NAME OR DESIGNATION OF PROGRAM, COMPUTER, DESCRIPTION OF PROGRAM 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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Program name | Package id | Status | Status date |
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COBRA-SFS | NESC1091/02 | Tested | 17-JAN-1990 |

Machines used:

Package ID | Orig. computer | Test computer |
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NESC1091/02 | CRAY 1 | CDC CYBER 830 |

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3. DESCRIPTION OF PROGRAM OR FUNCTION

COBRA-SFS is used for steady- state and transient thermal-hydraulic analysis of spent fuel storage systems as well as other heat transfer and fluid flow problems. It is designed to predict flow and temperature distributions under a wide range of flow conditions, including mixed and natural convection. Two auxiliary programs, RADX1 and RADGEN, generate blackbody view factors and calculate radiation exchange factors for unconsolidated spent fuel assemblies to be supplied as input to COBRA-SFS.

COBRA-SFS is used for steady- state and transient thermal-hydraulic analysis of spent fuel storage systems as well as other heat transfer and fluid flow problems. It is designed to predict flow and temperature distributions under a wide range of flow conditions, including mixed and natural convection. Two auxiliary programs, RADX1 and RADGEN, generate blackbody view factors and calculate radiation exchange factors for unconsolidated spent fuel assemblies to be supplied as input to COBRA-SFS.

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4. METHOD OF SOLUTION

The thermal-hydraulic analysis is separated into two parts - a flow field solution and an energy solution. COBRA-SFS solves a set of incompressible subchannel equations for mass and momentum conservation in the coolant and energy conservation in the fuel rods, solid structures, and coolant. The RECIRC solution method, a Newton-Raphson technique, is used to iteratively solve these equations. Radiation heat transfer between rod and slab surfaces is modeled using detailed radiation exchange factors, which are calculated from the geometry of the problem and the emissivities of the participating surfaces. The subchannel equations are fully implicit in time.

The thermal-hydraulic analysis is separated into two parts - a flow field solution and an energy solution. COBRA-SFS solves a set of incompressible subchannel equations for mass and momentum conservation in the coolant and energy conservation in the fuel rods, solid structures, and coolant. The RECIRC solution method, a Newton-Raphson technique, is used to iteratively solve these equations. Radiation heat transfer between rod and slab surfaces is modeled using detailed radiation exchange factors, which are calculated from the geometry of the problem and the emissivities of the participating surfaces. The subchannel equations are fully implicit in time.

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5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

PARAMETER statements presently impose a maxima of -

50 channel gap connections

40 channels

20 fuel rods

40 slab connections

1 fuel types

6 assemblies

9 fuel rods interacting with a channel

6 fuel nodes per fuel rod

4 axial fuel type divisions

By modifying PARAMETER statements, code dimensioning limits can be changed to fit any given problem, limited only by available storage.

PARAMETER statements presently impose a maxima of -

50 channel gap connections

40 channels

20 fuel rods

40 slab connections

1 fuel types

6 assemblies

9 fuel rods interacting with a channel

6 fuel nodes per fuel rod

4 axial fuel type divisions

By modifying PARAMETER statements, code dimensioning limits can be changed to fit any given problem, limited only by available storage.

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6. TYPICAL RUNNING TIME

Running times are dependent on the size of the problem. The sample problem required 6.5 CP seconds on a Cray1 and 30.3 CP seconds on a CDC CYBER170/875.

Running times are dependent on the size of the problem. The sample problem required 6.5 CP seconds on a Cray1 and 30.3 CP seconds on a CDC CYBER170/875.

NESC1091/02

NEA-DB ran the tests included in this package on a CDC CYBER 830 computer. CPU times were 295 seconds (COBRA-SFS); 21 seconds (RADGEN).[ top ]

7. UNUSUAL FEATURES OF THE PROGRAM

In addition to many features of the earlier COBRA codes, COBRA-SFS has additional features specific to spent fuel storage systems. These include a solution method that calculates three-dimensional conduction heat transfer through a solid structure network such as a spent fuel cask basket or cask body, a detailed radiation heat transfer model that calculates radiation on a detailed rod-to-rod basis, thermal boundary conditions to model radiation and natural convection heat transfer from storage system surfaces, and a total flow boundary condition that automatically adjusts the pressure field to yield the specified total flow for a system.

The lumped finite-volume nodalization used in COBRA-SFS allows great deal of flexibility in modeling a wide variety of geometries.

