Magnox
The acronym Magnox denotes the cladding material of the natural uranium fuel rods used in the British Magnox reactors . Magnox is not to be confused with MOX fuel assemblies .
Magnox (magnesium non oxidizing) is a wrought alloy made from 99% magnesium and 1% additions of aluminum , beryllium , calcium , iron , manganese , nickel , lead and tin . Special types contain up to 0.6% zirconium (in France ) or higher zinc content .
The melting point of the Magnox alloys is between 645 and 650 ° C. To prevent a chemical reaction with the cooling gas carbon dioxide , the surface temperature should not exceed 470 ° C. These low cladding tube loads mean very low power densities in the Magnox reactors. The economic efficiency of these power reactors is correspondingly low. Such fuel rods also melt faster if they are no longer surrounded by coolant due to an accident (see also core meltdown ).
A successor to the Magnox reactors is the Advanced Gas-cooled Reactor developed in Great Britain . He uses slightly enriched uranium dioxide instead of uranium metal as fuel. This enables higher power densities and coolant outlet temperatures and thus a higher thermal efficiency .