ML20209D266

Forwards Request for Addl Info Re Review of Geotechnical & Structural Aspects of Accident Sequences Resulting from Seismic Events.W/O Encl

ML20209D266
Person / Time
Site:	Seabrook
Issue date:	08/21/1984
From:	Lear G Office of Nuclear Reactor Regulation
To:	Reiter L Office of Nuclear Reactor Regulation
Shared Package
ML20209C800	List: ML20209C798 ML20209C897 ML20209D266 ML20209D278 ML20209D286 ML20209D327 ML20209D479 ML20209D512 ML20209D547 ML20209D870 ML20209E015 ML20209E274 ML20211C165 ML20211C259 ML20211C363 ML20211C389 ML20211C430 ML20211C484 ML20211C558 ML20211C632 ML20211C641 ML20211C679 ML20211C769 ML20211C792 ML20211C841 ML20211C904 ML20211C920 ML20211C942 ML20211D042 ML20211D068 ML20211D076 ML20211D092 ML20211D109 ML20211D129 ML20211D140 ML20211D169 ML20211D178 ML20211D191 ML20211D198 ML20211D208 ML20211D226
References
FOIA-87-6 NUDOCS 8408270527
Download: ML20209D266 (3)

Text

. . . .

Ah p tke mah UNITED STATES f *t NUCLEAR REGULATORY COMMisslON f.

.j WASHINGTON, D. C. 20555

%,,,,, AUG 211984 MEMORANDUM FOR: Leon Reiter, Acting Chief Geosciences Branch Division of Engineering FROM: George Lear, Chief Structural and Geotechnical Engineering Branch Division of Engineering

SUBJECT:

PROBABILISTIC SAFETY ASSESSMENT (PSA) - SEABROOK STATION We have conducted the preliminary review of the PSA report submitted by the applicant. Our review has been confined to evaluate the geotechnical and structural aspects of the analysis of accident sequences resulting from seismic events. Based on this preliminary review we have identified some concerns and comments (including needs for additional infonnation) as indicated in the enclosure.

Please note that this is not a complete list of concerns or camments as the review is still underway. We would also like to note that, in order to conduct a meaningful and thorough review, it is essential that calculations supporting the fragility detennination be obtained fran the applicant as soon as possible. The review of the geotechnical aspects was conducted by J. Chen and the review of structural aspects was conducted by N. Chokshi of the Structural and Geotechnical Engineering Branch.

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mn George Lear, Chief Structural and Geotechnical Engineering Branch Division of Engineering

Enclosure:

As stated cc: J. Knight A. Thadani '

• NY92" Fo18 -8 7-~ 6 D. Jeng L. Heller (3)y' <

R. Framm G. Bagchi S. Davis l P. Sebel l N. Chokshi l

l C0tGACTS: J. Chen, SGEB, x28153 N. Chokshi, SGEB, x28967 k 8Ahb

ENCLOSURE PROBABILISTIC SAFETY ASSESSMENT SEABROOK STATION STRUCTURAL AND GE0 TECHNICAL ENGINEERING BRANCH REQUEST FOR ADDITIONAL INFORMATION Based on the preliminary review of the structural fragility and geotechnical aspects (Chapter 9 and Appendix F) of Probabilistic Safety Assessment (PSA) report submitted by the applicant, the following additional infomation is needed to complete the review.

Structural Engineering Aspects

1. Provide supporting calculations for fragility data presented in Table 4-3 through Table 4-16 of Appendix F. Also, provide fragility calculations for components (7), (11), (13), and (23) of Table 9.2-3.

2. In several recent PRAs (e.g. Millstone), sliding failure mode of Category I structures have been found to be critical in that it affects the inter-connected piping. Explain, why such a failure mode has not been considered at Seabrook.

3. Section 2.1.3 of Appendix F states that the non-category I building are separated fran the category I structures by seismic gaps and that they were either designed to Category I criteria or their failure would not affect Category I structures. It is not clear that the above statement is still valid for accelerations higher than SSE. Please provide detailed basis for the judgement that the failure of the non-category I structures would not affect Category I structures.

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4. Discuss, whether or not the tank wall flexibility has been considered in the fragility detennination. In past, design calculations for tanks have been based on rigid wall assumption in many cases.

Geotechnical Engineering Aspects

1. Provide the fragility calculation for the safety related electrical duct bank and manholes.

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