January 27, 2022
Record-breaking results from an experimental Chinese fusion reactor made headlines earlier this month, as international cooperation to develop the potentially game-changing energy source continues to bear fruit. However, an innovative project at the Massachusetts Institute of Technology (MIT) also made a major step forward in November, which could prove to be an even more pivotal breakthrough in the struggle to make fusion energy a reality.
Energy derived from the fusion of atoms has been a long-standing goal of nuclear scientists. The theoretical basis is well known; when hydrogen atoms fuse together into helium, the excess matter is converted into thermal energy—in potentially vast amounts. This process takes place naturally in the central core of stars, and scientists believe that by replicating it and harnessing this power, enough energy could be created to easily cater for all of humanity’s needs. Such energy would be safe, as well as producing zero carbon emissions and minimal radioactive waste. It would also be practically limitless, with the raw materials needed to produce it abundant in sea water; one litre of seawater contains roughly enough fusion material to produce the same amount of energy as 300 litres of gasoline. Optimists have therefore long heralded nuclear fusion as the ‘ultimate energy’ of the future, which could make other types of energy generation obsolete.
The problem is that, without the immense gravitational pressure of a star, it is extremely difficult to recreate the specific conditions required to initiate the nuclear fusion process, which require plasma to be heated to over 100 million degrees Celsius in a doughnut-shaped reactor known as a tokamak. Scientists have been able to heat the plasma to the necessary temperatures for some time, but to prevent it from immediately melting every solid substance in its vicinity, it must be confined inside a powerful magnetic field. So powerful, in fact, that to create it has until now required significantly more power than is produced in the reaction itself, rendering the process uneconomical as a source of energy. “Nobody — no companies, universities, national labs, or governments — have achieved the goal of break-even fusion to date,” said Andrew Holland, CEO of the US Fusion Industry Association. The technical and scientific obstacles to building this ‘star in a jar’ have thus far frustrated researchers, leading to the cliché that nuclear fusion is “always 30 years away”, at least since the first tokamak was built in 1958 by Soviet scientist Natan Yavlinksy.
Every breakthrough is thus greeted with excitement, and so it was in early January when researchers at the Experimental Advanced Superconducting Tokamak (EAST) in Heifei, China, announced that they had superheated a loop of plasma to temperatures of 70 million C, five times hotter than the heart of the sun, for over 17 minutes, thereby smashing the previous record of 6 and a half minutes, set in France in 2003. Last May, the same reactor also broke the record for the hottest temperature recorded in a fusion reactor, running for 101 seconds at 120 million C. For reference, the core of the sun reaches highs of just 15 million C. While EAST was not itself designed to create a fusion reaction or generate power, its plasma-heating achievements have raised hopes that its successor projects will finally be able to produce ‘energy-positive’ nuclear fusion energy. “The recent operation lays a solid scientific and experimental foundation towards the running of a fusion reactor,” said Gong Xianzu of the Institute of Plasma Physics at the Chinese Academy of Sciences, the lead researcher on the project.
Costing over $1 trillion, EAST is part of an international cooperation between 35 countries, including China, India, Russia, Japan, South Korea, the US, the UK, and all EU states, and is being used to test technology for the preparation of the International Thermonuclear Experimental Reactor (ITER), an even bigger reactor being built near Marseilles, France. Described as the ‘most expensive scientific experiment in history’, ITER will contain the world’s most powerful magnet, 280,000 times the strength of the Earth’s magnetic field, and have ten times the plasma capacity of any tokamak ever built. Its fusion reactor is due for completion in 2025, but will not start conducting its first experiments with hydrogen fusion until at least 2035.
Given the urgency of the escalating climate crisis and the growing demand for energy, attention is therefore turning to the many private companies who are forging ahead with new technological innovations that could potentially speed up the process. Most promising at the moment is a partnership between MIT’s Plasma Science and Fusion Center (PSFC) and Commonwealth Fusion Systems (CFS), a start-up backed by Breakthrough Energy Ventures, the sustainable investment fund backed by Bill Gates, Jeff Bezos, and others. In September, CFS announced a breakthrough with potentially even greater impact for the commercialisation of nuclear fusion, by demonstrating the first proof of concept of a substantially more energy efficient method of creating the required magnetic field.
This method, known as SPARC, used high-temperature superconducting magnets, which have only become widely available in the last few years, to produce a magnetic field of 20 teslas – the most powerful ever. With the low-temperature superconductors used in ITER and elsewhere, which have a maximum magnetic field of 12 teslas, the only way to increase the magnetic field is to increase the size of the reactor. The high-temperature superconductor used at MIT, however, is made of flat tape, enabling a higher magnetic field in a smaller device. This means the core of the SPARC reactor can be three times smaller in diameter, and 60 to 70 times smaller in volume that ITER’s, delivering the huge consequent reductions in weight and cost critical for upscaling the technology to the market. Even more crucially, producing this kind of magnetic field required just 30 watts of energy; previous MIT experiments with copper-conducting magnets achieved similar scale and performance, but required 200 million watts.
Building a magnet device with these capabilities was considered to be the biggest technological obstacle to the viability of the project. A SPARC fusion reactor based on this technology is now under construction, for completion in 2025, when the team hope to be able to demonstrate the viability of full-scale commercial fusion, for the first time in the history of fusion research. While SPARC itself is experimental, and only designed to produce heat, the research team will then construct ARC, a power plant based on the same design, which should be generating the long-awaited fusion-based electricity by 2035.
Researchers from CFS and PSFC are therefore describing the successful test of this magnet as a “watershed moment” in the development of fusion energy. “This magnet will change the trajectory of both fusion science and energy, and we think eventually the world’s energy landscape,” said Dennis Whyte, Director of PSFC and founder of CFS. “It’s a big moment,” said Bob Mumgaard, CEO of CFS. “We now have a platform that is both scientifically very well-advanced, because of the decades of research on these machines, and also commercially very interesting. What it does is allow us to build devices faster, smaller, and at less cost.”
Another advantage, according to Martin Greenwald, a plasma physicist at MIT, is that such fusion power plants could replace fossil fuel plants directly, and would be much easier to integrate with existing power grids than renewable energy sources, which are often located in remote, inaccessible areas. As MIT said in a press release, the breakthrough might therefore “pave the way for practical, commercial, carbon-free power”. Andrew Holland of the Fusion Industry Association agreed: “This is not hype, this is reality. With advances from across the fusion industry, we’re seeing a new, clean, sustainable, always available energy source being born.”
