There's more bad mojo wrapped around the RBMK class nuclear reactor responsible for the Chorbobyl (Chernobyl) disaster than nearly any other machine in the world. Images of meltdowns, explosions, ...
The "High Power Channel-type Reactor", or RBMK (Russian abbreviation), is a generation II reactor. It uses a graphite moderator, a light water coolant, and uranium fuel, enriched to 2% U-235.