ML20212L036

Informs of 770621-23 ACRS Subcommittee Meeting in Los Angeles,Ca to Discuss Ongoing two-track Approach by Util Re Facility Seismic Design Reevaluation.Util Will Most Likely Propose to Be Granted Interim Conditional OL

ML20212L036
Person / Time
Site:	05000000, Diablo Canyon
Issue date:	05/09/1977
From:	Shao L Office of Nuclear Reactor Regulation
To:	Eisenhut D Office of Nuclear Reactor Regulation
Shared Package
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References
FOIA-86-391 NUDOCS 8608250174
Download: ML20212L036 (1)

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T MAY 9 1977 M MORANDLDI FOR:

D. G. Eisenhut. Assistant Director, OT, D0R 4

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L. C. Shao, Chief. Engineering Branch, DDR

SUBJECT:

DIABLO CANYON STATUS REPORT QfI An ACRS Subcommittee meeting will be held on June 21-23 in Los Angeles to discuss the ongoing two track approach by Pacific Gas and Electric Company (P6&E) concerning the Diablo Canyon. seismic design re-evaluation.

An update on the plant's structural and mechanical reenalysis will be made. Of primary interest will be a presentation by John A. Blume and M. D. Trifunac who independently have developed probabilistic ground response spectra for the Diablo Can/on site. Blume is a PG&E Consultant and Trifunac is an ACRS Consultant.

The procedures used by Blume and Trifunac are completely independent.

For a 905 confidence level, (i.e., for a confidence level of 905.. one is 905 confident that the value will not be exceeded in 50 years),

g there is. similarity between the Anderson-Trifunac (A-T) curves and the Blume curves. The curves are essentially equal in the 0.2 to 0.45 sec. range. Up to 0.2 sec. the Blume curve is more conservative, while beyond 0.45 sec., the A-T curve is more conservative. These results can be explained by the fact that the Blume spectral shapes are derived from close-in rocky site records, while the A-T shapes are based on data at greater epicentral distences. At the 50% confidence level, the A-T curves are less conservative than the Blume curves over the entire spectra. The reverse is true for a 99% confidence level.

The ovarall agreement in such an important period (0.2 sec. to 0.45 sec.)

and confidence level range (80% to 90%) is quite noteworthy.

P6&E will most likely propose that they :m granted an interim conditional operating license based upon Blume's probabilistic considerations.

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L. C. Shao, Chief PDR HOUGH 86-391 Engineering Branch Division of Operating Reactors cc:

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