ITER is not the only path we are taking towards commercial nuclear fusion. The reactor that an international consortium in which the European Union plays a prominent role is building in the French town of Cadarache is one of our best assets to reach this milestone, but, fortunately, it is not the only one.
Another very promising project is in the hands of the Massachusetts Institute of Technology (MIT) and the company Commonwealth Fusion Systems (CFS). The former contributes its resources in the field of research and innovation, and the latter is in charge of building SPARCwhich is what they call their prototype nuclear fusion reactor using magnetic confinement.
The fact that MIT is directly involved in the design of this reactor conveys confidence because it is objectively one of the most reputable research centers on the planet. It is also worth not forgetting that CFS was founded by various MIT professors and researchers, and, above all, that it relies on the financial muscle of Bill Gates and Jeff Bezos, who are two of its main investors.
The magnitude of the challenges that need to be overcome to make commercial nuclear fusion viable requires facing a large financial investment, and there is no doubt that having the financial backing of two of the richest people in the world helps. Indeed, the scientific and economic soundness of their proposal has prompted MIT and CFS to put on the table a very ambitious bet (perhaps too much): they want to have their nuclear fusion reactor prototype ready and operational in 2025.
The heart of SPARC is its high-power superconducting magnets
The backbone of ITER and SPARC is essentially the same: a type reactor tokamak. Inside, the plasma at a very high temperature that contains the nuclei of deuterium and tritium, the two isotopes of hydrogen that are involved in the nuclear fusion reaction, is confined by a very powerful magnetic field in order to prevent it from coming into contact with the walls of the vacuum chamber. If it did, it would damage them irreversibly.
So far the strategy of both projects is identical, but the way they are addressing some of the biggest challenges is different. The main ingredient in SPARC’s magnetic motor is high-power, high-temperature superconducting magnets that, according to their simulations, effectively keep the turbulence caused by plasma destabilization (This is one of the biggest challenges posed by nuclear fusion today.)
SPARC’s high-power superconducting magnets in simulations manage to keep turbulence that causes plasma destabilization at bay
Furthermore, according to Martin Greenwald, deputy director of MIT’s Center for Nuclear Fusion and one of the founders of CFS, the energy these magnets require to generate the magnetic field responsible for plasma confinement is much smaller that it is necessary to invest in other magnetic motors, such as, for example, the one used by ITER.
This property on paper allows SPARC to achieve a positive energy balance, so that the energy that is necessary to supply the reactor to initiate and sustain the fusion reaction over time is less than that produced. The proposal of the team led by Greenwald seems too optimistic, but it has something in its favor that is worth not overlooking.
In October 2020, MIT and CFS researchers published seven peer-reviewed articles in the magazine Journal of Plasma Physics in which they explain the keys to their technology. And already at that time, Greenwald argued that these articles allow them to trust that the strategy they have developed is reliable enough to bring the construction of the SPARC nuclear fusion reactor to fruition.
In addition, this project has another asset in its favor: its reactor tokamak it is much smaller than the one used by ITER, so the time needed to invest in its construction should theoretically be less.
Objective: to have the operational prototype with commercial ambition in 2025
If everything goes smoothly and the itinerary set by EUROfusion, which is the European Union organization that coordinates its scientific contribution to ITER, is not altered, the first tests with plasma will start in 2025. However, this is not the end of the road. Not much less. ITER is an experimental nuclear fusion reactor, and on the way to commercial fusion we must take into account two more projects: IFMIF-DONES and DEMO.
ITER is an experimental nuclear fusion reactor, and on the way to commercial fusion we must take into account two more projects: IFMIF-DONES and DEMO
Broadly speaking, IFMIF-DONES seeks to develop materials that, among other tasks, will cover the interior of the walls of the vacuum chamber in order to withstand the direct impact of high energy neutrons (14 MeV) produced by the fusion of deuterium and tritium nuclei. This is another of the great challenges of nuclear fusion. And then the DEMO project will have the responsibility of collecting everything learned in ITER and IFMIF-DONES to make possible the construction of a functional prototype of a commercial nuclear fusion reactor.
The EUROfusion itinerary foresees that the tests that will be carried out in DEMO will conclude in the 60s, and that will be the moment in which it will be demonstrated the commercial viability of nuclear fusion if everything goes according to plan. What is surprising is that the prototype that MIT and CFS plan to have ready in 2025 has an ambition comparable to that of ITER, but the difference is that they intend SPARC to be ready and fully operational within three years.
It would be amazing news if SPARC is ready in 2025. And if it is delayed and arrives before the end of this decade, it would still be an enormous feat.
Commercial nuclear fusion aspires, together with renewable energies, to have a leading role in the sustainable energy model that respects the environment in which we have embarked. And there is no doubt that the context of energy crisis and climate emergency in which we currently find ourselves requires putting in place effective solutions as soon as possible.
It would be amazing news if SPARC is ready in 2025. And if it is delayed and arrives before the end of this decade, it would still be an enormous feat. There is no doubt that the magnetic motor that the MIT and CFS researchers have designed is extraordinarily promising, but it seems risky to accept that, beyond what the simulations reflect, this is going to be the ultimate solution to turbulence that destabilize the plasma and with which the thousands of scientists who participate directly or indirectly in ITER are dealing.
In addition, the need to develop materials that must withstand the impact of high-energy neutrons is still on the table. This challenge is present in both ITER and SPARC, so both projects will benefit from advances in materials engineering that are already being carried outand also of those that will presumably arrive with IFMIF-DONES, whose facilities will probably be housed in Granada.
These are the ingredients of SPARC ReBCO magnets: copper oxide, barium and rare earths
In a context like this, in which it is necessary to overcome so many challenges of a titanic scale, the date proposed by EUROfusion for DEMO seems reasonably realistic. On the contrary, the one handled by those responsible for SPARC seems overly optimistic As much as this project has the scientific capacity of MIT and the financial backing of investors with the financial muscle of Bill Gates or Jeff Bezos, among others.
In any case, I hope we are wrong. CFS plans to have ARC list (Affordable, Robust and Compact reactor), the first commercial power plant equipped with a nuclear fusion reactor, at the beginning of the next decade. There is no doubt that it would be exceptional news for all of humanity if this technology becomes available in such a short time.
From then on, it would be necessary to build hundreds of nuclear fusion power plants scattered throughout the planet, since putting just a few would have minimal impact in our energy model. But, yes, the greatest challenges would have been left behind and we could look to the future with an optimism that, unfortunately, is not yet within our reach.
More information: CFS