Corium (nuclear reactor)

Corium is a molten mixture of nuclear fuel, structural materials, and other elements that can be produced in a nuclear reactor during a severe accident scenario, such as a meltdown. When the temperature in the reactor core rises significantly, the fuel rods (which contain nuclear fuel like uranium or plutonium) along with other materials, such as cladding and coolant, can melt and pool together at the bottom of the reactor vessel or containment structure.