Standard Code Description

1. Coding Language and Computing Platforms
   Fortran source code for Linux and Macintosh
2. Description of Purpose
   Nuclear reactors that rely upon the fission reaction have two modes of thermal energy deposition in the reactor system: neutron absorption and gamma absorption. The gamma rays are typically generated by neutron capture reactions or during the fission process which means the primary driver of energy production is of course the neutron interaction. In conventional reactor physics methods, the gamma heating component is ignored such that the gamma absorption is forced to occur at the gamma emission site. For experimental reactor systems like EBR-II and FFTF, the placement of structural pins and assemblies internal to the core leads to problems with power heating predictions because there is no fission power source internal to the assembly to dictate a spatial distribution of the power.
   
   As part of the EBR-II support work in the 1980s, the GAMSOR code was developed to assist analysts in calculating the gamma heating. The GAMSOR code is a modified version of DIF3D and actually functions within a sequence of DIF3D calculations. The gamma flux in a conventional fission reactor system does not perturb the neutron flux and thus the gamma flux calculation can be cast as a fixed source problem given a solution to the steady state neutron flux equation. This leads to a sequence of DIF3D calculations, called the GAMSOR sequence, which involves solving the neutron flux, then the gamma flux, and then combining the results to do a summary edit.
3. Typical Running Time
   The run time strongly depends on the time spent in DIF3D. The GAMSOR specific calculations take less than a few seconds to complete after the two DIF3D calculations for neutron and gammas are completed.
4. References
   1. M. A. Smith, C. H. Lee, and R. N. Hill, ​“GAMSOR: Gamma Source Preparation and DIF3D Flux Solution,” ANL/NE-16/50 revision 1.0, June 28, 2017.
5. Primary Author
   J. Beitel, Argonne National Laboratory
6. Materials Available
   The source code and compilation instructions are provided. Precompiled executables for Linux and Macintosh are also included. The source code and executables for all utility programs associated with the Argonne Reactor Code system are also included. Documentation on DIF3D and GAMSOR is provided along with all of the verification test cases for DIF3D and GAMSOR. Contact nera-​software@​anl.​gov for licensing and distribution information.
7. Sponsor
   U.S. Department of Energy, Office of Nuclear Energy