**1. NAME AND TITLE**

RMET21: Detailed Space and Energy Treatment of Neutron Resonances for Homoge neous Mixtures and Cylinderized Reactor Cells.

**AUXILIARY CODES**

TRBI: Binary Doppler tables construction from formatted tables, for Doppler broadening of generated resonance cross sections.

PROCES: Calculation of resonance capture distribution per resonance atom across a fuel rod, and fraction of total capture within a radius r versus r.

CONVER: Format conversion of RMET21 resonance integrals output for lambda factor calculations.

**2. CONTRIBUTOR**

National Commission of Atomic Energy, Rio Negro, Argentina.

**3. CODING LANGUAGE AND COMPUTER**

FORTRAN IV and FORTRAN 77; VAX family.

**4. NATURE OF PROBLEM SOLVED**

RMET21 is a lattice cell program which calculates different parameters associated with spatial and energy neutron resonance self-shielding, such as effective values of broad energy group absorption and fission cross sections, resonance integrals as functions of energy and space, and effective energy group lambda factors.

**5. METHOD OF SOLUTION**

RMET21 uses the integral form of the neutron transport equation to calculate the flux as a function of energy and position in the cell in a very fine energy mesh for the neutron resonance region. The fine energy mesh is arbitrary and the cross sections needed are internally generated by means of any set of resonance parameters or using evaluated data files and pre-processing codes.

**6. RESTRICTIONS OR LIMITATIONS**

The geometries that can be treated are: homogeneous and general cylinders, including rod arrays, homogenized rod clusters and annular fuels with central holes filled with any material.

**7. TYPICAL RUNNING TIME**

The run times for the 27 sample problems range from 15 seconds to 120 minutes on a VAX 11/780.

**8. COMPUTER HARDWARE REQUIREMENTS**

RMET21 runs on the VAX family of computers under the VAX/VMS operating system.

**9. COMPUTER SOFTWARE REQUIREMENTS**

The code was written in FORTRAN IV and FORTRAN 77 and was tested using the VAX FORTRAN compiler. The only system dependent routines included are called from Subroutine SALIDA and are the DATE and TIME routines.

**10. REFERENCES**

Francisco Leszczynski, ``RMET21 User's Manual,'' Informal Notes, Centro Atomico Bariloche, Rio Negro, Argentina (1991).

Francisco Leszczynski, ``Neutron Resonance Treatment with Details in Space and Energy
for Pin Cells and Rod Clusters,'' *Ann. Nucl. Energy*, 14(11), 589-601 (1987).

**11. CONTENTS OF CODE PACKAGE**

Included are the referenced documents and a 5.25-in. DS/DD (360 k) diskette.

**12. DATE OF ABSTRACT**

December 1991.

**KEYWORDS: ** CELL CALCULATION; CROSS SECTIONS; ENDF/B FORMAT;
NEUTRON; REACTOR PHYSICS