**1. NAME AND TITLE**

MIGROS3: A Code for the Generation of Group Constants for Reactor Calculations from Neutron Nuclear Data in KEDAK Format.

**2. CONTRIBUTOR**

Kernforschungszentrum, Karlsruhe, Germany.

**3. CODING LANGUAGE AND COMPUTER**

Fortran 77; IBM 3033 (P00265/I0370/00).

**4. NATURE OF PROBLEM SOLVED**

Group averaged neutron cross sections, energy resonance self shielding factors, elastic transfer elements up to P5 approximation, the inelastic, (n,2n) and (n,3n) transfer elements, fission spectra, etc., for coarse groups (26 groups in the standard case) in the fast neutron energy range are calculated.

**5. METHOD OF SOLUTION**

Microscopic group cross sections are calculated from pointwise nuclear data, from resolved Briet-Wigner resonance parameters and statistical resonance parameters. Energy resonance self shielding factors are calculated from resolved Briet-Wigner parameters, from statistical parameters and from pointwise tabulated neutron cross sections. The elastic transfer elements are based on experimental angular distributions. The inelastic transfer elements use the resolved excited levels. In the continuum's range a statistical model given by an analytic function or tabulated values are used for the calculation of transfer matrices for inelastic scattering, (n,2n), and (n,3n) reactions. The fission spectra are calculated by the Watt or the Maxwellian formula.

**6. RESTRICTIONS OR LIMITATIONS**

The evaluated neutron data used by MIGROS3 must be in KEDAK format.

**7. TYPICAL RUNNING TIME**

The sample problem took about four minutes of CPU time on the IBM 3033.

**8. COMPUTER HARDWARE REQUIREMENTS**

MIGROS3 runs on the IBM 3033.

**
9. COMPUTER SOFTWARE REQUIREMENTS**

A Fortran-IV compiler is required. In particular, the IBM Enhanced Fortran IV compiler was used.

**10. REFERENCES**

a: included in document:

I. Broeders and B. Krieg, "MIGROS-3: A Code for the Generation of Group Constants for Reactor Calculations from Nuclear Data in KEDAK Format," KFK 2388 (February 1977).

b: background information:

B. Krieg, "The KEDAK Program Compendium, Part II, KEDAK Basic Management," KFK 2387/II (February 1977).

**11. CONTENTS OF CODE PACKAGE**

Included are the referenced documents and 1 DS/HD 5.25-inch diskettes (1.44 MB) in self-extracting compressed DOS files, which contain source, JCL and test case input and output.

**12. DATE OF ABSTRACT**

September 1988.

**KEYWORDS:** NEUTRON CROSS SECTION PROCESSING; REACTOR PHYSICS;
SELF SHIELDING