1. NAME AND TITLE

PUFF2: Determination of Multigroup Covariance Matrices from ENDF/B-V Uncertainty Files.

2. CONTRIBUTOR

Oak Ridge National Laboratory, Oak Ridge, Tennessee.

3. CODING LANGUAGE AND COMPUTER

Fortran IV; IBM 3033 (P00157/I3033/00), CDC CYBER 176 (P00157/C0176/00).

4. NATURE OF PROBLEM SOLVED

PUFF2 processes ENDF/B-V formatted nuclear cross section covariance data into multigroup covariance matrices calculated for an energy group structure and weighting function specified by the user. It can also calculate the covariance matrices for ratio data. Covariances can then be folded with sensitivity coefficients to obtain uncertainties in selected integral parameters such as k-effective and breeding ratio.

5. METHOD OF SOLUTION

Cross section and flux values on a "super energy grid," consisting of the union of the required energy group structure and the energy data points in the ENDF/B-V file, are interpolated from the input cross sections and fluxes. Covariance matrices are calculated for this grid and then collapsed to the required group structure.

The materials represented are:

Ni, Cr, 16O, 12C, Fe, Na, 235U, 238U, 239Pu, 240Pu, 241Pu, and 10B (present due to its correlation to 238U).

6. RESTRICTIONS OR LIMITATIONS

PUFF2 includes a limited treatment of resonance data uncertainties. Only the Breit-Wigner formalism can be dealt with, and no account is taken of self-shielding uncertainties.

PUFF2 has no energy or angular distribution covariance processing accommodations, no provision for correlation of uncertainty in weighting function with uncertainty in cross section, and a somewhat crude resolved resonance covariance processing capability.

7. TYPICAL RUNNING TIME

No study has been made by RSIC of typical running times for PUFF2.

8. COMPUTER HARDWARE REQUIREMENTS

PUFF2 is operable on the IBM 3033 (P00157/I3033/00) or the CDC CYBER 176 (P00157/C0176/00) computers.

9. COMPUTER SOFTWARE REQUIREMENTS

Fortran IV and Assembler Language compilers are required.

10. REFERENCES

J. D. Smith, III, and B. L. Broadhead, "Multigroup Covariance Matrices for Fast Reactor Studies," ORNL/TM-7389 (ENDF-305) (April 1981).

J. D. Smith, III, "Processing ENDF/B-V Uncertainty Data into Multigroup Covariance Matrices," ORNL/TM-7221 (ENDF-295) (June 1980).

11. CONTENTS OF CODE PACKAGE

Included are the referenced documents and a DS/HD 5.25-in. (1.2 MB) diskette in self-extracting compressed DOS files which contains the source code, sample problem input, and ENDF/B-V cross sections, plus output from the sample problem.

12. DATE OF ABSTRACT

April 1984, July 1994.