New Experiment Could Pave the Way for More Practical, Affordable Nuclear Fusion

The MAST Upgrade is much smaller and uses a different design than other nuclear fusion reactors.

Many researchers consider nuclear fusion as inevitable, and a real viable solution for how to power a post-carbon world. But is it simply too expensive, and too difficult, to produce? A new experiment is looking to change that.

Autor*in Mark Newton, 10.31.20

A new experiment looking to unlock the secrets of nuclear fusion has been activated for the first time at a UK research institution. The project has been designed to investigate the potential of nuclear fusion at a much smaller, and cheaper scale than previous models. The team behind it hope its success could pave the way for rapid adoption, on a commercial basis, of nuclear fusion energy.

The machine, developed by the Culham Center for Fusion Energy in Oxfordshire, England is officially titled the Mega Amp Spherical Tokamak Upgrade – or MAST Upgrade for short. It differs from previous designs, including the Joint European Torus (JET) also housed at Culham, by featuring a more spherical design in which the reaction takes place. Previous fusion tokamaks (the devices that produce controlled thermonuclear fusion power) tended to resemble a doughnut in construction, with a large central hole. The MAST system has endeavoured to reduce the size of this hole to a minimum, taking on a more spherical appearance. It is hoped this design will enable higher performance, including a stronger magnetic field required for nuclear fusion.

Current nuclear energy is based on concepts of fission – the breaking of heavier chemical elements into lighter ones. When this occurs, vast amounts of energy can be released, however the approach comes with some significant – and well known – downsides. Firstly, the process also releases large amounts of radiation, which must be contained and controlled. Secondly, it also produces nuclear waste that can remain dangerous for thousands of years. Thirdly, it also depends on specific chemicals, such as uranium, which must be mined from the Earth’s crust and come with additional concerns regarding nuclear weapon proliferation.

Fusion, on the other hand, takes a different approach. Instead of splitting nuclear chemicals, lighter chemicals are fused together within a tokamak. Often this is achieved by using strong magnetic fields to confine hot ionised gas, known as plasma, into a vessel. Similar to fission, this process also releases energy, and essentially echoing the system that takes place in the energy-producing core of the sun. However, current attempts to achieve fusion require much more energy to be placed into the machine than are taken out, although this could soon change.

The Future of Limitless Clean Energy?

Nuclear fusion has long been seen as “the holy grail” of energy, and could potentially provide endless, unlimited and clean power. Unlike nuclear fission, fusion produces much less radiation, while its waste would lose its radioactivity in under 100 years, where it could once again be reused.

Instead, the basis of the fusion reaction are chemicals such as deuterium, tritium and lithium which are widely available in many parts of the Earth – although there are of course issues around the environmental and human cost of lithium mining in its current form. No long-lived radioactive nuclear waste is produced in the process, with the only major by-product being helium – an inert, non-toxic gas that is also currently in short commercial supply. While some radioactive material is produced, it is a much smaller amount than created by nuclear power plants and the radioactivity of it quickly declines. Unlike with fission reactors, fusion energy also comes with no meltdown risks. If practical nuclear fission became a reality, it could offer a clean, and virtually inexhaustible energy source for the future.

Currently, JET is the largest tokamak in operation, but it will soon be eclipsed by the ITER tokamak in Southern France. This multi-billion dollar project is truly international in scope, with funding being provided by the European Union, China, India, Japan, South Korea, Russia and the United States. The size of its budget is also matched by its physical scale, with the ITER site occupying a space of 180-hectares.

It is expected that when the ITER tokamak receives its first plasma in 2025, it will pave the way for workable fusion energy, however it does have some downsides. The vast scale of the project means its expense and the space it requires is likely beyond the resource capabilities of even the most heavily-industrialised nations. For some carbon intensive states, for example Malaysia, the start up costs and space requirements of fusion would likely be too high to practically consider, even if it proved cheaper in the long run.

This is the central issue the MAST Upgrade hopes to solve. By using a much more compact spherical tokamak, they hope to drastically reduce the initial costs and size requirements of nuclear fusion. The MAST system was comparatively cheap at around only 55 million GBP (!) and is small enough to be housed in conventional cities.

The problem is that smaller machines are naturally more susceptible to overheating, which is one of the largest challenges of nuclear fusion. To create the condition for forcing together chemicals in a tokamak, temperatures approaching ten times hotter than the Sun are required. This could rapidly melt instruments and break down components. To overcome these hurdles, the MAST Upgrade includes the Super-X diverter, an advanced exhaust system that channels plasma out of the machine at lower temperatures.

For many nuclear physicists, the arrival of nuclear fusion is a matter of ‘when’ not ‘if’. As such, many states are scrambling to become world leaders in this regard. The UK, which has arguably led development with the JET tokamak, hopes to have a fully functional nuclear fusion plant by 2040.

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