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NEA-0384 TRIGON.

TRIGON, 2-D Homogeneous and Inhomogeneous Fixed Source Neutron Diffusion for Triangular or Hexagonal Mesh

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1. NAME OR DESIGNATION OF PROGRAM:  TRIGON.
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2. COMPUTERS
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Program name Package id Status Status date
TRIGON NEA-0384/01 Tested 01-NOV-1979

Machines used:

Package ID Orig. computer Test computer
NEA-0384/01 UNIVAC 1110 UNIVAC 1110
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3. NATURE OF PHYSICAL PROBLEM SOLVED

The program solves the multigroup time-independent neutron diffusion equations with arbitrary group to group scattering in two space dimensions. In addition to homogeneous or K-effective calculations also inhomogeneous or fixed source calculations can be made. The problem may be specified with both external and internal logarithmic derivative boundary conditions.
Using pointwise flux distribution the program calculates automatically the average flux and power distributions over equal hexagons of arbitrary size into which the area of solution is divided by the user.
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4. METHOD OF SOLUTION

The diffusion theory equations are approximated  by 7-point difference equations for the uniform triangular or hexagonal mesh grid. In the former case, the mesh points are situated at the cross sections of the mesh lines separating different materials and in the latter case at the centre points of the homogeneous mesh hexagons. The difference equations are solved iteratively by the line over-relaxation technique utilizing an exponential over-relaxation procedure. Coarse mesh rebalancing and special asymptotic flux extrapolations are used to improve the convergence.
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5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

Because a variable dimensioning technique is employed, the only restriction on problem  size is the available core storage. The option of using auxiliary storage (drum, disk or tape) during iteration allows to run large problems even with rather small core storage.
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6. TYPICAL RUNNING TIME

For entirely core contained problems, the running time is about 0.2 msec per space-energy point per iteration. Since the program is designed for use in multiprocessing environment there is no simultaneous performance of computation and data transfer. Thus the running time will be increased in batch processing if auxiliary storage is used during iteration.
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7. UNUSUAL FEATURES: UNUSUAL FEATURES OF THE PROGRAM
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8. RELATED AND AUXILIARY PROGRAMS

TRIGON is in many respects similar to GAMTRI. The card output of the programs GGC-4 and THERMOS-OTA can be fed as input into TRIGON.
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9. STATUS
Package ID Status date Status
NEA-0384/01 01-NOV-1979 Tested at NEADB
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10. REFERENCES
NEA-0384/01, included references:
- E. Kaloinen:
  TRIGON, A Two-Dimensional Multigroup Diffusion Code for Trigonal
  or Hexagonal Mesh
  Nuclear Engineering Laboratory, Report 1 (May 1973)
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11. MACHINE REQUIREMENTS

Minimum about 20k words on UNIVAC 1108. In addition to input and output, up to 6 drum, disk or tape units are required, depending upon the size of the problem.
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12. PROGRAMMING LANGUAGE(S) USED
Package ID Computer language
NEA-0384/01 FORTRAN-IV
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13. OPERATING SYSTEM OR MONITOR UNDER WHICH PROGRAM IS EXECUTED:  UNIVAC-1108 EXEC-8.
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14. ANY OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS

Most of the data transfer during calculation is carried out by a special  routine NTRAN in UNIVAC 1108 which controls fast unbuffered read and write operations.
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15. NAME AND ESTABLISHMENT OF AUTHOR

E. Kaloinen
Nuclear Engineering Laboratory
Technical Research Centre of Finland
SF-02150 Otaniemi
Finland.
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16. MATERIAL AVAILABLE
NEA-0384/01
File name File description Records
NEA0384_01.001 SOURCE (F4 AND ASSEMBLER) 2840
NEA0384_01.002 SAMPLE PROBLEM INPUT 57
NEA0384_01.003 SAMPLE PROBLEM OUTPUT 240
NEA0384_01.004 JCL AND INFORMATION 82
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17. CATEGORIES
  • C. Static Design Studies

Keywords: difference equations, flux distribution, hexagonal configuration, iterative methods, multigroup, neutron diffusion equation, neutron flux, power distribution, two-dimensional.