ML20052A059
| ML20052A059 | |
| Person / Time | |
|---|---|
| Site: | Zion File:ZionSolutions icon.png |
| Issue date: | 02/23/1982 |
| From: | Trifunac M SOUTHERN CALIFORNIA, UNIV. OF, LOS ANGELES, CA |
| To: | Griesmeyer J Advisory Committee on Reactor Safeguards |
| Shared Package | |
| ML20052A001 | List: |
| References | |
| NUDOCS 8204260521 | |
| Download: ML20052A059 (3) | |
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7 _f (nm*ERsTIY PAPI Los A GEES. CAIlFORNIA 90007 1BrettrieiTechitf@tkM scnooL OF ENGINEERDiG ge gikgg [ggrJn gS h tigd 16 DEPARTMEhT OF C2VIL ENGINEERRiG gg*tMgf[ftSff M.Ctdct4TC. M estiset 44 reler.d c2 rui9.
c tis 4;tokt11;Lc:ac4:g,4 February 23, 1982 RECEIVED ADYl50KY MMMITTEE ON
' Mr. J. Michael Griesmeyer Staff Engineer A.C.R.S.
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Dear Mr. Gricsmeyer:
I have now comple'.ed my review of the material you mailed to me on December 21, 1981 and regarding the Zion probabilistic assessment.
I will first state a number of general coments and follow this with some more detailed remarks.
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The general methods and principles employed in the analysis of possible earthquake shaking and Zion site appear to apply the modern state of the art techniques.
In revieaing the specific steps involved in this analysis, I found that:
1.
The overall level of seismicity,3namely what I infer to be logjgt1 a -0.58 - 0.59 Iyy km2 for the Wisconsin arch-Michigan basin is not in /yr/10 obvious disagreement with what might be expected in this area.
I tested this seismicity using literature at rny disposal and found no difficulties. When I receive from you the paper by Nuttli and Hermann (1978), I can review this question again. The maximum cut off magnitude (intensity) for this area has been assum.ed to be 5.6 to 6.0
( VII to ~VIII). This again appears reasonable, but except for the general historic record, I wish I four)d other more physical support for this cut off range.
I wonder whether sensitivity studies were carried out for MMI=IX cut off?,
-2.
I calculated the approximate probabilisties of exceeding peak acceleration (analogous to the results presented in Figure 10
.ofDamesandMoorereport)andfoundthatthesolidcurvein Figure 10 for Wisconsin Arch - Michigan basin (using Nuttli modified attenuation) appears to give good results. The curves base' on TEPA (1979) attenuation should not be used since there d
is eviderice that this correlation may be biased towards smaller peak accelerations.
For smaller peak accelerations mainly resulting from more distant earthquakes, the Nutt11 attenuation seems to give reasonable results. However, the results for higher acceleratipns restilting from closer earthquakes rray be 8204260 Sal'
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Mr. J. Michael Griesmeyer February 22, 1982 Page Two highly suspect.
Figure II.7-1 clearly shows this to result from an assumption that the acceleration versus distance levels off at a constant acceleration and for the assumed maximum magnitude. The abrupt cut off of all curves in Figure 11.7-1 at
.45, ~.55 and ~.65 g is a consequence of certain assumptions which at present cannot be supported by the strong-motion observations. Even though the hypothetical arguments supporting such abrupt cut-off may be reasonable, the continuity of the physical nature of the problem and the lack of conclusive data strongly argue against introducing such hypothetical and theoretical assumptions into an engineering decision process.
In any case, why,not consider other alternatives? Especially when one is aware of the approximate Median Fragility Distribution
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shown in-Figure 11.7-1.
Even to an uninitiated reader, the rather unlikely event that the " upper bound of seismic transmissibility" just happens to be where the number of affected items begins to increase, would seem very unlikely (Figure II.7-8).
3.
The analysis of the " conditional probabilities of siumic induced-failures for structures and components for the Zion Nuclear Generating Station" by S.M.A. is very difficult to evaluate. It is just impossible ~to review and check this work without structural drawings and details.
Furthemore, such checking would be very time consuming and thus expensive.
I would recomend i
some serious spot checks to be made by a very experienced structural design engineer.
Selected Detailed Comments:
Page 11.7-6.65g is used as "the upper acceleration bound".
k' hat is the basis for this estimate?
Pages II.7-20 and II.7-21: These conclusions are based on the assumption that 0.65 g is the upper limit for the acceleration. How can these conclusion be made when it was not demonstrated that.65g is indeed the upper limit?
Page 7.2-2.
The idea of a sustained peak. acceleration (corresponding to the third largest peak of the acceleration time
. history) may be appealing to a time series analyst interested in simple yet stable scaling parameters for c random like function, but is neither an accepted measure of ground accelerations in engineering design, nor it has some general physically meaningful basis in the analytical dynamic response analysis.
Page 4-18 Reductions of 0.90 for the reactor building and o.85 for the, auxilliary building are assi ned to the 5
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Mr. J. KichEe'l Griesmeyer Februa ry 22, 1982 Page Three embed:ent effects. However, other consequences of the embedment, like rocking excitation for Rayliegh waves and torsional excitation for Love and SH waves are ignored? It is not clear then how the factor of safety 1.2 follows from this?
If you find any of these comments not to be clear, or if you have other specific questions, please let me know.
Sincerely,
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M.D. Trifunac Professor MDT:mdm 9
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