Warnings in OpenMc Simulation

[AnthonyB08]

Hi all,

My name is Anthony and I am excited to start my journey in computational neutronics. I am very new to this software ( both OpenMC and DAGMC) but I have a nuclear background and have read most of the documentation. That being said I am trying to solve a simple neutron transport problem being a spherical ball filled with plutonium (BC's vacuum). I have created the geometry and mesh using Cubit Coreform with the mesh being tetmesh scheme as seen below:

I export the file as a DAGMC .h5m file extension and Import it correctly as seen below:

Create DAGMC universes out of h5m files

NeutronBall= openmc.DAGMCUniverse(filename=mesh_file)
print(NeutronBall.material_names)
print(NeutronBall.bounding_region)
geo = openmc.Geometry(root=NeutronBall)
geo.export_to_xml()

Output:

Next, I create a mesh filer so I can determine the neutron flux spatially as such :

I, Then, run the simulation. During this time openmc returns these warnings:
Warning #1 :

Warning#2:

Then when I go to look at the tallie.out file I see no data was stored

What does the community recommend/advise?

Thank you very much! :)

[AnthonyB08]

First warning is removed if i add .bounded_universe to the openc.DAGMCUniverse(filename="NeutronBall.h5m")

[shimwell]

Yes this adds the missing surface with a vacuum boundary type to encompass the model automatically. Good find

openc.DAGMCUniverse(filename="NeutronBall.h5m").bounded_universe

[AnthonyB08]

Update: I wanted to see if I was missing any packages so I ran a known-working solution, i.e https://github.com/openmc-dev/openmc-notebooks/blob/main/unstructured-mesh-part-ii.ipynb. When I run this notebook all works well and converges, however when I go o paraview and import the .vtk file it shows no neutron flux. Note that I did not change anything in this note book.

[shimwell]

Is there any chance you can attach the vtk file and I can take a look over here

[AnthonyB08]

I cannot attach the file directly to GitHub . what would be the best way to send the files?

[AnthonyB08]

I am wondering if the second warning has anything to do with how MOAB is installed, as well as any of the installed packages.

I also noticed that when I export the CUBIT mesh to dagmc , through the plugin, the mesh is altered when doing a mbconvert h5m to vtx.

[shimwell]

Perhaps a zip file is accepted by github

[pshriwise]

Thanks for bringing this to our attention @AnthonyB08! I'll pull that notebook down and run it as well today to confirm. Hopefully I'll be able to get back to you soon.

[pshriwise]

Hi @AnthonyB08,

I re-ran that notebook and the VTK file it produced did contain the expected datasets when I opened it in Paraview.

Are you sure all of those values are truly zero? The scale indicates that the values have a max of .0022. I noted the scale of your flux was linear in the image above. It changes many orders of magnitude in this problem, so you might try it with log scaling instead.

[shimwell]

I get the same as you Patrick