1. NAME AND TITLE

CACA-2: Heavy Isotope and Fission-Product Concentration Calculation Code System.

2. CONTRIBUTOR

Oak Ridge National Laboratory, Oak Ridge, Tennessee.

3. CODING LANGUAGE AND COMPUTER

FORTRAN IV; IBM 360/370.

4. NATURE OF PROBLEM SOLVED

CACA-2 calculates nuclide concentration histories, power or neutron flux histories, burnups, and fission-product birthrates for fueled experimental capsules subjected to neutron irradiations. For a particular problem, a user-specified number of fuel regions may be treated. A fuel region is described by volume, length, and specific irradiation history. The irradiation history for each fuel region can be divided into time intervals, and a constant power density or a time-dependent neutron flux is specified for each time interval. Also, an independent cross-section set may be selected for each time interval in each irradiation history.

5. METHOD OF SOLUTION

A fourth-order Runge-Kutta calculational method solves the differential equations for nuclide concentrations as a function of time.

6. RESTRICTIONS OR LIMITATIONS

The time step used in the Runge-Kutta calculational method is set equal to six hours as explained in ORNL/TM-5266 (included in this document). In extreme cases (e.g., very high input neutron cross sections or neutron fluxes), oscillations in the calculated nuclide concentrations may occur. In such cases, the time step should be decreased.

7. TYPICAL RUNNING TIME

The sample problem took 4 seconds to run on the IBM 360/91.

Typical running time on the IBM 360/91 is approximately 4 seconds for one fuel region with a 300-day irradiation history. The running time increases linearly with the number of fuel regions and with irradiation time length.

8. COMPUTER HARDWARE REQUIREMENTS

CACA-2 is operable on an IBM 360/370 with standard I-O and 92 K of storage.

9. COMPUTER SOFTWARE REQUIREMENTS

The code is operable on the IBM 360/370 Operating System using OS 360 and a FORTRAN H compiler.

10. REFERENCE

E. J. Allen, "CACA-2: Revised Version of CACA--A Heavy Isotope and Fission-Product Concentration Calculational Code for Experimental Irradiation Capsules," ORNL/TM-5266 (February 1976).

11. CONTENTS OF CODE PACKAGE

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

12. DATE OF ABSTRACT

December 1981.