NEA-0184 DIXY-2.

1. NAME OR DESIGNATION OF PROGRAM:  DIXY-2.

3. NATURE OF PHYSICAL PROBLEM SOLVED

The multigroup neutron diffusion  equations are solved for two-dimensional x-y, r-z and r-theta geometries in the homogeneous or inhomogeneous case.

4. METHOD OF SOLUTION

The analytical equations are approximated by five-point difference formulas and the resulting numerical problem is solved by an inner-outer iteration technique, where inner iterations are performed along a cyclically reduced block overrelaxation with precalculated relaxation factors.

5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

The maximum number of mesh points and/or groups depends on the available core storage in the following manner:
Assume:
        C = total number of available core storage words
        P = program length in words
      NGP = number of groups
       NM = number of material compositions
      MXN = number of mesh points
Q = NM*NGP*(NGP+5)/2 - approximate store for cross sections then:
        C.GE.(P+Q+S+4.5*MXN) must be true.
If this relation holds, the program searches for an optimal way to solve the problem with a minimum number of I/O devices (max. 2) using the adjustable dimension feature.

6. TYPICAL RUNNING TIME

13*G seconds for a problem with 1000 mesh points and G groups on an IBM 370/168 at a source accuracy of 0.001.

7. UNUSUAL FEATURES OF THE PROGRAM

a) Three outer boundary conditions may be imposed - zero flux, zero current or constant current/flux.
b) Inner boundary conditions may be used for rod calculations.
c) Normal and adjoint eigenvalue problems, fixed source and criticality search problems are solved.
d) Scattering down from any group to any other is allowed.
e) Included is a perpturbation part for r-z geometry and a routine for calculating any reaction rates or densities.
f) Subsequent cases can be queued in one job step.
g) Automatic source interpolation within subsequent cases to reduce calculation time.
h) Time-eigenvalue calculation.
i) Calculation of dynamical neutron life time.
j) Calculation of beta-effective.
k) Included in DIXY-2 is a subroutine that prints out an input description if the program is started with only one input card, containing the character string 'DESCRIPTION', punched from card column 1 (apostrophes omitted).
l) DIXY-2 contains a plot facility.
m) Space-energy dependent fixed source problems.
n) Directionally dependent diffusion coefficients may be specified for streaming problems.

8. RELATED AND AUXILIARY PROGRAMS

This programme supersedes the former DIXY programme, which is a part of the Karlsruhe Nuclear Program system NUSYS.
An improved version of DIXY-2 has been implemented within the Karlsruhe Modular System KAPROS since 1974.

10. REFERENCES:  To be published.

11. MACHINE REQUIREMENTS

Concerning core storage requirements see point 5 of this abstract. A maximum of 2 tape drives or one disc pack is required.

13. OPERATING SYSTEM OR MONITOR UNDER WHICH PROGRAM IS EXECUTED:  Standard IBM OS.

14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS

ANY OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS

15. NAME AND ESTABLISHMENT OF AUTHOR

H. Bachmann, W. Hoebel
                                   Kernforschungszentrum Karlsruhe
                                   Germany

File name	File description	Records
NEA0184_02.001	DIXY-2 SOURCE (F4)	8058
NEA0184_02.002	DIXY-2 SAMPLE PROBLEM INPUT	166
NEA0184_02.003	DIXY-2 OVERLAY CARDS	34
NEA0184_02.004	DIXY-2 SAMPLE PROBLEM OUTPUT	2505
NEA0184_02.005	JCL	66