ML20235Y282
| ML20235Y282 | |
| Person / Time | |
|---|---|
| Site: | 05000000, 05000398, 05000399 |
| Issue date: | 11/15/1972 |
| From: | Hall W, Hendron A, Newmark N NATHAN M. NEWMARK CONSULTING ENGINEERING SERVICES |
| To: | |
| Shared Package | |
| ML20235X376 | List:
|
| References | |
| FOIA-87-462 NUDOCS 8710200286 | |
| Download: ML20235Y282 (8) | |
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' N A T H A-N : M.
N E W M A R K-CONSULTING ENGINEERING SERVICES 1114 CIVIL ENGINEERING BUILDING URBAN A, ILLINOIS 61 Bot 15 November 1972 -
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DRAFT COMMENTARY ON SEISMIC DESIGN STRUCTURAL CRITERI A FOR THE MENDOCINO POWER PLANT UNITS 1 AND 2 PACIFIC GAS AND ELECTRIC COMPANY AEC Docket Nos. 50-398 and 50-399 by
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.l N. M. Newmark, W. J. Hall, and A. J. Hendron, J r.
1.
Introduction The review of the structural design criteria for the Mendocino s
Power Plant Units I and 2 at the PSAR stage is based on our review of the material presented in the references listed at the end of this report, and on discussions with personnel of the AEC Directorate of Licensing.
2.
Foundations The Mendocino Power Plant site area'is underlain by stratified marine sedimentary rocks of Miocene age.. The bedrock at the site area is of the Monterey Formation, at least 5000 f t thick, and f rom bottom to top.-
.t const sts of shales, sil tstone, and sandy mudstone.
The description;in Section 2.5.7.3 on slope stability indicates that the massive strata underlying the. site area should be stable except in.
those few localities where the ~ rocks. have been' sheared or fractured.
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Along the extreme westerly margin of the site area, it is noted that the rock l
may be susceptible to seaward bedding-plane sliding along thin intervals of sheared sof t cl aystone.
it is indicated that final evaluation of the stability will be made as early as possible during the course of the project excavations.
Farther comment about block motion is presented in Section 2.5.7.4 entitled
" Sea Cl i f f Ret reat".
Tunneling conditions are described in Section 2.5.7.6 where it is indicated that tunneling conditions should be satisfactory but, as noted on 1
pages 2.5-10 and 2.5-11 (Amendment 7-A), there are occasional joint planes in the area which contain asphalt, and this topic is again brought up in the answer to Question 19 (Response to AEC letter of May 24,1972).
The matter of inflows of mobile asphal t and inflammable gas is also raised on page III-14 (Amendment 3 ef Append!x 2.5A (J ehns-Hamil ton) Report).
As noted ir, cur letter comments of 25 February 1972 to the AEC, we called attention to the f act that caution must be taken in the tunneling at the site to guard adequately against the a:cumul ation and subsequent explosion of natural gases such as methane.
l Moreover, careful attention needs to be given to tunnels or underground excavations located near the reactor to preclude the possibility of gas l
collection and explosion at some later time during operation of the plant.
The foundation conditions are described in detail in Section 2.5.8 to the extent that the evaluation has been carried forward at the moment.
It appears that the foundation conditions are adequate with regard to rock s t rength. The answer to Question 23 (Response to AEC questions of May 24,1972) indicates that the foundations as they are excavated will be examined in detail i
i by an experienced engineering geologist prior to placement of the concrete mat and that, should weak zones be identified remedial treatment of the foundation rock will be carried out.
3 The seismic summary of Section 2.6.5 indicates that the most recent break in the San Andreas Fault is about 4 1/2 miles from the site.
The Hathaway Creek Faul t is located near the site area; clarification on the anbiguity of statements in earlier reports as to this fault is given in the answer to Question 11 (Response to AEC Questions of 5/24/72).
Al so, in our' letter report of 25 February 1972, we made reference to the incoherent sands which had been encountered at some locations at the site, as noted on page 2.5-10 ( Amendment 7).
W'e assume from the discussion in Section 2.5.8 that these probably constitute isolated zones in the bedrock formation and assume that their existence will be considered in a selection of the final site.
On the basis of the information presented, and with knowledge that an ongoing program of exploration is proceeding (to be reported upon again in March 1973), we believe that the selection of the actual site for the structure and the special studies connected 6 herewith are proceeding in accordance wi th l
customary practice in a reasonable and satisfactory manner.
3.
Seismic Desian Criteria Seismic Hazard At the present time the PSAR in Section 2.6 Indicates that the seismic design of Class i structures and systems is planned to be made for a Design 1
Basis Earthquake characterized by a maximum transient horizontal ground acceleration of 0.509 and an Operating Basis Earthquake characterized by a horizontal maximum transient ground acceleration of 0.30. The vertical ground 9
acceleration in both cases is to be taken as two-thirds of the horizontal notion and is assumed to act simultaneously.
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It is our understanding that the seismic hazard is still under study l
by representatives of NOAA and USGS.
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Spectra The response spectra for the Design Basis Earthquake and the Operating l
Basis Earthquake are presented in Figs. C.2.1 and C.2.2.
Further information on j
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the development of the spectra is presented in the answer to Question C.I.1 I
(Response to AEC letter of 5/22/72). The spectral values in the velocity regions
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O for values of damping of 5 percent and greater appear to be slightly low in j
i relation to current AEC requirements, and this point should be clarified by the j
l applicant.
