A brief history of nuclear fusion

Since the 1950s, international cooperation has been the driving force behind fusion research. Here, we discuss how the International Atomic Energy Agency has shaped the field and the events that have produced fusion’s global signature partnership. By Matteo Barbarino

At the Second United Nations Conference on the Peaceful Uses of Atomic Energy held in Geneva, Switzerland, more than 60 years ago in September 1958, controlled nuclear fusion research was revealed to the world. After almost a decade of studies carried out in secrecy, and the realization that major difficulties lay ahead on the way to generating power from nuclear fusion, this event marked the beginning of global cooperation and the starting point of the International Atomic Energy Agency’s (IAEA) activities in support of nuclear fusion.

Four concepts for controlling thermonuclear fusion reactions were unveiled1. First, the tokamak — a configuration in the form of a torus in which ionized gas or plasma is confined by externally produced magnetic fields. Second, the pinch, in which plasma is kept in place thanks to magnetic fields self-generated within the plasma itself. Third, an open design — the magnetic mirror—where plasma is reflected from a high-end-density to a low-end-density magnetic field. Fourth, the stellarator, a helical system also relying on magnetic fields to hold the plasma. A short film about this conference is available online (https://go.nature. com/2LP10FD; relevant footage starts at around 09:43).

In the wake of the conference, IAEA Deputy Director General, Hubert de Laboulaye, wrote to his superior, Sterling Cole: “Complete exchange of information and coordinated research on an international scale appears to be the only means to get things going faster”. At the same time, the IAEA’s Board of Governors established a Scientific Advisory Committee with members drawn from among five of the six vice presidents of the Geneva conference: Homi Bhabha (India), John Cockcroft (United Kingdom), Vasili Emelyanov (Soviet Union), Wilfrid Lewis (Canada), and Isidor Rabi (United States). As one of its first actions, the Committee proposed the establishment of an international scientific journal and a series of conferences on nuclear fusion; the journal Nuclear Fusion and the Fusion Energy Conference (FEC) were born, which have since then shaped the field.

The tokamak leap.

During the early 1960s, pioneering results of nuclear fusion research were presented at the first FEC in Salzburg, Austria, in 1961 and at the second FEC in Culham, United Kingdom, in 1965.  Bad news came first: instabilities can develop in plasmas and eventually lead to the rapid loss of thermal and magnetic energy — a phenomenon today known as plasma disruption, which remains a major concern for tokamaks. Good news followed soon after. At the third FEC in Novosibirsk, Russia, in 1968, it was reported that the Soviet T-3 tokamak, had reached performance ten times higher than any other fusion machine at the time. Doubts lingered and within months a British team joined the Soviet group to

confirm the game-changing results (a short film about the mission to Moscow’s Kurchatov Institute is available at https://go.nature.com/2ykwP5W). The implications of the discovery rippled across the world; Europe, Japan and the United States immediately started their own domestic tokamak programs.

Stepping up cooperation

At the beginning of 1970, cooperation between countries was based solely on bilateral agreements, but this was about to change when the IAEA called for a panel meeting to discuss ways to improve international cooperation. During the preparation of the meeting, Henry Seligman, IAEA Deputy Director General, wrote to Rendel Pease, Director of the Culham Laboratory (today the Culham Centre for Fusion Energy): “In my secret inner heart, I hope that they will all say it would be wonderful to construct one or more fusion prototype reactors, manned by mixed US, USSR, UK and other’s crews8. A few months later, Seligman’s dream became a reality. The panel stated that “It was recognized that [large-scale international projects and common funding] may be the most economical way to achieve the ultimate goal within the shortest possible time”.

From the late 1970s onward, fusion power development became the focus of coordinated research under the stewardship of the IAEA, including studies on the environmental impact, safety, waste management and decommissioning, and fusion reactor technology. Initial definitions and requirements of a demonstration reactor (or DEMO) were internationally agreed upon and design studies on commercial power tokamak reactors commenced. In view of this progress, the International Tokamak Reactor (INTOR) was established by IAEA in 1979 to identify programmatic and technical objectives for a future reactor-scale experiment, to be built as a cooperative international enterprise, that would demonstrate and develop the science and technology required for a fusion power reactor.

Back to Geneva

The next decade started with a bang. In the ASDEX (Axially Symmetric Divertor Experiment) tokamak in Germany, confinement suddenly doubled as the plasma was exposed to intense heating. The discovery of this so-called high confinement was presented at the ninth FEC in Baltimore, United States, in 1982, and it would turn out to be one of the most important discoveries in the history of fusion research. In the cold war, attention turned to Geneva again where, in the fall of 1985, Mikhail Gorbachev and Ronald Reagan met to discuss a series of strategic items, including the international cooperation in controlled fusion for peaceful purposes.

