I am trying to construct a 3D geometry for an experimental validation. Right now, I am stuck on seemingly simple task of having Ni foils on the cavity walls (seen in blue around the yellow in the first image). I have attached the geometry.xml and associated plot from openmc. I have checked the values and corresponding signs for spaces multiple times and I am unable to locate the source of problem (can not see cell 41), as I can not see the Ni foil in the openmc plot (second image).
Additionally, I think visualizing this in 3D would be rather helpful but I have been having problem with generating an hdf5 output from the voxel plots. Any suggestions as how should I approach it, the documentation is helpful but I could not get any results from it.