1. NAME AND TITLE

LSL-M2: Least-Squares Logarithmic Adjustment of Neutron Spectra.

AUXILIARY ROUTINES

ACT: Converts from dosimeter activities to reaction rates.

CALACT: Determines calculated reaction rates from fluences and cross sections.

FLXPRO: Converts fluences, cross sections, and covariances from one group structure to another.

DATA LIBRARIES

CROSS.XSO: Dosimetry cross section file obtained from IRDF-85 as distributed with the REAL84 exercise.

DAMAGE.XSO: Contains dpa cross sections as given in ASTM Standard E693-79.

SPV.XSO: Based on the determination of fluence covariances in the ORR-PSV experiment.

LSLNUC.DAT: Obtained from the Nuclear Data Guide.

2. CONTRIBUTOR

Oak Ridge National Laboratory, Oak Ridge, Tennessee.

3. CODING LANGUAGE AND COMPUTER

Fortran 77; IBM PC or IBM PC-AT(A), VAX family (B).

4. NATURE OF PROBLEM SOLVED

LSL-M2 adjusts calculated neutron spectra to make the fluence values consistent with given neutron dosimetry measurements. The primary output is a set of values for the best estimates of damage parameter values; the solution is based on a least squares fit of all input data.

Several input spectra, possibly from different irradiations, can be processed simultaneously.

5. METHOD OF SOLUTION

In an adjustment procedure, consistency is achieved by adjusting the input data in such a manner that a weighted sum of squares of adjustments is minimized. The weights are assigned according to the input uncertainties, i.e., the larger the uncertainty, the smaller the weight. This sum, which is further modified by correlations, represents the negative logarithm of the probability of the outcome of the experiment if the adjusted values are the ``true'' data.

6. RESTRICTIONS OR LIMITATIONS

The results of the adjustment are valid only if the size of the adjustment does not exceed the input uncertainties. The user should also guard against adjustments that exceed the limitations given by the linearization of the problem.

The number of spectra times the number of energy groups may not exceed 400. The number of dosimetry measurements must not exceed 100.

7. TYPICAL RUNNING TIME

To compile and link source codes and execute 8 sample problems on an IBM PC required about 2 hours. Compiling LSL-M2 required more that 30 minutes. The AT is, of course, much faster.

On the VAX 6000, compilation and linking take only a few seconds. Each sample case takes very few seconds to execute.

8. COMPUTER HARDWARE REQUIREMENTS

LSL-M2 is operable on an IBM PC-AT or IBM PC with fixed disk, an 8087 math coprocessor and 640 K memory. It also runs on the VAX family of computers.

9. COMPUTER SOFTWARE REQUIREMENTS

IBM Personal Computer Professional Fortran, Version 1.0, is required. The VAX version runs under the VMS operating system, using the VAX Fortran compiler. The code was run at RSIC under PC DOS 3.1. The VAX version was tested on a VAX 6000.

10. REFERENCES

a. Included in documentation:

F. W. Stallmann, "LSL-M2: A Computer Program for Least-Squares Logarithmic Adjustment of Neutron Spectra," NUREG/CR-4349, ORNL/TM-9933 (March 1985).

J. L. Bartley, "Comments on Packaging PSR-233Micro/LSL-M2," Informal Notes (September 1986).

b. Background information:

D. E. Cullen and P. K. McLaughlin, "The International Reactor Dosimetry File (IRDF-85)," (April 1985).

W. L. Zijp, E. M. Zsolnay, and D E. Cullen, "Information sheet for the REAL84 exercise," Report INDC(NDS)-166 (March 1, 1985).

E. J. Szondi and H. J. Nolthenius, "Additional data and information for the REAL84 exercise," Report INDC(NDS)-167 (March 11, 1985).

R. E. Maerker, J. J. Wagschal, and B. L. Broadhead, "Development and Demonstration of an Advanced Methodology for LWR Dosimetry Applications," EPRI-NP-2188 (1981).

W. L. Zijp and J. H. Baard, "Nuclear Data Guide for Reactor Neutron Metrology, Part 1 and Part 2," ECN70/71 (1979).

11. CONTENTS OF CODE PACKAGE

Included are the referenced documents (10.a) and two (1.2MB) DOS diskettes for the IBM PC-AT version which contain the source codes, executable programs, and data files written in ASCII mode. For the IBM PC version, two (360 K) DOS diskettes are included (no executable programs provided). The VAX version is on one (1.2MB) DOS diskette.

12. DATE OF ABSTRACT

February 1991.