1. NAME AND TITLE
GASS: Monte Carlo Calculation of Self Shielding by Encapsulated Gamma-Ray Sources.
This code package originated in Office of Civil Defense programs in 1966; is retained by RSIC to
preserve the technology.
University of Illinois, Civil Engineering and Nuclear Engineering Program, Urbana, Illinois.
3. CODING LANGUAGE AND COMPUTER
FORTRAN IV; IBM 7090 and 7094.
4. NATURE OF PROBLEM SOLVED
GASS was designed to calculate the energy and angular distributions of photons emitted from a
cylindrical or spherical encapsulated source.
5. METHOD OF SOLUTION
GASS represents an approximate solution by Monte Carlo methods to the steady state transport equation.
A time-saving procedure utilizing a "do-nothing" cross section allows ray tracing to proceed without
many cross section look-ups and partial path length calculations. A choice is then made where the
collision occurs between scattering, absorption, or the straight-ahead "do-nothing" reaction.
6. RESTRICTIONS OR LIMITATIONS
There are no known restrictions implied by storage allocation.
7. TYPICAL RUNNING TIME
Processing of 20,000 histories in the sample problem required 3 minutes on the IBM 7090 and 1.3
minutes on the 7094.
8. COMPUTER HARDWARE REQUIREMENTS
The code was designed for the 32 K IBM 7094 computer with 3 tape units.
9. COMPUTER SOFTWARE REQUIREMENTS
The code may be compiled and executed on the IBM FORTRAN IV IBJOB Monitor and other
compatible systems. Standard I-O and systems tape assignments are made.
K. Preiss, "Monte Carlo Calculation of Self Shielding by Encapsulated Gamma Ray Sources," UI-NRSS-3 (August 1966).
11. CONTENTS OF CODE PACKAGE
Included are the referenced document and one (1.2MB) DOS diskette which contains the source code
and input and output for a sample problem.
12. DATE OF ABSTRACT
January 1968; updated July 1981, February 1985.
KEYWORDS: MONTE CARLO; GAMMA-RAY; RAY-TRACING