Reflective Boundary Hexagonal Multigroup problem

[pshriwise]

My reply in the post that @paulromano provided above might be useful here. @jerrylizy I think some of the same issues might show up in your model too.

The mesh tally outputs are broken by the ''reflective" boundary type planes

Hi @YimingZ, A very interesting problem! It took a bit for me to sort out what is going on here. I pulled your model (thanks for providing it!) and pulled it up in the plotter. This allowed me to look at the containing cell definition more clearly. It looked correct to me. [image] But of course when I ran the problem I saw the same issue as you: [image] So I stared at it for a bit and then broke the cell region definition up into 4 cells (one for each quadrant): [image] This helped me…