I D amping j
l The damping proposed for use in the design of the facility is presented l
l in Table C.2.1 for structures and further information with regard to equipment is presented in the answer to question C.2.14.
Additional information on damping is given on page C.2-1 where it is indicated that the maximum overall damping to be used for the combined soil-structure systems is 10 percent of critical 1
d ampi ng.
We believe the damping values presented.in the approach are in agreement with the current state-of-the-art.
l Dynamic Analysis of Structures, piping, Equipment and Critical Controls and Instrumentation l
The general seismic design analysis procedure to be employed in the design of this plant is presented in Section C.3 and the procedure outlined is in accord with the current state-of-the-art.
Additional 'information on tbc approach to' be employed, including the method of handling soil-structure 1..
interaction, is presented in the answer to Question C.2.4 and the Appendix 1
attached thereto; the approach outlined for handling the structural analysis
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l incorporating the soil-structure. interaction and for calculation of floor response spectra is in accord with the current state-of-the-art.
On the basis of the information presented, we believe the analysis approach to be l
I satisfactory as' outlined.
l For piping and equipment the seismic analysis procedures are described 1
in Sections J.5.3.2 and J.5.3.3, and the procedures described appear to be in accord with the state-of-the-art.
1 Methods for handling the relative displacement between floors or 1
points of support are described in the answer to Question C.2.11 (Response to
/IC let*.er of 5/22/72) and the approach described is acceptable.
The method of handling the analysis of the reactor internals is described in the answer to C.sestions 3.1 and 3.5 (Response to AEC letter of 2/7/72) and in the answers to a series of Ouestions J.5.3 (Response to AEC letter of 5/22/72) which, in addition to the descriptico given in Section J.5.3.1 of the PSAR, appear to indicate that the approach )s in accord with the current state-of-the-art.
No information was noted in the PSAR with regard to the criteria for buried piping at this installation, and this should be provided by the appl i can t.
Similarly, in the case of critical items of controls and equipment, cable trays, etc., the procedures outlined in Appendix J and in the answers to the series of Questions C.2 (Response to AEC letter of 5/22/72) indicate that the approaches outilned for use are in accord with the current state-of-the-art.
Other applicable design criteria for critical items of instrumentation and controls are covered in Appendix H under Identification - Resolution of AEC-ACRS and Staf f Conce rns, and particul arly under Section H.3.7.
In view of
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the high scismic hazard for which this plant is to be designed, it would be our recommendation that careful documentation of the actual des 1gn approaches e aployed be presented for review at the appropriate time.
Design Stresses
.The design stresses for the' containment structure for the extreme envi ronmental conditions are sunynarized in Table C.2.5, where it is indicated.
that wi th the Design Basis Earthquake, stresses will be limi ted 'to either the ACI Code or to stress limits below yield, as noted in item 3 at the bottom of the table. 'But, in certain conditions it is noted that " stress may exceed yield strength provided that an analysis is made to detennine that 'the energy.
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input does not result in deformations which would indicate loss or failure".
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in the event that this latter stress criterion is employed, the applicant I
should document in detail for raview the approach actually employed to demonstrate that the approach adopted does ' lead to an adequate margin of safety.
1 REFERENCES 1.
" Preliminary Safety Analysis Report, Mendocino Power Plant Units 1 and 2, including Amendments 3-5, 7, 9-11, and.13", Paci fic Gas and Electric Company, AEC Docke e Nos. 50-398 and 50-399,1971-72.
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'n N AT H A N.M.
N E.W M A R K
.1114 CIVIL ENGINEERING BUILDING CONSULTING ENGINEERING' SERVICES URBANA, ILLf NOIS 618o1 -
15 November 1972 r
1 DRAFT
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SEISMIC DESIGN STRUCTURAL CRITERIA q
FOR THE j
1 MENDOCINO POWER PLANT UNITS -1 AND 2 q
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PACIFIC GAS AND ELECTRIC COMPANY AEC Docket Nos. ' 504398 and 50-399 by N. M. Nevnark, W. J. Hall, and A.' J. Hendron, J r.
After our. review of the PSAR, including Amendments 3-5, 7, 9-11, and 13, it is believed that the criteria and methods proposed for the design i
of the Mendocino Power Plant Units 1 and 2 can be considered to f all within i
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the state-of-the-art for the current seismic hazard listed in the PSAR,.namely for safe shutdown for a Design Basis Earthquake of 0.50g maximum transient l
horizontal ground acceleration and.for an Operating Basis Earthquake of 0.30g horizontal ground acceleration. However, as noted in our' report,-this seismic-
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design hazard is still under review.
Our review was based on consideration, among other things, of the
.l foundations, seismic hazard, spectra, damping, dynamic analysis of..' structures, critical controls and instrumentation, and. design stresses.
On the basis of our review, we' conclude that the approach outilned In terms of design criteria and methods of' handling the designishould_. lead to-an acceptable range of margins of safety for the seismic hazards considered.
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I However, as noted in the report, we believe that the applicant should provide additional Information concerning (a) the basis for the establishment of the response spectra in the velocity region for damping values of 5 percent or greater, and (b) applicable design criteria for buried piping.
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