MCNP RHP/HEX Geometry Clarifications

[MadGander]

TL;DR

What are right hexagonal prism "facets" and how does one define them? Help with MCNP geometry.

Hi all,

I'm working on building a fuel compact using hexagonal lattice cells, but I'm running into trouble with the RHP/HEX definition. The deck is error free, but for one reason or another the lattice cell isn't replicating along the Z axis.. only the X and Y, or at least this is what I'm interpreting from the plotter. My guess is that it has to do with how I'm defining the right hexagonal prism cell (only using one facet). Any help is appreciated.

 

[nikhild]

MCNP commands (cards) have many different ways of doing things. I have not generated a 3D hex lattice the way you are trying to without specifying the extent in the three dimensions.

The way I have generated 3D hex lattices is to use the FILL= -1:1 -1:1 0:1 which specifies the indices in each of the three dimensions. Here it would be 3x3x2=18 copies of the basic cell.

I am the author of a python library that can ease the generation of MCNP input decks.
https://github.com/pnnl/CardSharpForMCNP
Test 5 in the geometry tests illustrates a hexagonal lattice using the method above.

If you are comfortable with using Python, I suggest giving the library a try.