First-generation Magnox nuclear reactors: history, characteristics and legacy

Magnox reactors, developed in the UK in the 1950s and 1960s, were among the first types of commercial nuclear reactors to be built. They take their name from the “Magnox” alloy used to clad nuclear fuel.

History of Magnox reactors

Magnox reactors were developed by the UK as part of its civil nuclear program, which aimed to generate electricity and support research into military applications of nuclear power [1]. The first Magnox reactor, the Calder Hall nuclear power station, was commissioned in 1956 and is considered the world’s first commercial nuclear power plant [2].

A total of 26 Magnox reactors were built in the UK between 1956 and 1971, with a total installed capacity of 4,430 MWe [3]. Some of these reactors were also exported to other countries, notably Italy and Japan. Most Magnox reactors were shut down in the 1990s and 2000s due to age and safety concerns. The last Magnox reactor in operation, Wylfa 1, was shut down in 2015 [4].

Characteristics of Magnox reactors

Magnox reactors are natural uranium graphite gas (UNGG) reactors, similar to those developed in France. They use natural uranium as fuel, graphite as moderator and carbon dioxide (CO2) as coolant [5].

The Magnox alloy cladding, composed mainly of magnesium with small amounts of aluminum and beryllium, is used to contain the nuclear fuel [6]. This alloy offers excellent corrosion resistance and low neutron absorption, enabling natural uranium to be used as fuel.

Magnox reactors have several advantages, not least their simplicity of design and their ability to use natural uranium, which reduces fuel and enrichment costs. However, they also have disadvantages, such as the production of a large amount of radioactive waste and low energy efficiency compared with newer nuclear technologies [7].

Legacy of Magnox reactors

Although Magnox reactors are no longer in operation, their legacy remains important to the nuclear industry and to the history of energy production. They played a key role in the development of the British nuclear industry and contributed to research into civil and military applications of nuclear energy. Magnox reactors were also among the first to demonstrate the viability of nuclear power as a large-scale source of electricity [8]. The decommissioning and waste management of the Magnox reactors is a major challenge for the UK. The decommissioning process is underway and is expected to continue for several decades, requiring significant investment in research and development of decommissioning and waste management technologies [9].

Conclusion

The Magnox reactors represent a milestone in the history of nuclear energy, demonstrating the feasibility of nuclear power as a source of electricity and supporting research into military applications of nuclear energy. Although they have been replaced by more advanced nuclear technologies, their legacy lives on in the nuclear industry and ongoing decommissioning efforts.

The challenge of dismantling UNGG reactors

One problem for reactors using graphite as a moderator is the enormous volume of the block. Radioactively contaminated, it poses specific challenges for dismantling. Several companies are working to meet this challenge, notably with the help of robotics. These include Graphitech and a European project, INNO4GRAPH.

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