**1. NAME AND TITLE**

MCRTOF: Monte Carlo Code System for Calculation of Multiple Scattering of Neutrons in the
Resonance Region.

**2. CONTRIBUTOR**

Japan Atomic Energy Research Institute, Tokai-mura, Naka-gun, Ibaraki-ken, Japan.

**3. CODING LANGUAGE AND COMPUTER**

Fortran IV; FACOM-M200 (A) or IBM 3033 (B).

**4. NATURE OF PROBLEM SOLVED**

MCRTOF systematically calculates capture and scattering probabilities for neutrons incident on
a material disk, with neutron cross sections calculated from the resonance parameters. Capture, front
and rear face scattering, transmission, etc., probabilities are obtained from the average destinations of
the incident neutrons.

**5. METHOD OF SOLUTION**

Paths of a neutron which impinges onto a disk inclined with an arbitrary angle to the incident
direction are simulated by the Monte Carlo method, using capture and scattering cross sections which
are produced from a given set of resonance parameters. For each incident energy, the probabilities
of capture, front and rear face scattering, and transmission are obtained by averaging over many
incident neutrons. The incident neutron energy is changed step by step in order to reproduce these
probabilities over resonances. All these probabilities are listed in a format convenient for comparison
with the experimental ones, and these probabilities are illustrated with sheet plots as functions of
incident energies. At some energy points, the spatial distributions of neutron capture reactions are also
illustrated in a projection on the plane normal to the disk surface.

**6. RESTRICTIONS OR LIMITATIONS**

The maximum number of resonances is five. Reactions other than capture and scattering are
neglected.

**7. TYPICAL RUNNING TIME**

Running time depends on resonance parameters and disk thickness. The sample problem ran in
22 seconds on the IBM 3033 computer.

**8. COMPUTER HARDWARE REQUIREMENTS**

MCRTOF was designed for the FACOM-M200 computer. It was converted by RSIC to run on
the IBM 3033 computer.

**9. COMPUTER SOFTWARE REQUIREMENTS**

A Fortran IV compiler is required.

**10. REFERENCES**

M. Ohkubo, "MCRTOF A Monte Carlo Program for Multiple Scattering of Neutrons in Resonance Energy Region," JAERI-M 7988 (November 1978).

M. Ohkubo, "Neutron Capture Probabilities for Think Samples at Resonance Energies," *Nucl. Sci.
Eng.* 66 (1978) 217-228.

M. Ohkubo, "A Normalization Standard for Neutron Capture Probability in the Resonance
Region," *Nucl. Instrum. Methods* 184, 465-467 (1981).

**11. CONTENTS OF CODE PACKAGE**

Included are the referenced documents and one DOS diskette which contains the source code and
sample problem input plus output from the sample problem written in list format (B).

**12. DATE OF ABSTRACT**

February 1983; revised September 1983.

**KEYWORDS: ** NEUTRON; MONTE CARLO; CYLINDRICAL GEOMETRY