During the Chernobyl disaster, the reactor’s fuel rods were central to turning a routine test into a catastrophe. An improper shutdown caused an unexpected power surge, and when graphite-tipped control rods were inserted, their design briefly increased reactivity, overheating the fuel rods. The overheated rods ruptured, turning water into steam and triggering a massive explosion that destroyed the reactor. Exposed to air, the graphite ignited, releasing radioactive material into the atmosphere.