RSICC CODE PACKAGE PSR-472
1. NAME AND TITLE
COBRA-SFS Cylce 3: Code System for Thermal Hydraulic Analysis of Spent Fuel Casks.
2. CONTRIBUTORS
Pacific Northwest Laboratory, Richland, Washington, through the OECD NEA Data Bank, Issy-les-Moulineaux, France.
3. CODING LANGUAGE AND COMPUTER
Fortran 77 and C; SGI R8000/R10000, IBM/ps2, INTELx86, IBM/unix, Sun, DEC stations, Cray, HP-9000, APPLE MAC-II/MPW workstation. (P00472MNYCP00).
4. NATURE OF PROBLEM SOLVED
COBRA-SFS (Spent Fuel Storage) is a code for thermal-hydraulic analysis of multi-assembly spent fuel storage and transportation systems. It uses a lumped parameter finite difference approach to predict flow and temperature distributions in spent fuel storage systems and fuel assemblies, under forced and natural convection heat transfer conditions. Derived from the COBRA family of codes, which have been extensively evaluated against in-pile and out-of-pile data, COBRA-SFS retains all the important features of the COBRA codes for single phase fluid analysis and extends the range application to include problems with two-dimensional radiative and three-dimensional conductive heat transfer. COBRA-SFS has been used to analyze various single- and multi-assembly spent fuel storage systems containing unconsolidated and consolidated fuel rods, with a variety of fill media, including air, helium and vacuum. Cycle 0 of COBRA-SFS was released in 1986. Subsequent applications of the code led to development of additional capabilities, which resulted in the release of Cycle 1 in February 1989. Since then, the code has undergone an independent technical review as part of a submittal to the Nuclear Regulatory Commission for a generic license to apply the code to spent fuel storage system analysis. Modifications and improvements to the code have been combined to form Cycle 2. Cycle 3., the newest version of COBRA-SFS, has been validated and verified for transient applications, such as a storage cask thermal response to a pool fire.
5. METHOD OF SOLUTION
The solution of the governing equations for fluid flow and heat transfer in COBRA-SFS is fully implicit and proceeds iteratively through a series of steps that address each of the conservation equations in turn. Within an iteration the code solves the momentum equations for the velocity field, then the energy equations for the temperature and enthalpies, and then the mass continuity equation for the pressure field. The finite difference equations for mass, momentum, and energy conservation are solved using a Newton-Raphson technique that is similar to Hirt's method, but has been made implicit in time. The fluid solution is applicable to single-phase flow at very low velocities, with or without buoyancy driven natural circulation. The code can also resolve flow and pressure fields in which the net flow is zero, allowing solutions for sealed storage or shipping casks. The strong coupling of the fluid energy equation and the heat transfer in the solid structure requires simultaneous solution of the energy equations for the fluid, fuel rods and solid structure nodes.
6. RESTRICTIONS OR LIMITATIONS
The code has extremely flexible noding features that allow almost any geometric configuration of storage cask or system to be modeled; it runs on a wide variety of platforms, and is reasonably fast, even for very large problems (i.e., on the order of 5,000 to 10,000 nodes).
7. TYPICAL RUNNING TIME
Run time depends on the size of the problem, and the platform on which it is run. The following list gives the run time on the various platforms for the test cases included in the transmittal package - tn24 vertical (large problem):
8. COMPUTER HARDWARE REQUIREMENTS
COBRA-SFS has run on SGI R8000/R10000, IBM/ps2, INTELx86, IBM/unix, Sun SPARCstation, DEC stations, Cray with COS operating system, Cray with uniCOS system, HP-9000 workstation, APPLE MAC-II/MPW workstation
9. COMPUTER SOFTWARE REQUIREMENTS
A Fortran 77 compiler is required on all computers. The source files are included in this package; however, no executables are included. Hewlett-Packard and SGI require one subroutine in C, for the elapsed time calculation. COBRA-SFS has been run on all of the above listed platforms, with a variety of operating systems. It has no specific operating system requirements, other than access to time, date and cpu time utilities, and no operating system modifications are needed in order to run. Operating systems include: SGI IRIX 6.X, Sun OS, IBM aix, DEC VMS, Cray UNICOS, INTEL with Microsoft Windows(TM) /NT/95, Hewlett-Packard HP-UX 9.05, and MacIntosh OS 7.0.
INTEL platforms need something equivalent to Microsoft's Power Fortran. A minimum of 8 MB of memory is recommended for any workstation applications. COBRA-SFS expects the input file to be a local file named 'input'. Optional grey body view factors are read from local file 'tape10'. Optional restart input is read from local file 'tape8'. Code results are written to local file 'output'. Optional ouput for later restart is written to local file 'tape8'.
An auxiliary code, RADGEN, is included in the package. This code can be used to generate the grey body view factors for radiative heat transfer within an enclosure modeled as an assembly in COBRA-SFS. Radgen calculates the grey body view factors from two-dimensional black body factors, using an extension of Cox's crossed-string correlation approach, for square and triangular pitch rod arrays. It can also be used to define the view factors for an arbitrary enclosure made up of user defined surfaces, and containing no internal structures to block or reflect radiation exchange among the surfaces. RADGEN can be used to create the code input read from logical unit 10 in input group RADG.
COBRA-SFS Cycle3 was tested at RSICC on a Sun UltraSparc60 running SunOS 5.6 using f77 5.0, on a DEC 500 Alpha running Digital unix version 4.0D with f77 5.1-8, and on a Pentium II running Windows 95b with Digital Visual Fortran Compiler Version 6.0A.
10. REFERENCE
T. E. Michener, D. R. Rector, J. M. Cuta, R. E. Dodge, and C. W. Enderlin, "COBRA-SFS: A Thermal-Hydraulic Analysis Code for Spent Fuel Storage and Transportation Casks, Documentation for Cycle 2," PNL-10782 (UC-800) (September 1995).
11. CONTENTS OF CODE PACKAGE
The package is transmitted as a Unix tar file and a self-extracting DOS file on a CD, which also contains the electronic document in file P472.PDF. The distribution files contain compressed source files an information file, test case input and output.
12. DATE OF ABSTRACT
November 2003. COBRA-SFS, Cycle 3 was first released by ESTSC in September 1997 then contributed to the NEA Data Bank and then to RSICC from which it was released in November 2003.
KEYWORDS: HEAT TRANSFER; THERMAL HYDRAULICS; WASTE MANAGEMENT