1. NAME AND TITLE

CYGNUS-C SPHERE: Monte Carlo Neutron Transport Code System in Spherical Geometry.

2. CONTRIBUTOR

Department of Engineering, Kyoto University, Japan.

3. CODING LANGUAGE AND COMPUTER

FORTRAN IV; IBM 360/370.

4. NATURE OF PROBLEM SOLVED

CYGNUS-C SPHERE uses the Monte Carlo method for calculating the neutron energy-angular distribution in an homogeneous sphere at the center of which there is a volume neutron source. The monoenergetic or energy-distributed neutrons are assumed to be uniformly distributed in the source and to be isotropically emitted from the source.

5. METHOD OF SOLUTION

CYGNUS-C SPHERE solves neutron transport problems in a spherical medium by the collision density Monte Carlo method. the Coveyou technique was adopted for selecting neutron elastic scattering angles.

6. RESTRICTIONS OR LIMITATIONS

The thermal neutron cannot be treated with this code system. The energy range to be calculated is equal to that of the cross section data. The energy mesh points of the cross section data are within 410 points. This code is presently limited to 5 elements in one medium.

7. TYPICAL RUNNING TIME

About 12 minutes are required in 20,000 histories for a graphite of 80-cm radius and the energy cutoff of 500 keV.

8. COMPUTER HARDWARE REQUIREMENTS

CYGNUS-C SPHERE is operable on the IBM 360/370 computers. It uses 52 K of storage.

9. COMPUTER SOFTWARE REQUIREMENTS

A FORTRAN IV compiler is required.

10. REFERENCES

H. Hirayama and T. Nakamura, "Monte Carlo Calculation of Neutrons Transmitted through Matter," Memoirs of the Faculty of Engineering, Kyoto University, Vol. XXXIV, Part 2, 187-204 (April 1972).

T. Nakamura, H. Hirayama, S. Nishino and T. Hyodo, "Spacial Distribution of Photoneutrons in an Iron Slab Produced by 20-MeV Electron Bombardment," Memoirs of the Faculty of Engineering, Kyoto University, Vol. XXXVI, Part 1, 60-69 (January 1974).

E. J. McGrath and D. C. Irving, "Techniques for Efficient Monte Carlo Simulation: Vol IIRandom Number Generation for Selected Probability DistributionsAppendix B, MIRANA Machine Independent Package for Generating Uniform Random Numbers," ORNL-RSIC-38, Vol II (SAI-72-590-LJ) (April 1975).

11. CONTENTS OF CODE PACKAGE

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

12. DATE OF ABSTRACT

July 1975; revised October 1982.