment for the site.
You should prepare to discuss the subject issue to the forthcoming meeting on October 21 and 22, 1982, and submit your response within 30 days after the meeting.
The reporting and/or recordkeeping requirements contaitednin this letter affect fewer than ten respondents; therefore, OMB clearance is not required under P.L.96-511.
Sincerely, Dennis M. Crutchfield, Chif Operating Reactors Branch No. 5 Divis6anoof Licensing
Enclosure:
As stated cc w/enclosure:
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.0 DATE NRC FORM 318 (10-80) NRCM 0240 OFFICIAL RECORD COPY USGPO: 1981-335-960
Mr. R. Dietch San Onofre Unit 1 Docket No. 50-206 Revised 3/30/82 cc Charles R. Kocher, Assistant General Counsel James Beoletto, Esquire Southern California Edison Company Post Office Box 800 Rosemead, California 91770 David R. Pigott Orrick, Herrington & Sutcliffe 600 Montgomery Street San Francisco, California 94111 Harry B. Stoehr San Diego Gas & Electric Company P. 0. Box 1831
.San Diego, California 92112 Resident Inspector/San Onofre NPS c/o U. S. NRC P. 0. Box 4329 San Clemente, California 92672 Mayor City of San Clemente San Clemente, California 92672 Chairman 4
Board of Supervisors County of San Diego San Diego, California 92101 California Department of Health ATTN: Chief, Environmental Radiation Control Unit Radiological Health Section 714 P Street, Room 498 Sacramento, California 95814 U. S. Environmental Protection Agency Region IX Office ATTN:
Regional Radiation Representative 215 Freemont Street San Francisco, California 94111 Robert H. Engelken, Regional Administrator Nuclear Regulatory Commission, Region V 1450 Maria Lane Walnut Creek, California 94596
San Onofre Unit 1, Docket No. 50-206 Review Comments on "Report of Soil Backfill Conditions San Onofre Nuclear Generating Station Unit 1", dated August 12, 1982 Prepared by:
Dr. Jerome R. Pearring, HGEB/GES
Background
In April, 1982, Southern California Edison Company (SCE) notified NRC.that backfill soil conditions encountered at the San Onofre Nuclear Generating Station Unit 1 site during excavation activities associated with foundation modifications to the turbine building were not consistent with prior backfill soil property assumptions. The initial concern was the effect that the differing backfill material surrounding, supporting and embedding Seismic Category I structures, manholes, piping and ducts would have on previous seismic design conclusions.
SCE has initiated a detailed evaluation of the in-situ backfill soil conditions throughout the site to determine the in-place engineering properties of the existing backfill materials and the effect of any deviation from past assumed conditions on the seismic design re-evaluation of affected structures. A report entitled "Report of Soil Backfill Condition San Onofre Nuclear Generating Station Unit 1" providing the results of this evaluation, was submitted to NRC by SCE in August, 1982 (Ref. 1).
Based upon a review of the above referenced report and of other geotechnical engineering related data previously submitted by SCE to NRC (Ref. 2, 3, 4, 5 and 6), the following paragraphs are presented for the licensee's considiration and appropriate action.
-2 Areal Extent of Loose Soils Insufficient information has been presented in the report to allow an independent verification of the areal extent of material compacted to less than the required 95% Modified Proctor. While assumptions of excavation widths and slope angles have been made by the licensee to attempt to place limits on possible areal extent of potentially loose soil, no evidence has been presented to support the validity or conservatism of the assumption.:
.Furthermore, the angle of slope assumed by the licensee is not in accord with a previously submitted construction drawing (Ref. 5). 'Due to the ambiguities associated with the licensee's method of defining areal extent, and considering the consequence of error in determining an acceptable, conservative slope, it is suggested that in-place soil density testing be accomplished to definitely establish the areal extent and actual densities at all locations where soil properties will affect the stability of Seismic Category I structures, buried ducts, and equipment.
