1. NAME AND TITLE

EXTREME: Two-Dimensional Discrete-Ordinates Code System with Exponential Expansion of Spatial Variables.

2. CONTRIBUTORS

University of Tennessee, Department of Nuclear Engineering, Knoxville, Tennessee.

Oak Ridge National Laboratory, Oak Ridge, Tennessee.

3. CODING LANGUAGE AND COMPUTER

Fortran IV; IBM 3033.

4. NATURE OF PROBLEM SOLVED.

EXTREME was designed for use in the development and testing of a new family of methods for the calculation of spatial dependence of neutron density in nuclear systems in two-dimensional Cartesian geometry. The computer code system is designed to handle an arbitrary number of spatial, energy, and angle subdivisions. Any degree of scattering anisotropy can be handled for either external source or fission systems.

5. METHOD OF SOLUTION

The basic approach is to (1) approximate the spatial variation of the neutron source across each spatial subdivision as an expansion in terms of a user-supplied set of exponential basis functions; (2) solve analytically for the resulting neutron density inside each region; and (3) approximate this density in the basis function space in order to calculate the next iteration flux-dependent source terms. In the general case the calculation is iterative due to neutron sources which depend on the neutron density itself.

6. RESTRICTIONS OR LIMITATIONS

EXTREME is designed to handle only Cartesian x-y geometry. It is required that the weights sum to one and that necessary reflection angles are present at reflection boundaries; if either of these is not met, the code will so indicate and stop.

7. TYPICAL RUNNING TIME

On the IBM 3033, the sample problem used 2 minutes and 15.29 CPU seconds.

8. COMPUTER HARDWARE REQUIREMENTS

EXTREME is operable on the IBM 3033.

9. COMPUTER SOFTWARE REQUIREMENTS

A Fortran IV compiler is required.

10. REFERENCE

R. E. Pevey, "Development of a New Two-Dimensional Cartesian Geometry Nodal Multigroup Discrete Ordinates Method," ORNL/CSD/TM-182 (July 1982).

11. CONTENTS OF CODE PACKAGE

Included are the referenced document and one (1.2MB) DOS diskette which contains the job control language used locally for execution, the source code plus sample problem input and output.

12. DATE OF ABSTRACT

December 1983.