NEA-0606 GENDY.

GENDY, Reactor Dynamic Program with Variable Time Step Control

NAME OR DESIGNATION OF PROGRAM, COMPUTER, DESCRIPTION OF PROBLEM 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 AUTHOR, MATERIAL, CATEGORIES

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1. NAME OR DESIGNATION OF PROGRAM: GENDY. A General Reactor Program.

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2. COMPUTERS

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Program name	Package id	Status	Status date
GENDY	NEA-0606/01	Tested	12-JUN-1985

Machines used:

Package ID	Orig. computer	Test computer
NEA-0606/01	TELEF. TR440	DEC VAX 11/780

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3. DESCRIPTION OF PROBLEM OR FUNCTION

GENDY solves a general system of up to 50 linear differential equations. The program is mainly meant to be a flexible instrument to solve arbitrary sets of geometrically independent reactor dynamics equations, which can suitably be formulated by the user.

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4. METHOD OF SOLUTION

Common methods of solution, such as Runge- Kutta and simple extrapolation, often require too small time steps for numerical stability from the fact that big eigenvalues may exist in a system of coupled differential equations. Therefore the back- ward extrapolation technique, also used very effectively in the code COSTANZA, was chosen. GENDY realizes this method for a general system of differential equations, provided that the first partial derivatives can be given.

The program contains a variable time step control which allows short computation times and uniform accuracy. When nonlinearity of the physical system is thought to be important for the accuracy of the solution, an iteration procedure is provided for optional use.

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5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

Max. 50 linear differential equations. Max. 10 additional functions may be defined.

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6. TYPICAL RUNNING TIME

On the TR 440 the ratio of calculation time to physical time is 0.4 for a system of 18 differential equations.

NEA-0606/01

NEA-DB executed the test cases included in the package on VAX-11/780. CPU times were 24 seconds for the System-1 test run and 13 seconds for the System-2 test run.

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7. UNUSUAL FEATURES OF THE PROGRAM

Backward extrapolation technique.
Variable time step control.

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8. RELATED AND AUXILIARY PROGRAMS: COSTANZA uses same solution technique.

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9. STATUS

Package ID	Status date	Status
NEA-0606/01	12-JUN-1985	Tested at NEADB

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10. REFERENCES

- G. Forti and E. Vincenti:
  The Codes COSTANZA for the Dynamics of Liquid-Cooled Nuclear
  Reactors
  EUR 3633e, 1967.

NEA-0606/01, included references:

- R. Fiebig and A. Krueger:
  GENDY - A General Reactor Dynamics Program
  GKSS 73/E/6 (1973)
- R. Fiebig and A. Krueger:
  Reprint "GENDY - A general Reactor Dynamics Program"
  Atomkernenergie (ATKE) Bd. 22 (1973) Lfg. 3

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11. MACHINE REQUIREMENTS

Problem dependent e.g. for TR4400 60 K words core storage, 1350 K words background storage.

NEA-0606/01

The program without the test case routine requires on VAX-11/780 33,280 bytes of main storage.

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12. PROGRAMMING LANGUAGE(S) USED

Package ID	Computer language
NEA-0606/01	FORTRAN-IV

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13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED: BS3.

NEA-0606/01

VMS V3.4 (VAX-11/780).

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14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS:

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15. NAME AND ESTABLISHMENT OF AUTHOR

          R. Fiebig and A. Krueger
          Gesellschaft fuer Kernenergieverwertung in Schiffbau
          und Schiffahrt mbH
          HAMBURG-GEESTHACHT
          Federal Republic of Germany.

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16. MATERIAL AVAILABLE

NEA-0606/01

File name	File description	Records
NEA0606_01.003	INFORMATION FILE	44
NEA0606_01.004	GENDY SOURCE PROGRAM WITHOUT ROUTINE F(T)	336
NEA0606_01.005	F(T) ROUTINE TO RUN SYSTEM 1 TEST CASE	137
NEA0606_01.006	F(T) ROUTINE TO RUN SYSTEM 2 TEST CASE	152
NEA0606_01.007	SYSTEM 1 TEST CASE INPUT DATA	31
NEA0606_01.008	SYSTEM 1 TEST CASE PRINTED OUTPUT	1018
NEA0606_01.009	SYSTEM 2 TEST CASE INPUT DATA	33
NEA0606_01.010	SYSTEM 2 TEST CASE PRINTED OUTPUT	433

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17. CATEGORIES

E. Space-Independent Kinetics
P. General Mathematical and Computing System Routines

Keywords: differential equations, iterative methods, numerical solution, reactor kinetics.