RSICC CODE PACKAGE PSR-453

1. NAME AND TITLE

SEISIM 1: Code System for Seismic Probabilistic Risk Assessment.

2. CONTRIBUTORS

Lawrence Livermore National Laboratory, Livermore, CA through the Energy Science and Technology Software Center, Oak Ridge, Tennessee.

3. CODING LANGUAGE AND COMPUTER

Fortran IV; CDC7600 (P00453C760000).

4. NATURE OF PROBLEM SOLVED

SEISIM1 calculates the probabilities of seismically induced failures for components and systems and propagates these calculations to determine the probability of accident sequences and the resulting total risk, which is quantified as an expected value of radiation release and exposure from a given nuclear power plant. SEISIM1 was developed as a fundamental tool for the systems analysis portion of the NRC's Seismic Safety Margins Research Program (SSMRP). The SSMRP provides a complete, self-contained methodology to assess and quantify the risk to nuclear power plants from seismic events and seismically induced failures.

5. METHOD OF SOLUTION

Accident sequence and system failure probabilities are computed from cut-set probabilities, utilizing three alternative approximation schemes, which represent the probabilities as unions of cut sets. All cut-set probabilities containing response-dependent basic events are converted to multinormal integrals, which are calculated using numerical integration. SEISIM1 computes each release sequence probability by multiplying the initiating event and accident sequence probabilities by the probabilities of earthquake and containment failure. Release category probabilities are computed by adding the probabilities of all release sequences associated with that release category.

6. RESTRICTIONS OR LIMITATIONS

Maxima of 5000 cut sets, 2000 basic events, 200 accident sequences, 200 response quantities, 50 unique fragility functions, 13 basic events per cut set, and 10 release categories

7. TYPICAL RUNNING TIME

NESC executed the sample problem, which consists of two initiating events, 12 accident sequences, three logical component groups, and 91 basic events, in 4 CP seconds on a CDC7600.

8. COMPUTER HARDWARE REQUIREMENTS

SEISIM1 was developed at Lawrence Livermore National Laboratory to run on a CDC 7600 and was originally distributed by the National Energy Software Center. It was transferred to the Energy Science and Technology Software Center then to RSICC. It was not tested, and no changes were made to the package when it was released by RSICC in March 2001.

9. COMPUTER SOFTWARE REQUIREMENTS

SEISIM is written in Fortran IV and was developed under the SCOPE 2.1.5 operating system.

10. REFERENCES

a) Included in documentation:

L. Eyberger, "SEISIM1 Tape Description and Implementation Information, NESC No. 1063 (July 14, 1986).

L. L. George, S. B. Guarro, P. G. Prassinos, J. E. Wells, "SEISIM - Systematic Evaluation of Important Safety Improvement Measures User Manual," UCID-20496 (July 1985).

P. D. Smith, D. L. Bernreuter, M. P. Bohn, T. Y. Chuang, etal, "An Overview of Seismic Risk Analysis for Nuclear Power Plants," UCID-18680 (September 11, 1980).

b) Background information:

J. E. Wells, L. L. George, and G. E. Cummings, "Seismic Safety Margins Research Program Phase I Final Report, Systems Analysis (Project VII)," NUREG/CR-2015, UCRL-53021, Vol. 8 (November 1981).

11. CONTENTS OF CODE PACKAGE

Included in the package are the referenced documents in (10.a) and one 3.5" diskette which includes Fortran source, data, and sample problem input and output written in a self-extracting compressed DOS file. No executables are included with the package.

12. DATE OF ABSTRACT

March 2001.

KEYWORDS: REACTOR SAFETY; RISK ASSESSMENT