Seismic Safety Margins Research Program. Phase I, final report - overview

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.

The Assessment of Probability Distributions from Expert Opinions with an Application to Seismic Fragility Curves

“…whose interpretation is crucial to the correct application of the method. In the case of a single expert supplying the estimate x1 we have 7r(xIx1) = k -' L ( x 1~x ) 7 r 0 ( x ) (2) In Eq. (2)' L dx, is the analyst's probability that the expert's estimate will be between x1 and x1 + dx, when the true value is x.…”

“…As part of the Seismic Safety Margins Research Program (SSMRP) at Lawrence Livermore National Laboratory, (2) questionnaires were sent to several experts to obtain estimates of the seismic capacity of nuclear power plant components. Table I shows the estimates of five experts for the loth, 50th and 90th percentiles of the seismic capacity of a particular component.…”

SSI response of a typical shear wall structure. Volume 1

“…The Seismic Safety MaTgins Research Program (SSMfcF) is a US NRC funded, multiyear research program conducted by Lawrence Livermore National Laboratory (LLNL) [1] .…”

Effect of Analytical Methodology for Assessment on Seismically Induced Core Damage

“…The risk of NPPs is classified under internal risk and external risk, and the external risk includes seismic risk. Since many NPPs are on the Pacific Ring of Fire, seismic PSA has been conducted to evaluate the seismic risk in terms of core damage frequency (CDF) of NPPs due to earthquakes [2][3][4][5][6][7] . Also in Japan, many NPPs are exposed to the seismic risk due to the active faults on the Pacific Ring of Fire.…”