Addition of Central Control Rod in Small Modular Reactor Geometry Using Serpent

[emilmammadzada]

TL;DR

Addition of Central Control Rod in Small Modular Reactor Geometry Using Serpent

Dear Experts I would like to create a small modular reactor-like geometry for Serpent code (example: ABV reactor). How can I add a control rod to the center like in the picture below? Which code scripts should I add in the geometry part. And how can I do this in Hexagonal laticce?