1. NAME AND TITLE

SPUNIT: Spectrum Unfolding Using Information Theory.

2. CONTRIBUTOR

Battelle Pacific Northwest Laboratory, Richland, Washington.

3. CODING LANGUAGE AND COMPUTER

Fortran IV; PDP-11 and VAX 8600.

4. NATURE OF PROBLEM SOLVED

SPUNIT unfolds the measurements made by a multisphere (Bonner sphere) neutron spectrometry system. Using count rates from each detector/moderator configuration and previously determined response function values, SPUNIT calculates the neutron energy distribution, dose rate, and dose equivalent rate for the measured radiation field.

5. METHOD OF SOLUTION

SPUNIT uses an iterative algorithm based on the principles of mathematical statistics and information theory (Doroshenko et al.) The code uses the Sanna response functions in the iterative unfolding technique.

6. RESTRICTIONS OR LIMITATIONS

Improper selection of the starting spectrum can influence the speed of convergence and, in some cases, the calculated spectrum.

7. TYPICAL RUNNING TIME

On the VAX 8600 the sample case required only a few seconds.

8. COMPUTER HARDWARE REQUIREMENTS

SPUNIT was developed on a PDP-11/24 minicomputer and, with minor modifications, was adapted to run on the VAX 8600.

9. COMPUTER SOFTWARE REQUIREMENTS

A Fortran IV compiler under RSX-11M was used for the PDP-11 version. The VAX version was compiled using the Fortran 77 compiler under the VMS 4.7 operating system.

10. REFERENCES

a. Included in documentation:

L. W. Brackenbush, and R. I. Scherpelz, "SPUNIT, A Computer Code For the Multisphere Unfolding," Pacific Northwest Laboratories Informal Documentation (1984).

"Instructions for Running SPUNIT," Pacific Northwest Laboratories Informal Notes (1984).

b. Background information:

J. J. Doroshenko, S. N. Kraitor, T. V. Kuznetsova, K. K. Kushnereva, and E. S. Lenov, "New Methods for Measuring Neutron Energy Spectra with Energy from 0.4 MeV to 10 MeV by Track and Activation Detectors," Nuclear Technology 33; 296-304 (1977).

11. CONTENTS OF CODE PACKAGE

Included are the referenced documents and one DS/HD diskette which contains the PDP-11 and VAX source codes, instructions, and sample output from an interactive run.

12. DATE OF ABSTRACT

August 1988.