1. NAME AND TITLE

PUFF: Determination of Multigroup Covariance Matrices from ENDF/B Uncertainty Files.

2. CONTRIBUTORS

Oak Ridge National Laboratory, Oak Ridge, Tennessee (P00093/I0360/00).

Los Alamos National Laboratory, Los Alamos, New Mexico (P00093/C7600/00).

3. CODING LANGUAGE AND COMPUTER

FORTRAN IV; IBM 360/370 (P00093I036000) or CDC-7600 (P00093C760000).

4. NATURE OF PROBLEM SOLVED

PUFF Processes evaluated and correlated energy-dependent uncertainty information into a multigroup covariance matrix formulation. These covariance matrices permit systematic sensitivity investigations to determine, in a credible fashion, which cross-section measurements, evaluation, or processing methods most need further refinement. The types of covariance representations permitted are those adopted for ENDF/B-IV.

5. METHOD OF SOLUTION

Sensitivity analysis is applied to the study of an air transport benchmark calculation to qualify and distinguish between cross-section and method uncertainties. The boundary detector response is converged with respect to spatial and angular mesh size, P1 expansion of the scattering kernel, and the number and location of energy grid boundaries.

For the ENDF/B-IV pointwise covariance descriptions, the multigroup covariance matrices are reduced to combinations of single integrals involving group fuxes and cross sections which can be calculated easily.

6. RESTRICTIONS OR LIMITATIONS

PUFF is variably dimensioned; the prime constraint is, therefore, on the amount of computer memory available. The input required is a BCD ENDF/B tape containing error file data for the material of interest.

7. TYPICAL RUNNING TIME

The running time is problem-dependent. A 22-group nitrogen run, including cross section processing on all reactions (and covariance between reactions), required less than 5 minutes on an IBM 360/91 computer. A similar run for oxygen took less than three minutes of actual CPU time.

8. COMPUTER HARDWARE REQUIREMENTS

PUFF is operable on the IBM 360/370 or the CDC 7600 computers. 400K bytes of storage and approximately 2000 tracks of direct access disk space are required.

9. COMPUTER SOFTWARE REQUIREMENTS

A FORTRAN H compiler is required.

10. REFERENCES

D. Muir, "Notes on LASL (CDC) Version of PUFF," (February 1976).

C. R. Weisbin, E. M. Oblow, J. Ching, J. E. White, R. Q. Wright, and J. Drischler, "Cross Section and Method Uncertainties: The Application of Sensitivity Analysis to Study their Relationship in Radiation Transport Benchmark Problems," ORNL-TM-4847 (August 1975).

11. CONTENTS OF CODE PACKAGE

Included are the referenced document and one DS/HD 5.25" diskette (1.2MB) which contains the source code and sample problem input written in BCD/EBCDIC card images, plus output from the sample problem.

12. DATE OF ABSTRACT

March 1984, updated December 1991.