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JET-ting Towards Fusion?

By Isaac Harris
JET-ting Towards Fusion?

At the end of February, in Culham, Oxford, the decommissioning of the Joint European Torus (JET) research facility began. The facility was first constructed in 1978 to allow for research into fusion to be conducted using the conditions that would be present in a fusion machine. The life of the machine was extended several times, and it led to a number of discoveries that will be used to design and improve future machines. In the machine’s final days of operation, it was also able to set the record for the highest energy output of a fusion machine.

What is fusion and how does it differ from fission?

Fusion is the process through which our sun generates heat. Hydrogen atoms are heated to extreme temperatures which allows for them to join to form helium and causing a release of energy. If fusion could be achieved on earth, this released energy could be harnessed to generate electricity in the same manner as existing power plants. Fusion is only possible due to the extreme heat causing the hydrogen atoms to change state into plasma. The density of the plasma is also linked to the amount of energy produced, with a higher density providing more power. The sun is able to achieve these conditions partly due to its size, which obviously cannot be replicated when designing a power plant. Any fusion machine therefore requires extreme temperatures, and a method of ensuring the fuel stays confined and dense enough to allow for a high energy output to be generated.

Generating energy through fusion does not involve the burning of fossil fuels, and so produces no emissions. However, fusion machines are an especially clean source of energy as, unlike the better-known fission machines, they do not create any long-lived radioactive waste that must be safely stored long after the machine is decommissioned. A fusion machine would also be capable of generating far more energy for a given weight of fuel than existing fission machines. Due to these benefits, a great deal of research and investment is being directed into achieving a working fusion machine.

A Tokamak (such as the JET facility) is a reaction chamber designed to allow controlled fusion to occur. The machine is able to achieve the temperatures required through the use of strong magnetic fields to confine the plasma within the central region of the machine. This prevents the plasma from contacting the side of the rector, which would cause the plasma to cool and prevent the required temperature for fusion from being reached. The chamber of the machine is toroidal, and shaped roughly like a doughnut. Magnets are then positioned in a loop around the chamber to create a magnetic field encircling the centre of the reaction chamber. A second set of magnets is then positioned horizontally around the chamber to create a spiral path. The end result of the magnetic field created is that the plasma will follow the lines of the magnetic field and not contact the machine walls, dissipating heat. The plasma is then able to reach the temperature required for fusion to occur. The machine may also include a central solenoid to assist with the creation of the secondary field and heat the plasma to the temperature required.

Although a number of Tokamak machines exist, JET was unique in that it was designed to produce a reaction using a mix of deuterium and tritium, which allowed for fusion to occur at relatively low temperatures compared to other nuclei.

What comes next?

The decommissioning work on the JET facility is expected to last until 2040. However, research into fusion will continue at the International Thermonuclear Experimental Reactor (ITER), currently being constructed in France. The ITER facility aims to show the practicality of fusion at a larger scale than JET. Current attempts to create a viable fusion machine have been unable to operate continuously with a Q value greater than 1. The Q value represents the amount of energy produced by the reaction in comparison to the amount of energy supplied to maintain the reaction. A Q value greater than 1 means that the machine is producing more energy than it is using, which is obviously a key requirement for a power plant. One of the goals of the ITER facility is to generate power with a positive Q value.

Closer to home, the UK government’s Spherical Tokamak for Energy Production (STEP) programme is hoping to build potentially the world’s first prototype commercial fusion machine, at a site in Nottinghamshire. Unlike JET and other experimental facilities, the plant is designed to actually provide energy, rather than simply carry out experiments. The facility is aiming to be operational in 2040.

Atomic energy and IP

In addition to generating energy, the atomic energy sector also generates a great deal of intellectual property. These patents can cover the entire life cycle of a machine, ranging from the materials used to build the machine, to devices used to safely classify and dispose of any waste products produced by the machine. Patent filings by the UK Atomic Energy Authority (UK AEA) show the range of subject matter covered by this sector, from improved methods for extracting and recovering tritium, to fire suppressing powders.

In 2021, the UK government published an overview of the patent landscape in atomic power, which shows ten times as many patents with a priority year of 2018, compared to patents with a priority year of 2001; recent years have also seen a rapid increase in the number of patents for inventions that were invented in the UK. With fusion forming a key part of the UK’s commitment to reaching net zero by 2050, it seems likely that innovation in the sector, and in fusion-related technologies in particular, will only increase over time.

J A Kemp has extensive experience in clean energy technologies, whether relating to innovating in the engineering, materials or control software, and related fields.