NAME OR DESIGNATION OF PROGRAM, COMPUTER, DESCRIPTION OF PROGRAM OR FUNCTION, METHODS, RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM, TYPICAL RUNNING TIME, FEATURES, AUXILIARIES, STATUS, REFERENCES, HARDWARE REQUIREMENTS, LANGUAGE, SOFTWARE REQUIREMENTS, OTHER RESTRICTIONS, NAME AND ESTABLISHMENT OF AUTHORS, MATERIAL, CATEGORIES

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Program name | Package id | Status | Status date |
---|---|---|---|

EVNTRE | PSR-0465/01 | Arrived | 06-MAY-2002 |

Machines used:

Package ID | Orig. computer | Test computer |
---|---|---|

PSR-0465/01 | DEC VAX 8650 |

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3. DESCRIPTION OF PROGRAM OR FUNCTION

EVNTRE is a generalized event tree processor that was developed for use in probabilistic risk analysis of severe accident progressions for nuclear power plants. The general nature of EVNTRE makes it applicable to a wide variety of analyses that involve the investigation of a progression of events which lead to a large number of sets of conditions or scenarios.

EVNTRE efficiently processes large, complex event trees. It can assign probabilities to event tree branch points in several different ways, classify pathways or outcomes into user-specified groupings, and sample input distributions of probabilities and parameters. PSTEVNT, a postprocessor program used to sort and reclassify the 'binned' data output from EVNTRE and generate summary tables, is included.

EVNTRE is a generalized event tree processor that was developed for use in probabilistic risk analysis of severe accident progressions for nuclear power plants. The general nature of EVNTRE makes it applicable to a wide variety of analyses that involve the investigation of a progression of events which lead to a large number of sets of conditions or scenarios.

EVNTRE efficiently processes large, complex event trees. It can assign probabilities to event tree branch points in several different ways, classify pathways or outcomes into user-specified groupings, and sample input distributions of probabilities and parameters. PSTEVNT, a postprocessor program used to sort and reclassify the 'binned' data output from EVNTRE and generate summary tables, is included.

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4. METHODS

EVNTRE processes event trees that are cast in the form of questions or events, with multiple choice answers for each question. Split fractions (probabilities or frequencies that sum to unity) are either supplied or calculated for the branches of each question in a path-dependent manner. EVNTRE traverses the tree, enumerating the leaves of the tree and calculating their probabilities or frequencies based upon the initial probability or frequency and the split fractions for the branches taken along the corresponding path to an individual leaf. The questions in the event tree are usually grouped to address specific phases of time regimes in the progression of the scenario or severe accident. Grouping or binning of each path through the event tree in terms of a small number of characteristics or attributes is allowed. Boolean expressions of the branches taken are used to select the appropriate values of the characteristics of

interest for the given path. Typically, the user specifies a cutoff tolerance for the frequency of a pathway to terminate further exploration. Multiple sets of input to an event tree can be processed by using Monte Carlo sampling to generate approximate mapping from input to output.

EVNTRE processes event trees that are cast in the form of questions or events, with multiple choice answers for each question. Split fractions (probabilities or frequencies that sum to unity) are either supplied or calculated for the branches of each question in a path-dependent manner. EVNTRE traverses the tree, enumerating the leaves of the tree and calculating their probabilities or frequencies based upon the initial probability or frequency and the split fractions for the branches taken along the corresponding path to an individual leaf. The questions in the event tree are usually grouped to address specific phases of time regimes in the progression of the scenario or severe accident. Grouping or binning of each path through the event tree in terms of a small number of characteristics or attributes is allowed. Boolean expressions of the branches taken are used to select the appropriate values of the characteristics of

interest for the given path. Typically, the user specifies a cutoff tolerance for the frequency of a pathway to terminate further exploration. Multiple sets of input to an event tree can be processed by using Monte Carlo sampling to generate approximate mapping from input to output.

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6. TYPICAL RUNNING TIME

Central processing time can vary from a few minutes to several hours depending on the size and complexity of the problem. The size of the event tree, the amount of sampling done where uncertainties exist, and the extent of branching and calculation of branch probabilities in the event tree are some of the conditions which can add to the processing time. NESC executed the EVNTRE sample problem in approximately 45 CPU minutes, and the PSTEVNT sample problem in approximately 9 CPU minutes on a DEC VAX6220.

Central processing time can vary from a few minutes to several hours depending on the size and complexity of the problem. The size of the event tree, the amount of sampling done where uncertainties exist, and the extent of branching and calculation of branch probabilities in the event tree are some of the conditions which can add to the processing time. NESC executed the EVNTRE sample problem in approximately 45 CPU minutes, and the PSTEVNT sample problem in approximately 9 CPU minutes on a DEC VAX6220.

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PSR-0465/01, included references:

- J.M. Griesmeyer and L.N. SmithA Reference Manual for the Event Progression Analysis Code (EVNTRE)

NUREG/CR-5174, SAND88-1607 (September 1989)

- S.J. Higgins

A User's Manual for the Postprocessing Program PSTEVNT

NUREG/CR-5380, SAND88-2988 (November 1989)

- L.Reed

EVNTRE, NESC No. R1132, EVNTRE Tape Description and Implementation Information

NESC Note 91-66 (April 26, 1991)

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PSR-0465/01

EVNTRE.EXE executable file containing the following :EVNTRE.FOR Fortran Source file

UFUN.FOR Function UFUN Fortran Source

PB1.DAT Peach Bottom Sample Input

PB2.DAT Peach Bottom Sample Input

PB3.DAT Peach Bottom Sample Input

PB4.DAT Peach Bottom Sample Input

PB5.DAT Peach Bottom Sample Input

PB.OUT Peach Bottom Sample Problem Output

CONV.FOR Data Conversion Program Source

EVNT.FOR EVNTSUB Utility Source

EVNT1.DAT EVNTSUB Sample Input

EVNT2.DAT EVNTSUB Sample Input

EXEC.COM EVNTRE Execution Command Procedure

ECHO.OUT Sample Problem Output

PBBIN.OUT Sample Problem Output

PSTEVNT.FOR PSTEVNT FORTRAN Source

UWGT.FOR Function UWGT Fortran Source

PST1.DAT PSTEVNT Sample Input

PST2.DAT PSTEVNT Sample Input

PST3.DAT PSTEVNT Sample Input

PST4.DAT PSTEVNT Sample Input

PST5.DAT PSTEVNT Sample Input

PST6.DAT PSTEVNT Sample Input

PST7.DAT PSTEVNT Sample Input

PSTEVNT.COM OSTEVNT Execution Command Procedure

POSTLHS.COM PSTEVNT Execution Command Procedure

PST1.OUT PSTEVNT Sample Problem Output

PST2.OUT PSTEVNT Sample Problem Output

PST3.OUT PSTEVNT Sample Problem Output

PST4.OUT PSTEVNT Sample Problem Output

PST5.OUT PSTEVNT Sample Problem Output

PST6.OUT PSTEVNT Sample Problem Output

PST7.OUT PSTEVNT Sample Problem Output

Readme.rsi Information file

Keywords: risk assessment.