ESTS0135 COBRA-SFS CYCLE3.

1. NAME OR DESIGNATION OF PROGRAM:  COBRA-SFS CYCLE3.

3. DESCRIPTION OF PROGRAM OR FUNCTION

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.

4. METHODS

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. 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):
  SGI R8000: 200 seconds
  Sun Sparcstation: 1600 sec
  RS/6000 (IBM/aix): 990 sec
  Intel (pentium): 650 sec
  DEC workstation: 650 sec
  Hewlett-Packard HP9000: 260 sec
  Apple/Mac-II MPW: 4200 sec
  CRAY mainframe: 2200 sec

7. UNUSUAL FEATURES

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).

8. RELATED OR AUXILIARY PROGRAMS

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. RADGEN is written in standard Fortran-77 and has no platform-dependent coding.

- Michener, T.E., Rector, D.R., Cuta, J.M., Dodge, R.E. and Enderlin, C.W.:
  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. MACHINE REQUIREMENTS

1.0 MB for executable up to 1.5 MB or more for output of large problem.

13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED:  Machine dependent.

14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS

INTEL platforms need something equivalent to Microsoft's PowerFortran. 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'.

15. NAME AND ESTABLISHMENT OF AUTHORS

        D.R. Rector, J.M. Cuta and C.W. Enderlin
        Pacific Northwest Laboratory
        Richland, WA, U. S. A.

testcase1_cycle3.inp.Z Input for RADGEN test case 1
testcase1_cycle3.out.Z Output for RADGEN test case 1
testcase2_cycle3.inp.Z Input for RADGEN test case 2
testcase3_cycle3.inp.Z Input for RADGEN test case 3
second.c.z C subroutine for time calculation on the HP9000
planar_devel_cycle3.inp.Z Input for transient dev. flow in a planar region
testcase2_cycle3_.out.Z Output for RADGEN test case 2
testcase3_cycle3.out.Z Output for RADGEN test case 3
mitsubishi_cycle3.inp.Z Input for single assembly Mitsubishi test case
tn24_vertical.inp.Z Input for multi-assembly TN24P cask test case
radgen_cycle3.f.Z RADGEN compilable source (suitable for all platforms)
mitsubishi_cycle3.out.Z Output for single-assembly test case
tn24v.tape10.z Tape10 TN24P vertical cask model
mitsubishi.tape10.Z Tape10 for Mitsubishi test case
tn24_vertical.out.Z Output for multi-assembly TN24P cask test case
sfs3_uniCOS.f.Z Compilable source for Cray UniCOS
sfs3_INT.f.Z Compilable source for Intel Windows
sfs3_DEC.f.Z Compilable source for DEC and Sun4
sfs_Sun.f.Z Compilable source for S un SPARCstation
sfs3_SGi.f.Z Compilable source for SGI R8000/R10000
sfs3_MAC.f.Z Compilable source for Macintosh MPW
sfs3_COS.f.Z Compilable source for Cray OS
sfs3_ps2.f.Z Compilable source for IBM PS/2
sfs3_aix.f.Z Compilable source for IBM AIX
sfs3_HP9.f.Z Compilable source for HP 90000 series
planar_devel_cycle3.out.Z Output for transient dev. flow in a planar region
read.me Software submittal abstract
install.inst List of transmittal diskette contents, installation instructions