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NESC0653 MOCUS

MOCUS, Minimal Cut Sets and Minimal Path Sets from Fault Tree Analysis

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1. NAME OR DESIGNATION OF PROGRAM:  MOCUS
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2. COMPUTERS
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Program name Package id Status Status date
MOCUS NESC0653/01 Tested 01-DEC-1976

Machines used:

Package ID Orig. computer Test computer
NESC0653/01 IBM 370 series IBM 370 series
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3. DESCRIPTION OF PROBLEM OR FUNCTION

From a description of the Boolean failure logic of a system, called a fault tree, and control  parameters specifying the minimal cut set length to be obtained MOCUS determines the system failure modes, or minimal cut sets, and  the system success modes, or minimal path sets.
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4. METHOD OF SOLUTION

MOCUS uses direct resolution of the fault tree  into the cut and path sets. The algorithm used starts with the main  failure of interest, the top event, and proceeds to basic independent component failures, called primary events, to resolve the fault tree to obtain the minimal sets. A key point of the algorithm is that an and gate alone always increases the number of path sets; an or gate alone always increases the number of cut sets  and increases the size of path sets. Other types of logic gates must be described in terms of and and or logic gates.
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5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

Output from MOCUS can include minimal cut and path sets for up to 20 gates.
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6. TYPICAL RUNNING TIME

Running  time  is problem  dependent.   The
sample test case requires 2 seconds on the Model 195.
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7. UNUSUAL FEATURES OF THE PROGRAM

MOCUS  guarantees that  all  the
minimal sets requested have been found.
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8. RELATED AND AUXILIARY PROGRAMS

PREP/KITT  (NESC  Abstract  528).
The fault  tree description  input to  MOCUS is  identical to  the
fault tree description  input to TREBIL in the  PREP package.  The
output from MOCUS  is compatible with KITT  input requirements for
quantitative reliability evaluation.
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9. STATUS
Package ID Status date Status
NESC0653/01 01-DEC-1976 Tested at NEADB
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10. REFERENCES

- W.E. Vesely and R.E. Narum,
  PREP and KITT: Computer Codes for the Automatic Evaluation of a
  Fault  Tree
  IN-1349, August 1970.
- J.B. Fussell,
  Synthetic Tree Model--A Formal Methodology for Fault Tree
  Construction
  ANCR-1098, March 1973.
NESC0653/01, included references:
- J.B. Fussell, E.B. Henry and N.H. Marshall:
  MOCUS - A Computer Program to Obtain Minimal Sets from Fault Trees
  ANCR-1156  (August 1974)
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11. MACHINE REQUIREMENTS:  222K bytes for execution and 7 I/O units
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12. PROGRAMMING LANGUAGE(S) USED
Package ID Computer language
NESC0653/01 FORTRAN-IV
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13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED:   OS/360.
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14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS

   The
sample problem uses more storage than  that given in the reference
report, ANCR-1156.  Sample problem execution  at Argonne used 222K
bytes.
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15. NAME AND ESTABLISHMENT OF AUTHORS

                 J. B. Fussell, E. B. Henry, and N. H. Marshall
                 EG&G Idaho, Inc.
                 P. O. Box 1625
                 Idaho Falls, Idaho  83401
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16. MATERIAL AVAILABLE
NESC0653/01
File name File description Records
NESC0653_01.001 PROGRAM SOURCE - FORTRAN IV 1739
NESC0653_01.002 SAMPLE PROBLEM DATA 20
NESC0653_01.003 SAMPLE PROBLEM OUTPUT LIST 19
NESC0653_01.004 SAMPLE PROBLEM OUTPUT CARDS 169
NESC0653_01.005 JCL 18
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17. CATEGORIES
  • G. Radiological Safety, Hazard and Accident Analysis
  • P. General Mathematical and Computing System Routines

Keywords: fault tree analysis, reliability, system failure analysis.