In addition to many features of the earlier COBRA codes, COBRA-SFS has additional features specific to spent fuel storage systems. These include a solution method that calculates three-dimensional conduction heat transfer through a solid structure network such as a spent fuel cask basket or cask body, a detailed radiation heat transfer model that calculates radiation on a detailed rod-to-rod basis, thermal boundary conditions to model radiation and natural convection heat transfer from storage system surfaces, and a total flow boundary condition that automatically adjusts the pressure field to yield the specified total flow for a system.

The lumped finite-volume nodalization used in COBRA-SFS allows great deal of flexibility in modeling a wide variety of geometries.

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8. RELATED AND AUXILIARY PROGRAMS

The equations governing mass, momentum, and energy conservation for incompressible flows are solved using a semi-implicit method similar to that used in COBRA-WC (NESC9973) that allows recirculating flows to be predicted. COBRA-SFS evolved from the earlier COBRA3C, COBRA4, and COBRA4I (NESC432) programs.

The equations governing mass, momentum, and energy conservation for incompressible flows are solved using a semi-implicit method similar to that used in COBRA-WC (NESC9973) that allows recirculating flows to be predicted. COBRA-SFS evolved from the earlier COBRA3C, COBRA4, and COBRA4I (NESC432) programs.

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NESC1091/02, included references:

- D.R. Rector, C.L. Wheeler and N.J. Lombardo :COBRA-SFS - A Thermal-Hydraulic Analysis Computer Code

Volume I: Mathematical Models and Solution Method

PNL-6049 Vol. I (November 1986).

- D.R. Rector, M.J. Cuta, N.J. Lombardo et al. :

COBRA-SFS - A Thermal-Hydraulic Analysis Computer Code

Volume II: User's Manual

PNL-6049 Vol. II (November 1986).

- N.J. Lombardo, J.M. Cuta, T.E. Michener, D.R. Rector et al. :

COBRA-SFS - A Thermal-Hydraulic Analysis Computer Code

Volume III: Validation Assessments

PNL-6049 Vol. III (December 1986).

- D.R. Rector :

RADGEN: A Radiation Exchange Factor Generator For Rod Bundles

PNL-6342 (October 1987).

- D.R. Rector, T.E. Michener:

COBRA-SFS Modifications and Cask Model Optimization

PNL-6706 (January 1989).

- L. Reed :

COBRA-SFS Edition D Tape Description and Implementation

Information

NESC Note 89-81 (August 24, 1989)

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NESC1091/02

The test case of COBRA-SFS requires on CDC CYBER 830 344,000 (octal) words of main storage; RADGEN requires 116,000 (octal) words.[ top ]

NESC1091/02

NOS2.5.1 (CDC CYBER 830) with FORTRAN V compiler.[ top ]

14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS

Although the COBRA-SFS source supplied is designed for execution on a Cray1, a CDC-specific UPDATE correction set is provided to permit implementation on a CDC CYBER170. COBRA-SFS is designed to perform both steady-state and transient calculations; however, the transient capability has not yet been validated. Memory must be set to zero prior to execution.

Although the COBRA-SFS source supplied is designed for execution on a Cray1, a CDC-specific UPDATE correction set is provided to permit implementation on a CDC CYBER170. COBRA-SFS is designed to perform both steady-state and transient calculations; however, the transient capability has not yet been validated. Memory must be set to zero prior to execution.

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NESC1091/02

File name | File description | Records |
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NESC1091_02.001 | INFORMATION FILE | 125 |

NESC1091_02.002 | COBRA-SFS UPDATE SOURCE | 10633 |

NESC1091_02.003 | UPDATE CORRECTION SET FOR CDC | 46 |

NESC1091_02.004 | COBRA-SFS FORTRAN-77 SOURCE FOR CRAY | 18845 |

NESC1091_02.005 | COBRA-SFS FORTRAN-77 SOURCE FOR CDC | 18841 |

NESC1091_02.006 | SAMPLE PROBLEM INPUT | 234 |

NESC1091_02.007 | SAMPLE PROBLEM TAPE10 INPUT | 28 |

NESC1091_02.008 | SAMPLE PROBLEM OUTPUT | 1851 |

NESC1091_02.009 | RADGEN FORTRAN SOURCE | 1983 |

NESC1091_02.010 | RADX1 FORTRAN SOURCE | 640 |

NESC1091_02.011 | RADGEN SAMPLE PROBLEM INPUT | 7 |

NESC1091_02.012 | RADGEN SAMPLE PROBLEM OUTPUT | 150 |

NESC1091_02.013 | RADGEN SAMPLE PROBLEM TAPE10 OUTPUT | 55 |

NESC1091_02.014 | CDC DAYFILES DURING TESTING | 112 |

Keywords: fluid flow, fuel rods, heat transfer, natural convection, radioactive waste storage, rod bundles, temperature distribution.