Magnox
As a Magnox reactor (short for Magnesium non- oxidising) is called one of the first commercial nuclear reactor series in the world.
Construction
Magnox reactors belong to the group of gas-cooled reactors ( Gas Cooled Reactors; GCR ). As the moderator is graphite, as a refrigerant, the gas carbon dioxide ( CO2) used. The fuel elements consist of natural uranium in metallic form. The name has received from the fuel cladding material of the reactor. Magnox is an alloy mainly composed of magnesium ( " magnesium non oxidizing ").
All fuel element cases have to improve the heat transfer ribs of various kinds, it even tubular fuel elements were developed, which are cooled from the inside and outside ( compare superheated steam reactor). The fuel elements are not more than 1 m in general, the uranium rod can be up to 3 cm thick.
The moderator is made of graphite in the form of large blocks that are connected by molded grooves and wedges of a relatively large play. The graphite blocks are traversed by cylindrical channels into which the fuel is introduced. The fuel itself be due to a plurality of guide bars, the so-called Fins, on the duct wall and stacked perpendicular to each other. This causes sector-shaped cross-sections through which the cooling gas can flow. More channels take on the absorber rods for reactor regulation.
The entire reactor core rests with its weight of several hundred tons on a welded steel grate. Since the fuel can be removed during reactor operation with special charging machines, the burnup of the uranium can be influenced, which may be interesting in the extraction of weapons-grade plutonium, for example. Due to the very large voluminous reactor core pressure vessel had to be welded on the sites. Pressure vessels were later developed from pre-stressed concrete in France.
Nuclear power plants
Due to the low power densities Magnox reactors operate very uneconomical in nuclear power plants and are outdated from today's perspective.
Magnox reactors in the strict sense were built exclusively in the UK. They went mainly in the 1950s and 1960s to the grid. The reactors at Berkeley, Bradwell, Calder Hall, Chapel Cross, Dungeness, Sizewell A, Hunterston, Hinkley Point A, Oldbury and Trawsfynydd were all shut down. Only the Wylfa nuclear power plant is still in operation.
The Magnox design has also been implemented in nuclear power plants Latina in Italy and in the nuclear power plant in Japan Tōkai, both plants are no longer in operation today. The Experimental Power Reactor in North Korea was built without British support based on the shared construction plans of the Magnox reactors at the nuclear power plant, Calder Hall and decommissioned in 2007.
The nine now disused UNGG reactors in France and Spain have a similar structure as the Magnox reactors, the nuclear fuel rods are there but covered with a magnesium -zirconium alloy instead of a magnesium -aluminum alloy.