RSIC CODE PACKAGE CCC-492

1. NAME AND TITLE

MULTI-KENO2: A Monte Carlo Code System for Criticality Safety Analysis.

2. CONTRIBUTOR

Japan Atomic Energy Research Institute, Ibaraki-Ken, Japan.

3. CODING LANGUAGE AND COMPUTER

Fortran IV; FACOM-M380.

4. NATURE OF PROBLEM SOLVED

MULTI-KENO2 solves the Boltzman neutron transport equation by assuming the media to be isotropic, ignoring the time dependence of the cross sections, and converting the equation to multigroup form.

5. METHOD OF SOLUTION

Modifying the Monte Carlo code KENO-IV, the MULTI-KENO code was developed for criticality safety analysis. A function added KENO-IV to divide a system into many subsystems SUPER BOXes where the size of BOX TYPEs in each SUPER BOX can be selected independently. SUPER BOX TYPE is an extension of BOX TYPE. MULTI-KENO2, an improvement on MULTI-KENO, allows multibox intersections.

The scattering treatment used in MULTI-KENO2 assumes that the differential neutron scattering cross section can be represented by a Pl Legendre polynomial. The weight of the neutron is reduced by the absorption probability at each collision point of a neutron tracking history. When the neutron weight has been reduced below a specified point for the region in which the collision occurs, Russian roulette is played to determine if the neutron's history is to be terminated at that and if the neutron is to survive with an increased weight. Splitting of high weight neutrons is allowed in order to minimize the variance in Keff for a system with regions of widely varying average weight.

6. RESTRICTIONS OR LIMITATIONS

MULTI-KENO2 is flexibly dimensioned so that the allowed size of a problem is limited only by the total data storage available.

7. TYPICAL RUNNING TIME

MULTI-KENO2 running times are highly problem dependent. Typical problems run between 2 and 50 minutes on the FACOM-M200, depending upon the number of histories requested, the statistical weighting used, the presence or absence of reflectors, the complexity of the geometry, the number of energy groups and the type of materials in the problem. An infinite cylinder of highly enriched 235U-H2O was executed on a FACOM-M380 in 11.08 minutes; neutron histories were 30,000 and the number of energy groups were 137.

8. COMPUTER HARDWARE REQUIREMENTS

MULTI-KENO2 requires the use of a CALCOMP plotter. An output file for graphic processing, called GDFILE, is determined for each computer system.

9. COMPUTER SOFTWARE REQUIREMENTS

MULTI-KENO2 was written in Fortran-IV (HE).

10. REFERENCES

a. Included in documentation:

Y. Naito, M. Yokota, and K. Nakano, "MULTI-KENO: A Monte Carlo Code for Criticality Safety Analysis," JAERI-M83-049 (March 1983).

Y. Komuro, "MULTI-KENO2: A Modified Version of MULTI-KENO," Informal Notes (July 1986).

b. Background information:

L. M. Peirie, N. F. Cross, "KENO IV: An Improved Monte Carlo Criticality Program," ORNL-4938 (November 1975).

11. CONTENTS OF CODE PACKAGE

Included are the referenced documents (10.a) and one (1.2MB) DOS diskette which contains the source codes and sample problem input and the library data.

12. DATE OF ABSTRACT

May 1986; update August 1986.