**1. NAME AND TITLE**

MORSE-CGA: A General Purpose Monte Carlo Multigroup Neutron and Gamma-Ray Transport
Code System with Array Geometry Capability, Version 2.

**AUXILIARY ROUTINES**

PICTURE: Geometry Input Diagnostic Code.

**2. CONTRIBUTOR**

Oak Ridge National Laboratory, Oak Ridge, Tennessee.

**3. CODING LANGUAGE AND COMPUTER**

Fortran 77 with some IBM assembler language for the IBM 3090 version; Cray, VAX, PC 386
with math co-processor, UNIX Workstations. (C00474/ALLCP/03)

**4. NATURE OF PROBLEM SOLVED**

MORSE-CGA was developed to add the capability of modelling rectangular lattices for nuclear
reactor cores or for multipartitioned structures. It thus enhances the capability of the MORSE code
system. The MORSE code is a multipurpose neutron and gamma-ray transport Monte Carlo code.
It has been designed as a tool for solving most shielding problems. Through the use of multigroup
cross sections, the solution of neutron, gamma-ray, or coupled neutron-gamma-ray problems may be
obtained in either the forward or adjoint mode. Time dependence for both shielding and criticality
problems is provided. General three-dimensional geometry may be used with an albedo option
available at any material surface. Isotropic or anisotropic scattering up to a P_{16} expansion of the
angular distribution is allowed.

The MORSE-CGA computer code system has been revised and version 2.0 has been issued. MORSE-CGA has as its geometry module, MARS, which is a multiple array system that uses combinatorial geometry; hence, the CGA suffix indicates combinatorial geometry array. Numerous changes have been made in order to minimize the differences in coding required for use on various computer systems. One sequential source file is available, and a preprocessor code CFLAG operates on this file to configure it for the different computers. A fatal geometry error fix-up has been implemented in order that users may recover useful results from computer runs that fail in this way. The collision density estimator is included in the standard package. All input data is in a free-form FIDO-type format. The PICTURE code, which makes printer plots of 2-D slices through a combinatorial geometry mock-up, handles the MARS geometry capability. MARS was originally developed for the CCC-466/SCALE system.

MORSE users should request CCC-474/MORSE-CGA.

**5. METHOD OF SOLUTION**

Monte Carlo methods are used to solve the forward and the adjoint transport equations. Quantities of interest are then obtained by summing the contributions over all collisions, and frequently over most of phase space.

Standard multigroup cross sections, such as those used in discrete ordinates codes, may be used as input; either CCC-254/ANISN, CCC-42/DTF-IV, or CCC-543/TORT-DORT cross section formats are acceptable. Both fixed and free format are acceptable. Anisotropic scattering is treated for each group-to-group transfer by utilizing a generalized Gaussian quadrature technique.

The MORSE code is organized into functional modules with simplified interfaces such that new modules may be incorporated with reasonable ease. The modules are (1) random walk, (2) cross section, (3) geometry, (4) analysis, and (5) diagnostic.

The MARS module was interfaced with MORSE-CG to produce MORSE-CGA. It allows the efficient modelling of complex lattice geometries. Computer memory requirements are minimized because fewer body specifications are needed and nesting and repetition of arrays is allowed.

While the basic MORSE code assumes the analysis module is user-written, a general analysis
package, SAMBO, is included. SAMBO handles some of the drudgery associated with the analysis
of random walks and minimizes the amount of user-written coding. An arbitrary number of detectors,
energy-dependent response functions, energy bins, time bins, and angle bins are allowed. Analysis
is divided for each detector as follows: uncollided and total response, fluence versus energy, time-dependent response, fluence versus time and energy, and fluence versus angle and energy. Each of
these quantities is listed as output. The diagnostic module provides an easy means of printing out, in
useful form, the information in the various labelled commons and any part of blank COMMON. The
module is very useful to debug a problem and to gain further insight into the physics of the random
walk.

**6. RESTRICTIONS OR LIMITATIONS**

Flexible dimensioning techniques require the use of a large container array in blank COMMON.

**7. TYPICAL RUNNING TIME**

A series of nine sample problems are provided. CPU time ranged from 1 s to 1.6 m on an IBM
3090. Run time on an IBM RISC 6000, model 590, ranged from 1 to 5 seconds for the included
sample problems.

**8. COMPUTER HARDWARE REQUIREMENTS**

The code requires computers with standard I-O plus one direct access storage device. PICTURE
uses approximately 100 K of core storage (including system library routines). MORSE-CGA uses
about 300 K storage (including system library routines) on the IBM 3090 plus 4*(blank COMMON
size)/1000. MORSE-CGA runs on mainframes, Workstations and Personal Computers.

**9. COMPUTER SOFTWARE REQUIREMENTS**

Standard software for each of the versions may be used. Any nonstandard library routines which were used have been included in the code package or a full description is given for the user's information.

The IBM 3090 new release has been run under MVS-XA, CRAY under UNICOS, VAX under
VMS, IBM RISC 6000 under AIX with the xlf 3.2.2 compiler, and on 80386 personal computers
(equipped with math coprocessors) under DOS using Silicon Valley Software Version 2.8.2, Microsoft
Version 5.0, and Lahey version 5.01 compilers and under OS/2 with the WATCOM Version 9.0
compiler. Note that executable files are not included in this package.

**10. REFERENCES**

M. B. Emmett, "MORSE-CGA, A Monte Carlo Radiation Transport Code with Array Geometry Capability," ORNL-6174 (April 1985).

M. B. Emmett, "The MORSE Monte Carlo Radiation Transport Code System," ORNL-4972 (February 1975); ORNL-4972/R1 (February 1983); ORNL 4972/R2 (July 1984).

J. T. West and M. B. Emmett, "MARS - A Multiple Array System Using Combinatorial Geometry," (December 1984). This is Volume 3, Section M9 of NUREG/CR-0200,"SCALE - A Modular Code System for Performing Standardized Computer Analysis for Licensing Evaluation," NUREG/CR-0200 (ORNL/NUREG/CSD-2), Revision 2.

M. B. Emmett, "PICTURE, A Printer Plot Package for Making 2-D Pictures of MARS Geometry," Section M13 of NUREG/CR-0200,"SCALE - A Modular Code System for Performing Standardized Computer Analysis for Licensing Evaluation," NUREG/CR-0200 (ORNL/NUREG/CSD-2/R4), Vol. III (Draft February 1990).

S. N. Cramer, "Applications Guide to the MORSE Monte Carlo Code," ORNL/TM-9355 (August
1985).

**11. CONTENTS OF CODE PACKAGE**

Included are the referenced documents and 2 DS/HD 3.5 inch (1.44MB) diskettes in DOS format
which contain source programs, special routines, and sample problem input and output from the nine
sample problems, and scripts for running the sample problems on Unix Workstations.

**12. DATE OF ABSTRACT**

June 1985; revised August 1985, September 1985, March 1987, and July 1993, November 1997.

**KEYWORDS:** MONTE CARLO; NEUTRON; GAMMA-RAY; MULTIGROUP; COMPLEX
GEOMETRY; COMBINATORIAL GEOMETRY; ADJOINT; ARRAY GEOMETRY; WORKSTATION; MICROCOMPUTER