Fusion, where are we now?
Nuclear is an energy and a technology for the future. If recent events have tried to convince us of the contrary, they reflect fluctuating, and – to put it bluntly – opportunistic political decisions.
The reality of underlying trends is quite different. Translated by research, supported by tangible industrial reality of the current generation of reactors and processes, it is made of major structural advances, progressing slowly but surely, and of technical revolutions to come, at the service of all human beings. And no longer just some.
Events are just the foam of things,
what interests me is the sea.
At the Voices, we therefore chose, on the contrary, to initiate a series on what constitutes the future of nuclear technology to which the whole industry contributes today. This will take the form of a few newsletters dedicated to materializing the importance of today if we want to give ourselves a chance to witness the advent of tomorrow.
And it would be a real shame to let that tomorrow, slip through our fingers.
In the name of the Voices
Chronicle (s) of the Other Nuclear – Volume 1
Fusion, where are we now?
By Greg De Temmerman, scientific coordinator at ITER
When we think of nuclear energy, we look to one of the now 57 reactors which supply around 72% of the electricity in France and allowing it to have one of the least carbon-intensive electricity systems in the world.
There is, however, another way of producing energy by nuclear process: fusion.
«Although we sometimes have the impression that fusion and fission oppose each other, these two fields have many complementarities, whether at technological, operational or even strategic level, in the context of the development of low-carbon energy sources»
Overview of current research and future perspectives
Fusion is the process that takes place at the heart of stars by which two atoms come together to form a heavier atom – the opposite of the fission process. Fusing atoms is very difficult and requires very high temperatures – the temperature in the center of the sun is around 15 million degrees Kelvin or Celsius. Matter at such temperatures is in the plasma state. This is why fusion research mainly focuses on the reaction between two isotopes of hydrogen: deuterium and tritium, being the “easiest” to produce, although it still requires a temperature of some 150 million degrees. The reaction produces an energetic charged neutron and a helium atom.
At that point appears one of the big challenges of fusion : to contain a plasma at such a temperature in a solid enclosure. To confine it, we use very strong magnetic fields to prevent it from touching the walls of the enclosure. The most efficient magnetic configuration is called tokamak, a concept invented in the 1960s in Russia. The plasma is then confined in the form of a torus.
Why then take an interest in a process that seems so difficult to master?
Several arguments make fusion an extremely attractive source of energy for the centralized production of electricity – some even speak of unlimited or ultimate energy.
- Resilient. The fusion reaction cannot become uncontrolled. Just turn off the plasma heater or the particulate feed and the plasma will cool off very quickly. The quantities of matter involved in the plasma are extremely small, its mass being of the order of a few grams.
- Safe. Even in the event of an accident causing the release of tritium, which is radioactive with a half-life of 12.3 years, evacuation of surrounding populations is not necessary.
- Produces little waste. Fusion does not produce high-activity, long-lived waste. The product of the fusion reaction is helium, an inert gas. Activation of structural materials by neutron impact creates waste, but the half-life is only up to a few decades, limiting the need for long-term storage, as the materials can be recycled after some hundred years.
- Concentrated. Fusion is the most concentrated source of energy: 1g of fuel contains the same amount of energy as 10g of uranium, and above all that of 16 tons of oil!
- Abundant. The tritium necessary for the reaction does not exist in nature. For ITER it will be produced, mainly in CANDU type heavy water reactors. A fusion reactor will therefore have to produce more tritium than it consumes. The production involves capturing the neutrons emitted by the reaction in the so-called tritium-breeding blanket surrounding the plasma which contains lithium. Deuterium and lithium are available in large quantities and above all well distributed geographically, making fusion in principle a very abundant energy.
Where are we?
Research on controlled nuclear fusion began towards the end of the Second World War in the United States and the USSR. Constant progress has been made since then, culminating in the 1990s with demonstration in the United States and England of energy generation by nuclear fusion. However, these experiments achieved fusion gains lower than 1 (the highest was 0.76) – that is, the energy produced was less than that injected into the plasma.
Generating net energy is the main objective of the ITER project – International Thermonuclear Experimental Reactor – under construction in Cadarache north of Aix-en-Provence, on which 35 countries are collaborating and which aims to demonstrate the scientific and technological feasibility of fusion energy.
«Objective: demonstrate the scientific and technological feasibility of fusion energy»
The objective is a gain of the order of 10, or 500 MW (thermal megawatts – there is no electrical conversion in ITER) produced for 50 MW injected. Begun in 2006, the ITER project initially suffered from the difficulty of establishing a complex international organization applied to one of the most ambitious technological projects ever carried out. The start of operations is now scheduled for 2025 and, after a gradual ramp-up, deuterium-tritium operations should start around 2035. ITER is a machine measuring about 30mx30m, using giant superconducting magnets (the largest has a diameter of 25m) whose components are extremely complex, massive but manufactured and assembled with extremely small tolerances.
«A complex international organization applied to one of the most ambitious technological projects ever carried out. […] Startup scheduled for 2025»
After ITER, the European roadmap for development of fusion foresees commissioning a demonstration reactor (called simply … DEMO) that will produce electricity (around 500MW), in the 2050s. The British government recently launched the first phase of the STEP (Spherical Tokamak for Electricity Production) project, whose goal is to design a compact fusion reactor that could be built in the 2040s. Finally, China several years ago launched the CFETR (Chinese Fusion Engineering Testing Reactor) project which is expected to demonstrate generation of continuous thermal energy (initially around 200MW and eventually around 1GW) plus production of tritium. CFETR is thus positioned between ITER and DEMO in the development of a fusion reactor. In parallel with this “institutional” research, private companies have embarked on the adventure (see the list of start-ups) with various concepts that all share the ambition to accelerate the development of nuclear fusion. One such company (Commonwealth Fusion Systems, a spin-off from MIT) caught the eye of the Breakthrough Energy Ventures investment fund, which includes as contributors Bill Gates and Jeff Bezos.
A sign that fusion is entering a new era?
Volume 2: Fission and Fusion, a family story