1. NAME AND TITLE

COMNUC3B: A Compound Nucleus Analysis Program

2. CONTRIBUTORS

Los Alamos National Laboratory, Los Alamos, New Mexico. Atomics International, North American Rockwell.

3. CODING LANGUAGE AND COMPUTER

Fortran IV; Cray XMP.

4. NATURE OF PROBLEM SOLVED

COMNUC3B was written to analyze compound nucleus interactions. Only reactions for which the incident particle is a neutron are considered.

5. METHOD OF SOLUTION

When the outgoing particle is a neutron, two types of reactions are considered. The first occurs when the target is left in a well-defined excited state. The other occurs when the target nucleus is left in one of many excited levels. These reaction types are known as individual channel inelastic and continuum inelastic respectively. The individual channel model is described by the known levels of the target nucleus. The continuum inelastic neutron calculation requires a model for the nuclear level density and a set of spin, parity, and energy dependent transmission coefficients. These two functions are convoluted for energies greater than the last identified target level. As with emerging neutrons, the fission component is separated into two parts: a part due to discrete channels and a part due to fission through a continuum of states.

6. RESTRICTIONS OR LIMITATIONS

The maximum number of levels for the individual channel model which can be specified is twenty.

7. TYPICAL RUNNING TIME

The code was tested on a Cray XMP under the CTSS operating system. The sample problem took 9 seconds of CPU time.

8. COMPUTER HARDWARE REQUIREMENTS

The code will run on the Cray computers.

9. COMPUTER SOFTWARE REQUIREMENTS

The code is written in Fortran IV. On the Cray, the compiler used was CFT under the CTSS operating system.

10. REFERENCES

a. Included in the package:

C. L. Dunford. Compound Nucleus Reaction Analysis Programs COMNUC and CASCADE, TI-707-130-013, Atomics International, January 19, 1971.

``Input Description for FTNCOMNUC ,'' Los Alamos Informal Notes, October 1980.

``Card Input for COMNUC8D,'' Los Alamos Informal Notes, October 1980.

11. CONTENTS OF CODE PACKAGE

Included are the referenced document and one DS/HD 5.25-inch diskette (1.2 MB), containing the source code, sample input and output.

12. DATE OF ABSTRACT

February 1991.