Interview with Paola Batistoni, former head of ENEA’s Fusion Energy Development Division and currently Italy’s representative on the Governing Board of the European agency Fusion for Energy
What do we mean by nuclear fusion energy?
Nuclear fusion is the process that takes place inside stars and powers them; a process in which, under certain conditions, the nuclei of light atoms fuse into heavier nuclei, releasing a large amount of energy. It is the opposite reaction to nuclear fission, in which very heavy nuclei, located at the other end of the periodic table of elements (typically uranium, plutonium), under certain conditions break apart, also in this case releasing a large amount of energy. There have already been plants producing energy from nuclear fission for decades, whereas fusion is still in the research and development phase. There is, however, great interest in this technology, which is being studied all over the world for the production of electricity, by virtue of the favourable characteristics it presents. First, it does not produce greenhouse gases, so it is an energy technology that can contribute to the decarbonisation of society; secondly, the fuel is practically unlimited. The nuclear fusion reaction envisaged involves, in fact, isotopes of hydrogen: deuterium, unlimited in nature (of approximately 6,000 hydrogen atoms, one is in the form of deuterium), and tritium, on the other hand, not present in nature but generable within a fusion plant starting from lithium. And even if it is true that lithium is a strategic material and a resource not so unlimited, for the purposes of nuclear fusion there is a sufficient quantity of lithium on Earth to produce fusion energy for hundreds of thousands of years, thanks to the fact that in nuclear processes the amount of energy produced per unit of mass is several million times greater than that generated in chemical processes, so very little matter is needed to generate a great deal of energy (just consider that the fusion of 1 kg of deuterium-tritium generates the same energy as is generated in the combustion of 6,000 tonnes of natural gas). Moreover, unlike what happens in fission, in the fusion process no high-intensity, long-term radioactive waste is generated. In the reaction between deuterium and tritium only neutrons and helium nuclei are produced; and although the neutrons produced, by interacting with the reactor structures, make them radioactive, with an appropriate choice of materials the induced radioactivity can decay over the course of about 150 years. Fusion is also safe, because the reaction must be continuously fuelled by introducing hydrogen from outside and can be interrupted at any moment; and by not using uranium, plutonium, or materials with military implications, it has no risks of nuclear proliferation, that is, of production of nuclear weapons. And last but not least, nuclear fusion is a programmable process: it can produce energy continuously and independently of weather, climatic or seasonal conditions. In this sense, it can optimise the energy mix that is taking shape in the coming years (certainly dominated by renewables), complementing other sources in providing what is known as the “baseload”, the minimum and constant level of electricity demand that a grid must meet at all times.
Let us take a step back. When did we start replicating the nuclear fusion process in the laboratory?
The history of fusion is extremely interesting and is deeply intertwined with the major events that have marked the last decades of human history. Until about one hundred years ago, there was not the faintest idea of how the Sun generated its energy. It was clear that it was billions of years old and it was known how much energy it produced, but classical physics was unable to explain its origin. Only with the birth of atomic physics did it become possible to hypothesise that this energy might be of nuclear origin, and it took all of the 1920s and 1930s to understand the theory of nuclear reactions that occur inside the stars. The idea of replicating these processes on Earth to produce energy then emerged in the years around the Second World War, and immediately after the war the first experiments began, in the United Kingdom, the United States and the Soviet Union, inaugurating the two main lines of research: magnetic confinement and inertial confinement. To obtain nuclear fusion reactions, in fact, particular conditions are required: the reactants, that is hydrogen, must reach extremely high temperatures – as in stars – so that the nuclei acquire sufficient kinetic energy to overcome Coulomb repulsion, come very close together, and allow the strong interactions to take over making nuclear fusion possible. In practical terms, hydrogen must be heated to approximately 150 million degrees, a temperature ten times higher than that at the centre of the Sun, beyond which hydrogen is neither solid, nor liquid, nor gaseous: it is in the plasma state, that is, a gas in which atoms are no longer intact but split into their components, nuclei and electrons. The problem is that the hotter gases are, the more they tend to expand, whereas to favour fusion it is instead necessary to be able to confine this gas within a very precise volume, as densely as possible, in order to increase the probability of collisions. Reliance was therefore placed on the properties of charged particles, which, in the presence of magnetic fields, are forced to move along the magnetic field lines without drifting away from them, just as a train is forced to move along its tracks: it was born this way, with the first experiments after the Second World War, the magnetic confinement technology, or the confinement of a gas within a well-defined volume using powerful magnetic fields. Over time, magnetic configurations became increasingly complex, in response to the need to maximise the temperature and particle density within the plasma, and also to counteract drift motions that tend to move particles away. But the real reason why this endeavour proved so arduous is that at the beginning no one knew anything about plasmas. It is thought that more than 99% of the matter in the universe is in the plasma state (stars, nebulae, interstellar space), and that only some extremely singular points, such as rocky planets, are not plasma. However, on Earth, examples of plasma are scarce: we have fire, a very low-temperature plasma, and lightning; but no one, at the time of the first experiments, had ever produced and observed plasma in the laboratory. There was an entire preliminary body of work to be done, years of in-depth study of the physical characteristics of this state of matter and its behaviour in the presence of magnetic fields, which led, after decades of experimentation and coordinated efforts at global level, to the JET result: keeping the plasma stable for five seconds at a temperature of tens of millions of degrees, in conditions close to those that must exist in a reactor.
