This is a remix of the original model by fabrik872: https://www.thingiverse.com/fabrik872
Original model site: https://www.thingiverse.com/thing:3693224
Chernobyl graphite block from inside the reactor RBMK with fragment version.
Recommend settings:
Print material: PLA with glitter (Galaxy black)
Slic3r: 0.2mm and variable layer hight on top layers
The author remixed this model.