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The importance of tungsten in nuclear fusion: Discover the metal that can guarantee the success of future commercial power plants
The arrival of the first power plants equipped with a nuclear fusion reactor will occur, if everything follows its course, during the 60s. This is, at least, what EUROfusion, the European consortium that promotes the development of fusion energy, argues. . You challenges that need to be overcome for this milestone to be possible there are numerous and, furthermore, their complexity is intimidating. It is necessary to control, sustain and stabilize the plasma; produce tritium inside the reactor; eliminate impurities resulting from the reaction.
Scientists involved in the development of magnetic confinement fusion energy are working to solve these challenges, and the innovations they are developing invite us to look to the future with reasonable and healthy optimism. However, there is a challenge that we have not yet addressed: for commercial fusion energy to be successful, it is essential to develop new materials capable of handling the rigors that this technology imposes.
As physicists and engineers involved in the development of nuclear fusion energy learned more about the reaction and behavior of plasma, they realized something disturbing: the ideal materials for some of the reactor's elements are not available, but they can be developed. This is precisely the main purpose of the IFMIF-DONES project, which has already started in Escúzar (Granada). Other materials are already available, but they need to be found and tested to see if they really suit the reactor's needs.
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What tungsten crystals can do for nuclear fusion
Tungsten or tungsten (W) is a relatively scarce metal in the Earth's crust. It is very dense and extremely hard (understanding hardness as its resistance to being scratched), but its most exotic physicochemical property consists of having the highest melting point of all the metals that we can find in the periodic table of chemical elements (no less than 3.422 °C). It has a very wide range of applications, but, interestingly, since the Second World War it has been highly appreciated for its suitability in configuring the armor of some vehicles and in the manufacture of ammunition.
If we limit ourselves to its role both in ITER (International Thermonuclear Experimental Reactor), the experimental nuclear fusion reactor being built by an international consortium in the French town of Cadarache, and in future nuclear fusion machines, tungsten is a true jewel . And it is because, in addition to having, as we have just seen, the highest melting point of all metals, it has a high thermal conductivity index, activates minimally when it receives the impact of high-energy neutrons and almost does not interact with the fuel used in fusion reactors.
These properties make it ideal for coating reactor components that are most exposed to plasma, whose temperature is at least 150 million degrees Celsius. It is used, among other components, in the thermal shields of the internal lining of the reactor's vacuum chamber, in the diagnostic sensors or in the divertor, which is, in some way, the “exhaust pipe” that allows the reactor to extract ash and impurities resulting from the interaction of plasma with the most exposed layer of the mantle.
Everything we've seen so far looks great, but using tungsten brings a very important challenge that we can't ignore: its extreme hardness makes it difficult and very expensive to machine with a computer numerical control (CNC) cutting machine. Fortunately, the synthesis of tungsten from the interaction of gases and through chemical deposition represents a great opportunity in the manufacturing processes of heat shields, as it allows researchers to avoid the limitations of CNC machines. Tungsten is a much appreciated chemical element for more than eight decades, and nuclear fusion is helping to cement its protagonism and position it as one of the most coveted metals.
Picture: ITER
Source: EUROfusion
