Magnox

thumb|350px|Schematic diagram of a magnox nuclear reactor showing gas flow. The heat exchanger is outside the concrete radiation shielding. This represents an early Magnox design with a cylindrical, steel, pressure vessel.

Magnox is a type of nuclear power / production reactor designed and produced in the United Kingdom. It was designed to run on natural uranium with graphite as the moderator and carbon dioxide gas as the heat exchange coolant. It belongs to the wider class of gas-cooled reactors. The name comes from the magnesium-aluminium alloy (called magnesium non-oxidising), used to clad the fuel rods inside the reactor. Like most other generation I nuclear reactors, the magnox was designed with the dual purpose of producing electrical power and plutonium-239 for the nascent nuclear weapons programme in Britain. The name refers specifically to the United Kingdom design but is sometimes used generically to refer to any similar reactor.