1. NAME AND TITLE

ALPHA-M: Least-Squares Resolution of Gamma-Ray Spectra in Environmental Samples.

2. CONTRIBUTOR

Tennessee Valley Authority, Muscle Shoals, Alabama.

3. CODING LANGUAGE AND COMPUTER

Fortran IV; IBM 360/370.

4. NATURE OF PROBLEM SOLVED

ALPHA-M is a standard least-squares computer program for analyzing gamma-ray spectral data obtained with NaI(Tl) scintillation detectors. This version of ALPHA-M has been prepared and tested to determine its capabilities and limitations for environmental monitoring. Either GEN4 or GENSTD is used to create standard libraries for ALPHA-M, and SIMSPEC is used to simulate spectra for ALPHA-M analysis.

5. METHOD OF SOLUTION

ALPHA-M determines the activities of radioisotopes by a weighted least-squares resolution of their gamma-ray spectra. The application of the least-squares method to gamma spectral data yields superior quantitative results as compared with any other commonly used technique:

1. Rapid data processing is possible.

2. Spectra with large statistical variations in counting can be handled.

3. The total spectrum, rather than just the photopeak regions, is used.

4. Spectra with superimposed peaks can be analyzed.

5. The standard error of the nuclide activity can be estimated.

6. RESTRICTIONS OR LIMITATIONS

Many gamma-ray emitting radionuclides can be quantified at activity levels of about 10 pico-Curies per liter or less, depending on counting time, at a confidence level of 95 percent.

7. TYPICAL RUNNING TIME

The sample problem input is a set of 3.5 liter water standards including 16 individual standard spectra for each of four 4" by 4" solid NaI crystals. The nuclide spectra are background stripped and the average background is an average of ten 4000-second backgrounds. The unit 5 input consists of a typical 3.5 liter water background spectrum and the spectrum from a 3.5 liter water cross-check from EPA. This problem took 7.73 cpu seconds on the IBM 370/3033.

8. COMPUTER HARDWARE REQUIREMENTS

On the IBM 370/3033 the sample problem required 196 K in the GO step.

9. COMPUTER SOFTWARE REQUIREMENTS

A Fortran IV compiler and an Assembler language compiler are required.

10. REFERENCE

L. G. Kanipe, S. K. Seale, and W. S. Ligget, "Least-Squares Resolution of Gamma-Ray Spectra in Environmental Samples," TVA/EP-78/02, EPA-600/7-77-089 (August 1977).

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

January 1982.