8. Volume File Format

The current version of the volume file format is 1.0.


  • filetype (char[]) – String indicating the type of file.
  • version (int[2]) – Major and minor version of the summary file format.
  • openmc_version (int[3]) – Major, minor, and release version number for OpenMC.
  • git_sha1 (char[40]) – Git commit SHA-1 hash.
  • date_and_time (char[]) – Date and time the summary was written.
  • domain_type (char[]) – The type of domain for which volumes are calculated, either ‘cell’, ‘material’, or ‘universe’.
  • samples (int) – Number of samples
  • lower_left (double[3]) – Lower-left coordinates of bounding box
  • upper_right (double[3]) – Upper-right coordinates of bounding box
  • threshold (double) – Threshold used for volume uncertainty
  • trigger_type (char[]) – Trigger type used for volume uncertainty


  • volume (double[2]) – Calculated volume and its uncertainty in cubic centimeters
  • nuclides (char[][]) – Names of nuclides identified in the domain
  • atoms (double[][2]) – Total number of atoms of each nuclide and its uncertainty