Stability of Output Format, mesh tallies.

User Support
1

Dear All,

Is there someone who can comment on the stability of the output format for the HDF5 files that contain the spatial mesh tallied fluxes and reaction rates?
We were looking to support OpenMC output in https://www.oecd-nea.org/meshtal-viewer/ but thought it prudent to gauge if there were plans to change the output format in the coming months (or years).

Ian

2

Hi Ian,

The statepoint files that contain tally results have been relatively stable for some time now and there are no immediate plans for changes in the coming months. I can’t guarantee that there won’t be any changes down the line, but generally we try to ensure that changes are “additive” if possible, which is easy with HDF5. Our file formats are also versioned, so an external application like MeshTal Viewer could check the version of the file format to ensure that it is a supported version.

I should also mention that we do have a GUI application for geometry and tally visualization that handles mesh tallies as well as other types of tallies. The way that tallies work in OpenMC is slightly different than other codes – a user can “compose” together multiple filters (including a mesh filter) in an arbitrary order, and the resulting tally bins correspond to the Cartesian product of all the filter bins. This does make it a little bit complicated for visualization purposes; you could take a look at our plotter application to see how it’s handled there. Anyway, happy to discuss further if you would find it helpful.

Best regards,
Paul

3

Hi all

Just to chime in, OpenMC structured mesh and unstructured mesh output files can also be output in VTK format which is a nice open format for 3d visualizations. Also the OpenMC geometry can be approximated and output as a VTK file

So one option apart from reading the h5m file would be to add vtk reading and I think the NEA viewer is written in Java and there are also Java VTK readers available which would help.

However there are several free 3D viewers for VTK files including Visit and Paraview and ways to interact with the VTK files like pyvtk

All the best

Jon