ML13304A643
| ML13304A643 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 08/15/1980 |
| From: | Greeves J Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML13304A641 | List: |
| References | |
| ISSUANCES-OL, NUDOCS 8008220121 | |
| Download: ML13304A643 (6) | |
Text
ATTACHMENT 1 UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION BEFORE THE ATOMIC SAFETY AND LICENSING BOARD In The Matter of
)
SOUTHERN CALIFORNIA EDISON COMPANY, Docket Nos. 50-361 OL ET AL.
)
50-362 OL (San Onofre Nuclear Generating
)
Station, Units 2 and 3)
)
AFFIDAVIT OF JOHN T. GREEVES CONCERNING INTERVENORS' CONTENTION 1(a) (DEWATERING WELLS)
- 1. I am employed as a Geotechnical Engineer in the Geotechnical Engineer ing Section of the Hydrologic and Geotechnical Engineering Branch, Division of Engineering, U.S. Nuclear Regulatory Commission. In this capacity, I am responsible for evaluating sites with respect to geo technical engineering aspects to assure adequate design measures to prevent adverse safety problems.
- 2. I hold a Bachelor of Science Degree in Civil Engineering from the University of Maryland (1968). In addition, I have completed nine (9) credit hours of graduate level studies in Civil Engineering at the University of Maryland. I am a Registered Professional Engineer with current registration in Mississippi and Virginia.
- 3. I have about twelve years of experience working in areas related to foundation design, construction and analysis required for both nuclear 8 008220/ J
-2 and conventional electric generating plants. These include nearly seven years with Bechtel Inc. in Gaithersburg, Maryland and six years with the U.S. Nuclear Regulatory Commission (formerly USAEC) in Bethesda, Maryland.
- 4. As the geotechnical engineering reviewer assigned to this case, I reviewed those sections of the FSAR dealing with geotechnical aspects of the site, all special submissions dealing with dewatering voids, attended a large number of meetings on that subject and conducted several site visits, inspecting the investigation and demobilization activities associated with the dewatering wells located at SONGS 2 and 3.
- 5. Southern California Edison Company (SCE) and San Diego Gas and Electric (Applicants) have investigated, identified, filled and evaluated a number of dewatering cavities at the San Onofre site. For the follow ing reasons, in my opinion the techniques used to identify the cavities and procedures used to fill the cavities were suitable and satisfy the need to identify and stabilize all these cavities. Further, their evaluation of the response of the foundation soil and cavity fill material to dynamic loading is conservative.
- 6. Exploration drilling, mechanical measurements and geophysical surveys were performed by SCE to identify and define the location and extent of
-3 each and every cavity at or near the site.-'
These standard geological investigating techniques for nuclear power plants are in conformance with and exceed the standard practice contained in Regulatory Guide 1.132 entitled "Site Investigations for Foundations of Nuclear Power Plants",
dated September 1977.
- 7. In the investigations of the twelve dewatering wells at the site, the most intensive effort was applied to wells 6, 7 and 8,.the only cavities of sufficient size and proximity to the San Onofre units to have an impact on seismic category I structures. All other wells were free of large cavities.
- 8. Based on inspection of the Applicants reports and my own site investi gations, I found that grout was placed in cavities to fill any void spaces and provide some densification of the in-fill sand within the disturbed zone. Grouting was performed in stages on a grid pattern.
The water-cement ratio varied from 5:1 to 3/4:1 for the grout mixes used. Grout pressures were generally limited to one psi per foot of depth. These grouting procedures and the close spacing of the grout holes constitutes an intensive effort for the application of standard foundation treatment techniques and provide a great assurance that cavities have been filled. In addition, substantial efforts to verify the results of the grouting techniques have been provided in the Applicants' reports and reviewed by the Staff. The staff found these 1/ Two of the cavities in question are located offsite.
-4 procedures used by the Applicants to be adequate and the results have been satisfactorily documented.
- 9. The cavities at wells 6, 7 and 8 were evaluated to determine the effects on adjacent seismic category I structures. These structures included the Auxiliary Building, the Fuel Handling Buildings for Units 2 & 3 and the Unit 3 containment structure.-
These evaluations were made by calculating the potential reduction in stiffness and support character istics of the foundation soil which would be caused by an increase in pore water pressure in an adjacent grouted cavity. These valuations were provided in a report titled "Report on the Results of Analyses Performed on Well 8 at the SONGS Units 2 and 3, San Onofre, California,"
which is reference number 7 in the Applicants' Motion for Summary Disposition.
This report provides analyses of the potential effects of seismic shaking on the cavity at Well 8, and the resulting potential effects on the adjacent structures. The results of the analyses for Well 8 were extrapolated to the Well 6 and 7 cavities. There are two basic elements to this report: (1) the evaluation of the generation and dissipation of excess water pore pressure in the soil foundation during seismic loading; and (2) evaluation of the overall reduction in stiffness of the soil supporting the containment structure. Two very conservative 2/ Unit 1 structures and the Unit 2 containment building are located too far from the cavities to be affected by them.
-5 assumption were considered with respect to excess pore water pressure generation and dissipation. These assumptions were: (1) the geometry of the sand fill within the cavity at Well 8 is two-dimensional (plane strain or axisymmetric) and (2) the shortest drainage path beneath the containment structure is equal to the diameter of the basemat.
The first assumption implies that the volume of the pore pressure generating source is much greater than the actual size of the cavity. For the axisymmetric case, which is considered to model the cavity size more realistically than that of the plane strain case, the volume of the cavity is calculated to be more than one order of magnitude larger than the actual cavity size. The second assumption increases time required for dissipation of excess pore pressures and overestimates pore pressure at any given time during periods of dissipation as compared to the actual field condition. Regarding the applicants' assessment of the generation and dissipation of excess pore pressure, although many assumptions are required in this analysis, for the reasons listed above, the analysis is a conservative estimate of design conditions.
The report concludes that the maximum effects on the Unit 3 containment building is a 4 to 5% reduction in overall soil stiffness, the effects of the cavity on settlement (less than a 1/10 inch increase) and bearing capacity of the containment structure are very small and will not affect the containment or other structures on site. Staff review of that report has shown that conclusion to be conservative.
-6
- 10.
In addition to the above structures, on electrical tunnel (described further in the Lipinski Affidavit, Attachment 2), passes over the Well 8 cavity and for that reason has been assessed by the applicants. The effect of the cavity on the tunnel was based on the assumption that the tunnel would be unsupported in the area of the cavity. The staff found that the applicants' analysis uses a conservative assumption for geotech nical engineering considerations for the tunnel. The reasons for this finding and the structural spanning capabilities of the tunnel are discussed by the Structural Engineering Branch in the affidavit of R. Lapinski (Attachment 2, infra.)
- 11.
For the reasons listed above, the staff finds that the applicants have performed acceptable geotechnical investigations, treatment and analyses to determine the extent of all the cavities existant at the site and to assess their potential impact on adjacent structures during seismic or other conditions.
fidohn T. Greeves I hereby certify that the information listed above is true and accurate to the best of my personal knowledge.
Personally appeared before me this LSjf day of August, 1980, was John T.
Greeves who swore that the information above is true and accurate to the best of his personal knowledge.
W COMLYS10 XPIRES JULY T, 14m