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NESC0432 COBRA4I.

COBRA, Transient Thermohydraulics Fuel Elements Clusters, Subchannel Analysis Method

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1. NAME OR DESIGNATION OF PROGRAM:  COBRA4I.
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2. COMPUTERS
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Program name Package id Status Status date
COBRA-4I NESC0432/09 Tested 26-JUL-1983
COBRA-4I NESC0432/10 Tested 08-SEP-1987
COBRA-4I NESC0432/11 Tested 18-MAY-1987
COBRA-4I NESC0432/12 Tested 22-OCT-1997

Machines used:

Package ID Orig. computer Test computer
NESC0432/09 CRAY 1 CRAY 1
NESC0432/10 CDC 7600 CDC CYBER 740
NESC0432/11 IBM 3033 IBM 3084
NESC0432/12 DEC VAX series DEC VAX 8810
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3. DESCRIPTION OF PROBLEM OR FUNCTION

COBRA4I performs steady-state and transient thermal-hydraulic analysis of rod bundle nuclear fuel  elements and cores via the subchannel analysis method.
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4. METHOD OF SOLUTION

The conservation equations of flow and energy are solved for interconnected subchannel control volumes via conventional finite differencing techniques. The steady-state calculations are solved by implicit finite differencing whereas the  transient calculations are performed by either an implicit or explicit finite difference scheme. Internal rod temperatures are calculated by an orthogonal collocation approximation to the heat conduction  equation.
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5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

Using the COBRA4I code option to store variables on peripheral storage devices eliminates any practical limit as to maximum problem size. However,  computer core requirements and code execution time is always a consideration when determining the complexity of the problem to be solved.
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6. TYPICAL RUNNING TIME

On a CDC 7600 running time is 0.004 seconds per cell-iteration using the implicit solution scheme and 0.00006 seconds per cell-iteration using the explicit scheme. The number of  cells is determined as the number of subchannels times the number of axials nodes. The number of iterations required per time-step varies according to convergence criteria and complexity of physics; however, typical values are from 10 to 20 iterations for the implicit scheme and 10 to 50 iterations for the explicit scheme. The three sample problems run in less than 30 seconds on the CRAY1. The  U-tube and fuel thermal sample problems each run in less than 2 minutes and the 7-pin sample problem in less than 1 minute on an IBM3033.
NESC0432/09
NEA-DB executed the test case on CRAY-1 in 27 CPU seconds.

NESC0432/10
NEA-DB executed the three test cases included in this package on a CDC CYBER 740 computer. The following CPU times were required: 35 seconds (7-pin problem); 227 seconds (fuel therma  model problem); 206 seconds (U-tube problem).

NESC0432/11
NEA-DB executed the three test cases included in this package on an IBM 3084 computer. The following CPU times were required: 7 seconds (7-pin problem); 47 seconds (fuel thermal model  problem); 52 seconds (U-tube problem).

NESC0432/12
NEA-DB executed the two test cases included in this package on a VAX 8810 computer. The following CPU times were required: 45 seconds (thermal model problem); 45 seconds (U-tube problem).
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7. UNUSUAL FEATURES OF THE PROGRAM

The improved capabilities of COBRA4I over its predecessor COBRA3C include:
(a) A new explicit solution scheme to calculate severe transients  involving flow reversals, recirculations and expulsion and  reentry flows with either a flow or pressure boundary       condition specified.
(b) Improved storage allocation to reduce central memory       requirements and improved running time.
(c) Improved fuel rod heat conduction model to calculate interior-   rod temperatures with axial conduction and variable thermal  conductivity included. Each rod may now consist of axially-       varying materials.
(d) Addition of a set of correlations to calculate the properties  of superheated steam and a set of heat transfer correlations  covering the complete range of heat transfer from subcooled       through boiling.
(e) Problem "Dump and Restart" capabilities which allow the  solution to be saved for subsequent use either to continue  calculations or to be used as an initial guess for a different  problem which can result in significant time savings for       similar problems.
(f) Auxiliary program to re-dimension COBRA based on user  specified input defining problem size and code options       desired, thus minimizing storage requirements.
(g) Auxiliary program to generate COBRA input for hexagonal rod-  bundle geometry. Input for card groups 4, 7, and 8 can be  generated, thus greatly reducing the amount of input required.  (h) Line-printer plotting capability to display pressure drop,  mass flux, enthalpy and crossflow versus axial position for       all or a specified number of gaps and channels.
(i) A thermally-conducting wall model which can conduct heat       between two channels on opposite sides of a wall.
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8. RELATED AND AUXILIARY PROGRAMS

