NESC0482 COMNUC/CASCADE

1. NAME OR DESIGNATION OF PROGRAM:  COMNUC/CASCADE

3. DESCRIPTION OF PROBLEM OR FUNCTION

COMNUC   calculates   neutron
reaction cross sections using a statistical model for decay of the
compound nucleus.  Competing reaction types permitted are elastic,
discrete  and continuum  inelastic, gamma  ray emission,  capture,
fission, and n,2n.
   CASCADE solves the  intranuclear gamma ray cascade  equation to
determine  secondary particle  emission probabilities.   Competing
processes considered are gamma ray  emission, neutron emission and
fission.

4. METHOD OF SOLUTION

In COMNUC Hauser-Feshbach  theory as modified
by Moldauer is  used to determine competition in the  decay of the
compound nucleus.  Physical models for  the various reaction types
permit  the user  to input  parameters for  those models.   Direct
reaction components  may be provided  by card input.   These cross
sections  are  combined  with calculated  compound  nucleus  cross
sections  to provide  a complete  self-consistent  set of  neutron
cross sections at each incident neutron energy.
   In CASCADE a coupled set of inhomogeneous Volterra equations of
the  second   kind  describing  the   energy  dependence   of  the
probability for  particle termination  of a  gamma ray  cascade is
solved  numerically.   Branching  ratios   determined  from  these
probabilities may be used as input to the COMNUC program.

5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

   COMNUC - Only reaction types listed  above may be analyzed, but
other reactions such as n,p and n,alpha may be included easily.
   CASCADE - Only  dipole radiation is permitted in  the gamma ray
cascades.  No  discrete channels  are permitted  - only  continuum
particle emission.

6. TYPICAL RUNNING TIME

For low incident-neutron energies and few open channels COMNUC running time is about 15 seconds per case on an IBM360/65. Cases of the complexity of the sample cases can take as much as 1.5 minutes. Approximately 15 minutes are required on an IBM360/65 for a CASCADE case exercising all options and incident neutrons up to 5 MeV in energy.

NEA-DB executed the test cases included in this package on a VAX-11/780 computer. The COMNUC test problem (U-238 and Pu-239) required 24 seconds; the CASCADE test problem (U-238) required 187 seconds of CPU time.

7. UNUSUAL FEATURES OF THE PROGRAM:

8. RELATED AND AUXILIARY PROGRAMS

CASCADE   generates   gamma   ray
cascade branching ratios for input to COMNUC.  Output from CASCADE
can be used  as input for COMNUC when  calculating neutron capture
cross sections.

10. REFERENCES:

- C.  L.  Dunford:  A Unified  Model  for  Analysis  of Compound
  Nucleus Reactions
  AI-AEC-12931, July 1970.
- C.  L. Dunford:  Compound  Nucleus Reaction  Analysis Programs
  COMNUC and CASCADE
  AI-TI-707-130-013, March 1971.

11. MACHINE REQUIREMENTS:  150K bytes

On VAX-11/780, the execution of the test problems required a peak working set size of 750 pages.

13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED:   OS/360.

VMS V4.4 (VAX-11/780).

14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS:

15. NAME AND ESTABLISHMENT OF AUTHOR

   Author        C. L. Dunford
   Contact       Alex Nickols, Code Coordinator
                 Atomics International
                 P. O. Box 309
                 Canoga Park, California  91304

File name	File description	Records
NESC0482_02.001	Information File	82
NESC0482_02.002	COMNUC Source Program (FORTRAN)	2245
NESC0482_02.003	COMNUC Sample Problem Input (U-238, Pu-239)	219
NESC0482_02.004	COMNUC Sample Problem Punched Output	6
NESC0482_02.005	COMNUC Sample Problem Printed Output	662
NESC0482_02.006	CASCADE Source Program (FORTRAN)	1111
NESC0482_02.007	CASCADE Sample Problem Input (U-238)	29
NESC0482_02.008	CASCADE Sample Problem Punched Output	59
NESC0482_02.009	CASCADE Sample Problem Printed Output	389