1. NAME AND TITLE

NAC: Neutron Activation Analysis and Product Isotope Inventory Code System.

DATA LIBRARY

NDL: NAC Data Library.

NAC is a subset of NAP (CCC-101).

2. CONTRIBUTOR

National Aeronautics and Space Administration, Lewis Research Center, Cleveland, Ohio.

Babcock and Wilcox, Lynchburg, Virginia.

Ebasco Services Incorporated, New York, New York.

3. CODING LANGUAGE AND COMPUTER

FORTRAN IV; IBM (A) or CDC (B); IBM PC, FORTRAN 77 (C).

4. NATURE OF PROBLEM SOLVED

NAC was designed to predict the neutron-induced gamma-ray radioactivity for a wide variety of composite materials. The NAC output includes the input data, a list of all reactions for each constituent element, and the end-of-irradiation disintegration rates for each reaction. NAC also compiles a product isotope inventory containing the isotope name, the disintegration rate, the gamma-ray source strength, and the absorbed dose rate at 1 meter from an unshielded point source. The induced activity is calculated as a function of irradiation and decay times; the effect of cyclic irradiation can also be calculated.

5. METHOD OF SOLUTION

The standard neutron activation and decay equations are programmed.

A data library is supplied which contains target element names, atomic densities, reaction indices, individual reactions and reaction parameters, and product isotopes and gamma energy yields.

6. RESTRICTIONS OR LIMITATIONS

Each composite material may consist of up to 20 different elements and up to 20 different decay times may be included. Both limits may be increased by the user by increasing the appropriate items in the DIMENSION statement.

7. TYPICAL RUNNING TIME

Execution time for 3 sample problems (a: 9 elements, 4 decay times; b: 6 elements, 1 decay time; c: 6 elements, 1 decay time) was 0.62 CPU seconds on the IBM 3033.

Execution time for the same sample problems on an IBM PC/XT with a math co-processor took about 45 seconds.

8. COMPUTER HARDWARE REQUIREMENTS

The code was originally designed to run on the IBM 7094 with standard I-O equipment and it was converted to be operable on the IBM 360/75/91, the IBM 3033 and also on the CDC 7600. The new PC version will run on most PC's with or without a math co-processor.

9. COMPUTER SOFTWARE REQUIREMENTS

The packaged codes are operable on the IBM OS/VS2 operating system using the VS Fortran compiler with the language level 66 option and on the CDC 7600 FORTRAN IV systems.

For the PC Version, MICROSOFT FORTRAN Version 4.01 was used for compilation and linking under DOS 3.3 operating system.

10. REFERENCE

"README.ASC," informal notes (3 pages) (1990).

S. T. Weinstein, "NAC: Neutron Activation Code," NASA TM X-52460 (1968).

J. T. West, "Informal Notes" (November 1973).

11. CONTENTS OF CODE PACKAGE

Included are the referenced document and one (1.2MB) DOS diskette which contains the source code, data library, and sample problem, plus output from the sample problem.

12. DATE OF ABSTRACT

June 1972; revised December 1984, March 1988, October 1990.