Czech fusion reactor to take over from Americans

It has been two years since the renowned US research university Massachusetts Institute of Technology (MIT) announced a world record. It concerned research into nuclear fusion, which could eventually meet humanity’s energy needs for millennia – in an environmentally very friendly way. The new COMPASS-U fusion reactor in Prague is expected to take over the baton in this field of research. Czech scientific diplomacy is also working towards this.

What world record at MIT was it? At the Alcator C-mod fusion reactor, US scientists achieved plasma pressure of 2.05 atmospheres, something no one else had managed. The ability to achieve high hydrogen plasma pressure thanks to its high density and temperature (in this case more than 35 million degrees Celsius) is one of the key parameters for using the fusion of nuclei of light elements to generate energy – unlike the more familiar fission of nuclei of heavy elements in nuclear power plants.

To be sure, the news of the record was primarily intended to send a signal to the world, including the wider public, that intensive efforts to harness thermonuclear fusion are continuing. Radomír Pánek, director of the Institute of Plasma Physics of the Czech Academy of Sciences in Prague, points out that the record is rather a symbolic culmination of the high-quality research carried out at MIT thanks to its fusion reactor – or tokamak.

It should be added that the Alcator C-mod tokamak’s record came at the very end of its life – it was decommissioned at MIT and the world has had no replacement since. This reactor had two important features at the same time: first, it generated a strong magnetic field, used to confine (isolate) the hot plasma; and second, its plasma had a shape similar to that which plasma will have in the future international ITER reactor being built in France. The ITER project is crucial in this respect for scientists worldwide – Europeans, Americans, Russians, Chinese, Indians, Koreans and Japanese are all collaborating on it.

The ball is in Czech hands

The new Czech COMPASS-Upgrade tokamak is now expected to build on MIT’s fusion reactor. The Institute of Plasma Physics of the Czech Academy of Sciences currently uses research infrastructure centred on the existing experimental COMPASS reactor. In around five years, it is to be replaced by a new tokamak, for whose construction the institute has secured almost CZK 800 million from European Union funds. Specifically, this comes from the Research, Development and Education Operational Programme, which falls under the Czech Ministry of Education. Other parts of the current infrastructure, including buildings, energy supplies and the diagnostic system, will be retained and expanded.

COMPASS-U, which will weigh more than 250 tonnes, will be the only facility in the world to meet the same criteria simultaneously as the MIT tokamak once did, while also surpassing it in a number of other parameters. Its magnetic field will reach 5 Tesla, and its plasma geometry will be similar to that in the ITER tokamak and, most importantly – which Radomír Pánek considers particularly significant – the DEMO prototype of a future European fusion power plant, whose construction will follow on from the ITER project.

“The design of the COMPASS-U tokamak is based on a detailed study of similar facilities around the world and responds to the key challenges that can be identified in this field,” says Czech science diplomat in Washington Luděk Moravec, who is negotiating cooperation with the US Department of Energy.

In July this year, a US delegation visited Prague’s Institute of Plasma Physics, including representatives of leading research organisations and companies – including MIT, the Princeton Plasma Physics Laboratory and General Atomics. “US scientists showed great interest. They would like to take part in both the construction and the future scientific use of the COMPASS-U tokamak. We are now discussing possible financial support from the US Department of Energy,” says Radomír Pánek.

Plasma changes its behaviour

Cooperation with the Americans is particularly promising in two areas. The first possible direction concerns collaboration on developing strong-magnetic-field tokamak technology and related fusion plasma physics. The second area is research into the use of liquid-metal technology in fusion reactors.

In the first case, we return to the research whose results came to public attention thanks to the aforementioned Alcator C-mod tokamak record. “These experiments indicate that at a high magnetic field of around 5 Tesla, which will be used by both ITER and the DEMO reactor, plasma begins to behave somewhat differently – more stably,” Director Pánek explains. The aim now is for another tokamak to confirm and build on MIT’s results in this regard. Given the parameters described above, no fusion reactor in the world other than the planned COMPASS-U will be capable of doing so in the foreseeable future.

This is also apparent from the project description in the application for EU funding. According to it, COMPASS-U is a unique facility that is currently lacking both in the European fusion programme and globally.

