1. NAME AND TITLE

SNOW: Two-Dimensional Discrete Ordinates Multigroup Transport Code System in Plane and Cylindrical Geometry with Isotropic and Anisotropic Scattering.

2. CONTRIBUTORS

Karlsruhe Nuclear Research Center, Karlsruhe, Germany.

OECD NEA Data Bank, Gif-sur-Yvette, France.

3. CODING LANGUAGE AND COMPUTER

FORTRAN IV and Assembler Language; IBM 360/370.

4. NATURE OF PROBLEM SOLVED

SNOW was designed to solve the two-dimensional multi-group neutron transport equation by the discrete ordinates (S_N) method. Geometries included are (x,y)-plane and (r,z), (r, theta)-cylinder, isotropic and anisotropic scattering and several other special options are permitted. Three methods of convergence acceleration are incorporated.

5. METHOD OF SOLUTION

The discretization of the Boltzmann equation is effected by the diamond difference scheme of B. Carlson and K. Lathrop and the numerical integration of the angle-dependent fluxes by means of B. Carlson and C. E. Lee's procedure. In view of the large dimensions of the matrices the introduction of effective convergence accelerations was essential for the external and internal iterations. In addition to the rebalancing and Tschebyscheff accelerations a further option was incorporated which, without great additional effort, enabled the calculation of the problem to be carried out with different step widths and different S_N orders and also with a favorable combination of step widths produced an approximately 50% saving of computer time (rough lattice technique). Depending on the required results, the user can feed in a ``flux-oriented'' accuracy interrogation or one based on the eigenvalue k_eff. The following further options are available: calculation of inhomogeneous problems (foreign source), use of bucklings, anisotropy, adjoint calculation, various boundary conditions.

6. RESTRICTIONS OR LIMITATIONS

None noted.

7. TYPICAL RUNNING TIME

No typical running time has been established.

8. COMPUTER HARDWARE REQUIREMENTS

The code system was designed to run on the IBM 360/370 computers.

9. COMPUTER SOFTWARE REQUIREMENTS

The code packaged is operable on the IBM 360/370 computers.

10. REFERENCE

G. Gunther and W. Kinnebrock, "SNOW: A Two-Dimensional SN Program for Solving the Neutron-Transport Equation in Rectangular and Cylindrical Geometry," EURFNR-1130 (KFK 1826) (July 1973).

11. CONTENTS OF CODE PACKAGE

Included are the referenced document and one (1.2MB) DOS diskette which contains the source codes and sample problem input and output.

12. DATE OF ABSTRACT

December 1981.