Magnox refers to a type of nuclear reactor that uses magnesium alloy cladding to contain the nuclear fuel. Developed in the United Kingdom in the 1950s, these reactors primarily use natural uranium as fuel and are moderated by graphite. They were among the first generation of nuclear power plants and played a significant role in the early development of nuclear energy. The name "Magnox" comes from the magnesium non-oxidizing alloy used for the fuel cladding. These reactors are known for their simplicity and reliability, but many have been decommissioned due to age and the shift towards more advanced reactor designs, such as Advanced Gas-cooled Reactors (AGRs) and Pressurized Water Reactors (PWRs).