1. NAME AND TITLE

URR: Calculates Resonance Neutron Cross-Section Probability Tables, Bondarenko Self-Shielding Factors and Self- Indication Ratios for Fissile and Fertile Nuclides.

2. CONTRIBUTOR

Oak Ridge National Laboratory, Oak Ridge, Tennessee.

3. CODING LANGUAGE AND COMPUTER

Fortran 77; VAX family.

4. NATURE OF PROBLEM SOLVED

URR was developed to calculate cross-section probability tables, Bondarenko self-shielding factors, and self-indication ratios for fertile and fissile isotopes in the unresolved resonance region.

5. METHOD OF SOLUTION

URR uses Monte Carlo techniques to select appropriate resonance parameters and to compute the cross sections at the desired reference energy. The neutron cross sections are calculated by the single-level Breit-Wigner formalism with s-, p-, and d-wave contributions. The cross-section probability tables are constructed by sampling the Doppler broadened cross-section. The various self-shielded factors are computed numerically as Lebesgue integrals over the cross-section probability tables.

6. RESTRICTIONS OR LIMITATIONS

None noted.

7. TYPICAL RUNNING TIME

URR is interactive and executes in a few seconds.

8. COMPUTER HARDWARE REQUIREMENTS

The code runs on any VAX computer.

9. COMPUTER SOFTWARE REQUIREMENTS

The code was written in Fortran 77 and was tested on the VAX 6000 under the VMS operating system.

10. REFERENCE

L. C. Leal, G. de Saussure and R. B. Perez, "URR Computer Code: A Code to Calculate Resonance Neutron Cross-Section Probability Tables, Bondarenko Self-Shielding Factors and Self-Indication Ratios for Fissile and Fertile Nuclides," ORNL/TM-11297 (August 1989).

11. CONTENTS OF CODE PACKAGE

Included are the referenced document and one (360 K) DOS diskette including the source and sample case.

12. DATE OF ABSTRACT

June 1990.