Corium (nuclear reactor) Corium (nuclear reactor) Corium (also called fuel containing material (FCM) or lava-like fuel containing material (LFCM)) is the lava-like mixture of fissile material created in a nuclear reactor's core during a nuclear meltdown. It consists of nuclear fuel, fission products, control rods, structural materials from the affected parts of the reactor, products of their chemical reaction with air, water and steam, and, in the event that the reactor vessel is breached, molten concrete from the floor of the reactor room. The heat causing the melting of a reactor may originate from the nuclear chain reaction, but more commonly decay heat
Organic nuclear reactor Organic nuclear reactor An organic nuclear reactor, or organic cooled reactor (OCR), is a type of nuclear reactor that uses some form of organic fluid, typically a hydrocarbon substance like polychlorinated biphenyl (PCB), for cooling and sometimes as a neutron moderator as well. Using an organic fluid had a major advantage over conventional designs using water as the coolant. Water tends to corrode and dissolve metals, both the nuclear fuel and the reactor as a whole. To avoid corrosion of the fuel, it is formed into cylindrical pellets and then inserted in zirconium tubes or other "cladding" materials. The rest