1. NAME AND TITLE

TIMS-1: Processing Code System for Production of Group Constants of Heavy Resonant Nuclei.

2. CONTRIBUTORS

Japan Atomic Energy Research Institute, Tokai-mura, Japan.

OECD Nuclear Energy Agency Data Bank, Gif-sur-Yvette, France.

3. CODING LANGUAGE AND COMPUTER

Fortran IV, Assembler Language; FACOM-M200. Fortran IV; VAX.

4. NATURE OF PROBLEM SOLVED

TIMS-1 calculates the infinitely dilute group cross sections and the temperature dependent self-shielding factors for arbitrary values of sigma₀ and R where sigma₀ is the effective background cross section of potential scattering and R the ratio of the atomic number densities for two resonant nuclei, if any. TIMS-1 is specifically programmed to use the evaluated nuclear data file of ENDF/B or JENDL as input data.

5. METHOD OF SOLUTION

In the unresolved resonance region, the resonance parameters and the level spacings are generated by using Monte Carlo method from the Porter-Thomas and Wigner distributions, respectively. The temperature dependent cross sections are calculated with the Breit-Wigner single-level and multi-level formula. The Doppler broadened cross sections are calculated on the ultra-fine lethargy meshes of about 10^-3~10^-5 using the generated and resolved resonance parameters.

The effective group constants are calculated by solving the neutron slowing down equation with the use of the recurrence formula for the neutron slowing down source.

6. RESTRICTIONS OR LIMITATIONS

The maximum numbers of energy groups, temperatures, and compositions are 60, 4, and 10, respectively.

7. TYPICAL RUNNING TIME

The computation time depends considerably on the materials to be calculated and the permissible errors to be assumed for the generated cross sections in the unresolved region. On the FACOM 230/75, the computation times are about 12 minutes for the production of group constants of ²³⁸U for one temperature and 8 composition variables.

8. COMPUTER HARDWARE REQUIREMENTS

Version A is operable on the FACOM M-200 computers. A 97000 word core is needed and auxiliary disk storage is required. Version B has been tested on VAX 11/780 computers.

9. COMPUTER SOFTWARE REQUIREMENTS

The FACOM-M200 Operating System and a Fortran IV H-level compiler are required for Version A. The VAX version runs under VMS.

10. REFERENCE

H. Takano, Y. Ishiguro and Y. Matsui, "TIMS-1: A Processing Code for Production of Group Constants of Heavy Resonant Nuclei," JAERI 1267 (September 1980).

11. CONTENTS OF CODE PACKAGE

Included are the referenced document and one (1.2MB) DOS diskette which contains the source code, ENDF/B-4 library data, and sample problem input and output.

12. DATE OF ABSTRACT

April 1984, revised August 1990.