COBRA4I is an extended version of the COBRA3C computer program. The auxiliary program SPECSET re- dimensions COBRA4I according to user-specified problem size, and the auxiliary program GEOM calculates COBRA input for data groups 4, 7,  and 8 for hexagonal rod bundles. The IBM version also contains auxiliary program CSPECS which replaces pseudostatements of the form *CALL SPECx in COBRA4I with the correctly sized set of FORTRAN declarative statements comprising COMDECKx.
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9. STATUS
Package ID Status date Status
NESC0432/09 26-JUL-1983 Tested at NEADB
NESC0432/10 08-SEP-1987 Tested at NEADB
NESC0432/11 18-MAY-1987 Tested at NEADB
NESC0432/12 22-OCT-1997 Tested at NEADB
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10. REFERENCES

- C.L. Wheeler, C.W. Stewart, R.J. Cena, D.S. Rowe, and A.M. Sutey,
  COBRA-IV-I: An Interim Version of COBRA for Thermal-hydraulic
  Analysis of Rod Bundle Nuclear Fuel Elements and Cores,
  BNWL-1962, March 1976.
- C.W. Stewart, C.L. Wheeler, R.J. Cena, C.A. McMonagle, J.M. Cuta,
  and D.S. Trent,
  COBRA-IV: The Model and the Method,
  BNWL-2214, July 1977.
- C.W. Stewart, C.A. McMonagle, M.J. Thurgood, T.L. George, D.S.
  Trent, J.M. Cuta, and G.D. Seybold:
  Core Thermal Model: COBRA-IV Development and Applications,
  BNWL-2212, January 1977.
- D.M. Lister and P.A. Jallouk,
  COBRA IV-I An IBM Compatible Version,
  NUREG/CR-0519 (ORNL/NUREG/CSD-9), December 1978.
- COBRA4I, NESC No. 432.7600G, Tape Contents Description,
  National Energy Software Center Note 77-37, Revised May 23, 1981.
- COBRA4I, NESC No.432.CRA1, COBRA4I Tape Description,
  National Energy Software Center Note 82-108, August 20, 1982.
- COBRA4I, NESC No. 432.3033, COBRA4I Tape Description and
  Implementation Information,
  National Energy Softawre Center Note 86-05, October 25, 1985.
NESC0432/09, included references:
- C.L. Wheeler et al.:
  COBRA-IV-I: An Interim Version of COBRA for Thermal-Hydraulic
  Analysis of Rod Bundle Nuclear Fuel Elements and Cores.
  BNWL-1962, UC-32  (March 1976)
- C.W. Stewart et al.:
  Core Thermal Model: COBRA-IV Development and Applications.
  BNWL-2212, NRC-4  (January 1977)
- C.W. Stewart et al.:
  COBRA-IV: The Model and the Method
  BNWL-2214, NRC-4  (July 1977)
- D.M. Lister and P.A. Jallouk:
  COBRA-IV-I - An IBM-Compatible Version
  NUREG/CR-0519  (December 1978)
- M. Birgersson:
  COBRA4I Tape Description and Implementation Information
  NESC Note 86-05  (October 25, 1985)
NESC0432/10, included references:
- C.L. Wheeler et al.:
  COBRA-IV-I: An Interim Version of COBRA for Thermal-Hydraulic
  Analysis of Rod Bundle Nuclear Fuel Elements and Cores.
  BNWL-1962, UC-32  (March 1976)
- C.W. Stewart et al.:
  Core Thermal Model: COBRA-IV Development and Applications.
  BNWL-2212, NRC-4  (January 1977)
- C.W. Stewart et al.:
  COBRA-IV: The Model and the Method
  BNWL-2214, NRC-4  (July 1977)
- M. Birgersson:
  COMBRA4I Tape Description and Implementation Information
  NESC Note 86-05  (October 25, 1985)
NESC0432/11, included references:
- C.L. Wheeler et al.:
COBRA-IV-I: An Interim Version of COBRA for Thermal-Hydraulic Analysis of Rod
Bundle Nuclear Fuel Elements and Cores. BNWL-1962, UC-32  (March 1976)
- C.W. Stewart et al.:
Core Thermal Model: COBRA-IV Development and Applications.
BNWL-2212, NRC-4  (Jan. 1977)
- C.W. Stewart et al.:
COBRA-IV: The Model and the Method. BNWL-2214, NRC-4  (July 1977)
- D.M. Lister and P.A. Jallouk:
COBRA-IV-I - An IBM-Compatible Version, NUREG/CR-0519  (December 1978)
- M. Birgersson:
COBRA4I Tape Description and Implementation Information
NESC Note 86-05 (Oct. 25, 1985)
NESC0432/12, included references:
- C.L. Wheeler et al.:
  COBRA-IV-I: An Interim Version of COBRA for Thermal-Hydraulic
  Analysis of Rod Bundle Nuclear Fuel Elements and Cores.
  BNWL-1962, UC-32  (March 1976)
- C.W. Stewart et al.:
  Core Thermal Model: COBRA-IV Development and Applications.
  BNWL-2212, NRC-4  (January 1977)
- C.W. Stewart et al.:
  COBRA-IV: The Model and the Method
  BNWL-2214, NRC-4  (July 1977)
- D.M. Lister and P.A. Jallouk:
  COBRA-IV-I - An IBM-Compatible Version
  NUREG/CR-0519  (December 1978)
- M. Birgersson:
  COBRA4I Tape Description and Implementation Information
  NESC Note 86-05  (October 25, 1985)
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11. MACHINE REQUIREMENTS

