International Thermonuclear Experimental Reactor (ITER)

Jack Chabolla
February 22, 2017

Submitted as coursework for PH241, Stanford University, Winter 2017


Fig. 1: A model cross section of ITER. (Source: Wikimedia Commons)

It is unequivocal that mankind has contributed to climate change through its use of fossil fuels. However, despite forecasts of its harmful environmental impact, fossil fuels continue to be used as a main source of energy - and at an increasing rate. The global population is projected to grow from 7 billion to 8.5 billion by 2030, significantly increasing the demand for energy. [1] With this realization, paired with new technological capabilities, steps are being taken to develop a new method of obtaining a cleaner, more sustainable source of energy - nuclear fusion.

Nuclear fusion is a reaction in which two atomic nuclei (namely hydrogen) create energy by fusing together to form a nucleus. There are many benefits associated with the energy produced. Mainly, nuclear fusion does not produce greenhouse gasses, it cannot explode in a chain reaction, there is little nuclear waste, and the cost of fuel (Deuterium-Tritium) is low. [2] This makes nuclear fusion much safer, cleaner and cheaper than nuclear fission - a current controversial alternative to fossil fuels.

Research of nuclear fusion started in the 1920s, but it wasn't until the 1950s that Soviet physicists Igor Tamm and Andrei Sakharov invented the tokamak - the leading design for modern fusion reactors. [3] This design is currently being used to build the international thermonuclear experimental reactor (ITER), a project, which is hoped to unveil mysteries surrounding large scale nuclear fusion and the feasibility of commercial production, see Fig. 1. In this report, I will discuss the specific goals of ITER and the many challenges in the way of sustainable nuclear fusion.


ITER is an experimental reactor currently under construction in Saint-Paul-lez-Durance, France. Because ITER is experimental, it will not be used to capture energy for commercial use, but rather to test whether the underlying physics and engineering hold at scale. Scientists will use the opportunity to study plasma and technology in conditions likely similar to those of future fusion power plants. When ITER is up and running, the main benchmark will be to produce 500 MW of fusion power with an input of approximately 50 MW - it is hoped ITER will be able to net positive energy production. Another goal is to test tritium breeding. As mentioned before DT fuel is cheap - however, this is because Deuterium is accessible in seawater. Tritium, on the other hand, is limited and it is essential for ITER to have an effective "breeding" system. [2] Debatably the most important goal of ITER (and most regulated) is its ability to control the fusion reaction in a safe way and have an insignificant impact on the environment. [4] While much of the physics and engineering behind ITER has been tested in smaller tokamaks (mainly the Joint European Torus "JET"), it has never been tested at such a massive scale and the results are uncertain.


While JET has provided some hope and direction for the development of ITER, it has not proved that nuclear fusion will be sustainable at scale. There are many challenges that have yet to be solved and will be put to test when the construction of ITER is completed. One of these challenges is sustaining high-grain burning plasma. The risk is that the plasma won't be able to capture fusion energy without causing instabilities, melting the inner walls, or being susceptible to contamination. To make the situation more uncertain, it is not yet known what material will work best for ITERs inner-walls - currently, scientists are exploring the reliability of beryllium and tungsten. DT fusion reactions emit large quantities of highly energetic neutrons and it is imperative that the ITER fusion blanket (which covers the inner-wall) is able to handle high neutron fluxes - minimizing neutron-induced damage. [2] There are many more technical challenges that scientists will face when assembling and testing ITER.

The ITER project has had its fair share of non-technical challenges, as well. Because of its massive scale, there have been many delays. The original plan called for plasma testing by 2020 and full fusion by 2023, however because of a series of delays the ITER may not test its first full-power fusion before 2035. [5] One reason for the delays is that ITERs construction relies on up to ten million parts being shipped from several different countries - this shipping process has been riddled with communication errors and logistical oversights. [4] Additionally, these delays will add to the already exorbitant costs, which had once been estimated 5 billion euros and are now an estimated 15 billion euros. [5] ITER is being "funded" by the European Union, Japan, Russia, USA, China, South Korea and India. However, these countries have not committed to pay - the project risks that any country may back out of the agreement, which would increase the burden on the other countries. [4] Lastly is the issue of nuclear proliferation - when nuclear energy is being produced at the international level measures must be taken to keep the technology out of the wrong hands. However, because the project is funded by an range of countries, potentially with different motives, it is much harder to enforce any given measure.


The ultimate goal of fusion research is to find a way to produce commercial fusion energy. Essentially, ITER represents a stepping-stone in this process. It will allow scientists to test and confirm various unknowns, which, in turn, will be essential for the creation of a commercial fusion energy plant. If ITER proves to be successful, the next stage of the process will be to develop project DEMO - the first commercial fusion energy plant. [2]

© Jack Chabolla. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.


[1] "Population 2030," United Nations, 2015.

[2] C. L. Smith and S. Cowley, "The Path to Fusion Power," Philos. Trans. R. Soc. London A 368, 1091 (2010).

[3] V. P. Smirnov, "Tokamak Foundation in USSR/Russia 1950-1990," Nucl. Fusion 50, 014003 (2009).

[4] R. L. Hirsch, "Fusion Research: Time to Set a New Path," Issues in Science and Technology, 31, No. 4 (Summer 2015).

[5] G. De Clercq, "Nuclear Fusion Reactor ITER's Construction Accelerates as Cost Estimate Swells," Reuters, 7 Oct 16.