NESC0674 SAFTAC

SAFTAC, Monte-Carlo Fault Tree Simulation for System Design Performance and Optimization

NAME OR DESIGNATION OF PROGRAM, COMPUTER, DESCRIPTION OF PROBLEM OR FUNCTION, METHOD OF SOLUTION, RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM, TYPICAL RUNNING TIME, UNUSUAL FEATURES OF THE PROGRAM, RELATED AND AUXILIARY PROGRAMS, STATUS, REFERENCES, MACHINE REQUIREMENTS, LANGUAGE, OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED, OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS, NAME AND ESTABLISHMENT OF AUTHORS, MATERIAL, CATEGORIES

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1. NAME OR DESIGNATION OF PROGRAM: SAFTAC

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2. COMPUTERS

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Program name	Package id	Status	Status date
SAFTAC	NESC0674/01	Tested	01-DEC-1976

Machines used:

Package ID	Orig. computer	Test computer
NESC0674/01	IBM 370 series	IBM 370 series

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3. DESCRIPTION OF PROBLEM OR FUNCTION

SAFTAC is a Monte Carlo fault
tree simulation program that provides a systematic approach for
analyzing system design, performing trade-off studies, and
optimizing system changes or additions.

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4. METHOD OF SOLUTION

SAFTAC   assumes   an   exponential   failure
distribution  for  basic  input  events and  a  choice  of  either
Gaussian distributed or constant repair  times.  The program views
the system represented by the fault tree as a statistical assembly
of  independent  basic  input events,  each  characterized  by  an
exponential  failure distribution  and,  if  used, a  constant  or
normal repair distribution.

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5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

The   program   is
dimensioned to  handle 1100  basic input  events and  1100 logical
gates.  It can  be redimensioned to handle up to  2000 basic input
events and 2000 logical gates within the existing core memory.

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6. TYPICAL RUNNING TIME

Running time is dependent upon the fault
tree size and structure and the degree of resolution in the
quantitative evaluation desired.

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7. UNUSUAL FEATURES OF THE PROGRAM

The    fault   tree    technique
provides analysis flexibility which ranges from equipment analysis
to  over-all  plant  analyses incorporating  all  the  influencing
elements on a total-system basis.   The deductive approach used in
this technique  is useful  for evaluating  design consistency  and
reliability,   for    judging   alternatives,    for   determining
acceptability of  trade-offs, and  for analyzing  multiple failure
combinations and  common mode  failures in  complex systems.   The
fault tree  method allows analyses to  consider the rate  at which
failures or events are detected  after they occur (detection time)
and the rates at which they  are restored to normal (repair time).
The fault tree method is concerned with assuring that all critical
activities are identified and eliminated or controlled.  A system,
when defined in terms of  the all encompassing analysis capability
of fault tree analysis, is a  composite of operational and support
equipment,  personnel,  facilities  and software  which  are  used
together  as  an  entity  and are  capable  of  performing  and/or
supporting an operational role.

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8. RELATED AND AUXILIARY PROGRAMS

SAFTAC is an improved version of
an earlier program. See reference 5.

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9. STATUS

Package ID	Status date	Status
NESC0674/01	01-DEC-1976	Tested at NEADB

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10. REFERENCES

- P.A. Crosetti:
  Fault Tree Simulation Computer Program
  DUN-7697 (June 1971).
- P.A. Crosetti and R.A. Bruce:
  Commercial Application of Fault Tree Analysis, Ninth Reliability
  and Maintainability Conference
  Annals of Reliability and Maintainability, Vol. 9, p. 230 (1970).
- P.A. Crosetti:
  Fault Tree Analysis with Probability Evaluation
  DUN-SA-157 (November 3, 1970).
- P.A. Crosetti:
  Fault Tree Analysis for Reactor Systems
  DUN-SA-165 (February 25, 1971).
- P.A. Crosetti:
  Computer Program for Fault Tree Analysis
  DUN-5508 (April 1969).

NESC0674/01, included references:

- P.A. Crosetti:
  Fault Tree Simulation Computer Program
  DUN-7697  (June 1971)
- Description of Subroutine DOY
  Excerpt from: CSCX RJE/CRJE Reference, Vol. 2; Library Elements
  E00003-02-00 (April 1971).
- Notes on the IBM Version of STAFAC
  (November 22, 1976).

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11. MACHINE REQUIREMENTS

300K bytes for compilation, 140K bytes for
running the sample problem on an IBM370.

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12. PROGRAMMING LANGUAGE(S) USED

Package ID	Computer language
NESC0674/01	FORTRAN-IV

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13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED: CSCX or EXEC2
(UNIVAC1108), OS/360,370 (IBM360,370).

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14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS

   The
CALL OVERFL(K000FX)  statement on UNIVAC1108 execution  causes the
overflow  condition  to be  set  for  K000FX=1; for  K000FX=2  the
condition is not set.

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15. NAME AND ESTABLISHMENT OF AUTHORS

   1108          P. A. Crosetti
                 United Nuclear Industries, Inc.
                 P. O. Box 490
                 Richland, Washington  99352
   360           L. Garcia de Viedma
                 NEA Data Bank
                 B. P. 9
                 Batiment 45
                 91190 Gif-sur-Yvette, France

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16. MATERIAL AVAILABLE

NESC0674/01