**1. NAME AND TITLE**

GGTC-ENEL: Code System for Producing Few-Group Neutron Cross Sections from Multigroup Data Libraries.

**DATA LIBRARIES**

GAM: Flux Spectra and Multigroup Constant Generator.

GATHER:

THERMOS: Multigroup Integral Transport Code System.

**2. CONTRIBUTOR**

Ente Nazionale per l'Energia Elettrica, Milano, Italia, through the OECD NEA Computer Program Library, Ispra (Varese), Italy.

**3. CODING LANGUAGE AND COMPUTER**

Fortran IV; IBM 360/370 (P00128I036000).

**4. NATURE OF PROBLEM SOLVED**

GGTC-ENEL is a new formulation of the Intermediate Resonance (IR) method.

**5. METHOD OF SOLUTION**

This formulation of the IR method for heterogeneous media starts from the following assumptions: 1) the flux is assumed to be spatially flat in the absorbing and in the moderating region; 2) single term rational approximation to escape probability is used; 3) the absorbing region (lump) can contain an arbitrary number of ``internal'' (admixed) moderators; 4) the external moderating region can contain an arbitrary number of moderators; 5) interference scattering is taken into account; 6) the intermediate character of the resonance with regard to all nuclides (moderators and absorber) involved is introduced at K integral operator level; 7) the equations for evaluating IR parameters kappa, lambda, and mu are deduced rigorously by equating first and second order approximations to resonance integral and using the intermediate expressions of integral operators K; 8) to allow for a drastic reduction in computer time, accurate rational approximations in the treatment of the Doppler effect have been introduced; 9) the use of energy mean values suitably defined refines the value of resonance integral and resonance absorption cross sections.

**6. RESTRICTIONS OR LIMITATIONS**

None noted.

**7. TYPICAL RUNNING TIME**

No study has been made by RSIC of typical running times for GGTC-ENEL.

**8. COMPUTER HARDWARE REQUIREMENTS**

GGTC-ENEL is operable on the IBM 360/370 computers.

**9. COMPUTER SOFTWARE REQUIREMENTS**

A Fortran IV compiler is required.

**10. REFERENCES**

O. Chiovato, S. Corno, and F. Di Pasquantonio, "An Improved Intermediate Resonance Method for
Heterogeneous Media," *Annals of Nuclear Energy*, Vol. 4. Northern Ireland: Pergamon Press (1977)
91-106.

O. Chiovato and F. Di Pasquantonio, "A New Version of GGC Code Including an Improved Intermediate Resonance Method and a Modified THERMOS Code."

**11. CONTENTS OF CODE PACKAGE**

Included are the referenced documents and nine DS/HD 3.5-in. (1.44 MB) diskettes in self-extracting compressed DOS files, which contain the source code and sample problem input, the data libraries written in binary format, plus output from the sample problem written in list format.

**12. DATE OF ABSTRACT**

March 1984.

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