ML20215N009
| ML20215N009 | |
| Person / Time | |
|---|---|
| Site: | 05000000, Diablo Canyon |
| Issue date: | 04/06/1967 |
| From: | Woodard K US ATOMIC ENERGY COMMISSION (AEC) |
| To: | US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML20197J003 | List: |
| References | |
| FOIA-86-371 NUDOCS 8611040167 | |
| Download: ML20215N009 (4) | |
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UNITED STATES GOVERNMENT -
Memorandum To The Files
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DATE:
APR 6 1967
- (THRU) Robert L. Tedesco, Chief Reactor Pro ct Branch 2, DRL 3
FROM K. Woodard f,/
Reactor P M Branch 2, DRL SUllJECT:
MEETING WITH PG&E TO DISCUSS SEISMICITY OF THE DIABLO CANYON SITE -
DOCKET No. 50-275 On March 21, 1967, a meeting was held with representatives of the Pacific Gas and Electric Company (PG&E) to discuss the seismic char-acteristics of the proposed Diablo Canyon site. The following persons attended:
AEC S ta f f Staff Consultants M. M. Mann W. Hall, Newmark Assoc.
R. S. Boyd, DRL L. Murphy, USC4GS R. L. Tedesco, DRL H. Coulter, USGS K. Woodard, DRL A. J. Rizzo, DRL J. Newell, DRL
- 1. Spickler, DRL L. Kornblith,QO i
J. Hard, CO 9141rMell F. Schauer, C&cTB PG&E PG&E Consultants D. Kelly S. Smith, Caltech 7
J. Schuyler J. Blume, J. Blume & Assoc.
B. Shackelford G. Richards Westinghouse P. Crane t
J. Morrissey J. Stadelman I
l Dr. S. Smith, seismic consultant to PG&E, made a presentation concerning I
the magnitudes of credible earthquakes which could affect the site. He stated that since there are -good records of past earthquakes and since active faults are readily identifiable in California, ascertaining the magnitude of ground motion which could occur is simplified as compared j
to other parts of the country. All evidence indicates that there are no active faults in the innsediate area of the site. Thus, Dr. Smith has chosen to assume that a large earthquake occurs along known faults 8611040167 861023 PDR FOIA PDR HOUCH96-371 Buy U.S Sarir:gs Bonds Regularly on the Payroll Latings ?lan t
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y-Files App g gg7 (50-275) i at their closest distances to the site or,to assume that an af tershock occurs at some depth at the site.
On these bases, the effects of four earthquakes were explored for application - to this plant. The four earthquakes are classified as Earthquakes A through D.
Earthquake A is assumed to be a great earthquake on the San Andreas Fault 48 miles distant, B is a large earthquake on the Nasimiento Fault 20 miles sway, C is an offshore earthquake 50 miles away and D is an earthquake associated with an af tershock about 6 miles in depth under the site.
The l
magnitudes used were estimated based on recorded data from around the world.
Dr. S. Blume then described how he extrapolated the intensity of the earthquakes prescribed by Dr. Smith (at the location of the epicenter)
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to the reactor site itself. This was done using a computerized model which uses empirical data and measured characteristics of bedrock at the site. The spectral response superimposed on the ground motion was obtained from measured earthquakes in San Francisco and Taf t.
Thus, a ground acceleration at the site was assigned for each earthquake.
It was found that two of the four were controlling; i.e., B and D, the D earthquake having a zero period acceleration of 0.2g has a peak spectral acceleration at the high frequencies and the B earthquake having a zero period acceleration of 0.12g had a spectrum which peaked at lower frequencies. Thus, an earthquake spectrum envelope is developed for design purposes. We inquired as to whether the two earthquakes should not be considered to occur simultaneously since the M
aftershocks could occur during the time that the major movement was I
still occuring. They stated that they did not believe this would result in an increased acceleration but would look into it.
Dr. Hall referred to the new response spectra to be used and equated the design acceleration of past plants in California with the equiv-alent acceleration proposed for this one.
It appeared to him that the PG&E design spectrum would result in a design which was less conserv-ative in terms of design acceleration at the natural period by a factor of two or more. He also established with Dr. Blume that the damping in considering the rocking mode of the containment on its foundation would be about 10%.
Dr. Hall said that this was not con-sidered conservative on other plants but they could discuss it later with the geologis ts.
The method of dynamic analysis for Class I s tructures was discussed but the details have not been established by the designer.
After listening to the applicant's presentation, Messrs. Coulter and l
Murphy summarized their viewpoints with respect to the seismicity of the site.
Mr. Coulter stated that the apparent fault zone which does run very close to (if not under) the reactor containment is not of seismic origin but rather was formed over 100,000 years ago when what
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Files APR 6 56I (50-275) is now referred to as bedrock was in the sof t condition and folding of the earth caused a shear failure. The numerous trenches which were dug at the site at the depth of at least 3 feet into the bedrock show that there has been no movement along the fault for more than 100,000 years.
The basic. premise for this belief is that in every case where the fault was exposed the overlaying material was not displaced; i.e., no movement has occurred since the loose material has been presenc. Thus, the fault is considered to be inactive and probably was never active since the soft material in which it was formed has hardened.
It was estab-lished that this fault was of a difierant nature than those found at the Malibu site or at the Bodega Bay site in that those both showed that some movement of the overlaying material had occurred.
Mr. Coulter commented on the problem of containing the earth slides which have occurred near the site of the switchyard. The applicant stated that they were well aware of this problem but did not think it would be too difficult to cope with.
Mr. Murphy stated that he thought Dr. Smith's methods of choosing the magnitudes and locations of earthquakes were excellent, complete, and were similar to the procedures used by the USC&GS.
He believed that the magnitudes chosen were conservative with one exception - the B earthquake should have a ground acceleration of 0.15g as opposed to the chosen value of 0.12g.
The applicant had no comment concerning this statement. Since Dr. Hall has pointed out that the design acceleration had been considerably reduced from that of other ENUdII California reactors, Mr. Murphy said that the increased study and knowledge concerning earthquakes enabled the USC&GS to come down some-what on their recommended magnitudes. He believes that the present knowledge of the seismic activity and characteristics in the vicinity of the site supports the proposed zero period magnitudes established by the applicant. However, he did not comment on the applicant's proposed design spectra.
Regarding the tsunami problem both Mr. Coulter and Mr. Murphy had reviewed the applicant's report.
Mr. Coulter thought that the characteristics of the small Diablo Bay should be considered in locating the cooling water intake to assure that a tsunami would l
not damage it.
Mr. Murphy reflected the USC&GS feelings regarding tsunamis caused by close-in earthquakes in the ocean. There does not appear to be' tsunami problems at this site due to the natural sea wall which will not be removed by the construction. The sea wall is about j
80 feet high and should protect the plant from the effects of a l
tsunami. With regard to outfall, we will review the ability to provide emergency cooling water during the lowering of water level accom-panying a tsunami.
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Files 'APR 6 1967 (50-275)
At the conclusion of the meeting, we atteipted to establish that the small fault at the site was definitely inactive, not of. earthquake origin, and different from that of other faults which characteristically run through the location of other containment vessels in California.
As suggested, it would seem prudent to locate the containment structure to the side of this apparent fault zone regardless of its origin.
Distribution DRL Reading RPB 2 Reading Originator:
KWoodard R. S. Boyd S. Levine J. Newell N
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