ML16341C167
| ML16341C167 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 05/30/1984 |
| From: | Thompson G Advisory Committee on Reactor Safeguards, STANFORD UNIV., STANFORD, CA |
| To: | Okrent D, Seiss C Advisory Committee on Reactor Safeguards |
| References | |
| ACRS-CT-1750, NUDOCS 8406210558 | |
| Download: ML16341C167 (4) | |
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and that interpretation vas accepted as a vorst case.
(2)
The H 7.3, 1927 Lompoc earthquake vas debated at length in earlier revievs, and I concluded (partly on evidence of sea-bottom o fset in reflection records) that it vas most likely associated vith the Transverse Range structures and not vith the Hosgri fault.
Because the earthouake data are old and not totally convincing, it vas possible to assume that the Lompoc earthquake occurred on the Hosgri fault again a vorst-case assumption.'oth'oints (1) and (2) add a measure of reassurance for Diablo Canyon.
I recommend (1) a critical reviev and evaluation of the regional tectonic questions such as those noted in the preceding paragraph, (2) independent examinat'ion of the relevant seismic reflection records, (3) revXev and reconsideration of all onshore and near-offshore faults in light of the nev evidence that they may connect vith an underlying thrust fault (at vhat depth'?)
(I consider this to be otentiall the biR est roblem.),
(4) analyze the engineering consequences of the nev fault geometry.
I am not fficiently I gy'9 igssS
~ C. Siess and D. Okrent ACPS Subcommittee Nay 30, 1984 expert to make any independent prediction of the outccrne of an engineering restudy recommended in point ('4).
To put some perspective on the new developments at Diablo Canyon, I agree with James Devine bf the U.S. Geological Survey who was quoted by the HRC staff as regarding the new information to be "not startling".
Xt's reassuring that the Hosgri does not appear to be a major strike-slip fault.
Me have always knee.that there were reverse faults and therefore a component of compres ion perpendicular to the San Andreas fault in the region.
We also know that regionally the maximum principal stress in California is oriented north-south to slightly clockwise of that direction, and this explains the dominant movements such as the San Andreas.
Preliminary staff
'stimates of the design consequences of the new findings suggest that, the changes will not be drastic.
I tend to agree in the sense that most of the geologic factors will likely make hazard estimates, smaller, but the geometry of the underlying thrust fault still needs to be evaluated in detaQ..'-,And, as stated before, I am not prepared to make any estimate regarding the engineering calculations.
In summary, my information so far as it goes, indicates that Diablo Canyon could be safely allowed to operate while review and re-study is continued.
In foming this opinion, however, I must rely heavily on preliminary statements of the NRC staff and U.S. Geological Survey consultants.