Computer Programs

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 AUTHOR, MATERIAL, CATEGORIES

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Program name | Package id | Status | Status date |
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VENUS-2 | NESC0511/03 | Tested | 01-DEC-1981 |

Machines used:

Package ID | Orig. computer | Test computer |
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NESC0511/03 | IBM 3033 | IBM 3033 |

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3. DESCRIPTION OF PROBLEM OR FUNCTION

VENUS-2 is an improved edition of the VENUS fast-reactor disassembly program. It is a two- dimensional (r-z) coupled neutronics-hydrodynamics code that calculates the dynamic behavior of an LMFBR during a prompt-critical disassembly excursion. It calculates the power history and fission energy release as well as the space-time histories of the fuel temperatures, core material pressures, and core material motions. Reactivity feedback effects due to Doppler broadening and reactor material motion are taken into account.

VENUS-2 is an improved edition of the VENUS fast-reactor disassembly program. It is a two- dimensional (r-z) coupled neutronics-hydrodynamics code that calculates the dynamic behavior of an LMFBR during a prompt-critical disassembly excursion. It calculates the power history and fission energy release as well as the space-time histories of the fuel temperatures, core material pressures, and core material motions. Reactivity feedback effects due to Doppler broadening and reactor material motion are taken into account.

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4. METHOD OF SOLUTION

The power and energy release are calculated using a point-kinetics formulation with up to six delayed neutron groups. The reactivity is a combination of an input driving function and feedback effects due to Doppler broadening and material motion. An adiabatic model is used to calculate the temperature increase throughout the reactor based on an initial temperature distribution and power profile provided as input data. These temperatures are, in turn, converted to fuel pressures through one of several equation of state options provided. The material motion that results from the pressure buildup is calculated by a direct finite difference solution of a set of two-dimensional (r-z) hydrodynamics equations. This is done in Lagrangian coordinates. The reactivity change associated with this motion is calculated by first-order perturbation theory. The displacements are also used to adjust the fuel densities as required for the density dependent equation-of- state option. An automatic time-step-size selection scheme is provided.

The power and energy release are calculated using a point-kinetics formulation with up to six delayed neutron groups. The reactivity is a combination of an input driving function and feedback effects due to Doppler broadening and material motion. An adiabatic model is used to calculate the temperature increase throughout the reactor based on an initial temperature distribution and power profile provided as input data. These temperatures are, in turn, converted to fuel pressures through one of several equation of state options provided. The material motion that results from the pressure buildup is calculated by a direct finite difference solution of a set of two-dimensional (r-z) hydrodynamics equations. This is done in Lagrangian coordinates. The reactivity change associated with this motion is calculated by first-order perturbation theory. The displacements are also used to adjust the fuel densities as required for the density dependent equation-of- state option. An automatic time-step-size selection scheme is provided.

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5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

VENUS-2 is written so that the dimensions of the storage arrays can be readily changed to accomodate a broad range of problem sizes. In the base version, the total number of mesh intervals is restricted such that (NR+3)*(NZ+3) is less than 700, where NR and NZ are the total number of mesh intervals in the r and z directions, respectively. The total number of spatial regions used in the mockup must be no greater than 20. The number of spatial grid points in the input material- reactivity-worth distribution cannot exceed 26 by 26 in any region. The program requires about 380K bytes of central storage with these restrictions. If the available storage is increased, these restrictions can be relaxed accordingly.

VENUS-2 is written so that the dimensions of the storage arrays can be readily changed to accomodate a broad range of problem sizes. In the base version, the total number of mesh intervals is restricted such that (NR+3)*(NZ+3) is less than 700, where NR and NZ are the total number of mesh intervals in the r and z directions, respectively. The total number of spatial regions used in the mockup must be no greater than 20. The number of spatial grid points in the input material- reactivity-worth distribution cannot exceed 26 by 26 in any region. The program requires about 380K bytes of central storage with these restrictions. If the available storage is increased, these restrictions can be relaxed accordingly.

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6. TYPICAL RUNNING TIME

Typical problems require from 2 to 15 minutes of IBM 360/75 CPU time, with some cases taking up to 45 minutes.

Rather mild excursions in reactors that have little initial void space usually require the longer running times. The sample problem requires about 2 minutes on an IBM 3033 and less than a minute on a CDC 7600.

Typical problems require from 2 to 15 minutes of IBM 360/75 CPU time, with some cases taking up to 45 minutes.

Rather mild excursions in reactors that have little initial void space usually require the longer running times. The sample problem requires about 2 minutes on an IBM 3033 and less than a minute on a CDC 7600.

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7. UNUSUAL FEATURES OF THE PROGRAM

Several special subroutines were developed for VENUS-2 that partially alleviate some of the basic modeling restrictions in the code. These include approximate treatment of the following effects: a) fuel-sodium interaction (heat transfer), b) fission gas pressures, and c) nonhomogeneous material motion due to preferential axial sodium expulsion. Although these were not included as standard options in the code, the models are discussed in ANL-7951.

