ML19318A255
| ML19318A255 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 06/03/1980 |
| From: | Chan S Office of Nuclear Reactor Regulation |
| To: | Schauer F Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML19318A252 | List: |
| References | |
| NUDOCS 8006190095 | |
| Download: ML19318A255 (3) | |
Text
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UNITED STATES hg [
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NUCLEAR REGULATORY COMMISSION 3
j WASHINGTON, D. C. 20555 jyN 3 50 MEMORANDUM FOR: Franz P. Schauer, Chief Structural Engineering Branch Division of Engineerirg THRU:
David r, Jeng, Section A Leader Structural Engineering Branch Division of Engineering FRON:
S. P. Chan Structural Engineering Branch Division of Engineering
SUBJECT:
Trip Report - Review of Comparative Studies en Soil -
Structure Interaction Analysis Performed for La Salle Nuclear Plant by Sargent and Lundy A meeting was held in Chicago at Sargen, and Lundy's office on April 24 and 25, 1980 to review the Sargent and Lund, s procedures used for soil-structure interaction analysis. Present at the meeting were A. K. Singh, S. L. Chu, T..I. Hsu, S. Singh (Part time) of Sargent and Lundy.and D. C. Jeng, S. P. Chan of N.R.C.
The main purpose of the meeting was to review the analytical procedure and calculations that Sargent and Lundy chose to use, i.e., Option No. 1 of Question 130-22: Use the compliance functions based on the two layered elastic half-space theory and consider that the soil medium is one layer and the bed rock is another. Sargent and Lundy called it "Luco's Method" since it is based on the paper by J. E. Luco, " Vibration of a Rigid Disc on a Layered Visco-Elastic Medium" Nuclear Engineering and Design, No. 35, pp. 325-340, 1976.
We expressed the following concerns on soil properties to be used in analysis:
1.
The shear modulus value used in the analysis was judged to be relatively low for the following reasons:
a.
The undrained shear strength value, Su, measured in the triaxial compression test (Figure 2.5 - 79 of the FSAR) seems to be low compared with those obtained from the pocket penetrometer and the unconfined compression tests, b.
The 0.35% strain value used in determining the shear modulus is higher than that expected for a 0.2 g earthquake.
J
Contact:
S. P. Chan x29460 8006190o95 A.
, c.
Recent paper by I. Arango, Y. Moriwaki, and F. Brown "In-Situ and Laboratory Shear Velocity and Modulus," Proceedings of the ASCE Geotechnical Division Specialty Conference on Earthquake Engineering and Soil Dynamics, June 19 - 21, 1978. Passadena, California, indicates that the reductions in shear modulus with increasing cyclic shear strain are not as large as those shown in Figure 2.5 - 55 of the FSAR.
2.
The hysteretic soil damping halues used in the compliance function solution are judged to be high.
3.
Analytical steps performed.by Sargent and Lundy in answer to Question 130.22 Option 1 do not provide sufficient information.
We recommended additional analysis be performed with soil parameters as defined below in order to address the above~ concerns.
1.
IncreasetheSuhaluesbyafactorof2.5;reducethemaximum effective shear strain by a factor of.4; adjust the shear modulus value in light of the paper.by.Arango et.al. These steps would lead to an estimated shear modulus value of 2000 ksf for analysis.
2.
Useaconservatihely.lowhystereticsoildampingof3%inplaceof 13% - 18% shown in Table 130.33 - 1 of the FSAR.
Subsequent to an in-depth discussion among the participants, Sargent and Lundy agreed to perform additional analysis although they believed that the parameters requested by the staff were etremely conservative.
The meeting was then adjourned in order that Sargent and Lundy may perform the analysis on a priority basis.
Bothpartiesreconhenedthenextday. Werehiewedthepreliminaryresults and found that the La Salle design spectra in general. enveloped those obtained by.the above analysis except at Elevation 820' - 6" (fuel pool)..
At this elevation the new spectra exceeded the design basis in the 8 to 10 Hz.
range by an average of 15%.
In hiew of the assumptions made in the analysis, we beliehe that.the present.
La Salle design spectra are consistent with the intent of the staff position.
Sargent and Lundy/Comonwealth Edison Co. have provided us copies of related reference information which supports the above analysis.
Wealsorehiewed.thedesigncalculationsandprocedureswhichformedthe basis of the above analyses and found them acceptable in general.
. Sargent and Lundy agreed to submit for staff review the new analysis results as part of an amended response to Question.130.23 which will supersede and void the original response in Amendment No. 48 of the FSAR dated February 1980.
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S. P. Chan Structural Engineering Branch Division of Engineering cc:
J. P. Knight B. J..Youngblood A. Bournia L. Heller
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