At the summit — driven by, among other factors, the success of INTOR in demonstrating the feasibility of a global technical cooperation — the diplomatic impetus for a new scientific partnership emerged, marking the slow dissolution of the Iron Curtain. A joint statement was issued on 21 November 1985 stating that “The two leaders emphasized the potential importance of the work aimed at utilizing controlled thermonuclear fusion for peaceful purposes and, in this connection, advocated the widest practicable development of international cooperation in obtaining this source of energy, which is essentially inexhaustible, for the benefit for all mankind”. The announcement did not go unnoticed; Hans Blix, IAEA Director General, wrote to the IAEA International Fusion Research Council, “I view with great interest the recent agreement arrived at the Geneva Summit Meeting to expand [IAEA] activities”. Following discussions, the United States, in consultation with Japan and the European Community (today the European Union), responded with a proposal on the implementation of such an activity. It was not long until — at the invitation from Blix — delegations from the European Community, Japan, the Soviet Union, and the United States met in Vienna, first in 1987, to develop a joint detailed proposal, and finally in April 1988, to start a joint venture called International Thermonuclear Experimental Reactor (ITER), currently under construction in the South of France. ITER’s mission was to demonstrate the scientific and technological feasibility of fusion power. The joint activities on ITER design started on 2 May 1988 in Garching, Germany.

After attending the opening ceremony, John Clarke, Associate Director for Fusion Energy at the US Department of Energy, Office of Energy Research (today the Office of Fusion Energy Sciences), shared his excitement about how international parties have come together with Hans Blix: “Several of those present at the Garching ceremonies noted that this was the first time that the EC [European Community] and Soviet flag flew together. I think you would have enjoyed the sight of the flags from the four Parties [sic], the hosts, and the IAEA flying together”21.


ITER era and a broader perspective

With ITER as a clear goal in mind, experimental efforts intensified to achieve a better understanding of the physics of nuclear fusion essential for ITER design.  In 1991, the Joint European Torus (JET) tokamak made headlines for producing a peak power of 2 MW with a mixture of deuterium and tritium fuel. The crew at the US Tokamak Fusion Test Reactor (TFTR) took up the gauntlet and raised the bar to over 10 MW in 1994. On the wave of these record-breaking results, JT-60U (Japan Torus-60 Upgrade) achieved a performance with deuterium fuel equivalent in a simulation with deuterium–tritium fuel to a fusion gain above one (the ratio of fusion power to input auxiliary heating power), which is a projection of what could have been produced with deuterium– tritium fuel. The JET crew struck back by extending the peak fusion power to 16 MW and generating 4 MW of fusion power over 4 s, with a total fusion energy yield in one shot of 22 MJ. The performance obtained in all these experiments provided confidence that the first and foremost scientific goal of the ITER project — a gain of a factor ten (or higher) — would be achievable. The decision to build ITER in France, with a satellite tokamak, JT-60SA (Japan Torus-60 Super Advanced) in Japan as part of a Broader Approach Agreement between the European Union and Japan, was taken in 2005. Two years later, the Agreement on the Establishment of the ITER International Fusion Energy Organization for the Joint Implementation of the ITER Project was finally formalized26. The Agreement was symbolically deposited into the IAEA’s safekeeping, emphasizing the crucial role played by the IAEA in the evolution of the ITER project since its inception and through the development activities and negotiations held under its auspices. As of today, the ITER members are the People’s Republic of China, Euratom, the Republic of India, Japan, the Republic of Korea, the Russian Federation, and the United States of America. As ITER’s organizational structure was being finalized, the world fusion research program was stirred into action to support ITER’s science and technology development. Superconducting tokamaks like EAST (Experimental Advanced Superconducting Tokamak) in China and KSTAR (Korea Superconducting Tokamak Advanced Research) in Korea began operation to address challenges associated with long pulse operation, while JET’s research program was focused on the hurdles associated with interactions between the plasma and the fusion reactor’s plasma-facing components. The construction of ITER began in 2010 and is now roughly 70% complete. In 2012, ITER became the first licensed nuclear fusion facility under French law governing nuclear facilities regulations. The first plasma discharge is expected for 2025 and, following a commissioning period, fusion power operation is foreseen to start in 2035.

The stellarator’s comeback and the rise of the private sector

In parallel, the efforts in tokamak research and development were complemented by sustained experiments and studies to optimize the stellarator concept from the point of view of equilibrium, stability, and confinement. These attempts resulted in the completion of the world’s largest stellarator, Wendelstein 7-X (W7-X), which started running at the end of 2015 and very recently achieved world-record results in performance, which were presented at the 28th FEC in Ahmedabad, India, in 2018.  While large-scale experiments such as ITER, JT-60SA, JET and W7-X continue to progress — incorporating advances drawn from the experimental and technological validation efforts undertaken on small and medium-sized devices, coupled with the advancements in theory, modelling and simulation — research in fusion science and technology is also being conducted in the private sector. As of June 2020, nearly two dozen start-ups are working on a variety of devices, fuels, and approaches such as alternative confinement geometries using new technologies like high-temperature superconducting magnets. Although many challenges remain ahead on the way to a fusion-powered future,

the enormous scientific and technological progress achieved through consistent high-level global partnership as well as the increased publicly and privately funded research and development demonstrate trust in fusion as a promising option to provide a sustainable, worldwide supply of energy for centuries to come. The IAEA stands ready to serve its Member States to help close the existing gaps in materials science, physics, technology, and safety with the objective of encouraging the development of new technologies and science for ITER and facilitating the coordination of the global effort for the development of future fusion power plants. Moreover, fusion’s international signature partnership may continue to provide a blueprint for how the world can work together harmoniously to tackle global challenges through scientific collaboration.

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