Hi Michael,
There are potentially a couple of things to address:
- the
waterzone
cell is defined as the positive and negative side of surface 5, so it effectively occupies no space. - the regions between the fuel and first cladding layer and the region outside of the outer cladding cell need to be defined, even if they are intended to be empty space (void). They are interpreted as a void region by OpenMC if no fill is specified on the cell in the Python script.
I hope this helps!
Cheers,
Patrick