1. NAME AND TITLE

NEUPAC: Neutron Unfolding Code System for Calculating Neutron Flux Spectra from Activation Data of Dosimeter Foils.

2. CONTRIBUTOR

Japan Atomic Energy Research Institute, Ibaraki, Japan.

3. CODING LANGUAGE AND COMPUTER

Fortran IV; FACOM M-200.

4. NATURE OF PROBLEM SOLVED

As a part of the measurement and analysis plan for the Dosimetry Experiment at the "JOYO" experimental fast reactor, neutron flux spectral analysis is performed using the NEUPAC (Neutron Unfolding Code Package) code system. NEUPAC calculates the neutron flux spectra and other integral quantities from the activation data of the dosimeter foils.

5. METHOD OF SOLUTION

NEUPAC is based on the J1-type unfolding method and the estimated neutron flux spectra are obtained as its solution. The code system is able to determine the integral quantities and their sensitivities, together with an error estimate of the unfolded spectra and integral quantities. It also performs a chi-square test of the input/output data and contains many options for the calculational routines.

NEUPAC consists of three module groups of input, processing, and output. The input section assembles a linear equation based on entered data. The processing section solves the linear equation. The output section performs the output of spectrum and integral quantity, chi-square test of output data, plotter output, or error analysis (including sensitivity analysis) of integral quantity.

6. RESTRICTIONS OR LIMITATIONS

Compilation requires 512 K.

The reaction cross section data are prepared from ENDF/B-V. However, all the uncertainties on the non-threshold reaction foils are not from ENDF/B-V.

7. TYPICAL RUNNING TIME

CASE 1 (IDIG = 1 CASE 2 (IDIG = -1

In-core processing) external storage used)

Number of foils: 7 15

Number of groups: 26 620

Window function: 5 9

CPU time: 12.1 sec 3240.0

Region size: 1176 KB 3332 KB

I/O time: 2.6 sec 452.4 sec

Case 1 uses the example input data for unfolding.

8. COMPUTER HARDWARE REQUIREMENTS

NEUPAC is operable on a FACOM M-200 computer.

9. COMPUTER SOFTWARE REQUIREMENTS

A Fortran IV compiler is required.

10. REFERENCE

M. Sasaki and M. Nakazawa, "Production of Analysis Code for 'JOYO' Dosimetry Experiment. User's Manual of Neutron Unfolding Code Package," NEUPAC, PNC N941 80-192 Tr (January 1981).

11. CONTENTS OF CODE PACKAGE

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

12. DATE OF ABSTRACT

June 1982.