FAQs

The main answer to this question comes from the nature of these two sciences and their technological applications. In terms of complexity (in both science and technology), there is more than one order of magnitude of difference between fusion and fission.

The core science of fusion is plasma physics, which is highly complex due to its non-linear and stochastic processes. The mastery of the physics is not yet sufficient to enable the construction of a fusion power plant, which requires cutting-edge technologies like superconductivity, high vacuum, and cryogenics. An important mission of ITER is to prove once and for all that it is possible to integrate all these technologies into a single device. The technologies for fission, on the other hand, have evolved over generations of fission machines.

The next decades are crucially important to putting the world on a path towards much reduced greenhouse gas emissions. Current and near-term technologies should be deployed as soon as possible for this purpose. However world population will continue to grow and the proportion of populations living in cities is expected to continue to increase. Together with the need for a more equitable distribution of energy among the world's inhabitants, this means that even more large-scale, low-CO₂ sustainable energy will be needed later in the century. 

The quest for fusion energy represents one of the most ambitious scientific and technological endeavours of our time. Fusion offers the promise of carbon-free, sustainable, large-scale energy, but realizing its potential requires overcoming significant scientific and engineering challenges. Among the most pressing are: the development of materials that are resistant to the harsh environment of a fusion reactor; the management of heat exhaust in the divertor region; the development of remote handling tools for maintenance and repair; the demonstration of large-scale tritium production and recycling; and the demonstration efficient heat removal for the production of electricity. (Read more about all these challenges on this page.)

ITER will contribute to addressing each of them, in an integrated manner, but more R&D will be necessary for a demonstration reactor (usually called DEMO, for DEMOnstration fusion power plant). The presence of other publicly funded fusion research devices, combined with a surge in private sector projects, offers the opportunity to address some of these challenges in a complementary way, but only with enhanced transversal engagement. Continued R&D, international and multi-sector collaboration, and technological innovation will be crucial in overcoming the remaining challenges and to bringing fusion energy to fruition in the shortest time horizon possible.

The timescale to commercial fusion therefore depends strongly on the will to invest in this area of research. Lev Artsimovitch, the famous Russian academician and one of the major figures in fusion history, used to say: "Fusion will be ready when society needs it."
 

ITER is an essential bridge between today's smaller-scale experimental fusion devices and the demonstration fusion power plants of the future. Building on the knowledge and know-how acquired within ITER, as well as research carried out in parallel on other fusion devices, the next-phase machines—industrial demonstrators generically referred to as DEMOnstration fusion reactors (DEMOs)—would demonstrate the large-scale production of electrical power and tritium fuel self-sufficiency. Several conceptual designs for such a machine are already on the table in the ITER Members; these designs will be refined as ITER enters operations.

For more on the DEMO projects planned or underway, see this ITER webpage.

Of course there are likely to be political and economic constraints that we cannot foresee. The final timescale to commercial fusion depends strongly on political and private sector will to invest in this area of research.
 

The power output of the kind of fusion power reactor that is envisaged for the second half of this century will be similar to that of a fission reactor, i.e., between 1 and 1.7 gigawatts. In theory, the larger the reactor, the more efficient it would be to operate and the more power it would produce, so it may be advantageous to go larger in the future. For the moment, it is envisaged that future fusion power plants would occupy buildings no bigger than those that presently house fission or coal-fired power stations.

The main goal of ITER and future fusion reactor-based power plants is to develop a new source of clean and sustainable energy. The average cost per kilowatt of electricity can not yet be extrapolated, however, as this would require the operational experience which will only be available after ITER has been operated for some years. As with many new technologies, costs will be more expensive at first, when the technology is new, and gradually less expensive as economies of scale bring the costs down.

In order to have a rapid market penetration, fusion will have to demonstrate the potential for competitive cost of electricity. Although this is not a primary goal for DEMO, the perspective of competitively priced electricity production from fusion has to be set as a target. One way to do this is to minimize DEMO capital costs (and that of fusion power plants). The ITER Tokamak is a first-of-a-kind experimental machine, built with a vast array of diagnostic systems (over 50!) to learn as much as possible about what is happening in the plasma. A fusion power plant on the other hand would be conceived in quite a different way.

ITER and future fusion devices will use the hydrogen isotopes deuterium and tritium to fuel the fusion reaction.

Deuterium can be distilled from all forms of water. It is a widely available, harmless, and virtually inexhaustible resource. In every cubic metre of seawater, for example, there are 33 grams of deuterium. Deuterium is routinely produced for scientific and industrial applications.

Tritium, however, is only present in nature in trace amounts. The only source of readily available tritium comes from heavy-water fission reactors such as the CANDU type (developed by Canada in the 1950-60s, and adopted since in Argentina, China, India, Pakistan, Romania, and South Korea). However, the tritium generated by these reactors is just a by-product and quantities remain relatively small. The accumulated stock of tritium produced from CANDU reactors worldwide does not exceed 20 kilos in any given year—just enough to fuel ITER for the planned fifteen years of its deuterium-tritium operation phase.

Operating an industrial electricity-producing fusion plant, by contrast, will require an average of 70 kilos of tritium per gigawatt of thermal power (per year at full power). And if all goes well, there could be hundreds, if not thousands, of fusion plants operating in the early decades of the 22nd century. How then, will these reactors be fuelled?

