CCC-0195 TWOTRAN-GG-FC.

1. NAME OR DESIGNATION OF PROGRAM:  TWOTRAN-GG-FC. TWOTRAN-GG-VW.

3. DESCRIPTION OF PROBLEM OR FUNCTION

TWOTRAN is designed to solve the multigroup discrete ordinates approximation to the two- dimensional Boltzmann equation for particle transport problems in x-y, r-z and r-theta geometries. Three special versions allow for new methods by using the major parts of TWOTRAN. Both direct and adjoint, homogeneous (keff or parametric eigenvalue searches) or inhomogeneous time-independent problems are solved subject to vacuum, reflective, white, periodic, or input specification of boundary flux conditions. Both anisotropic inhomogeneous problems and general anisotropic scattering problems are treated. Arbitrary numbers of groups of up- or down-scattering are allowed.

4. METHOD OF SOLUTION

The LASL general-geometry TWOTRAN is the basic  two-dimensional transport code designed for ease in alteration for use in conjunction with three special versions employing new methods:

TWOTRAN-GG-FC computes the analytic flux due to a point source on the axis of a finite cylinder and automatically uses this flux to compute the first collision source of particles for further transport.

TWOTRAN-GG-VW uses a variable weight diamond different scheme for calculating spatial derivatives.

TWOTRAN-PNVW is a variable weighted version which solves optionally the discrete ordinate equations which have been converted to spherical harmonics equations to eliminate ray effects. This version is more fully described under abstract NESC0573.

All versions operate from TWOTRAN and offer the options available in it for three two-dimensiona geometries.

Energy dependence is treated by the multigroup approximation and the angular dependence by a discrete ordinates approximation. Space  dependence is approximated by the diamond difference scheme with a set-to-zero negative flux control. Anisotropic scattering and aniso- tropic inhomogeneous sources are represented by finite spherical harmonics expansions. Within-group iterations, upscattering iterations, keff iterations, and eigenvalue search iterations are accelerated by a coarse-mesh particle rebalancing algorithm.

5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

The variable dimensioning capability of FORTRAN-IV is used so that any combination of problem parameters leading to a blank common vector length less than MAXLEN can be used. MAXLEN is slightly greater than 15000 words for the CDC 7600. With a few exceptions, only within- group problem data are stored in fast memory, data for all other groups are stored in auxiliary bulk memory such as extended core storage, but can easily be increased by the user.

6. TYPICAL RUNNING TIME

TWOTRAN-GG-FC uncollided flux test problem with one group, S4 with a 30 x 30 mesh ran in 3.5 to 2 minutes on CDC 6600.
TWOTRAN-GG-VW test problem with two groups, S6 with a 10 x 10 mesh ran in 1.9 to 1 minutes on CDC 6600.

7. UNUSUAL FEATURES OF THE PROGRAM

Unusual features include coarse- mesh convergence acceleration; coarse-mesh spatial and angular organization to permit larger problems; general anisotropic scattering and inhomogeneous source option; input specification of top, bottom, or right boundary fluxes; built-in discrete-ordinates constants (S2, S4,...S18); diamond difference scheme with negative flux fixup; detailed edit provision; pointwise cross-section density variation option; overlay program organization; general dump and restart options; and FIDO cross-section input option.

8. RELATED AND AUXILIARY PROGRAMS:  TWOTRAN-GG, TWOTRAN-PNVW.

10. REFERENCES

- R. Douglas O'Dell and Raymond E. Alcouffe:
  Transport Calculations for Nuclear Analyses: Theory and
  Guidelines for Effective Use of Transport Codes
  LA-10983-MS and UC-32 (September 1987)

- K. D. Lathrop, F. W. Brinkley, and P. Rood:
Theory and Use of the Spherical Harmonics, First Collision Source
and Variable Weight Versions of the TWOTRAN Transport Program
LA-4600 (March 1972)
- K. D. Lathrop and F. W. Brinkley:
Theory and Use of the General-Geometry TWOTRAN Program
LA-4432 (May 1970)
- K.D. Lathrop:
TWOTRAN, A Fortran Program for Two-Dimensional Transport
GA-8747 (July 22, 1968)
- D.W.G. Harris:
The Two-Dimensional General Geometry Transport Code Twotran
a Users Guide to the Winfrith Fortran IV Version for use on the IBM 370 computer
AEEW-R 841 (June 1973)
- K.D. Lathrop:
User's Guide for the TWOTRAN (x,y) Program
LA-4058, UC-32, Mathematics and Computers TID-4500 (Dec. 1968)
- K. D. Lathrop, F. W. Brinkley, and P. Rood:
Theory and Use of the Spherical Harmonics, First Collision Source
and Variable Weight Versions of the TWOTRAN Transport Program
LA-4600 (March 1972)
- K. D. Lathrop and F. W. Brinkley:
Theory and Use of the General-Geometry TWOTRAN Program
LA-4432 (May 1970)
- K.D. Lathrop:
TWOTRAN, A Fortran Program for Two-Dimensional Transport
GA-8747 (July 22, 1968)
- D.W.G. Harris:
The Two-Dimensional General Geometry Transport Code Twotran
a Users Guide to the Winfrith Fortran IV Version for use on the IBM 370 computer
AEEW-R 841 (June 1973)
- K.D. Lathrop:
User's Guide for  the TWOTRAN (x,y) Program
LA-4058, UC-32, Mathematics and Computers TID-4500 (Dec. 1968)

11. MACHINE REQUIREMENTS

Five output units (disk, drums or tapes) in addition to two system input-output units. A CDC extended core storage unit or a large bulk memory is also required. (Disk, drums or tapes can be substituted for this requirement.)

13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED:  SCOPE 2.1.

14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS:

15. NAME AND ESTABLISHMENT OF AUTHOR

K.D. Lathrop, F.W. Brinkley
Los Alamos Scientific Laboratory
P.O. Box 1663
Los Alamos, New Mexico 87544, U.S.A.

File name	File description	Records
CCC0195_01.001	INFORMATION	8
CCC0195_01.002	TWOTRAN-GG-FC SOURCE - FORTRAN EBCDIC	6628
CCC0195_01.003	SAMPLE PROBLEM INPUT	48
CCC0195_01.004	SAMPLE PROBLEM OUTPUT	784

File name	File description	Records
CCC0195_03.001	INFORMATION	8
CCC0195_03.002	TWOTRAN-GG-VW SOURCE - FORTRAN EBCDIC	5923
CCC0195_03.003	SAMPLE PROBLEM DATA	48
CCC0195_03.004	SAMPLE PROBLEM OUTPUT	1255