What is JET and why are these five seconds significant?
JET (Joint European Torus) has been – it has recently concluded – the most advanced European experiment on fusion. On 3 October 2023 it succeeded, within the magnetic confinement line, in producing a plasma that generated 12 megawatts of power and 69 megajoules of energy in a controlled manner for five seconds: an interval that may seem negligible, but that is in fact very long when compared with the characteristic timescales of plasma, which, in the absence of control, extinguishes itself in fractions of a second. Clearly, JET’s result represents only a starting point. For fusion to have civilian applications, such as the production of electrical energy, experiments will have to continuously generate an amount of energy 30-40 times greater than that required to bring the plasma to fusion conditions. And although magnetic confinement experiments have come very close to power parity (the so-called breakeven), this parity has not yet been achieved. The situation is different for inertial confinement experiments, namely those experiments which, under the action of external agents, typically the radiation from powerful lasers, compress small deuterium-tritium targets of millimetre dimensions to temperatures and densities such that conditions for nuclear fusion occur at their centre. The most important among them, that of the National Ignition Facility (NIF) in Livermore, in the United States, achieved energy breakeven in 2022, and more recent experiments based on the same technology have even surpassed breakeven, while still remaining far from the energy multiplication levels required for feeding into the electricity grid.
Which experiment are we focusing on today?
At present, the most important project in the world is ITER, a magnetic fusion reactor designed to produce 500 megawatts of power with a power gain of 10, which is interesting in many respects. I mentioned at the beginning that fusion has been influenced by international events, as often happens with Big Science, precisely because it is a large and ambitious undertaking, involving substantial resources and broad participation worldwide. In the 1980s, Reagan and Gorbachev, who aimed to significantly reduce military spending in their respective countries, agreed to collaborate on nuclear fusion, and this agreement took concrete form in the ITER project. Europe had already built and was in fact beginning to operate JET, but was also thinking about the next step, a machine larger than JET that could truly produce electrical energy. Therefore, when ITER got underway, the question arose as to whether it was appropriate to continue with the European project or to join the global ITER collaboration, and in the end Europe chose ITER. Like Europe, Japan, China, South Korea and India also chose ITER: today the project involves almost the entire world, seven major partners (with Europe considered as a single entity), and after a long journey, construction of the experiment is nearing completion in southern France, at Cadarache. It has been a remarkable undertaking. It is often said that fusion is “lighting a star”, but it is also about building the box that will safely contain this star and be able to collect the energy produced and transform it into electrical energy. When ITER began, many of the technologies for this “box” did not exist, but the project has succeeded in developing them. The very large superconducting magnets made of niobium–tin (Nb₃Sn) are an example: 17-metre magnets capable of generating extremely intense magnetic fields, up to 12 tesla, which are the largest and most powerful in the world; or the divertor technology, the component located in the inner part of the reactor, which receives and dissipates the portion of fusion energy that neutrons do not carry out and which therefore remains inside the box. It is an enormous heat flux, the same amount that the divertor would receive if it were on the surface of the Sun. So, while it is true that better results have been achieved in terms of energy gain in inertial fusion, it is important to emphasise that magnetic fusion is further ahead in terms of technology.
Is the acquired technological maturity sparking industry interest in fusion?
