**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.

**KEYWORDS; ** MULTIGROUP; GAMMA-RAY; NEUTRON; X-RAY; PLUTONIUM;
COMPLEX GEOMETRY