ML20215N012
| ML20215N012 | |
| Person / Time | |
|---|---|
| Site: | 05000000, Diablo Canyon |
| Issue date: | 03/30/1967 |
| From: | Newmark N NATHAN M. NEWMARK CONSULTING ENGINEERING SERVICES |
| To: | Morris P US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML20197J003 | List: |
| References | |
| FOIA-86-371 NUDOCS 8611040173 | |
| Download: ML20215N012 (4) | |
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NATHAN M.
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til Talbot Labora tory, Urbana, lilinois Consult,ng Engineering Serv. ices 30 March 1967 Dr. Peter A.
Morris, Director Division of Reactor Licensing U.S. Atomic _ Energy Commission Washington, D.C. 20545 Re:
Contract No. A f (49-5)-266 7 Nuclear Plant--Diablo Canyon Site Pacific Gas and Electric Company Doc ke t No. 50-275 gni: ry Cg.,1 Fila Cy.
Dear Dr. Morr,
s:
i The f ollowing comments and questions are based on the review by Dr. W.
J. Hall and myself of the material presented in " Preliminary Safety.
Analysis Report " Volumes I and II, for the Diablo Canyon Site Nuclear Plant, submitted by the Pacific Gas and Electric Company.
The reactor will consist of a four-loop pressurized water reactor, similar to indian Point No. 2 except that the steam genera tors are slightly.
larger.
The plant is to have a power output of 3250 MWt (1060 MW(e) net).
The primary containment consists of a steel lined, reinforced concrete cylinder with the hemispherical roof supported on a substantial foundation base which in turn is supported on rock. The plant is located in San Luis Obispo County, California, 12 miles WSW of San Luis Obispo on the Pacific Ocean, and adjacent to Diablo Canyon Creek.
1.
As a result of the study of f our sources of ~ earthquakes, the report recommends the use of two earthquakes for design purposes, namely, Earthquake B, patterned after the Taft 1952 N69*W earthquake, and Earth-quake 0, patterned after the Golden Gate 1957 580 E earthquake.
These two earthquakes are characterized by the applicant as corresponding to maximum ground acceleration values of 0.129 and 0.209 at the sites, respectively.
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However, the response spectra associated with the time histories of these two earthquakes are quite different.
In the region of probabic design interest for the containment structure and for other items of equipment,
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Earthquake B controls the response for frequencies between about 0.5 to 4 or 5 cycles per second, whereas in the higher frequency range above about 5 cycles per second Earthquake D controls the response.
Comparison of the spectra as just indicated indicates that the containment design is probably to be made for a 0.129 earthquake, which seems entirely too low f or t he region under consideration. A more reasonable value for the design earthquake would correspond to a maximum ground acceleration of 0.20, with the spectrum 9
amplified over the entire frequency range.
Such a properly amplified spectrum in the low f requency range would be significantly greater (by a factor of nearly two) than the values now obtained using Earthquake 8.
On the basis of our evaluation of the information presented, we are agreeable to the use of a value of 0.20g ground acceleration as describing the design earthquake, and a value twice as great as describing the maximum.
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7 credible earthquake.
However, the response spectra presented by the applicant are not acceptable to us.
We request tha t new spectra be prepared which are representative of the proper velocities and accelerations over the entire range of frequencies of interest so that we can be assured of a reasonable margin of safety for design throughout the entire frequency range.
2.
It is our understanding that two types of analyses ney be carried out, one involving a modal analysis in which the spectra are employed, modal exci tat ion handled through the use of participa tion f actors, and the combination of modes handled by the square root of the sums.of the squares, which is acceptable if at least three modes are included in the analysis.
The alternative involves a time history of motion, employing carthquake records wi th the amp l i tude va lues sca led, used as the excitation for the base motion of a lumped-mass spring-dashpot model of the system.
Both approaches are acceptable, provided that they are employed in a consistent manner.
By this we mean that the time history employed for the model analysis must yield a response spectrum over the entire frequency range which falls on or above the response spectrum that is used in the spectral modal analysis, in the event that a time history analysis is to be used, we would insist on a calculation being made by the applicant of the response spectra for various degrees of damping corresponding to the time history input used.
3.
It is our understanding, f rom examination of the material presented in the PSAR, that an inactive shear zone may be located near'the containment vessel site.