Nature offers a solution that combines elegance and efficiency—if, successful, the fusion reaction itself will produce the tritium that, in turn, will continue to fuel the reaction. What's more, the process will take place within the vacuum vessel in a safe, continuous, closed cycle. The key to this process is isotope 6 of lithium (Li-6) which, when impacted by neutrons, generates tritium. ITER will test different concepts of "tritium breeding modules," each one with a unique architecture and composition. Whether liquid or solid, compounds will consist of enriched lithium with a proportion of Li-6 in the 50 percent range (compared to the natural isotopic fraction of 7.5%).

Now we must ask: Will there be enough lithium to sustain tritium production for fusion?

Yes, enough for at least several thousand years. Let's look at the numbers. There are approximately 50 million tonnes of proven lithium reserves in the world (half in brine deposits, half in rocks), which means about 3 million tonnes of Li-6. Like most minerals, lithium is also present in seawater. At a concentration of 0.1 part per million, the mass of lithium contained in the oceans of the planet is estimated at 250 billion tonnes. However, a cost-effective method of recovering lithium from seawater does not yet exist.

It takes 140 kilos of Li-6 to obtain the 70 kilos of tritium necessary to producing one gigawatt of thermal power for one year. Assuming an availability of 80 percent and a conversion efficiency from thermal to electrical power of 30 percent, then the production of one gigawatt of electrical power (the estimated size of an average fusion reactor) will require approximately 500 kilos of Li-6 per year.

That brings the total requirement for 10,000 reactors to 5,000 tonnes of Li-6 annually.

Fusion will not be the only avid consumer of lithium. The ever-growing lithium-ion battery market for laptops, mobile phones, cordless power tools (and of course electrical vehicles) will claim its share. However lithium-ion batteries will not necessarily be in "competition" with fusion. At the scale of the global economy, one could imagine that the "waste" product of the lithium enrichment plants for fusion, namely Li-7, could well be used to produce lithium-ion batteries, thus maximizing the efficiency (and cost) of the overall lithium cycle.

Fusion specialists generally consider that, in a world where all energy would be produced by fusion, the quantity of lithium ore present in landmass would be sufficient to provide the required tritium for several thousand years. And as for the lithium present in oceans, it could last millions of years. As for the immediate needs of the tritium breeding module testing at ITER, Li-6 enriched lithium will be supplied from existing lithium enrichment plants. The next fusion reactors such as DEMO will likely require new dedicated facilities to produce Li-6 enriched lithium in sufficient amounts.

Future fusion power plants will have to produce tritium; however, tritium self-sufficiency is not necessary in ITER. Rather, one of the missions for the later stages of ITER operation is to demonstrate the feasibility of several (4) concepts of tritium production through the Test Blanket Module (TBM) program. The TBM program will build on tritium breeding studies that have been carried out for a number of years, in particular by the European Union which has substantial expertise in this field. The accumulated knowledge permits a high level of confidence that results from ITER will contribute to full tritium self-sufficiency in next-generation devices.

ITER and future fusion machines based on present superconductor technology would require only a fraction of the present total world helium production.

One of the major helium reserves is the US strategic helium storage reserve; this was released for sale and quantities will reduce in the coming years but will be compensated with new helium sources going into production around the world at the same time. There are also several other untapped helium reserves that ensure sufficient production for party balloons and MRI magnets (some of the main users of helium).

While it is uncertain what the price of helium will be in the coming decades (it will depend on supply and demand), there shouldn't be any significant shortage for fusion.

In the future, fusion machines will have the capability to breed not only their own fuel (tritium) but also helium to preserve natural reserves.

Fusion and fission are totally different scientific and technological concepts, although both involve nuclear reactions. The fuel assemblies in the core of a fission reactor contain several tons of radioactive fuel which generates energy by the splitting ("fissioning") of atomic nuclei in a chain reaction. Fusion is not a chain reaction. The entire system contains a few kilograms of the radioactive fuel component (tritium) with only a few grams reacting at any given time in the reaction chamber.

Three very unique safety features make fusion technology an attractive option to pursue for future large-scale electricity production.

First, fusion presents no risk of nuclear proliferation. Unlike the fissile materials such as uranium and plutonium used in fission reactors, tritium is neither a fissile nor a fissionable material. There are no enriched materials in a fusion reactor like ITER that could be exploited to make nuclear weapons.

Second, nuclear fusion reactors would produce no high activity/long-life nuclear waste. The "burnt" fuel is helium, a non-radioactive gas. Radioactive substances in the system are the fuel (tritium) and materials activated while the machine is running. The goal of the ongoing R&D program is for fusion reactor material to be recyclable in less than 100 years.

Third, fusion reactions are intrinsically safe. A "runaway" reaction and the resulting uncontrolled production of energy is impossible with fusion. Fusion reactions cannot be maintained spontaneously: any disturbance or failure stops the reaction. This is why it is said that fusion has inherent safety aspects. Moreover, the loss of the cooling function due to an earthquake or flood would not affect the confinement barrier at all. Even in the case of the total failure of the water cooling system, ITER's confinement barriers will remain intact. The temperatures of the vacuum vessel that provides the confinement barrier would under no circumstances reach the melting temperatures of the materials.

Nuclear risks associated with fusion relate to the use of tritium, which is a radioactive form (isotope) of hydrogen. However, the amount used is limited to a few grams of tritium for the reaction and a few kilograms on site. During operation, the radiological impact of the use of tritium on the most exposed population is much smaller than that due to natural background radiation. For ITER, no accident scenario has been identified that would imply the need to take countermeasures to protect the surrounding population.