The Tianwan nuclear power plant on the coast of the Yellow Sea in China
Xinhua/Alamy
Chinese researchers have developed an extremely energy efficient and low-cost technology for extracting uranium from seawater, a potential boon to the country’s nuclear power ambitions. China currently leads the world in building new nuclear power plants, and shoring up its supply of uranium will help these efforts.
The world’s oceans hold an estimated 4.5 billion tonnes of uranium – more than 1000 times that available to mining – but it is extremely dilute. Previous experimental efforts have harvested uranium from seawater by physically soaking it up with artificial sponges or a polymer material inspired by blood vessel patterns, or by the more efficient and more expensive electrochemical method of trapping uranium atoms with electric fields.
Shuangyin Wang at Hunan University in China and his colleagues have developed an upgraded electrochemical technique that is cheaper and requires less energy than any other for use with seawater. Unlike typical electrochemical systems, which only pull uranium atoms from water at the positive electrode, their device contains two copper electrodes, one positive and one negative, that can both gather uranium.
This approach was able to extract 100 per cent of the uranium atoms from a salty seawater-like solution within 40 minutes. By comparison, physical adsorption methods typically extract less than 10 per cent of the available uranium.
When tested with small amounts of natural seawater – about 1 litre running through the system at any time – the new method was able to extract 100 per cent of uranium from East China Sea water and 85 per cent from South China Sea water. In the latter case, the researchers also achieved 100 per cent extraction with larger electrodes.
The experiments also showed the energy required was more than 1000-fold less than other electrochemical methods. The whole process cost about $83 per kilogram of extracted uranium. That is twice as cheap as physical adsorption methods, which cost about $205 per kilogram, and four times as cheap as previous electrochemical methods, which cost $360 per kilogram.
Scaling up the size and volume of the new devices – along with potentially stacking or connecting them together – could lead to “industrialisation of uranium extraction from seawater in the future”, the researchers wrote. Given a 58-hour test in 100 litres of seawater, their largest experimental array extracted more than 90 per cent of the available uranium.
One of the most successful previous demonstrations of harvesting uranium from seawater came in the 1990s, when the Japan Atomic Energy Agency extracted a kilogram of the element from the ocean using a physical adsorption method. That set a milestone that has inspired Chinese academic and industry researchers ever since.
In 2019, a Chinese state-owned nuclear company teamed up with research institutes to form the Seawater Uranium Extraction Technology Innovation Alliance. This organisation aims to build a demonstration plant by 2035 and achieve ongoing industrial production by 2050, according to the South China Morning Post.
Half of the nuclear reactor projects currently under construction are in China. The country is on track to surpass the US and the European Union in total installed nuclear power capacity by 2030, according to the International Energy Agency.
But China’s nuclear industry also imports most of the uranium that it uses. So any it can economically extract from seawater will be more than welcome.
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