It is our recommendation that the reactor and containment structure be relocated of f this zone, to avoid any question of possible relative motions occurring.
4.
On page 1-25 and page 6-48, comment is ma'de concerning the containment isolation valves.
It is our understanding, from discussions with the applicant and their consultants. that these valves will be designed to withstand seismic l oa d i ng.
We should like to be advised of the nature of the design to insure that these valves will operate under seismic l oa d i ng.
5.
On page 2-29, and later in Appendix 0, the statement in made to the effect that all modes having a period greater than 0.08 seconds shall be included in the analysis. We see no reason for this limit. We believe that a sufficient number of modes of excitation should be included in the analysis of the containnent structure, piping, or other items to insure that the analysis is meaningful. A be tter cri terion, perhaps, would be to s ta te the number of modes that are to be included.
In nany cases we can conceive of equipment items or piping which will have periods of much less than the limit cited.
It is our belief that there can be no restrictive bound placed on the period as such, and that the proper response spectra and frequency should be employed as appropr:3te.
6.
The table of damping values is given on page 2-29, and the f ollowing two paragraphs thereaf ter indicate that the rocking of the structure on its foundation will be considered in the analysis.
No value for the damping to be employed with this rocking motion is presented. We should like to be advised of the value that is to be employed.
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. 7.
On page 2-30, in the last paragraph, a statement is made,
"... (2) in pressure. vessels and piping systems, there will be regions of local bending where the stresses will be equivalent to 120 percent of the yield stress, based on an clastic analysis;..." ~ This statement is used in conjunction wi th the cri teria to satisfy the "no loss of function" cri terion, which we interpret to mean safe shutdown of the reactor and system under the maximum carthquake.
Such a provision has little or no' rational interpretation in terms of limiting deformation.
It is our belief that a more rational and acceptable criterion would be one that places a limit on the total deformation, such as, for example, a maximum of two or-three times the yield point deforma-tion, to insure tha t no s igni f icant distortion or rupture is likely to occur in the system.
An increased yield stress value may not provide the necessary constraint on the amount of def ormation that may occur, under certain condi-tions of dynamic loading.
8.'
The base slab analysis, as described briefly on page 5-22, needs to be re-evaluated. S tatements are made therein that the base slab will be treated as a flat circular plate supported on a rigid, non-yielding foundation.
For the rigid, non yielding situation noted, it is impossible to understand how the analysis will be carried out.
9.
The large openings receive brief mention on page 5-22.
Much more detail on the method of analysis to be employed is required. The problem is one of providing for stif fening around the opening, and also providing for a proper distribution of deformations and forces around the opening to insure that no distress will occur in the transition zone between the reinforced opening and the vessel shell.
10.
Of particular interest in the penetration design is the detailing of the reinforcement, both radia l, ver t ica l, and. dia gona l, in the vicinity of the openings.
Reference to the reinforcing sketch on Fig. 5-1 leaves some question as to what happens to the diagonal bars in the vicinity of both the large and the small penetrations.
11.
Chapter 7 is devoted to a discussion of plant instrumentation.
We should like to be apprised of the steps taken in designing the instrumen-tation with relation to the.carthquake loadings that may be experienced.
This discussion should include not only the effect of the inertial forces arising f rom the ef fects of the carthquake, but also any ef fects of tilt or other motions that might have some influence on the critical i ns t rumen ta t ion required for safe shutdown.
12.
The compounding of the loading that is to be employed in arriving at the design is described in Chapter 5.
We find little discussion of the stress or deformation' levels that will be permitted in the design under the maximum earthquake loading condi tion. Amp l i f i ca t i on on this aspect of the desig.: is requested.
13.
Although it is not stated in Chapter 2 explicitly, we assume that the table of damping values given therein will be employed for both the design and maximum earthquake conditions.
Is this assumption correct?
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Little information appears to be available in the PSAR concerning the design of the piping for earthquake loading and the types of support and method of analysis that will be e,mployed.
Elaboration on these aspects is desired.
15.
A description of the types and locations of the instrumen-tation to be employed in the proof test of this vessel is desired for further consideration and study.
Respectfully submitted.
N.
N. M.
Newmark bd cc:
W. J. Hall
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