1. NAME AND TITLE

BMC-MG: Multigroup Monte Carlo Neutron and Gamma-Ray Shielding Code System for Plutonium.

2. CONTRIBUTOR

Battelle Pacific Northwest Laboratories, Richland, Washington.

3. CODING LANGUAGE AND COMPUTER

FORTRAN IV; CDC 6600.

4. NATURE OF PROBLEM SOLVED

BMC-MG is a neutron and gamma-ray transport Monte Carlo code system designed for solving shielding problems. General three-dimensional geometry is used and some albedo options are available.

This code system was especially developed for use in plutonium shielding situations. Special subroutines are included which calculate gamma-ray and neutron source strength and spectra from several plutonium compounds as a function of isotopic composition and time since reprocessing for an energy group structure consisting of 27 neutron groups and 16 gamma-ray groups. A neutron, gamma-ray and coupled neutron-gamma-ray cross-section library based on this group structure is provided. This library was produced for use in calculating dose rates in plutonium shielding situations encountered in plutonium fabrication facilities.

5. METHOD OF SOLUTION

The transport equations are solved by Monte Carlo methods. Point detector quantities are obtained by summing flux contributions from every collision and multiplying by a suitable response function. Response functions can be input by the user or kerma and dose rate response functions included in the system for the 27 neutron and 16 gamma-ray group structure can be used. Fluxes and reaction rates are summed by region.

The multigroup cross-section data are in a format compatible with those used in discrete ordinates codes such as CCC-82/ANISN, CCC-42/DTF-IV or CCC-89/DOT. Anisotropic scattering is treated by choosing a scattering angle based on a probability function derived from a Legendre polynomial representation of the angular cross section.

6. RESTRICTIONS OR LIMITATIONS

None noted.

7. TYPICAL RUNNING TIME

Running time is dependent on the number of particle histories and associated collisions needed to obtain the desired statistical precision. Therefore running time is problem dependent.

8. COMPUTER HARDWARE REQUIREMENTS

A CDC 6600 computer is required.

9. COMPUTER SOFTWARE REQUIREMENTS

A FORTRAN IV compiler is required.

10. REFERENCES

a. Included in the documentation:

M. G. Zimmerman, "Transmittal of BMC-MG Code and Information Package," (December 1976).

M. G. Zimmerman and D. H. Thomsen, "A Shielding Calculational System for Plutonium," BNWL-1855 (August 1975).

b. Background information:

D. H. Thomsen and T. M. Traver, "BMC-1: The Battelle Monte Carlo Code," BNWL-1433 (June 1970).

11. CONTENTS OF CODE PACKAGE

Included are the referenced document (10.a) and one (1.2MB) DOS diskette which contains the source code and sample problem input.

12. DATE OF ABSTRACT

December 1981.