1. NAME AND TITLE

GLUCS: A Generalized Least-Squares Code System for Updating Cross Section Evaluations with Correlated Data Sets.

AUXILIARY PROGRAMS:

INPUT: Reads evaluated nuclear data files, selects appropriate material and puts it into a form that GLUCS can read.

OUTPUT: Writes output data from GLUCS and INPUT programs in ENDF/B-V format to PDP-10 disk files.

2. CONTRIBUTOR

Oak Ridge National Laboratory, Oak Ridge, Tennessee.

3. CODING LANGUAGE AND COMPUTER

Fortran IV; PDP-10 or VAX.

4. NATURE OF PROBLEM SOLVED

GLUCS is a generalized least-squares code system for updating cross section evaluations with correlated data sets. Simultaneous evaluation of cross sections is required where ratio data exist. Since ratio measurements do not require absolute neutron flux determination, which is usually the largest source of uncertainties, correct use of ratio data could establish the relative magnitudes of various cross sections quite well. High-precision absolute data for one reaction would improve the absolute magnitudes of all other cross sections connected by high-precision ratios. The idea is to combine the new set of measurements with the evaluation, which is assumed to represent older data.

5. METHOD OF SOLUTION

This code system includes the PDP-10 Fortran IV computer programs INPUT.F4, GLUCS.F4 and OUTPUT.F4, which employ generalized least-squares for simultaneous evaluation of reaction cross sections. Evaluations of cross sections and covariances are used as input for incorporating correlated data sets, particularly ratios. These data are read from Evaluated Nuclear Data File (ENDF/B-V) formatted files. Measured data sets, including ratios and absolute and relative cross section data, are read and combined with the input evaluations via the least-squares technique. The resulting output evaluations have not only updated cross sections and covariances, but also cross-reaction covariances. These output data are written into ENDF/B-V format.

6. RESTRICTIONS OR LIMITATIONS

The code is general in that it is capable of handling large numbers of correlated evaluations, a variety of data types that may be correlated, and the most commonly used ENDF/B-V covariance formats and interpolation laws. However, the user should make note of the following restrictions:

a) the new data cannot be correlated to the old evaluation,

b) there are specific classes of ratio data allowed,

c) no significant energy uncertainty is allowed,

d) there are no energy resolution problems,

e) specific ENDF/B-V interpolation laws are used,

f) only "NI-type" sub-subsections in file 33 of the ENDF/B-V data can be used to compute the covariance matrix; "NC-type" sub-subsections are not allowed implying that NC in file 33 must be equal to 0.

7. TYPICAL RUNNING TIME

Each sample problem involves three runs and required the following running times (in min:sec cpu) on the ORELA PDP-10:

Problem #1 Problem #2

INPUT 0:27 cpu 1:30 cpu

GLUCS 0:18 1:41

OUTPUT 0:12 0:33

8. COMPUTER HARDWARE REQUIREMENTS

GLUCS runs on the DEC PDP-10 and, with minor modifications, has been successfully implemented on the CDC 7600 computer at Los Alamos Scientific Laboratory and on VAX computers running VMS.

9. COMPUTER SOFTWARE REQUIREMENTS

A Fortran IV compiler is required.

10. REFERENCES

a. Included in the documentation:

D. M. Hetrick, C. Y. Fu, "GLUCS: A Generalized Least-Squares Program for Updating Cross Section Evaluations with Correlated Data Sets," ORNL/TM-7341, ENDF-303, (1980).

b. Background information:

J. B. Dragt, J. W. M. Dekker, H. Gruppelaar, and A. J. Janssen, "Methods of Adjustment and Error Evaluation of Neutron Capture Cross Sections; Application to Fission Product Nuclides," Nucl. Sci. & Eng., Vol. 62 (1977) p. 117.

F. G. Perey, "Spectrum Unfolding by the Least-Squares Method," Proceedings IAEA Technical Committee Meeting on Current Status of Neutron Spectrum Unfolding, Oak Ridge, Tennessee (October 1977).

R. Kinsey, "Data Formats and Procedures for the Evaluated Nuclear Data File," ENDF, BNL-NCS-50496 (ENDF-102) 2nd Edition (ENDF/B-V) (1979).

11. CONTENTS OF CODE PACKAGE

Included are the referenced document (10.a) and one (1.2MB) DOS diskette which contains the source code and sample problem input and output.

12. DATE OF ABSTRACT

August, 1982; revised October 1983; approved August 1984, revised December 1988.