As Magnox (short for Mag nesium n Non- ox idierend ) refers to one of the first commercial nuclear reactor series in the world.
Magnox reactors belong to the group of gas-cooled reactors (Gas Cooled Reactors; GCR). As moderator is graphite , as a coolant , the gas carbon dioxide (CO 2 used). The fuel elements consist of natural uranium in metallic form. The reactor got its name from the cladding material of the fuel elements : Magnox is an alloy that mainly consists of magnesium (“magnesium non oxidizing”).
All fuel element casings have various types of ribs to improve the heat transfer. Even tubular fuel elements have been developed which are cooled from the inside and outside (compare superheated steam reactor ). The fuel elements are usually no longer than 1 m, and the uranium rod can be up to 3 cm thick.
The moderator consists of graphite in the form of large blocks, which are connected by molded grooves and wedges with a relatively large amount of play. The graphite blocks are traversed by cylindrical channels into which the fuel elements are inserted. The fuel assemblies themselves lie against the channel wall with several guide strips, the so-called fins, and are stacked vertically on top of one another. This creates sector-shaped cross-sections through which the cooling gas can flow. The absorber rods for the reactor control take up further channels.
The entire reactor core, weighing several hundred tons, rests on a welded steel grate. Since the fuel elements can be removed with special loading machines while the reactor is in operation, the burn-up of the uranium can be influenced in a targeted manner. B. can be interesting in the extraction of weapons-grade plutonium. Due to the very voluminous reactor core, large pressure vessels had to be welded on the construction sites. Pressure vessels made of prestressed concrete were later developed in France .
Nuclear power plants
Due to the low power densities, Magnox reactors in nuclear power plants work very uneconomically and are out of date from today's perspective.
Magnox reactors in the strict sense were built exclusively in Great Britain. Most of them went online in the 1950s and 1960s. The reactors at Berkeley , Bradwell , Calder Hall , Chapelcross , Dungeness , Sizewell A, Hunterston , Hinkley Point A , Oldbury , Wylfa, and Trawsfynydd have all been shut down. With the decommissioning of Wylfa-1 on December 30, 2015, the era of the Magnox reactors ended.
The Magnox design was still implemented in the Latina nuclear power plant in Italy and in the Tōkai nuclear power plant in Japan , both plants are no longer in operation today. The Experimental Power Reactor in North Korea was built without British support based on the approved construction plans of the Magnox reactors at the Calder Hall nuclear power plant.
The nine UNGG reactors in France and Spain, which have since been shut down, have a similar structure to the Magnox reactors, but the nuclear fuel rods there are encased in a magnesium- zirconium alloy instead of a magnesium- aluminum alloy.