ITER

ITER (initially the International Thermonuclear Experimental Reactor, iter meaning "the way" or "the path" in Latin) is an international nuclear fusion research and engineering megaproject aimed at creating energy through a fusion process similar to that of the Sun. It is being built next to the Cadarache facility in southern France. Upon completion of the main reactor and first plasma, planned for 2033–2034, ITER will be the largest of more than 100 fusion reactors built since the 1950s, with six times the plasma volume of JT-60SA in Japan, the largest tokamak operating today.

The long-term goal of fusion research is to generate electricity; ITER's stated purpose is scientific research, and technological demonstration of a large fusion reactor, without electricity generation. ITER's goals are to achieve enough fusion to produce 10 times as much thermal output power as thermal power absorbed by the plasma for short time periods; to demonstrate and test technologies that would be needed to operate a fusion power plant including cryogenics, heating, control and diagnostics systems, and remote maintenance; to achieve and learn from a burning plasma; to test tritium breeding; and to demonstrate the safety of a fusion plant.

ITER is funded and operated by seven member parties: China, the European Union, India, Japan, Russia, South Korea and the United States. In the immediate aftermath of Brexit, the United Kingdom continued to participate in ITER through the EU's Fusion for Energy (F4E) program until September 2023. Switzerland participated through Euratom and F4E until 2021, though it is poised to rejoin in 2026 following subsequent negotiations with the EU. ITER also has cooperation agreements with Australia, Canada, Kazakhstan and Thailand.

Construction of the ITER complex in France started in 2013, and assembly of the tokamak began in 2020. The initial budget was close to €6 billion, but the total price of construction and operations is projected to be from €18 to €22 billion; other estimates place the total cost between $45 billion and $65 billion, though these figures are disputed by ITER. Regardless of the final cost, ITER has already been described as the most expensive science experiment of all time, the most complicated engineering project in human history, and one of the most ambitious human collaborations since the development of the International Space Station (€100 billion or $150 billion budget) and the Large Hadron Collider (€7.5 billion budget).

ITER's planned successor, the EUROfusion-led DEMO, is expected to be one of the first fusion reactors to produce electricity in an experimental environment.