Settlement of Backfill Insufficient information has been presented to allow an independent analyses of estimates of settlement. Calculated estfmates based upon procedures of Silver and Seed (Ref. 7) and Lee and Albaisa (Ref. 8) have been adjusted by the licensee using unspecified techniques. Information related to the adjustments made to the calculated estimates to account for "variations of depth of fill below the foundations" and "proximity of adjacent boundaries which constrain the development of shear strains" is required.
-3 Shear Moduli Reduction Factors Independent calculation of shear modulus reduction factors based upon data presented in past licensee submittals (Ref. 6), and correlation data regarding relative density and shear moduli values for typical sands presented by Seed (Ref. 9) indicates that reduction factors of 0.8, 0.7, and 0.5 are appropriate for sand at relative compaction of 90%, 85% and 80% respectively. It is therefore suggested that the licensee consider a reduction factor of about 0.7 for Sands at 85% relative compaction (50% Relative Density) and a reduction factor of 0.5 for sand near 80% relative compaction (30% Relative Density) rather than the licensee proposed reduction factor of 0.74 for sands at 80%
relative compaction. It is pointed out that these reduction factors are considered valid only when applied to calculations based upon shear moduli/
strain curves for reconstituted (i.e. backfill) San Mateo Sand. Previous calculations which assumed the backfill possessed equal properties as native San Mateo Sand at low strain (10- 4%) must of course be reduced further at low strain levels to account for the loss of the high strength at low strain levels attributed to cohesion in the undisturbed state for native San Mateo Sand.
Liquefaction Potential of Backfill Because the areal extent of the loose backfills soils has not been definitely established, it is not possible to identify areas where a potential for liue faction exists. The position of the licensee, that San Mateo Sand soils compacted
.to below 85% Relative Compaction i.e. less than 50% relative density should be considered as potentially liquefiable, is concurred in. The position of the
-4 0
licensee, that San Mateo Sand material compacted to greater than 95%
Relative Compaction can be considered as non liquefiable, is also acceptable.
Without more definiti.ve data regarding the areal extent of soils which are compacted to less than 95% it is not possible to assess the liquefaction potential of the affetted soils or the posstble impact of liquefaction on settlement of structures such as the sea wall, buried pipes, ducts and foundations resting upon backfill soils.
-5 References
- 1. "Report of Soil Backfill Conditions - San Onofre Nuclear Generating Station, Unit 1", August 12, 1982 submitted under cover of K. P. Baskin, Southern California Edison Company letter to D. M. Crutchfield, NRC, dated August 17, 1982,
Subject:
In-situ Soil Conditions SEP Topic 111-6, Seismic Design
'Considerations San Onofre Nuclear Generating Station, Unit 1.
- 2. "Final Safety Aanlysis Report, San Onofre Nuclear Generating Station, Unit 1" Southern California Edison Company.
- 3. "Final Safety Analysis Report, San Onofre Nuclear Generating Station Units 2 and 3" - Southern California Edison Company.
- 4. Southern California Edison Company letter Moody to D. M. Crutchfield, November 2, 1981
Subject:
"SEP Topic II-4.D and II-4.F San Onofre Nuclear Generating Station Unit 1".
- 5. Excavation Plan Plant Area - Drawing No. 567760 Date 9/16/64.
- 6. "Additional Information Regarding SEP Topic II-4.F" submitted under cover letter R. W. Krieger Southern California Edison Company to D. M. Crutchfield, Feb. 1, 1982 subject:
"SEP Topics II-4.D and II-4.F - San Onofre Nuclear Generating Station Unit 1".
- 7. M. L. Silver and H. B. Seed - "Volume Changes in Sands During Cyclic Loading" ASCE Journal of the Soil Mechanics and Foundations Division, Vol.
97, No.
SM9 Sept. 1971, pps. 1171-1182.
- 8. K. L. Lee and A. Albaisa -
"Earthquake Induced Settlements in Saturated Sands" ASCE Journal of the Geotechnical Engineering Division, Vol. 100, No.
GT4, April 1974, pps. 387-406.
- 9. H. B. Seed and I. M. Idriss - "Soil Moduli and Damping Factors for Dynamic Response Analyses" University of California Earthquake Engineering Research Center Report No. FERC 70-10 December 1970.