1. NAME AND TITLE
NAC: Neutron Activation Analysis and Product Isotope Inventory Code System.
NDL: NAC Data Library.
NAC is a subset of NAP (CCC-101).
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
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.
"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.
KEYWORDS: ACTIVATION; ISOTOPE INVENTORY; MICROCOMPUTER.