2024 was a difficult year for Iter (International Thermonuclear Experimental Reactor). This ambitious nuclear fusion reactor is under construction in the French town of Cadarache by an international consortium led by the European Union . Initially conceived in 2006, the project officially commenced in 2007, but the assembly of this colossal machine didn’t kick off until 2020.
The original timeline established by Eurofusion—the institution responsible for promoting and facilitating the scientific research necessary for the European Nuclear Fusion Plan—set the completion of the assembly for 2025. However, that same year was slated to mark another vital milestone: the initiation of plasma tests . Subsequent milestones were scheduled for 2028, when Iter engineers would begin low power operations utilizing hydrogen and helium, followed by the first high-power experiments in 2032 with the same gases.
Boldly, it was projected that by 2035, Iter would undertake high-power tests with deuterium and tritium . Fast forward to 2040, and this experimental reactor was expected to demonstrate the energy profitability of nuclear fusion. However, these timelines have faced significant delays. In 2022, the French Nuclear Safety Authority (ASN) flagged multiple technical irregularities in the vacuum chamber sectors, prompting the Iter organization to respond appropriately by forming a working group to address ASN’s supplementary requests and continue advancing the assembly of the Tokamak .
Iter’s Technical Challenges Are Unprecedented
The assembly of such a complex machine is anything but straightforward. The vacuum chamber alone weighs 8,000 tons and is constructed from stainless steel and boron, requiring a hermetic seal. Engineers have faced incredibly strict local tolerances of just 0.1% , compounded by the chamber’s intricate shape and the use of plates up to 60 mm thick . To tackle these challenges, technicians have resorted to cutting-edge technologies, such as Electron Beam Welding —a technique that utilizes an electron beam for welding—or advanced AI models specifically designed to identify weld defects in the chamber.
<img alt="Universal quantum computers are closer thanks to this unexpected discovery" width="375" height="142" src="https://i.blogs.es/4c4247/ising-ap/375_142.jpeg"/>The COVID-19 pandemic , which peaked sharply during 2020 and 2021, alongside the technical challenges stemming from the unprecedented nature of many components, has caused significant delays in the main milestones of this project. Nonetheless, the current updated timeline proposes several key dates worth noting.
In 2039, Iter will be able to undertake high-power tests with deuterium and tritium.
By 2034, the first experiments in the reactor are anticipated; in 2036, the magnetic system responsible for plasma confinement will be tested; and in 2039, Iter aims to start high-power tests with deuterium and tritium—this last milestone was initially expected in 2035.
Despite these challenges, assembly progress on Iter has advanced well over the past year. The cover image of this article showcases two of the substantial sectors of the vacuum chamber; however, one of the milestones achieved this year occurred in May. The superconductor magnets installed on the exterior of the vacuum chamber bear the critical responsibility of generating the magnetic field required to confine the plasma internally while simultaneously controlling and stabilizing it.
These magnets, weighing around 10,000 tons , are manufactured from an alloy of niobium and tin or niobium and titanium. They achieve superconductivity when cooled with supercritical helium to an astounding temperature of -269 ºC . This extreme requirement justifies the need for a powerful cooling system, which has been meticulously planned for Iter by European collaborators. In the construction of this experimental nuclear fusion reactor, contributions have come from the US, Russia, China, India, South Korea, Japan, and the UK, with the refrigeration plant developed by Fusion for Energy (F4E) , the European Union’s organization coordinating its contribution to Iter, in collaboration with the French company Air Liquide .
Superconductor magnets acquire superconductivity when they reach a temperature of -269 ºC.
This cryogenic facility will provide liquid helium at 4.5 Kelvin (-269 °C) to the superconductor magnets and cryobombs, as well as gaseous helium at 80 Kelvin (-193 ºC) to thermal shields, which are crucial for protecting vital components like superconductor magnets from the heat emitted by the confined plasma. Cryobombs work to eliminate gases from within the vacuum chamber, necessitating operation at extremely low temperatures. Thermal shields ensure protection for critical reactor elements from plasma heat exposure.
Iter’s cryogenic plant spans an area comparable to a football field (over 7,100 m² ) and houses several 26-meter high storage tanks . Such dimensions testify to the enormity of this vital installation, without which nuclear fusion would be utterly infeasible. A statement from F4E manager Grigory Kouzmenko inspires optimism for Iter’s future, declaring, “We have entered the most exciting phase of the project, in which all efforts of previous years are finally coming to fruition, benefiting from the collaboration and trust among all parties involved.”
Image | Fusion for Energy
More information | ITER
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