Liquid metals

As for the use of liquid metals (such as lithium, tin or their alloys), the relevant research is linked to a broader issue: how to ensure trouble-free removal of plasma and energy from the plasma core out of the reactor through the so-called divertor. It will transfer energy from the tokamak to the primary and subsequently secondary circuit of a future fusion power plant, which resembles today’s thermal power plants or the secondary circuits of existing nuclear power plants – heat is used to produce steam, which drives a turbine.

The problem is that extreme energy fluxes place high demands on the materials from which the individual parts of the tokamak, and especially the divertor, will be made. This part of the tokamak must withstand an energy flux comparable to being near the surface of the Sun. Liquid metals represent a promising technology here, potentially ensuring continuous renewal of the divertor surface, which would otherwise rapidly degrade and be destroyed under the extreme energy flux from the plasma.

“Colleagues in the US and Russia have the most experience in this area of research. However, COMPASS-U will be the first facility capable of testing this technology under conditions that are in many respects close to those of future fusion power plants,” adds Radomír Pánek. The US national laboratory Princeton Plasma Physics Laboratory has expressed particular interest in cooperation in this area.

The European EUROfusion consortium, which coordinates thermonuclear research within the European Union, also expects the COMPASS-U tokamak to serve as Europe’s test facility for the use of liquid-metal technologies in developing an energy source based on thermonuclear fusion.

US shift

While the Czechs are succeeding in gaining a relatively significant role in European Union nuclear fusion research and specifically in the EUROfusion consortium, the question was how strong the support for US scientists working on thermonuclear fusion would be. The US environment is known for its unrelenting debate over which specific research should or should not be supported. It seemed that nuclear fusion might not fare particularly well under Donald Trump’s administration, but recent months suggest quite the opposite.

Science diplomat Luděk Moravec says nuclear fusion is now receiving greater attention from the US government, culminating in this year’s increase of the budget for relevant research by around 40 percent. “The largest part of this is an increase in US participation in the ITER project,” Moravec notes. From the Czech perspective, another of Moravec’s observations may also be favourable: “President Trump’s administration insists on actively and thoroughly seeking synergies in scientific infrastructures being built abroad, rather than maintaining the broadest possible range of its own facilities.”

Sharing know-how

When it comes to the benefits of Czech-US cooperation, it will be important not only what financial contribution the US side offers and whether Americans could also contribute some equipment to the research infrastructure at Prague’s Institute of Plasma Physics.

The absolutely crucial opportunity for both sides lies in knowledge and overall research capacity. “Americans will have an opportunity to continue their research and develop their know-how. For us, it is naturally very attractive that we could share the experience and know-how of leading US research institutions,” says Radomír Pánek.

Czech scientists themselves are also building on a long tradition of nuclear fusion research, and their findings are undoubtedly highly beneficial to the global scientific community. Looking back into history, Czechoslovak scientists were the first, in the mid-1970s, to provide experimental evidence that a high-frequency wave in plasma can drive an electric current. Electric current in a tokamak is crucial for both plasma confinement and its stability.

Czech tokamaks

The history of domestic tokamaks also says something about the progress made by the Czechs. There are currently two in the Czech Republic. The older tokamak (now called Golem), which currently serves educational purposes at the Faculty of Nuclear Sciences and Physical Engineering of the Czech Technical University in Prague, was obtained by the Czechs in 1974 from Moscow’s I.V. Kurchatov Institute of Atomic Energy. It was later modernised and served the Institute of Plasma Physics for a long time. The second tokamak – the aforementioned COMPASS, used by the Institute of Plasma Physics today – arrived in Prague in 2006 from the UK fusion energy centre in Culham near Oxford.

At the beginning of the millennium, the British built another tokamak, MAST, but as COMPASS still offered significant potential for use, the European Commission provided it to the Czechs, who built new infrastructure for it. Now, thanks to the planned unique COMPASS-U project, there is a prospect that the Czechs could in turn hand over the existing experimental reactor to one of their foreign partners, who have already expressed informal interest.

“We have reached the stage where, thanks to financial support from the European Union and the gradually developed in-house know-how of an ambitious young team, we can independently develop a tokamak with unique parameters. Conversely, we can afford to pass on the facility that we have used so far,” Director Pánek notes.

The author of the article is a consultant and energy projects specialist at the HATcom agency.

Lead photograph: cross-section of the COMPASS-U tokamak