Hope you all are doing well.
I am trying to design a pincell/lattice with rectangular elements (fuel rods) like box in box approach. where a box fuel pin is surrounded by clad, similarly its very next (all four adjacent) neighbour is a box water element surrounded by clad, somewhat like in the attachment.
I designed 3 rectangular prisms for each component, the water and fuel elements having identical dimensions while 1 outer box with larger dimension to encompass the four alternative boxes to create a pincell using the lattice approach. But I am having trouble in syntax for filling the inside and outside of these boxes as the geometry only shows the root universe being filled and not any other universes that I defined.
Can someone please point out where the syntax is wrong, and possibly share the link to any similar box geometry examples. With thanks.