Several special subroutines were developed for VENUS-2 that partially alleviate some of the basic modeling restrictions in the code. These include approximate treatment of the following effects: a) fuel-sodium interaction (heat transfer), b) fission gas pressures, and c) nonhomogeneous material motion due to preferential axial sodium expulsion. Although these were not included as standard options in the code, the models are discussed in ANL-7951.

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8. RELATED AND AUXILIARY PROGRAMS

VENUS-2 offers a number of improvements and refinements over the original VENUS code. In particular, the ANL density-dependent equation-of-state option was substantially improved. In addition, an option was added that greatly improves the accuracy of calculations where sodium is present in the core. Other areas of improvement include time-step control, accounting for the heat-of-fusion of the fuel in the energy balance, calculating the energy in molten fuel, and improved data edits.

VENUS-2 will optionally plot the Lagrangian mesh grid at specified time intervals during the excursion and create a three- dimensional isometric plot displaying the pressure as a function of two space variables. The CalComp plotter is used.

VENUS-2 offers a number of improvements and refinements over the original VENUS code. In particular, the ANL density-dependent equation-of-state option was substantially improved. In addition, an option was added that greatly improves the accuracy of calculations where sodium is present in the core. Other areas of improvement include time-step control, accounting for the heat-of-fusion of the fuel in the energy balance, calculating the energy in molten fuel, and improved data edits.

VENUS-2 will optionally plot the Lagrangian mesh grid at specified time intervals during the excursion and create a three- dimensional isometric plot displaying the pressure as a function of two space variables. The CalComp plotter is used.

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10. REFERENCES

- J.F. Jackson, R.B. Nicholson:

VENUS-II: An LMFBR Disassembly Program

ANL-7951, September 1972

- W.T. Sha, T.H. Hughes:

VENUS-A, Two-Dimensional Coupled Neutronics-hydrodynamics Com-

puter Program for Fast Reactor Power Excursions

ANL-7701, October 1970

- VENUS2, NESC No. 511.360, Tape Description, Implementation

Information, Sample Output, and ANL-7951 Erratum,

National Energy Software Center Note 80-53, August 12, 1980.

- VENUS2, NESC No. 511.7600, Sample Problem Output,

National Energy Software Center Note 80-52, August 12, 1980.

- J.F. Jackson, R.B. Nicholson:

VENUS-II: An LMFBR Disassembly Program

ANL-7951, September 1972

- W.T. Sha, T.H. Hughes:

VENUS-A, Two-Dimensional Coupled Neutronics-hydrodynamics Com-

puter Program for Fast Reactor Power Excursions

ANL-7701, October 1970

- VENUS2, NESC No. 511.360, Tape Description, Implementation

Information, Sample Output, and ANL-7951 Erratum,

National Energy Software Center Note 80-53, August 12, 1980.

- VENUS2, NESC No. 511.7600, Sample Problem Output,

National Energy Software Center Note 80-52, August 12, 1980.

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11. MACHINE REQUIREMENTS

440k bytes are used for the IBM version when storing the data in double-precision. Single-precision storage is adequate for the converted CDC 7600 version which requires 160,000 (octal) words of memory for execution. One peripheral storage device is needed if the graphical output option is used.

440k bytes are used for the IBM version when storing the data in double-precision. Single-precision storage is adequate for the converted CDC 7600 version which requires 160,000 (octal) words of memory for execution. One peripheral storage device is needed if the graphical output option is used.

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15. NAME AND ESTABLISHMENT OF AUTHOR

J.F. Jackson

NRC Programs

Los Alamos Scientific Laboratory

P. O. Box 1663

Los Alamos, New Mexico 87545, U. S. A.

R.B. Nicholson

Research and Technology Center

Exxon Nuclear Company

2955 George Washington Way

Richland, Washington 99352, U. S. A.

D.P. Weber

Reactor Analysis and Safety Division

Argonne National Laboratory

9700 South Cass Avenue

Argonne, Illinois 60439, U. S. A.

J.F. Jackson

NRC Programs

Los Alamos Scientific Laboratory

P. O. Box 1663

Los Alamos, New Mexico 87545, U. S. A.

R.B. Nicholson

Research and Technology Center

Exxon Nuclear Company

2955 George Washington Way

Richland, Washington 99352, U. S. A.

D.P. Weber

Reactor Analysis and Safety Division

Argonne National Laboratory

9700 South Cass Avenue

Argonne, Illinois 60439, U. S. A.

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NESC0511/03

File name | File description | Records |
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NESC0511_03.001 | INFORMATION | 42 |

NESC0511_03.002 | JOB CONTROL | 64 |

NESC0511_03.003 | OVERLAY CARDS | 6 |

NESC0511_03.004 | VENUS FOTRAN SOURCE | 3343 |

NESC0511_03.005 | DUMMY PLOTTING ROUTINES | 11 |

NESC0511_03.006 | PLOTTING ROUTINES | 296 |

NESC0511_03.007 | SAMPLE PROBLEM INPUT | 291 |

NESC0511_03.008 | SAMPLE PROBLEM OUTPUT | 5161 |

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- F. Space - Time Kinetics, Coupled Neutronics - Hydrodynamics - Thermodynamics

Keywords: LMFBR reactors, excursions, fast reactors, feedback, hydrodynamics, pressure, r-z, reactor safety, temperature, two-dimensional.