United States Nuclear Regulatory Commission - Protecting People and the Environment

Seismic Safety Margins Research Programs Phase I Final Report - Overview (NUREG/CR-2015, UCRL-53021, Volume 1)

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Publication Information

Manuscript Completed: March 1981
Date Published: April 1981

Prepared by:
P. D. Smith, R. G. Dong, D. L. Bernreuter, M. P. Bohn, T. Y. Chuang,
G. E. Cummings, J. J. Johnson, *R. W. Mensing, J. E. Wells

Lawrence Livermore Laboratory
7000 East Avenue
Livermore, CA 94550

*Structural Mechanics Associates

NRC FIN No. A0126, A0130, A0138, A0139, AQ142

Prepared for:
Office of Nuclear Regulatory Research
U. S. Nuclear Regulatory Commission
Washington, DC 20555

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Abstract

The Seismic Safety Margins Research Program (SSMRP) is a multiyear, multiphase program whose overall objective is to develop improved methods for seismic safety assessments of nuclear power plants, using a probabilistic computational procedure. The program is being carried out at the Lawrence Livermore National Laboratory and is sponsored by the U.S. Nuclear Regulatory Commission, Office of Nuclear Regulatory Research. Phase I of the SSMRP was successfully completed in January 1981: A probabilistic computational procedure for the seismic risk assessment of nuclear power plants has been developed and demonstrated. The methodology is implemented by three computer programs: HAZARD, which assesses the seismic hazard at a given site, SMACS, which computes in-structure and subsystem seismic responses, and SEISIM, which calculates system failure probabilities and radioactive release probabilities, given (1) the response results of SMACS, (2) a set of event trees, (3) a family of fault trees, (4) a set of structural and component fragility descriptions, and (5) a curve describing the local seismic hazard. The practicality of this methodology was demonstrated by computing preliminary release probabilities for Unit 1 of the Zion Nuclear Power Plant north of Chicago, Illinois. Studies have begun aimed at quantifying the sources of uncertainty in these computations. Numerous side studies were undertaken to examine modeling alternatives, sources of error, and available analysis techniques. Extensive sets of data were amassed and evaluated as part of projects to establish seismic input parameters and to produce the fragility curves.

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