The results of JET and NIF, and, above all, the construction of ITER, have greatly changed the international fusion landscape. Industrial interest has grown, and over the past five or six years we have witnessed a truly massive increase in private investment, amounting today to several billion. Dozens of start-ups have been founded in the UK, Europe and, mostly, the US, such as Commonwealth Fusion Systems (CFS), created precisely with the aim of building the ARC reactor within the next decade, to initiate the transition towards commercial fusion power generation. Alongside private investment, public investment has also increased, first and foremost in China, where the acceleration in terms of new experiments and technological development in the sector is truly impressive. Overall, there is great ferment, and we hope that Europe will manage to remain competitive on the international stage. Europe’s commitment to fusion dates back to 1957, to the Treaties of Rome, which established Euratom, the European Atomic Energy Community. From then on, all the framework programmes of the European Union have supported and financed fusion research, fostering the growth of expertise in almost all European countries, and ensuring that Europe held scientific and technological leadership in the sector. JET has so far been the most successful nuclear fusion experiment, and today Europe is the majority partner in ITER, with a 50% share.
What has been Italy’s contribution?
Italy is the second largest contributor to the European programme after Germany. It has been involved in fusion since the Euratom treaties of the 1950s, and the first research on ionised gases in Frascati dates back to 1958. Since then, we have developed extensive expertise, present at ENEA, at the CNR, at INFN, in the research consortia CREATE and RFX in Padua, and in many university groups. ENEA coordinates a very extensive network on nuclear fusion, and the current Director-General of ITER, Pietro Barabaschi, is Italian. We have a very strong school, which has grown thanks to the many experiments, such as the FT Tokamak and its FTU upgrade in Frascati, and the RFX experiment in Padua. Over time, we have also built numerous technological facilities, such as the 14 MeV neutron source in Frascati (Frascati Neutron Generator), built to study the effect of neutrons produced in the fusion reaction on surrounding materials; the Neutral Beam Test Facility in Padua, which is developing the structure for the neutron injection system that will heat the ITER plasma; the facilities for studying the components inside the reaction chamber, known as mantles, which use neutrons interacting with lithium to produce the tritium needed to continue the fusion reactions. Italian research is engaged on all fronts, both in physics and in technology for fusion, and has always involved, in a close collaborative relationship, Italian industry, with the result that the latter has secured contracts to produce high-technology components for ITER worth more than €2 billion. In this sense, fusion research in Italy is a success story: it has strengthened our national system, generating a truly significant economic and skills-based return. Furthermore, all the expertise acquired so far enables us to take the next step: building a new magnetic confinement experiment, the Divertor Tokamak Test (DTT) facility in Frascati, with the aim of studying, developing and testing solutions for power exhaust on the divertor under reactor conditions. The solution developed for ITER may in fact prove insufficient in reactors with higher power levels, and advanced solutions are required both in terms of magnetic configurations and in terms of materials and engineering layouts. DTT will be the most important and technologically advanced European fusion experiment in Europe in the coming years, and is already under construction at the ENEA centre in Frascati. The project involves Italy’s leading research institutions (including INFN), several Italian universities and consortia active in fusion, and, for the first time, ENI, Italy’s largest energy company – a clear indicator of industry interest. The endeavour is an integral part of the European fusion programme and currently represents Italy’s largest commitment alongside its participation in ITER and IFMIF-DONES, an intense neutron source based on a deuterium ion accelerator on a lithium target, dedicated to the development of materials for fusion. Already under construction in Spain, IFMIF-DONES will be an infrastructure in which different materials will be subjected to neutron bombardment, at levels similar to those occurring inside the reactor, to test their resistance and their capacity to maintain good physical and structural properties for prolonged periods. Italy has joined the project through INFN, which will be responsible for building the injector and the low-energy section of the accelerator, and will soon see the involvement of ENEA, which will collaborate in the construction of the target.
When can we expect fusion energy to enter our electricity grid?
Fusion has the reputation of always arriving “in fifty years’ time”. In recent years, however, significant progress has been made, the level of commitment has changed, and many partnerships between research and industry are now emerging for the development of fusion technologies. If this commitment is confirmed, we will witness a significant acceleration towards fusion energy in the coming years, also because there are no insurmountable obstacles. What is needed is a very pragmatic, results-oriented approach, which is precisely what industry is bringing.
BIO
Paola Batistoni was Head of the Fusion Energy Development Division at ENEA, where she has been working on nuclear fusion since 1984. She has taken part in numerous magnetic confinement fusion experiments in Italy and abroad, including JET, and has led several European projects aimed at the design and construction of the experimental fusion reactor ITER. During her professional career, she has also been editor of one of the leading international journals on fusion (Fusion Engineering and Design) and responsible for industry relations in Italy, actively promoting its involvement in the fusion programme. She currently represents Italy on the Governing Board of the European agency Fusion for Energy.