202,000 (octal) words and 4 scratch units besides the standard input/output units (CDC7600), 450K bytes and 6
units besides the standard input/output units (IBM3033).
NESC0432/10
To run the test cases on a CDC CYBER 740 computer, 104,327 (octal) words of main storage and 114,440 (octal) words of ECS were required.

NESC0432/11
To run the test cases on an IBM 3084 computer, 560K bytes of main storage were required.
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12. PROGRAMMING LANGUAGE(S) USED
Package ID Computer language
NESC0432/09 FORTRAN-IV
NESC0432/10 FORTRAN-IV
NESC0432/11 FORTRAN+ASSEMBLER
NESC0432/12 FORTRAN
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13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED

SCOPE (CDC6600,7600), NOS (CDC CYBER175), COS (CRAY1), MVS (IBM3033), VM/CMS (IBM4331).
NESC0432/10
NOS 2.5.1 (CDC CYBER 740) with compiler FTN 4.8+650.

NESC0432/11
MVS (IBM 3084).

NESC0432/12
VMX V5.0-1 (VAX 8810).
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14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS:
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15. NAME AND ESTABLISHMENT OF AUTHOR

  7600     C.L. Wheeler, C.W. Stewart*, J.F. Cena,
           D.S. Rowe, and A.M. Sutey
           Pacific Northwest Laboratories
           Battelle
           P.O. Box 999
           Richland, Washington 99352

  CRAY1    T. Hosokawa
           Century Research Center Corporation
           No. 2, 3-Chome, Hon-cho
           Nihonbashi, Chuo-Ku
           Tokyo, Japan

  IBM      D.M. Lister and P.A. Jallouk
           Oak Ridge National Laboratory
           P.O. Box X
           Oak Ridge Tennessee 37831

