**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 sigma_{0} and R where sigma_{0} 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 ^{238}U 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.

**KEYWORDS: ** MONTE CARLO; MULTIGROUP CROSS SECTION PROCESSING; NEUTRON CROSS SECTION PROCESSING