Magnox is an alloy—mainly of magnesium with small amounts of aluminium and other metals—used in cladding unenriched uranium metal fuel with a non-oxidising covering to contain fission products in nuclear reactors.Magnox is short for Magnesium non-oxidising.This material has the advantage of a low neutron capture cross section, but has two major disadvantages: * It limits the maximum temperature (to about 415 Celsius), and hence the thermal efficiency, of the plant. * It reacts with water, preventing long-term storage of spent fuel under water in spent fuel pools.