           Elba Pezzoni
           Comision Nacional de Energia Atomica
           Buenos Aires, Argentina
* Contact
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16. MATERIAL AVAILABLE
NESC0432/09
File name File description Records
NESC0432_09.001 COBRA-4I INFORMATION FILE 21
NESC0432_09.002 COBRA-4I SOURCE PROGRAM (FORTRAN-4) 6780
NESC0432_09.003 GEOM SOURCE PROGRAM (FORTRAN-4) 622
NESC0432_09.004 SPECSET SOURCE PROGRAM (FORTEAN-4) 210
NESC0432_09.005 U-TUBE OSCILLATION TEST CASE DATA 44
NESC0432_09.006 THERMAL MODEL TEST CASE DATA 118
NESC0432_09.007 7-PIN WIRE-WRAPPED BUNDLE TEST CASE DATA 51
NESC0432_09.008 GEOM DATA FOR 7-PIN BUNDLE PROBLEM 8
NESC0432_09.009 SPECSET INPUT DATA EQUIVALENCED TO FT05 18
NESC0432_09.010 SPECSET INPUT DATA EQUIVALENCED TO FT10 207
NESC0432_09.011 SPECSET UPDATA INPUT DATA 28
NESC0432_09.012 COBRA-4I JCL 69
NESC0432_09.013 U-TUBE OSCILLATION CASE OUTPUT 1697
NESC0432_09.014 THERMAL MODEL CASE OUTPUT 1744
NESC0432_09.015 7-PIN BUNDLE CASE OUTPUT 491
NESC0432/10
File name File description Records
NESC0432_10.001 information file 59
NESC0432_10.002 control information 94
NESC0432_10.003 COBRA4I source deck (FORTRAN-66) 6754
NESC0432_10.004 COBRA4I U-tube problem input data 44
NESC0432_10.005 COBRA4I fuel thermal problem input data 118
NESC0432_10.006 COBRA4I 7-pin problem input data 52
NESC0432_10.007 dummy comdecks 263
NESC0432_10.008 SPECSET source program (FORTRAN-66) 210
NESC0432_10.009 SPECSET input data 18
NESC0432_10.010 GEOM source deck (FORTRAN-66) 622
NESC0432_10.011 GEOM 7-pin problem input data 8
NESC0432_10.012 COBRA4I U-tube problem printed output 1697
NESC0432_10.013 COBRA4I fuel thermal problem printed output 1744
NESC0432_10.014 COBRA4I 7-pin problem printed output 491
NESC0432/11
File name File description Records
NESC0432_11.001 Information file 154
NESC0432_11.002 Assembly routines source file 267
NESC0432_11.003 COBRA4I master file 8169
NESC0432_11.004 Preprocessor for the COBRA4I master file 225
NESC0432_11.005 GEOM fortran program 617
NESC0432_11.006 SPECSET fortran program 214
NESC0432_11.007 COBRA4I unsized COMDECKs 226
NESC0432_11.008 CSPECS data 1
NESC0432_11.009 FT10 input 2
NESC0432_11.010 SPECSET data 18
NESC0432_11.011 Fuel thermal sample problem input 118
NESC0432_11.012 7 pin sample problem input 52
NESC0432_11.013 U-tube sample problem input 44
NESC0432_11.014 GEOM sample problem input 8
NESC0432_11.015 Original JCL cards 220
NESC0432_11.016 NEA DATA BANK sample JCL cards 541
NESC0432_11.017 GEOM sample problem output 49
NESC0432_11.018 7 pin sample problem output 487
NESC0432_11.019 Fuel thermal sample problem output 1740
NESC0432_11.020 U-tube sample problem output 1693
NESC0432/12
File name File description Records
NESC0432_12.001 Information file 127
NESC0432_12.002 Changes made in VAX conversion 1148
NESC0432_12.003 COBRA-4I FORTRAN Source 6788
NESC0432_12.004 VAX FORTRAN Include file 9
NESC0432_12.005 VAX FORTRAN Include file 13
NESC0432_12.006 VAX FORTRAN Include file 26
NESC0432_12.007 VAX FORTRAN Include file 53
NESC0432_12.008 VAX FORTRAN Include file 32
NESC0432_12.009 VAX FORTRAN Include file 30
NESC0432_12.010 VAX FORTRAN Include file 13
NESC0432_12.011 VAX FORTRAN Include file 7
NESC0432_12.012 VAX FORTRAN Include file 5
NESC0432_12.013 VAX FORTRAN Include file 8
NESC0432_12.014 VAX FORTRAN Include file 5
NESC0432_12.015 VAX FORTRAN Include file 3
NESC0432_12.016 VAX FORTRAN Include file 10
NESC0432_12.017 VAX FORTRAN Include file 4
NESC0432_12.018 VAX FORTRAN Include file 15
NESC0432_12.019 VAX FORTRAN Include file 13
NESC0432_12.020 VAX FORTRAN Include file 6
NESC0432_12.021 VAX FORTRAN Include file 16
NESC0432_12.022 VAX FORTRAN Include file 8
NESC0432_12.023 VAX FORTRAN Include file 26
NESC0432_12.024 VAX FORTRAN Include file 3
NESC0432_12.025 VAX FORTRAN Include file 4
NESC0432_12.026 VAX FORTRAN Include file 2
NESC0432_12.027 VAX FORTRAN Include file 3
NESC0432_12.028 VAX FORTRAN Include file 2
NESC0432_12.029 VAX FORTRAN Include file 2
NESC0432_12.030 VAX FORTRAN Include file 2
NESC0432_12.031 VAX FORTRAN Include file 2
NESC0432_12.032 VAX FORTRAN Include file 77
NESC0432_12.033 Command file for compilation 14
NESC0432_12.034 Command file for linking 13
NESC0432_12.035 Command file for running (brief) 58
NESC0432_12.036 Command file for running (complete) 226
NESC0432_12.037 Test case 1 input data Utube problem 44
NESC0432_12.038 Test case 2 input data thermal model problem 118
NESC0432_12.039 Test case 1 output 1744
NESC0432_12.040 Test case 2 output (original) 1791
NESC0432_12.041 Test case 2 output (NEADB) 1791
NESC0432_12.042 Command file to rename file names 42
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17. CATEGORIES
  • G. Radiological Safety, Hazard and Accident Analysis
  • H. Heat Transfer and Fluid Flow

Keywords: LMFBR reactors, blowdown, enthalpy, fluid flow, heat transfer, hydraulics, reactor cores, reactor safety, rod bundles, transients, water cooled reactors.