The International Thermonuclear Experimental Reactor (ITER), or the world’s largest nuclear fusion project, achieved a major machine assembly milestone earlier this month, with the first sub-section of the ITER plasma chamber being lifted out of tooling and lowered into the machine well, according to an ITER announcement.
The ITER machine, the assembly of which began in July 2020 in France, is designed to replicate the fusion power of the sun to enable generation of clean unlimited energy. When light atomic nuclei fuse together to form heavier ones, a large amount of energy is released, which fusion reaction is to be housed in the ITER plasma chamber.
ITER’s plasma chamber, or vacuum vessel, will be formed from nine wedge-shaped steel sectors that measure over 14 metres in height and weigh 440 tonnes. The section of the ITER machine which has been lowered represents one-ninth of the toroidal plasma chamber.
This particular vacuum vessel sector subassembly, that has been lowered from the assembly hall into the tokamak pit, consists of silver-coated thermal shields and two D-shaped vertical superconducting electromagnets called toroidal field coils. Eight other similar assemblies will form the complete chamber and surrounding toroidal field coil superstructure.
The “tokamak” (derived from the Russian words for “toroidal magnetic confinement”) machine, which will produce thermonuclear fusion power, relies on magnets to propel and shape its plasma stream. It initiates plasma current, as well as drives and shapes the plasma during operation. ITER expects to generate its first ultra-hot plasma in late 2025.
“The first-of-a-kind operation was spectacular at many levels. The sheer weight of the component plus rigging—1,380 tonnes—came the closest yet to the nominal lift capacity (1,500 tonnes) of the double overhead bridge crane in the ITER Assembly Hall. The teams achieved millimetre-level tolerances in the positioning of a component that towers six storeys high and weighs the equivalent of four fully loaded Boeing 747s”, ITER Organisation said about the successful operation.
The ITER vacuum vessel, with an interior volume of 1,400 cubic metres, is unique — it can contain 840 cubic metres of plasma, which is ten times larger than that of the largest tokamak currently operating in the world. Once assembled, the ITER vacuum vessel will have an outer diameter of 19.4 metres, a height of 11.4 metres, and weigh approximately 5,200 tonnes. With the subsequent installation of in-vessel components such as the blanket and the divertor, the vacuum vessel will weigh 8,500 tonnes.
ITER is a 35-nation partnership composed of the European Union, the UK, Switzerland, China, India, Japan, South Korea, Russia and the US. Each partner contributes in-kind hardware to support their share of project construction while sharing all of the science and technology. The world’s largest science project is intended to demonstrate that fusion power can be generated on a commercial scale.
“Many project actors have had a part in today’s successful milestone. Vacuum vessel sector Number 6, at the centre of the assembly, and associated thermal shielding was manufactured and delivered by the Korean Domestic Agency. India fabricated the in-wall shielding inside the double walls of the sector and Russia supplied the upper port. The toroidal field coils (TF12 and TF13) were procured by the Japanese Domestic Agency”, an ITER Organisation statement said.
“Korea designed and built the upending tool, the giant sector sub-assembly tools, the lift attachment closest to the load, and the column tool in the pit that will support the vacuum vessel during welding, while the European Domestic Agency supplied the overhead bridge cranes and the next-in-line rigging attachment that allows the cranes to work together”, it said.
“This successful lift operation will be celebrated across the ITER community as a major assembly milestone, bringing the project another step closer to First Plasma. The component is currently suspended only 50 centimetres above its supports in the assembly pit, as the assembly team carries out the final positional operations. It will then be lowered to its supports, arriving ‘home’ after a long and complex journey”, the statement added.
ITER’s realising of a self-heating plasma is expected to generate 10 times more heat than is put in. Fusion provides clean, reliable energy without carbon emissions, with minute amounts of fuel and no physical possibility of an accident with meltdown. The fuel for fusion is found in seawater and lithium, while it is abundant enough to supply the world for millions of years. A football-sized amount of this fuel is equivalent to around 10,000 tons of coal.
