ML25167A175
| ML25167A175 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 06/14/1984 |
| From: | Advisory Committee on Reactor Safeguards |
| To: | |
| References | |
| Download: ML25167A175 (1) | |
Text
June 14, 1984 Sulllllary of Comnents by M. D. Trifunac Made During the June 14, 1984 ACRS Meeting Washington, D.C. on Reevaluation of Diablo Canyon Seismic Design At present an effort is being considered to reevaluate the seismic design criteria for the Diablo Canyon nuclear power site in California.
It has been proposed to complete this reevaluation by 1988 and to incorporate into analyses all current geological and seismological infonnation. Since the ultimate objective of this effort is to fonnulate and implement specific engineering design and analysis to verify the adequacy of safety related structures and components, may I suggest that the following be considered during the course of this--,ork.
- 1.
Modern and advanced methods should be employed throughout the reevaluation with proper consideration of their uncertainties which cannot be resolved at present.
For example, the following would be emphasized in the analysis:
- a.
Near field strong ground motion above a thrusting fault should be considered.
- b.
A11 components of near field strong ground motion should be included in the analysis simultaneously. Torsional and rocking input ground motion should not be ignored.
- c.
Three-dimensional soil structure interaction should be employed to provide estimates of structural response.
Damping in structures should be allowed to increase with response amplitude but should not be set to a high constant value throughout the entire response. "Effect" reduction of spectural amplitudes should be excluded from any stage in the analysis.
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M. D. Trifunac Co11111ents d.
Non-linear structural response to simultaneous base excitations with 6 degrees of freedom for input strong ground motion should be considered.
Methods and knowledge are available to carry out such analyses, but it is essential to balance all procedures into the overall package properly emphasizing all relevant steps. For example, the fault geometry, magnitude or rate of slip on Hosgri fault, as uncertain as those may be, may not be the principal contributors to the ultimate uncertainty of the engineering estimates of structural response.
- 2.
An independent group of experts could be retained to carry out or to direct the work on the key elements of the reevaluation task.
This might help the NRC Staff by contributing through outside independent expertise to their ongoing reevaluation program. This would also also be very advantageous to the ongoing PG&E effort is that it would help them to promote, support and benefit from mor~
agressive and modern engineering analyses, beyond the 0 routine" current interpretations of the design criteria.
- 3.
Unless some qualitative "jump" can be incorporated into the proposed reevaluation of the seismic design procedures and criteria for the Oiablo Canyon site in California, it seems to me that we might experience a "repetition" of the difficulties exemplified there during the past 10 years.
- 4.
An experimental verification program would be very helpful for reducing a number of uncertainties in the analysis and response characterization. The program would include:
(1) the analysis of the strong motion data recorded in and near the structures at the Diablo Canyon site, and (2) low amplitude vibration tests of selected structures to verify the analytical calculations.
381