NEA-1375 COSIMA

1. NAME OR DESIGNATION OF PROGRAM:  COSIMA

3. DESCRIPTION OF PROGRAM OR FUNCTION

A static BWR core simulator suited for performing core follow studies in time steps. Coupled neutronic and hydraulic calculations provide as results Keff and flux-, power-, temperature-, and density distributions.

4. METHOD OF SOLUTION

The (2-group) flux distribution is obtained by  the Nodal Expansion method. Neutron cross sections are interpolated  from input tables with the following entries:
- Fuel type
- Average void during burnup
- Control rod in/out during burnup
- Burnup
- Actual control rod position in/out
- Actual void
- Actual fuel temperature
- Actual coolant temperature
Void, fuel temperature, and coolant temperature are found in the hydraulic part, and iterations between neutronics and hydraulics are performed until convergence.
Provisions for detailed pin power reconstruction are included and activated via input instructions.

5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

The size of the problems can be redefined by changing the parameter values stated in the beginning of the COMMON area. The present values are: NCHANM = Max. number of channels (assemblies)         =   450
NNODEM =  "     "    "  nodes                         = 12000
NZMAX  =  "     "    "  axial nodes                   =    26
NFTYPM =  "     "    "  fuel types                    =     6
NXMAX  =  "     "    "  nodes in x- or y-direct.      =    32
NGMAX  =  "     "    "  energy groups                 =     2
NAPMAX =  "     "    "  expansion order in NEM        =     5
NBUSTM =  "     "    "  burnup steps                  =    30
NAVVOM =  "     "    "  average void values           =     4
NPINMX =  "     "    "  fuel pins along assembly edge =     8

6. TYPICAL RUNNING TIME

Strongly dependent on problem size. With the  above max. values 1 1/2 minutes per neutronics/hydraulics iteration. Typically 40 iterations are needed after a thorough change of control rod pattern. If control rod settings are unchanged only 2-3  iterations are needed per burn-up step.

7. UNUSUAL FEATURES OF THE PROGRAM

Reflectors are represented as a layer of one node thickness with cross sections and albedos on the outside boundary. This greatly reduces the influence of the albedos. The history effect of control rods is treated in a special way according to ref. 5.

8. RELATED AND AUXILIARY PROGRAMS

The cross section tables are automatically produced by the assembly program LEWARD, but if they are supplied from elsewhere, the program is a stand-alone code.

10. REFERENCES

Neutronics:
1. The BWR Core Simulator COSIMA with 2 group Nodal Flux Expansion
   and Control Rod History. C.F. Hojerup, Riso-M-2804, Aug. 1989.
2. Pin Power Reconstruction in COSIMA. C.F. Hojerup, Riso-M-2892,
   Sept. 1990.
3. Three-Dimensional Static and Dynamic Reactor Calculations by the
   Nodal Expansion Method. Brian Christensen, Riso-R-496, May 1985.
4. Core-Follow Studies of QUAD CITIES cycle 1 and 2 with special
   emphasis on pin power comparisons at the end of cycle 2. C.F.
   Hojerup and E. Nonbol, Pittsburgh.
5. A Method of Taking Control Rod History into Account in Core
   Simulation Calculations for BWR's.  C.F. Hojerup and E. Nonbol,
   PHYSOR 90, Vol. 4, Marseilles 1990.
Hydraulics:
6. RAMONA I., A Fortran Code for Transient Analysis of Boiling
   Water Reactors and Boiling Loops. P. Baksted and K.O. Solberg,
   Kjeller Report KR-135, 1968.
7. SCHOUGAARD, B.F., A Short Description of the Programme NOTAM,
   RP-19-79, 1979.
8. BABALA, D. et al., ANDYCAP - A Three-Dimensional Computer
   Programme for Transient Analysis of Boiling Water Reactors.
   Reaktortagung, Bonn, March 30-April 2, 1971.

11. MACHINE REQUIREMENTS:  Page file quota: 30000.

13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED:  VAX/VMS.

14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS:

15. NAME AND ESTABLISHMENT OF AUTHORS

C.F. Hojerup, Riso National Laboratory, Postbox 49, DK-4000
Roskilde.

File name	File description	Records
NEA1375_01.001	Information file	53
NEA1375_01.002	COSIMA source program (FORTRAN-77)	5578
NEA1375_01.003	COMMON_COSIMA.FOR INCLUDE file (FORTRAN-77)	152
NEA1375_01.004	Test case 0 input data	558
NEA1375_01.005	Test case 1 input data	559
NEA1375_01.006	Test case 0 output	2081
NEA1375_01.007	Test case 1 output	1464
NEA1375_01.008	DIFFDATA_DEMO_1.DAT x-sec library	12392
NEA1375_01.009	DIFFDATA_DEMO_2.DAT x-sec library	12392
NEA1375_01.010	DIFFDATA_DEMO_3.DAT x-sec library	12392
NEA1375_01.011	DIFFDATA_DEMO_4.DAT x-sec library	12808
NEA1375_01.012	DIFFDATA_DEMO_5.DAT x-sec library	12392
NEA1375_01.013	DIFFDATA_DEMO_6.DAT x-sec library	12392
NEA1375_01.014	DIFFDATA_DEMO_7.DAT x-sec library	12392
NEA1375_01.015	DIFFDATA_DEMO_R.DAT x-sec library	24
NEA1375_01.016	Input description	1076
NEA1375_01.017	COSIMA batch execution command procedure	38
NEA1375_01.018	COSIMA interactive exec command procedure	18